Amiga ISO Collection/AmigaDemoCD2.iso/ASCII/TEXTE/DOCS/LsdDOCS35.DMS/LsdDOCS35.adf/SimEarth.doc2.pp/SimEarth.doc2

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            SIM EARTH PART 2


EARTH: MODERN DAY
~~~~~~~~~~~~~~~~~
This scenario takes place on the Earth of today.  We live in a world
with  pollution,  war, famine, greenhouse warming, energy shortages,
and the possibility of nuclear winter.

The problems: Too many to list here. Read your newspaper.

Time Scale  : Technology

Your mission: Solve  all  the  world's problems and lead us into a
future of peace, abundant food, clean air, and plentiful energy.

The methods : If I knew how to solve all these problems, I'd be
running the U.N. instead of making computer games.

Hints:   The  best  way  to  prevent  war in SimEarth is to allocate
energy  to  philosophy  in  the  CIVILISATION  MODEL  CONTROL PANEL.
Increasing  allocation to Agriculture will increase the food supply.
Allocating  to  Art/Media  improves  the  quality of life.  Wars and
plague  have  a  greater impact in this scenario than they do in the
real world.

Notes:   This scenario can be difficult, but still more fun than the
real  thing.   If  you click and hold on the Terrain Map Icon in the
MAP  WINDOW, you will see the names of the continents displayed.  If
you  click and hold on the Drift icon in the MAP WINDOW you will see
the names of the major tectonic plates displayed.

                > 114 <


MARS
~~~~
For  this  scenario,  you are a citizen in a nanotech level society.
Your home planet is overcrowded, and the population is increasing.

You show up for work, and find a memo from the boss that informs you
that  you've  been  put  in  charge of a new project.  The promotion
involves  a small raise, but you'll have to move--to Mars.  Your new
job  is to turn Mars into a planet capable of supporting human life.
If  you  fail  to  complete  this project within 500 years you'll be
fired.

The  problem:   No water, almost no atmospheric pressure, no oxygen,
no  plants,  no  animals,  no  nothing  except  rock.   The  average
temperature is -53 degrees C.

Time Scale: Technology

Your mission: Terraform Mars and make it a place fit for human
occupation, and Colonise the planet.

The methods: The  MODEL CONTROL PANELS (except for the CIVILISATION
MODEL  CONTROL  PANEL)  have been disabled to make this a challenge.
You'll  need the TERRAFORMERS available through the PLACE LIFE tool.
Gaian  regulation  has  been  disabled--no  life  will spontaneously
generate.   The  REPORT  WINDOW  gives  you special feedback on your
terraforming progress.

                > 115 <

Hints:   Start  off  with  a few ice meteors to create oceans.  Then
start   producing  CO2  and  other  greenhouse  gases  to  build  up
atmospheric  pressure  and  begin  planetary  warming.   Use the CO2
generator  or  better  yet,  plant  some  single-Celled  life  in the
oceans--they  are  more  efficient  than terraformers at building an
atmosphere.

Notes:   Click and hold on the TERRAIN MAP icon in the MAP WINDOW to
see  a  display  of  Martian landmarks.  Landmark names shown in all
capital  letters  designate  large  regions,  other  names designate
smaller regions or individual spots.

                > 116 <

VENUS
~~~~~
Venus  is SimEarth's ultimate challenge in terraforming.  While Mars
is  far  too  cold,  Venus  is  far  too  hot for life:  its average
temperature is 417 degrees C.

The problem: Too hot for life

Time Scale: Technology

Your mission: Cool this planet down, and make it a fit place for Earth
life-forms.

The  methods:  The MODEL CONTROL PANELS (except for the
CIVILISATION MODEL CONTROL PANEL) have been disabled.
You'll need the TERRAFORMERS available through the PLACE LIFE
tool. Gaian regulation  has  been disabled--no life will
spontaneously generate. The  REPORT  WINDOW  gives you special
feedback on your terraforming progress.

Hints:  The first thing you have to do is cool the planet down.  Ice
meteors  won't  help--but go ahead and try them if you want.  It's so
hot  that  ice  meteors  melt  and boil off into water vapor.  Since
water vapor is a greenhouse gas, it just makes things hotter.

To  cool  things  down,  you've got to reduce the greenhouse effect.
The  Oxygenator  takes CO2 (a greenhouse gas) out of the atmosphere.
As  soon  as  it  cools enough, start placing biomes on Venus, which
will  also  lower the CO2 in the air.  When placing biomes, remember
that the higher the elevation, the cooler the temperature.

Notes:   Click and hold on the TERRAIN MAP icon in the MAP WINDOW to
see  a  display  of Venusian landmarks.  Landmark names shown in all
capital  letters  designate  large  regions,  other  names designate
smaller regions.

                > 117 <

DAISYWORLD
~~~~~~~~~~
Unlike  the  other  scenario  planets,  the terrain of Daisyworld is
randomly generated each time you load it.

According  to  the  Gaia  theory,  life and the environment together
constitute  a  system  that  self-regulates  climate and atmospheric
composition.

This  scenario  is  based  on  the original Daisyworld program James
Lovelock developed as a test of the Gaia theory.

During  the  past 3.6 billion years, the output of heat from the Sun
has  increased  by  25%,  but  the  Earth's  average temperature has
remained almost unchanged during the same time period.

According  to  theory,  Gaia  has controlled the temperature to keep
Earth  cool  enough  for  life.   Daisyworld tests Gaia's ability to
regulate temperature.

In  Daisyworld,  as  in all SimEarth planets and scenarios (and real
life),  the  Sun's  heat output is slowly but constantly increasing.
If  Gaian  regulation  works,  the average temperature on the planet
should  remain  fairly  constant  in  spite  of the increasing solar
radiation.

The  biomes  have  been  changed  to  eight  shades of Daisies.  The
different  shades,  ranging  from  white to black, reflect different
amounts of light and heat that regulate the planet's temperature.

Daisies  are  available  for  planting in the PLANT BIOME tool.  The
ratio  of  the various shades of Daisies can be tracked in the BIOME
RATIO GRAPH.

                > 118 <


The  problem:   The heat from the Sun is steadily increasing.  If it
isn't  somehow  regulated,  the oceans will boil off and all life on
this planet will die.

Time Scale: N/A

Your mission:  Test Caia's ability to regulate temperature, and fill
the world with Daisies.

The method:   Keep  an  eye  on  the  Temperature  Map and the Air
Temperature  graph  in  the HISTORY WINDOW to observe the regulation
cycles.

The  REPORT  WINDOW gives you special feedback on your Daisy-raising
progress .

Hints  and  cautions:   Place  life on the planet to eat the Daisies.
See how this complication affects regulation.

Notes:   There  will  eventually be a breakdown point where the heat
from  the  Sun  is  too  great  for  Caia  to  regulate.   Adding or
subtracting  land  areas  where  Daisies  can  live  will  move this
breakdown point forward or backwards.

Also note the change in the Daisies' color as the landmass increases
and decreases.

Try  testing  the stability of the system by killing off many of the
Daisies.   How  many can be killed before the system collapses?  How
much  of  the  planet's  surface  must  be  covered  by  Daisies for
regulation to occur?

HOW DAISYWORLD WORKS
~~~~~~~~~~~~~~~~~~~~
Daisyworld  is  a  planet  like  Earth,  but  with  few clouds and a
constant low concentration of greenhouse gases.  The output from the
planet's sun is constantly increasing.

The planet's temperature is a balance between the heat received from
the  sun  and  the  heat loss by radiation from the planet to space.
The   albedo--the   reflectiveness--of  the  planet  determines  the
temperature.

The  planet  is  well-seeded  with  Daisies,  whose growth rate is a
function  of  temperature.   There are two colors of Daisies:  Black
and White, which only grow between 5 and 40 degrees C, and grow best
at  22.5  degrees  C.   Assume plenty of water and nutrients for the
plants.

                > 119 <

Taking  into account only the heat from the sun and the albedo of
the planet, we get the results in the following graphs.

The  bottom  graph shows the increasing solar heat (dotted line).
The  temperature  of  the  planet  rises in direct proportion to the
increase  of  solar  heat.   The  top graph shows life on the planet
(Daisies) during the same time.

When  the  temperature  hits  5 degrees C the Daisies begin to grow.
When the temperature hits 40 degrees C they all die.

Now we add the albedo (heat and light reflectiveness) of the Daisies
to the system.

When  the planet's temperature reaches 5 degrees C, Daisies begin to
grow.   During  the first season, the Black Daisies will grow better
since  they  will  be  warmer than the planet's surface (dark colors
absorb  heat).   White  Daisies  won't  grow  very  well, since they
reflect heat and will be colder than the planet's surface.

At  the  end of the first season there will be many more Black Daisy
seeds in the soil that will soon grow.  As the Black Daisies spread,
they will not only warm themselves, but the whole planet.

Eventually,  because  of the warming from both the Black Daisies and
the  Sun,  the  planet's  temperature  will  rise to 22.5 degrees C.
Since  the  Black Daisies are warmer than the planet, they are above
their optimum living temperature, and their growth rate will slow.

Since  the White Daisies are cooler than the planet, they will start
to  grow  better  as  the  temperature  gets higher.  When there are
enough  White  Daisies,  they  will  reflect enough heat to cool the
planet.


                > 120 <



Eventually,  the  solar  heat  gets  so great that the White Daisies
cannot reflect enough heat to cool the planet.

The  important  thing  to  note  here is that the life on the planet
affected  the  climate  of the planet in a way that is beneficial to
life.   It  regulated the temperature, and nearly doubled the amount
of time life could survive.

This  is  only  a  simple  demonstration,  and  only  deals with one
life-form  and  one  climactic feature, but it does demonstrates the
two-way connection between life and environment.

                > 121 <

INSIDE THE SIMULATION EVENTS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Events  are noteworthy occurrences on your planet.  They will happen
randomly,  controlled  by  the simulation, and you can cause most of
them to happen through the TRIGGER EVENTS TOOL in the EDIT WINDOW.

The cost in energy for triggering an event is 50 E.U.

There are 11 events in SimEarth, eight of which can be triggered
manually:

HURRCANE
~~~~~~~~
With winds of 74 m.p.h.  or greater, usually accompanied by
rain, thunder and lightning.  Hurricanes can cause tidal waves.

They  can  wipe  out cities and destroy a lot of life.  In SimEarth,
hurricanes  are  caused  by  warm  oceans.   The  only way to defend
against them is to keep your oceans cool.

You  can  use  hurricanes  to increase rainfall in specific areas on
your planet.

TIDAL WAVE
~~~~~~~~~~
An unusually high sea wave that can be caused by earthquakes,
high winds, hurricanes, volcanos and meteor impact.

Tidal  waves  can  destroy  coastal  cities  and  land life. They
generally travel from deeper water to shallower water.

Tidal waves are useful for eliminating unwanted coastal cities.

METEOR
~~~~~~
Meteors are huge hunks of rock  from space that smash into the
planet, causing much damage and creating craters on land and tidal
waves in the sea.

                > 122 <


Meteors  that  crash  into the land will put dust into the air.  Too
much  dust  will  block the sun and cause extinctions.  Meteors that
crash  into water put water vapor into the air, increasing rainfall.
Meteorites also affect magma flow.

Meteors  are  useful  for  adding  water  vapor  to  the  atmosphere
(increasing  rainfall),  creating  lakes  in  large land masses, and
destroying pesky life-forms.

VOLCANO
~~~~~~~
A volcano is a vent in the planetary crust that that  lets  a
flow of molten rock to the surface.

Volcanos raise the terrain elevation, creating mountains on land and
islands  in  the sea.  Volcanos in the ocean cause tidal waves.  The
severity  of  volcanos is less when the planet is young and the core
is large.

Volcanos in SimEarth are huge upwellings that make recent real Earth
events like Krakatoa look like pimples.

Volcanos put a lot of dust into the air, which can block the sun and
cause  extinctions.   They  also  add a lot of carbon dioxide to the
air,  which  is great ior plants, but above a certain point, bad for
animals.

Volcanos  are  useful  for  creating  islands and mountains, and for
doing general damage to life-forms.

ATOMIC TESTS
~~~~~~~~~~~~
Atomic tests are the firing of atomic bomb. They occur `naturally`
in wars between groups of your sentient species.

Atomic tests do much damage, spread radiation, and put a lot of dust
into  the  atmosphere.   Too  many  atomic tests can cause a nuclear
winter, which causes mass extinctions.

                > 123 <


Atomic  tests  are useful as a destructive tool, and for testing the
effects of nuclear winter.

FIRE
~~~~
Fire occurs when the oxygen content  of  your atmosphere is too high.
To protect against fires, keep your oxygen levels down.

Fires  are  useful for regulating the oxygen in your atmosphere, and
causing general destruction.


EARTHQUAKE
~~~~~~~~~~
A major shake-up of an  area  of  the  planet.  When you point
to the Trigger Earthquake option  a  sub-submenu  will  appear,
allowing  you to select the direction  of  energy expended by
the earthquake.  This will let you affect  continental drift.
Earthquakes under water will cause tidal waves.

When  earthquakes  appear naturally in SimEarth, they occur at plate
boundaries  (places  where  two  land masses meet).  To avoid damage
from earthquakes, don't place cities near plate boundaries.  To find
these  boundaries,  look  at  the  MAGMA display in the EDIT WINDOW.
Wherever  arrows that point in different directions are next to each
other is a plate boundary.

In  SimEarth,  earthquakes are very useful events.  You can use them
to  affect  the  movement of land masses, and change the magma flow.
Forcing two land masses into movement toward each other is a fun way
to create a mountain range.

To  easily see the effect your earthquake has on the planet, turn on
the  MAGMA layer in the EDIT WINDOW before you trigger it, and watch
the direction of the magma flow arrows change.

This  is actuallythe opposite of what happens in the real world.  We
have  reversed cause and effect.  In reality, earthquakes are caused
bythe  movement  of  the plate boundaries, and don't cause or change
magma  flow.   It's  not  accurate,  but its a great tool for making
mountain ranges.

                > 124 <


PLAGUES
~~~~~~~
Plagues are very dangerous diseases  that can wipe out entire cities,
and will spread to nearby cities.   They  happen  more often in
low-technology areas, but once they happen there, they can spread
to nearby high-technology areas.

To  prevent plagues, you must invest in Medicine in the CIVILISATION
MODEL   CONTROL   PANEL  Plagues  aren't  useful  for  anything  but
destruction.


WAR
~~~
Wars can be triggered by the TRIGGER  EVENTS  icon.
War  in SimEarth represents battles between
cities, as well as rebellions and revolutions within cities.

Wars  are  often  caused by competition for resources such as fossil
and  atomic  fuel.   This is a self-regulating process:  Cities grow
too  big, too close, and too fast for the local fuel supply; they go
to war over the fuel; they kill enough of each other off so they can
all  live  happily  on  the  existing fuel; then they declare peace.
Sometimes  wars  just  happen--SimEarthlings  can  be  as  stupid as
Earthlings.

World wars occur in higher technology levels, and consist of lots of
battles going on all over the planet.

The  only  way to prevent wars, or reduce the number and severity of
wars,  is  by  allocating  energy  to Philosophy in the CIVILISATION
MODEL CONTROL PANEL.


POLLUTION
~~~~~~~~~
Pollution events are warnings  that  the  pollution in an area
of your planet has reached levels that are dangerous to life.

They  are  primarily  caused by industrial waste and pollutants, and
can  only  be prevented and controlled by investing in non-polluting
energy sources.

                > 125 <



Pollution events cannot be triggered by the TRIGGER EVENTS tool, but
if you want one, invest heavily in fossil fuels.

EXODUS
~~~~~~
When the sentient SimEarthlings  reach  a high enough level of
development, they leave the  planet  to Colonise other worlds.
The planet is then "retired" to the status of a wildlife preserve
to be visited and cherished.

At  this  point, the planet returns to the Evolution Time Scale, and
the race to sentience begins again.

The  EXODUS  event  is  the  closest  thing  in  SimEarth  to a "win
condition."

                > 126 <

GEOSPHERE
~~~~~~~~~
The  Geosphere  in  SimEarth  simulates  planet formation, planetary
cooling, 6EOSPHERE continental drift, volcanic activity and erosion.
For an explanation of geology and atmosphere of the real Earth, take
a look at the Introduction to Earth Science section.

PLANET FORMATION
~~~~~~~~~~~~~~~~
SimEarth  simulates  a  planet  just  after  interstellar  dust  has
condensed  into a lump of dirt.  It is tightly packed, with a molten
core.   The  surface  is  solid,  but the ' J surface temperature is
still very hot.  The atmosphere is mostly steam.

The  flowing  currents  in  the molten core cause parts of the solid
surface  of  the  planet  to start moving around, crashing into each
other.   This crashing results in the creation of huge mountains and
deep ditches.

PLANETARY COOLING
~~~~~~~~~~~~~~~~~
With   time,  the  core  of  the  planet  solidifies  to  a  plastic
consistency,  and  gets  larger  as the planet gets olde The rate at
which the core forms can be set in GEOSPHERE MODEL CONTROL PANEL.

The  larger  the core, the smaller the magma layer.  The smaller the
magma  layer,  the  slower  the  magma  currents, and the slower the
continental drift.

CONTINENTAL DRIFT
~~~~~~~~~~~~~~~~~
Continental  drift  is the movement of the solid crust of the planet
on  the liquid magma inside the planet.  The faster and stronger the
magma  currents,  the  faster  the drift.  Continental drift is also
affected  by core heat.  The rate of continental drift can be set in
the GEOSPHERE MODEL CONTROL PANEL.

CORE HEAT
~~~~~~~~~
Core  heat  is the temperature of the planet's core.  The higher the
core  heat,  the larger and more severe the volcanos are.  Also, the
hotter  the core, the  more the direction of magma flow will change.
Core heat can be adjusted in the GEOSPHERE MODEL CONTROL PANEL.

                > 127 <

FORMATION OF THE OCEANS
~~~~~~~~~~~~~~~~~~~~~~~
The  planet  eventually cools enough for the steam in the atmosphere
to condense and form oceans.  Once oceans are formed, your planet is
ready for life.

VOLCANIC ACTIVITY
~~~~~~~~~~~~~~~~~
Volcanos  are vents in the surface of the planet that allow magma to
flow  to  the  surface.  The volcanos in SimEarth are huge explosive
events that make recent volcanic activities like i~rakatoa look like
pimples.   When  volcanos occur in water, they create islands.  When
they occur on land, they create great mountains .  The frequency and
violence of volcanos is directly affected by core heat.

You can also control the frequency and violence of volcanos with the
GEOSPHERE MODEL CONTROL PANEL.

EROSION
~~~~~~~~
Erosion is the "smoothing" of the terrain bywind and water.  Younger
planets  will  have higher, more jagged mountains than older planets
that  have  suffered  the  effects  of erosion longer.  Erosion aiso
creates  large  continentai shelves.  The rate of erosion can be set
in the CEOSPHERE MODEL CONTROL PANEL.

Erosion increases the CO2 level in the atmosphere.

                > 128 <


The  atmosphere  in  SimEarth  consists of four gases--Nitrogen (N2,
Oxygen  (O2)'  Carbon  Dioxide  (CO2)  and Methane (CH4) plus water
vapor (H2O) and dust particles.

NITROGEN
~~~~~~~~
Nitrogen  is released by the soil through geochemical reactions with
the  air,  and  is  absorbed  into the soil by microbes.  It is also
released into the atmosphere by volcanos.  It is the most common gas
in the atmosphere.

OXYGEN
~~~~~~~
Oxygen is released into the atmosphere by plants and microbes during
photosynthesis.   It  is  consumed by animals and fires.  Too little
oxygen  in the atmosphere (<15%) and animal life can't survive.  Too
much  oxygen  (>251Yo) and fires will break out all over the planet.
Fires act as an oxygen regulator.

CARBON DIOXIDE
~~~~~~~~~~~~~~
Carbon  dioxide  is  released  into  the  atmosphere  by geochemical
reactions  and erosion, and is absorbed by plants and microbes.  Too
little  carbon  dioxide  (<.1%)  and  plants  can~t survive.  Carbon
dioxide  is  a greenhouse gas, and will contribute to global warming
due to the greenhouse effect.  If your CO2 level exceeds 1% you will
have greenhouse warming.

METHANE
~~~~~~~
Methane  is  released into the atmosphere by bacteria (prokaryotes).
It  is  a  greenhouse  gas,  and  will  contribute to global warming
through the greenhouse effect.

WATER VAPOR
~~~~~~~~~~~
Water  vapor  evaporates  from warm oceans and lakes, and returns to
the  land  and seas through rainfall.  Water vapor in the atmosphere
is  increased  by  hurricanes and meteors hitting the oceans.  Water
vapor is a greenhouse gas.

DUST PARTICLES
~~~~~~~~~~~~~~~
Dust  is  released into the air by volcanic activity, fires, nuclear
explosions,  and  meteor  strikes.   Too much dust in the atmosphere
causes solar blockage, planetary cooling, and mass extinctions.

                > 129 <

ATMOSPHERIC PRESSURE
~~~~~~~~~~~~~~~~~~~~
Atmospheric pressure is a measure of how much atmosphere, by weight,
is  around  the  planet.   The air pressure of the real Earth is 1.0
atmospheres.   A  higher  atmospheric  pressure  allows  a planet to
better retain heat.

TRACKING THE ATMOSPHERE
~~~~~~~~~~~~~~~~~~~~~~~~
You  can  keep track of your atmospheric composition by watching the
ATMOSPHERIC COMPOSITION GRAPH.

                > 130 <

CLIMATE
~~~~~~~
The  climate  of  SimEarth  is  much simpler than on the real Earth.
When modelling

climate,  SimEarth  primarily  takes  into account air currents, air
temperature, and rainfall.

Air  currents,  air  temperature, and rainfall are influenced by sea
temperature,  ocean  currents,  solar  input, cloud formation, cloud
albedo, surface albedo, greenhouse effect, air-sea thermal transfer,
and atmospheric pressure.

In  addition,  ice  caps  indirectly  affect  climate  through their
ability  to cool the planet.  Cold oceans are necessary for ice caps
to form.

In  SimEarth,  as on the real Earth, the heat from the Sun is slowly
increasing.

AIR CURRENTS
~~~~~~~~~~~~
The planetary winds.

AIR TEMPERATURE
~~~~~~~~~~~~~~~
The  average  annual air temperature.  The heat displayed here comes
primarily from the sun, and secondarily from warm ocean areas.

RAINFALL
~~~~~~~
The  amount  of  rainfall  on  the planet.  It includes all types of
precipitation.

SEA TEMPERATURE
~~~~~~~~~~~~~~~
The  average  annual  ocean  temperature.   In  most cases this will
correspond closely with the air temperature, but it will change much
more slowly.

OCEAN CURRENTS
~~~~~~~~~~~~~~
The surface currents of the oceans.

SOLAR INPUT
~~~~~~~~~~~
The  incoming  solar  radiation, also calledlnsolation.  This is the
amount of energy that reaches the planet from the sun.

CLOUD FORMATION
~~~~~~~~~~~~~~~
The amount of clouds formed from a given amount of evaporation.

CLOUD ALBEDO
~~~~~~~~~~~
The  reflectivity  of  the  clouds,  which  controls  the  amount of
sunlight (heat) that passes through them to the planet.

                > 131 <

SURFACE ALBEDO
~~~~~~~~~~~~~~
The  reflectivity  of  surface  biomes,  and therefore the amount of
sunlight (heat) which is blocked by them.

GREENHOUSE EFFECT
~~~~~~~~~~~~~~~~~
The  planet-warming  greenhouse  effect.   The  greenhouse effect is
caused  by  certain  gases  that  block outgoing infrared radiation.
This keeps more of the Sun's heat in the atmosphere, which warms the
whole  planet.   In  SimEarth,  the greenhouse gases are water vapour
(HO2), methane (CH4), and carbon dioxide (CO2)

AIR-SEA THERMAL TRANSFER
~~~~~~~~~~~~~~~~~~~~~~~~
The rate at which the air and ocean can exchange heat.

ATMOSPHERIC PRESSURE
~~~~~~~~~~~~~~~~~~~~
A measure of how much atmosphere, by weight, is around the planet.
The  air  pressure  of  the real Earth is 1.0 atmospheres.  A higher
atmospheric pressure allows a planet to better retain heat.

AFFECTING CLIMATE
~~~~~~~~~~~~~~~~~
You  can  affect  the  way  SimEarth  models climate by changing the
settings on the ATMOSPHERE MODEL CONTROL PANEL.

                > 132 <

LIFE AND EVOLUTION
~~~~~~~~~~~~~~~~~~
As  far  as the model in SimEarth is concerned, life is any plant or
animal on your planet.

The  number  and  variety  of  plants,  animals,  niches  and biomes
included  in SimEarth has been limited to enable the model to run on
a home computer, but there are enough to demonstrate the principles
involved with planet management.

ORIGINS OF LIFE IN SIMEARTH
~~~~~~~~~~~~~~~~~~~~~~~~~~~
In  SimEarth,  the  only  necessary  factor  for life to form is the
presence  of  some deep sea (greater than 2500 meters deep) or ocean
(between  1000 and 2500 meters deep).  We assume the presence of ail
necessary chemicals and elements.

Ocean  will  form  as soon as the planet cools, and if there is some
deep ocean, life will form.

The  formation  of  life on the real Earth is much more complicated,
and still very controversial.

LIFE IN SIMEARTH
~~~~~~~~~~~~~~~~
Life in SimEarth is much simpler and less varied than on the real
Earth. SimEarth has 15 classes of life, each with 16 species.  The
real Earth has millions of species.

SimEarth has seven biomes, the real Earth has many more.

EVOLUTION IN SIMEARTH
~~~~~~~~~~~~~~~~~~~~~
Evolution  in  SimEarth  depends  on  many factors.  For sea life to
evolve, there must be shallow shelves.  For land life, there must be
the  proper  atmosphere, with enough carbon dioxide, oxygen, and air
pressure.   The  air  and  water temperatures must be within livable
limits.   And  there must be enough of the proper biome for the life
to evolve in.

Life  advances from simple to more complex forms, and, hopefully, to
intelligence.

Evolutionary  advancement also depends on population size.  The more
of  a  life-form  you  have on your planet, the more likely it is to
advance to another level.

                > 133 <



There  are  two  sizes  of  steps  SimEarthlings  can  take in their
progress towards sentience:  ADVANCEMENT and MUTATION.

ADVANCEMENT  is  a  small  step.   It is a step up to a more complex
species,  but  stays within the same class of life.  The ADVANCEMENT
RATE can be set in the BIOSPHERE MODEL CONTROL PANEL.

MUTATION RATE is a big step. It is a jump to a new class of life.

COMPETITION
~~~~~~~~~~~
There  is  competition within the evolutionary process.
If  two life-forms land on the same spot, the more advanced one will
kill  the  other.   The  rating of which life- form is more advanced
than  another  involves, among other smaller factors, the class, the
species, and the IQ of each life-form.  Some of these factors change
over  time  and  vary  with  the planet, so there can be no win/lose
chart of life-form rankings.

Also,  if and when a new, higher class of life mutates, it will take
precedence over all lower forms.

BIOMES IN SIMEARTH
~~~~~~~~~~~~~~~~~~
There  are  seven  available  biomes  in  SimEarth, plus ROCK, which
represents  a lack of a biome in a location.  To survive and spread,
biomes require carbon dioxide and rainfall.


ROCK--        No biome.

ARCTlC--    Can survive in a cold and dry climate.

BOREAL FOREST--    Can survive in cold temperatures, with moderate to
                   high rainfall.

DESERT--    Can survive in moderate to hot temperatures,
        with very little rainfall.

                > 134 <


TEMPERATE GRASSLANDS--Can survive in areas with moderate temperatures
                     and rainfall.

FOREST--Can survive with moderate temperatures and high rainfall.

JUNGLE--Can survive with high temperatures and rainfall.

SWAMP --Can survive with high temperatures and moderate rainfall.

BIOME PREFERENCE CHART
~~~~~~~~~~~~~~~~~~~~~~~
            DRY        MODERATE         WET
            ----------- -----------      ----------------
COLD (<0C)             Arctic         Boreal Forest    Boreal Forest
MODERATE (0-25C)       Desert       Temp. Grasslands Forest
HOT (>25C)           Desert        Swamp            Jungle


Biome  preferences are also influenced by altitude and the amount of
CO2 in the atmosphere.

LIFEFORMS IN SIMEARTH
~~~~~~~~~~~~~~~~~~~~~
There are 15 classes of life represented in SimEarth; eight on land,
seven  in the sea.  Only 14 of these are available in the PLACE LIFE
tool.  The 15th, the Carniferns--mobile, carnivorous plants that can
evolve sapience--will sometimes appear through evolution.

Each class consists of 16 species.  There are a total of 240 species
in  SimEarth.   If  a  class  of  life  reaches the 16th species, it
becomes  sentient.   You  will never see the 16th species of many of
the classes unless you can help that class develop intelligence.

                > 135 <


Below is an explanation of each class of life, with a graphic of all
16  species  for  that  class  of  life.   The possible evolutionary
advancements  and mutations are also shown.  Advancement is in steps
from  left to right through ail the species of that class.  Mutation
is a jump to a new class.

For each class of life below is a chart of its possible evolutionary
paths.   The  progression of advancement within the same class, from
simplest to most advanced (intelligent) is shown from left to right.
Possible mutations to higher classes of life are shown as steps up.

Only  certain  species within a class of life can mutate.  There are
many evolutionary dead-ends.

SEA LIFE CLASSES
~~~~~~~~~~~~~~~~

PROKARYOTE
----------
Simple single celled life that has no distinct nucleus, including bacteria
and blue-green algae. Prokaryotes  release  methane  into  the
atmosphere.  In SimEarth, Prokaryotes  are all treated as anaerobic,
methane consuming organisms, which is an extreme simplification.

The  eight  most  advanced Prokaryote species can possibly mutate to
Eukaryotes.

Eukaryote
---------
Single-celled life with a nucleus; includes all single-celled life
except  prokaryotes. In SimEarth, all Eukaryotes  are  treated
as aerobic, photosynthesizing organisms, which is an extreme
simplification.

Eukaryotes  evolve  from Prokaryotes.  The four most evolved species
of Eukaryote can mutate into Radiates.

                > 136 <


RADIATE
~~~~~~~
Simple, radially symmetrical multicellular life  with  definite  tissue
layers (three at most), but no distinct internal   organs,   head,  or
central  nervous  system. Includes jellyfish and sea anemones.

Radiates evolve from Eukaryotes.  The first eight species of Radiate
can  mutate  into Arthropods.  The next four species can mutate into
Trichordates.

ARTHROPOD
~~~~~~~~~~
Animals with jointed legs and a hard outer  skeleton,  including
crabs,  lobsters,  and  crayfish.  (Spiders,  scorpions, centipedes,
millipedes, and insects are - also arthropods, but they live on land.)

Arthropods evolve  from Radiates.  The first four species of
Arthropod  can  mutate into Mollusks, the next eight can mutate into
Insects.

MOLLUSK
~~~~~~~
Fairly  complex  animals, most of which possess shells,
including  snails,  clams, oysters, scallops, octopi, and squid.

Mollusks  evolve  from ArthroDods.  The middle eight species of Mollusks
can mutate into Fish.

                > 137 <


FISH
~~~~
Very  advanced  and complex sea life with an internal bony
skeleton.

Fish evolve from Mollusks.  The first eight species of Fish
can  mutate  into  Amphibians, the next four species can mutate into
Trichordates.


CEIACEAN
~~~~~~~~
Marine mammals with a highly developed nervous   system,
including whales, dolphins, and porpoises.
Cetaceans  can  survive  in Jungle biomes, as shown in the chart of
Life Classes and Preferred Biomes. They actually live in the
Jungle's rivers and tributaries that are too small to show in the.

Cetaceans  evolve  from  Mammals.  The last four species of Cetacean
can mutate back into Mammals.


LAND LIFE CLASSES
~~~~~~~~~~~~~~~~~

TRICHORDATE
~~~~~~~~~~~
Trichordates were a class of animal with three-chord
spines.   They  lived  and died out long ago on real Earth.  We felt
sorry  for  them,  and are giving them a chance for survival in
SimEarth.

Trichordates  evolve  from Radiates and/or Fish.  They cannot mutate
into anything else.

                > 138 <


INSECT
~~~~~~
The most numerous type of life on Earth they have six legs and three
body sections.

Insects  evolve from Arthropods.  Insects don't evolve
into  anything  else,  but,  as  shown  in  the chart, there is a
co-evolution  situation with Carniferns.  The Carniferns don't actually
evolve  from  Insects: they  evolve  from  plants  because  of the
presence of Insects.


AMPHIBIAN
~~~~~~~~~
Cold-blooded vertebrates somewhere between fish and reptiles,
including frogs, toads, and newts.

Amphibians evolve from Fish.  The first eight species
of Amphibians can mutate into Reptiles.


REPTILE
~~~~~~~
Cold-blooded vertebrates, including
alligators, crocodiles, lizards, snakes, and turtles.

Reptiles evolve from Amphibians. The first eight
species of Reptile can mutate into Dinosaurs.  The next four species
can mutate into Mammals.

                > 139 <


DINOSAUR
~~~~~~~~
Very big reptiles that long ago died out on real Earth.
SimEarth gives them a new lease on life.

Dinosaurs evolve from Reptiles. The first four
species of Dinosaurs can mutate into Avians. The next four species
can mutate into Mammals.

AVIAN
~~~~~
(A fancy word for bird.) Warm-blooded
vertebrates with bodies more or less completely covered by feathers,
with wings for forelimbs.

Avians evolve from Dinosaurs. Avians cannot mutate into anything else.


MAMMAL
~~~~~~~
The highest form of vertebrate, including man,  apes,  rodents,  dogs,
cats, etc.  Mammals nourish their young with  milk  secreted from
mammary glands, and have skin more or less covered with hair.

Mammals  evolve  from  Cetaceans,  Reptiles,  and/or Dinosaurs.  The
middle eight species of Mammals can evolve into Cetaceans.

                > 140 <


CARNIFERNS
~~~~~~~~~~
Carniferns  will  evolve, but are not available to manually
place with the PLACE LIFE tool.  They are mobile, carnivorous plants
that  for  simulation  purposes  are treated like animals.  They are
just  above  insects  in  evolutionary  complexity, and evolved from
plants  taking  advantage  of  insects  as  a food source.  They can
achieve intelligence, but it is rare.

Carniferns  co-evolve  with  Insects.   They  actually  evolve  from
plants, but their existence depends of the existence of Insects.


CHARTS OF LIFE CLASSES AND PREFFERRED BIOMES
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1 = X   Life class cannot exist here.
2 = 8-( Can exist here, but barely.
3 = 8-| Can exist here fairly well.
4 = 8-( Paradise.

                > 141 <


CIVILISATIONS IN SIM EARTH
~~~~~~~~~~~~~~~~~~~~~~~~~~~
There are seven levels of civilization represented in SimEarth, from
the Stone Age of our past to the Nanotech Age of our future.  For an
in-depth  look  at  these civilisations as they appeared on the real
Earth, see the Introduction to Earth Science section of this manual.

Civilisations  are represented by cities and travelling populations.
Each  city  has three different population densities; the darker the
city  icon,  the  higher  the  population.   Travelling  populations
represent  expansion,  communication  and  trade, and travel between
cities.

The  Nanotech  age  has  four  levels  of density, and no travelling
population.  We assume they use transporters for trade and travel.

The   advance   of  technology  is  a  double-edged  sword.   Higher
technology  allows  more  efficient  use  of energy, shorter working
weeks,  and  a  higher  quality  of life.  It also allows pollution,
competition  for  fuel  sources,  wars, world wars, atomic wars, and
other by-products of advanced civilisation.

Below  is  a  description  of the civilisations in SimEarth with the
graphics  for  the  three  (or  four)  levels  of  density  and  the
travelling  populations Qf any), as they are displayed over land and
over water.

STONE AGE
~~~~~~~~~
The Stone Age in SimEarth relates to civilisations
on  the  real Earth thought to begin as far back as a million
years ago, and lasting, in some places on the Earth, until
today. It is characterised by the use of stone tools.

BRONZE AGE
~~~~~~~~~~
The Bronze Age began with the regular  use of metals for tools and
weapons. The earliest established Bronze Age dates back to 3500 B.C.
in the Middle East.

IRON AGE
~~~~~~~~
The Iron Age began nearly 2000 years ago, and still exists in places
today.  It is characterised by the use of iron for tools and weapons.

                > 142 <


INDUSTRIAL AGE
~~~~~~~~~~~~~
The Industrial Age in SimEarth relates  to  the  time from the
Industrial Revolution of the mid- 18th century to the beginning of
the Atomic Age.  It is characterized by the use advanced tools and
powered machinery.

ATOMIC AGE
~~~~~~~~~~
The Atomic Age begins with the use of atomic energy. It is the present
highest technology level on the real Earth.

INFORMATION AGE
~~~~~~~~~~~~~~~
The Information Age in SimEarth is the next technological step
after the Atomic Age. In this age, information is the most
important tool.

NANOTECH AGE
~~~~~~~~~~~~
The ultimate level of technology in SimEarth is reached in the Nanotech
Age.  This is far enough in the future that we can only guess and
dream about it.  It will be characterised by a level of sophistication
and technology that allows terraforming and colonising other planets.

The  Nanotech  Age  has  four  levels  of density, and no travelling
population.  We assume they use transporters for trade and travel.

ALTERNATE INTELLIGENT SPECIES
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
SimEarth  doesn't  limit  intelligent species to humans or even just
mammals.  Any class of life other than Prokaryote and Eukaryote--can
become intelligent.

Development of civilisation in SimEarth requires land because of the
need  of fire, tools, and forges.  Water creatures can be civilised,
but need access to land for toolmaking.

In  SimEarth, the most likely classes of life to evolve intelligence
are:  reptiles, dinosaurs, birds, and mammals.

The next most likely group are:  cetaceans, insects, amphibians, and
carniferns.

The  least  likely  to evolve intelligence are:  radiates, mollusks,
arthropods and fish.

                > 143 <


Aside  from  the  above  ranking,  the  evolution of intelligence is
influenced  by  the  amount of the proper biome for a species on the
planet.  Also, if an evolutionarily higher form of life appears, it
will have an advantage over an advanced lower form of life.

All intelligent, sentient SimEarthlings act very much like humans in
development of civilization, cUies, industry, etc.

THE MONOLITH
~~~~~~~~~~~~
The  Monolith  is  a  tool  to  help  accelerate  the advancement of
intelligent species.  It is an Evolution Speed-up Device (our thanks
to Arthur C.  Clark).  Once you select the Monolith, if you click on
a  life-form,  there  is  a  one-in-three  chance  of that life-form
suddenly  mutating to a higher level, which immediately moves you to
the  next  Time  Scale.  The Monolith won't work on all the animals.
If you try to use the Monolith on the wrong animal, the program will
beep at you, but there will be no energy charge.  It costs 2500 E.U.
to use a Monolith--whether or not it works.

A  disadvantage  to  using the Monolith is that you could jump ahead
into  the  civilisation  Time  Scale before enough fossil fuels have
been  generated,  and  civilisation  will collapse.  You need a wide
population base to advance to the next technology level.  Don't rush
to a new Time Scale at the expense of your population.

INFLUENCING CIVILISATION
~~~~~~~~~~~~~~~~~~~~~~~~
The  main  way  you influence your sentient life-forms is by telling
them  what  energy  sources  to  invest  in, and how to allocate the
energy.  This is done through the CIVILISATION MODEL CONTROL PANEL.

                > 144 <


ENERGY
~~~~~~
In  SimEarth  there are two uses of energy.  You, the player, use it
to  make,  mold,  modify  and  manipulate  the planet, and civilised
SimEarthlings make and use it to carry on their daily lives.

The  energy  in  SimEarth  is measured in Energy Units, or E.U.

Intelligent  SimEarthlings  will  produce  and  use energy.  You can
control  their  choice of energy sources and their use of the energy
they  produce,  but you don't have direct access to their energy for
your purposes.

Depending  on  the  difficulty  level  of  the  game,  you will have
different amounts of energy to affect the planet and the simulation.
These  amounts are both your starting supply and the maximum you can
accumulate at any one time.

If you are in experimental mode, you will have an unlimited support of
energy.

EXPERIMENTAL MODE        Unlimited Energy
EASY GAME            5000 E.U.
MEDIUM GAME            2000 E.U.
HARD GAME            2000 E.U.

Energy  for a game comes from the stores of the planet itself in the
form of geothermal, wind, and solar energy, as well as fossil fuels.
As  you  deplete  your energy supplies during a game, it will slowly
build  back up over time as the planet increases its energy from the
above  sources.   This  continual  tapping  of the planet's energies
happens automatically.

The amount of energy you have to use is displayed in the EDIT WINDOW
in the AVAILABLE ENERGY DISPLAY.

Your  energy  reserves  are  depleted  by every action you take that
affects  the  planet or simulation.  New energy becomes available on
the  planet  through time from various sources explained below.  You
can  tap some of this new energy.  It will automatically be added to
your available energy each Time/Simulation cycle.

As  technology develops, your sentient SimEarthlings generate energy
for  their  own  use.   As  technology  on the planet advances, they
generate more energy more efficiently.

                > 145 <


You  don't have direct access to the SimEarthlings' energy, but some
of  it will be automatically tapped and added to your reserves.  The
amount   of   energy  automatically  added  to  your  reserves  each
Time/Simulation   cycle  increases  with  the  increasing  level  of
technology  on  your planet.  The rate at which your energy reserves
increase is as follows:

GEOLOGIC TIME SCALE                1EU per cycle
EVOLUTION TIME SCALE                1EU per cycle
CIVILISATION TIME SCALE  Stone Age        2EU per cycle
                         Bronze Age        3EU per cycle
                        Iron Age        4EU per cycle
TECHNOLOGY TIME SCALE    Industrial Age        5EU per cycle
                        Atomic Age        6EU per cycle
                        Information Age    7EU per cycle
                        Nanotech Age        8EU per cycle.

SOURCES OF ENERGY
~~~~~~~~~~~~~~~~~
There are five sources of energy in SimEarth.

BIOENlERGY
---------
Burning  wood,  animal power, plant power (farming),
and  work done by hand by the sentient species.  Bioenergy gets more
efficient  through  time  because  of better, more efficient farming
tools,  and scientific breakthroughs such as recycling biowaste into
fuel.  Using bioenergy releases CO2 into the atmosphere, so it has a
minor polluting effect.


SOLAR/WIND
----------
 Sun-drying  of  food and clothes, windmills, sailing
ships, solar heating, wind-powered generators, solar electric cells,
and  satellites  collecting solar energy.  Improves in efficiency as
technology advances.


HYDRO/GEO
---------
Waterwheels, dams, steam power, hydroelectric power, and
geothermal power.  Improves in efficiency as technology advances.

FOSSIL FUEL
-----------
Coal  made from long-dead animals.  A by-product of
burning  fossil  fuels  is  the release of greenhouse gases into the
atmosphere.

NUCLEAR
-------
Atomic reactors, bombs, etc.  Atomic explosions release
dust and radiation into the atmosphere.

                > 146 <

ENERGY COSTS
~~~~~~~~~~~~
There  is  no  free  lunch  in  SimEarth,  and the price you pay for
everything is energy.  Here is the price list.

                    Energy Units
                    ~~~~~~~~~~~~
PLACE PROKARYOTE            35
PLACE EUKARYOTE                70
PLACE RADIATE                105
PLACE ARTHROPOD                140
PLACE MOLLUSK                175
PLACE FISH                210
PLACE CETACEAN                245
PLACE TRICHORDATE            280
PLACE INSECT                315
PLACE AMPHIBIAN                350
PLACE REPTILE                385
PLACE DINOSAUR                420
PLACE AVIAN                455
PLACE MAMMAL                490
PLACE STONE AGE                500
PLACE BRONZE AGE            1000
PLACE IRON AGE                1500
PLACE INDUSTRIAL AGE            2000
PLACE ATOMIC AGE            2500
PLACE INFORMATION AGE            3000
PLACE NANOTECH AGE            3500
PLACE BIOME FACTORY            500
PLACE OXYGENATOR            500
PLACE NO2 GENERATOR            500
PLACE VAPORATOR                500
PLACE CO2 GENERATOR            500
PLACE MONOLITH                2500
PLACE ICE METEOR            500
TRIGGER ANY EVENT            50
PLANT ANY BIOME                50
SET ALTITUDE                50
MOVE ANYTHING                30
EXAMINE ANYTHING            5
CHANGE CONTROL PANEL            30 per click
                    150 per drag.

                > 147 <


===========================================================================
===========================================================================


            AN INTRODUCTION TO EARTH SCIENCE
            ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

SimEarth  is  a computer simulation of the Earth as a living system,
developed in the spirit of James Lovelock's Caia hypothesis.  To get
the  most  out  of SimEarth, a little background in earth science is
necessary.

This  section  of  the  manual  is  a  primer to give you a start in
understanding  how  our planet works.  You will become familiar with
many cause and effect relationships that are key to the dynamic play
you will experience in SimEarth.

                > 150 <


In  the  last  30 years, more than 200 men and women from 18 nations
have  travelled  in space and looked back at earth.  These astronauts
took beautiful pictures that provide a new look at our planet.

The view of Earth from space is having a deep impact on our culture:
it is changing the way we look at our world and our place in it.  It
is  a  surprising  view for those who came from a Western scientific
background  in  which  the  study  of  the Earth was divided up into
separate segments, and the Earth was viewed as a "dead" planet.

Earth  science  is  a  relatively  recent approach to looking at our
planet.    It   encompasses   all  the  other  sciences  focused  on
understanding  the  Earth.  It involves physics, chemistry, biology,
astronomy, psychology, sociology and other areas of research.  James
Lovelock's  Gaia  hypothesis provides a framework for us to view the
planet as a living system.

            ----------------------

EARTH AND THE OTHER PLANETS
~~~~~~~~~~~~~~~~~~~~~~~~~~~

Earth is different from every other planet in our solar system.


Earth is the biggest of the four inner planets.  It is the
only  planet  with an atmosphere suitable for oxygen-breathing life.
The Earth also has the biggest moon in proportion to its size in the
Solar System:  so big that some think we are a two-planet system.

No  other  planet  (that  we know of) has plate tectonics, a dynamic
atmosphere  and  a  hydrosphere.  No other planet has an atmospheric
composition  like  ours,  nor  the  systems  of  life we have in our
biosphere.   This  is  not to say that other planets have no life in
the broadest sense of the word, but not as we know it on Earth.

Earth scientists divide the earth into four interrelated components:

the LithoSphere-The solid, rocky part of the Earth:  continents and
                ocean  floor;
the Hydrosphere-the liquid part of the Earth:  oceans, lakes and
        rivers;
the AtmoSphere -the gaseous part of the Earth: air and clouds; and
the Biosphere  -the living part of the Earth: humans, plants and animals.

Mercury is the closest planet to the Sun and so small that the light
gases such as Oxygen (O2) and carbon dioxide(CO2) evaporated during the
planet's formation.

                > 151 <


ABOUT THIS INTRODUCTION TO EARTH SCIENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Venus  has so much carbon dioxide (CO2) that its surface temperature
is  more  than 700C--what is usually known as a runaway greenhouse
effect.  Venus probably had some plate tectonics in the past, but no
longer.

Mars  definitely had plate tectonics, volcanos, and mountains in the
past,  but  being smaller than the Earth, it cooled more rapidly and
is  now  geologically  dead.   The  Martian atmosphere is so thin it
would be impossible for humans to survive in it.

The  rest  of  the  Solar  System,  which includes Jupiter, Neptune,
Saturn, Uranus and Pluto, are either so large or so far away from the
Sun  that  they  are  too  cold  for life.  They are mostly gaseous,
unlike the rocky, solid inner planets.

This Introduction to Earth Science is presented in five sections:


          Geology (Lithosphere)
          Climate (Atmosphere and Hydrosphere)
          Life (Biosphere)
          Humans and Civilisations (Biosphere)
          Theories of the Earth


                > 152 <


GEOLOGY
~~~~~~~
This  section deals with the Lithosphere--the solid rocky part of the
Earth.  It covers the following subjects:

* the Origin of the Earth;
* the Evolution of the  Earth;
* the Composition and Structure of the Earth;
* Special  Characteristics  of the Earth; and
* the Divisions of the Earth.

            ----------------------

THE ORIGIN OF THE EARTH.
~~~~~~~~~~~~~~~~~~~~~~~~
How  did our solar system come into existence?  Scientists currently
lean towards the solar nebula hypothesis.

This hypothesis states the following series of events:

A primordial cloud of gas and dust, called a nebula, once rotated in
space.   The  gravitational  attraction  of  the material inside the
nebula  caused  contraction of the primordial cloud, speeding up its
rotation.   The  shape  changed  to  that  of  a flattened disk as a
consequence of the increased rotation.  Matter then migrated towards
the centre, and formed what is called a proto Sun.  The formation of
the  proto-Sun  and  the  possible  explosion  of a nearby supernova
caused the collapse of the nebula and triggered the formation of the
solar  system.   The  collapse  increased  the  temperature  of  the
proto-Sun  due  to  a thermonuclear chain reaction (high-temperature
fusion  of  hydrogen  atoms  to  form  helium atoms).  The proto-Sun
started  to  shine.   Matter  began  to  form out of the material in
space.   The  hot  proto-Sun  and  the surrounding gas and dust that
still  remained  after  the  collapse  began  cooling down.  Gaseous
material  started  to  condense.   Small  chunks  of  matter  called
planetesimals clumped together.  The biggest ones pulled most of the
matter   due  to  their  higher  gravitational  attraction.   If the
planetesimals  were  too  close  to  the  Sun the lightest materials
(hydrogen,  helium,  etc.)  were  blown away by the Sun's wind.  The
planetesimals  closest  to the Sun were also composed of the densest
materials (the ones with the highest melting points), like

                > 153 <


iron.   A  good  example  is  Mercury, with a density more than five
times  the  density of water.  As the planetesimals got farther away
from  the  Sun  and  therefore  colder,  lighter  materials, such as
silicon  and oxygen, condensed and formed the rocky silicate planets
(Venus,  Mars, Earth).  The biggest and farthest-away planetesimals,
which  eventually  became the giant planets Jupiter and Saturn, were
able  to  retain  the very light compounds such as hydrogen, methane
and ammonia.

This hypothesis, although not completely tested, explains the basics
of  planetary  formation  and  gives  us  the  background to develop
hypotheses  for  the  evolution  of  the  Earth  from  a  condensed,
homogeneous planetesimal to the differentiated, layered medium it is
now.

            ----------------------

THE EVOLUTION OF THE EARTH
~~~~~~~~~~~~~~~~~~~~~~~~~~

THE First BILLION YEARS
------------------------
Age-dating  of meteorites and the oldest rocks on the planet tell us
that  the  oldest  solid  rocks  on the Earth are about four billion
years old, and that the Earth is about 4.7 billion years old.

Five  billion  years  ago,  what was later to become the Earth was a
homogeneous   conglomeration   of   silicon  compounds,  some  iron,
magnesium,  and  oxygen  compounds, and smaller amounts of the other
elements.

The pre-Earth was not as large as the planet we know today.  It grew
to  its  present size by the gradual addition of other planetesimals
and meteorite bombardment.

The  continuous  bombardment  not  only  increased  the  size of the
planet,  but  it  also heated it up.  The rise in temperature due to
impacts  and  gravitational compression, linked with the radioactive
decay  of  heavy  elements  (which  also produces heat), most likely
partially  melted  the primordial Earth.  The partially molten Earth
was  then  affected bywhat is known as the iron catastrophe, which then
led to the formation of the core.

FORMATION OF THE EARTH'S CORE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Within  the partially molten primordial Earth, iron droplets, denser
than  the  surrounding liquid, started falling towards the centre of
the  planet  forming a liquid iron core.  Other dense elements (such
as nickel and gold) followed.  Since then, the Earth's core has been
composed  mainly  of  iron and nickel.  Initially all liquid, it has
slowly cooled from the centre out, so that the Earth now has both an
inner  solid  core  and  outer  liquid  core.  The outer core, being
liquid  and  very  hot, convects like boiling water in a pan), which
generates the Earth's unique

                > 154 <


and strong magnetic field. The accumulation of iron at the centre
of the Earth released a large amount of energy that caused the rest
of the Earth to melt.

DIFFERENTIATION AND THE FORMATION OF THE ATMOSPHERE AND OCEANS.

The Earth, now almost completely molten, began a periof of rapid
differentiation.

The molten material, lighter than its surrounding solid parent, rose
to the surface of the Earth and formed a primitive crust. It later
separated into the lighter continental crust and the denser oceanic
crust. The material left between the dense icon core in the centre
and the core became the mantle.

Differentiation was also responsible for the initial escape of gases
from the interior, called OUTGASSING, which eventuially led to the
formation of the atmosphere and the oceans.

        -------------------------------------------

COMPOSITION AND STRUCTURE OF THE EARTH
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

The Earth is made of 3 main layers, the crust, the mantle and the
core.

CRUST
~~~~~
The crust is the uppermost layer of the Earth. There are two types
of crust:OCEANIC, made of basalt, and continental, composed mainly of
granite. Oceanic rock is dense, has deep trenches and varies from
six to ten kilometres in thickness. Continental crust is 35 kilometres
thick on average. The crust is rigid and elastic at the same time.

MANTLE
~~~~~~
The mantle is divided into several layers and is separated from the
crust by a discontinuity, or break called the MOHOROVICIC. The
UPPERRMOST mantle extends for approiximately 100km under the MOHO,
below the oceanic and continental crust. This part of the mantle
is composed of mainly two minerals. (olivine and pyroxene)

                > 155 <

and  has  the  same rheological (deforming) properties as the crust:
it is both rigid and elastic.

Because  they  have  the  same theological properties, the crust and
uppermost mantle behave in unity.

Together,  the crust and uppermost mantle comprise the lithosphere,
which reaches down as far as 150 km belowthe surface.  Surface plate
tectonics,  which  are  described later in the manual, explain the
behavior of the lithosphere.

Below the lithosphere is the asthenosphere.  This layer extends to a
depth of 300 km below the surface of the earth.

Composed  of  the  same  materials  as  the  uppermost  mantle,  the
asthenosphere  is  considered  a separate layer from the lithosphere
because  it  behaves  differently.   The  asthenosphere  is  hotter,
weaker,  and  plastic:   it deforms permanently under pressure.  The
hotter a material gets the less elastic and more plastic it becomes.

To  give  you an example with everyday materials, let's use a rubber
band  and  toffee.   An  elastic  rubber band stretches to a certain
limit  and  then it breaks--a sudden, clean break.  If we release it
before  it  breaks it will go back to its original form.  Toffee, on
the  other  hand, will deform plastically under the same forces.  If
you  pull  on it, it stretches just like the rubber band, but if you
release  it  before it breaks it will stay stretched or deformed; it
will  not  bounce  back to its original shape.  The lithosphere acts
like the rubber band, the asthenosphere like the toffee.

Below the asthenosphere is the transition zone, the area between 300
and  700  km  beneath  the  surface.   The transition zone, although
hotter than the asthenosphere, is not partially molten.

The  transition  zone  gets its name from the fact that the minerals
(mainly  olivine  and  pyroxene,  but also some garnet) transform to
denser  forms  within  this  region  due to heat and pressure.  They
reach  their  most  dense possible structure at 700 km, the boundary
between  the upper mantle (lithosphere, asthenosphere and transition
zone) and the lower mantle.

                > 156 <


The lower mantle extends from 700 km to 2700 km below the surface of
the  Earth.   From 2700 to 2900 km is another transition region that
separates the mantle and the core.

CORE
~~~~
The  centre of the Earth is called the core and has two layers.  The
outer  core, comprised of iron and nickel, extends from 2900 to 5120km
beneath  the  surface.   The  outer core is liquid and hot.  The
motion  of the fluid in this region generates the Earth's unique and
strong magnetic field.

The  inner  core  begins at 5120 km and extends to the centre of the
Earth,  6400 km below the surface.  The temperature at the centre of
the Earth is about 10,000C hotter than the surface of the Sun.

        --------------------------------------------


SPECIAL CHARACTERISTICS OF THE EARTH
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The Earth possesses unique characteristics that separate it from the
rest  of  the  planets:   a powerful magnetic field, the presence of
plate   tectonics   which   have   changed   the  surface  structure
significantly  over time, and the existence of an atmosphere, oceans
and life.

MAGNETIC FIELD
~~~~~~~~~~~~~~
By  slow  convective  movements  in  the  liquid iron core, electric
currents  are  produced  in the core which generate and maintain the
Earth's magnetic field.

The  magnetic  field is what enables us to navigate the seas or find
our  way through a deep forest by using a compass.  In simple terms,
the  Earth's  magnetic field can be described as a giant magnet with
North  and  South poles.  The North magnetic pole coincides with the
geographic North pole.

At certain points in time, the magnetic field reverses--the magnetic
North  becomes South and magnetic South becomes North.  By examining
very  old rocks with magnetic minerals that preserve the orientation
of  the magnetic field at the time they formed, geologists have been
able  to  construct  the  magnetic  polarlty  time scale, key in the
development   of  the  theory  of  sea-floor  spreading  and  plate
tectonics.   The  last  magnetic  field  reversal was over a million
years ago.

PLATE TECTONICS AND CONVECTION
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The Earth is also unique in that its surface layer, the lithosphere,
is  broken  up  into  pieces,  or plates, that move and deform.  The
movement and deformation of the plates - -plate tectonics -- is
responsible for mountain building, earthquakes  and volcanos. There
are 12 major plates on the planet.

                > 157 <


The  plates  move  in  response  to  the  convection  of  the mantle
underneath.  Convection is a mechanism of heat transfer in which hot
material  from  the bottom rises to the top (hotter material is less
dense  and  therefore  weighs less), and the cooler surface material
sinks.  Convection is the most effective form of heat transport.

ATMOSPHERE, OCEANS, AND LIFE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Another  important  characteristic of the Earth is its fluid sphere:
the  atmosphere  and  oceans.   Earth  is  the  only planet in which
two-thirds  of the surface is covered by water, and is surrounded by
an  atmosphere  composed  mostly  of oxygen and nitrogen.  These two
features  have  enabled  the  Earth to develop an amazing variety of
living organisms.

There are many theories for the origin of the atmosphere and oceans.
The  most widely accepted theory states that in the Earth's earliest
beginnings,  it  had  no  gaseous atmosphere.  It was too small, and
didn't  have  enough  gravity to retain the lighter gaseous elements
that existed at that time.

As  time  passed,  the  Earth  increased  in  size  and mass:  large
meteorites  and  planetesimals added their mass by crashing into the
Earth, and the Earth's

                > 158 <

gravity attracted smaller particles of matter. Eventually Earth
was big enough to retain an atmosphere.

The original atmospheric gases (very different from todays oxygen-
nitrogen) must have been produced by outgassing during the initial
duifferentiation.

The early atmosphere must have been a similar composition to the
gases released during volcanic eruptions today, and consisted of
water vapour, hydrogen, hydrogen chlorides, carbon dioxide and
monoxide, and nitrogen. The light Hydrogen compounds could not and
cannot be held by Earths gravity, and so they must hav escaped
away as they do today. As the planet cooled, the water vapour in
the atmosphere condensed into water that formed the oceans.

The present atmospheric compoition was achieved later by several
chemical reactions and evolution of life.

INFLUENCE OF THE SUN AND MOON
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The prescence of the moon has one major visible effect on the Earth,
most notably, the behaviour of the oceans in the form of tides. The
gravitational pull of the Moon and the Sun on the Earth causes the
sea level to alternately rise and fall during the day. Gravitational
effeects are observed in both the oceans and the solid earth, though
the latter can only be detected by very sensitive instruments.

The tides in the water can be seen and measured accurately and the
time of occurrence calculated. The side of the Earth facing the moon
feels the strongest tide and the side opposite to it feels the minimum
tide. As the Earth rotates the tides move around it. The sun, although
farther away, is so large that it has the same effect. Solar tides
are half the tide of lunar tides, and are not in phase with the lunar
tides. Solar tides occur every 24 hours, lunar tides occur every
six hours.

When the earth, moon and sun line up the tides are very strong. These
are called spring tides and they occur every two weeks, at full and new
moon. When the moon and the sun are at right-angles to each other
with respect to the Earth we have the lowest tides, known as neap tides,
which will occur between first and third quarter moons.

Tides cause loss of energy through friction between the water and the
sea floor. The energy is enough to slow down the rotation of the earth
by a very small amount. This effectively lengthens the day.

                > 159 <

DIVISIONS OF THE EARTH
~~~~~~~~~~~~~~~~~~~~~~
We  can  summarise the behaviour of the Earth in a fairly concise way
by dividing its processes in two:  surface processes of the external
heat engine and internal processes of the internal heat engine.

A  heat  engine  is  a mechanism that converts high-temperature heat
(energy) into work.  It is composed of four main "parts":

1) High T(temperature) source;
2) Working fluid;
3) Work to be done; and
4) Low T sink (something that cools by absorbing heat).

These parts in the internal and external heat engines are identified
below.

            EXTERNAL HEAT ENGINE     INTERNAL HEAT ENGINE
SOURCE      Radiation from the Sun     Heat from radioactive decay
                                        Latent heat from fusion of the
                    core Mantle rocks
WORKING     Atmosphere and oceans    Mantle rocks
FLUID
WORK        Erosion, weathering, etc.   Plate Tectonics
SINK        Outer space            Outer space.

EXTERNAL HEAT ENGINE
~~~~~~~~~~~~~~~~~~~~~
Many  of the surface processes of the Earth are the direct result of
the work done by the external heat engine.  These processes are what
determine  many, but not all, of the short- and long-term changes in
the Earth's landscape.

The  processes  that  occur  within  the external heat engine can be
classified into four groups:

Erosion:
--------
the set of processes that results in the loosening of soil
and rock, as well as its removal downhill or downwind.

Weathering:
-----------
The  set  of  processes,  chemical  or  physical, that
results in the breakup and decay of bedrock.  Of the four processes,
this  is now the most important for human concerns.
Weathering breaks up  and  chemically  changes  bedrock,
transforming it into soil essential for agriculture. Our abusive
agricultural system is eroding  good  soil  at  a  rate  faster
than  it can be created by weathering.

Transportation:
--------------
the  set  of processes involved in moving loosened
material from one place to another.

                > 160 <


Deposition:
-----------
the set of processes resulting in the settling down of
the transported sediment.

These  four  processes  are carried out by three main agents:  wind,
water and glaciers.

WIND
~~~~
Wind  is  an important agent of erosion and deposition.  In deserts,
for  example, all the erosion, transportation and deposition of sand
is  exclusively  carried  out by winds.  Normal winds can only carry
very small particles, but strong winds, as in the Sahara sandstorms,
can carry a markedly heavier load.

WATER
~~~~~
Water  in  its  fluid  form  is the most important agent of erosion,
transport  and deposition on the surface of the Earth.  Water is also
important  in  chemical  and  physical weathering as it is the fluid
that enables many of the chemical reactions that break down bedrock;
it also enlarges cracks in the freezing and thawing processes.

Water  causes  erosion  of soil by runoff after heavy rain, in river
channels  kom  the  head  to  the mouth (mostly at the head), and by
ocean  currents  both  along  coasts and on the bottom of the ocean.
Water  in  rivers  is  extremely important in shaping the landscape,
i.e., the Grand Canyon and the Colorado River.

Transport of sediments by water occurs in runoff channels, in rivers
and in currents in the ocean or along the shore.

Water  allows  deposition  of sediment in river channels and deltas.
Deposition  by  water is very clearly seen in the inside part of the
curves of rivers, in deltas, and also in the ocean bottom as a river
enters  the  ocean and dumps its sediment load on the bigger body of
water.

Water   reservoirs  on  land  are  rivers,  groundwater  and  lakes.
Glaciers  are  also  a  reservoir of water, but they will be treated
separately.

GLACIERS
~~~~~~~~
Large  bodies  of  water  accumulated  as  ice  are usually known as
glaciers.   There  are several types of glaciers:  mountain glaciers
like  those  that  covered  Yosemite  in  California, continent-sized
glaciers  known as ice-sheets like those in Greenland or Antarctica,
and others.

                > 161 <


Glaciers  are  a very powerful and rapid agent of erosion, transport
and deposition.  Glaciers can carve a valley in a shorter time scale
than  any  river.  They can transport sediment that ranges from sand
grains to boulders the size of a house.

Glacier  landscapes  are recognised by their U-shaped valleys, while
river  valleys  are  V-shaped.   The  valley  floors have striations
caused  by  the boulders scraping the bedrock, and the sides and end
of  the  valley  have  an assortment of rock sizes we generally call
moraines.

OTHER SURFACE PROCESSES
~~~~~~~~~~~~~~~~~~~~~~~
Two  hot  topics  of  public debate are the processes and effects of
global  warning  and  air pollution.  The following section will lend
insight  into  these  topics  as we discuss the basics of the carbon
cycle and element transport by rivers to the oceans.

THE CARBON CYCLE
~~~~~~~~~~~~~~~~
Carbon  dioxide (CO2) is used by photosynthetic organisms (organisms
that  make  their  own food) such as plants, to generate the complex
carbohydrates  and  the  energy  they  need  for  survival.  In this
process  the  carbon is locked up in complex molecules and oxygen is
returned to the atmosphere.

Non-photosynthetic  organisms  such  as  humans  and  other  animals
breathe  oxygen  and  give  back CO2 to the atmosphere.  When either
type  of  organism dies, the organic matter decays and the carbon in
the complex molecules is released generally in the form of CO2.

Carbon  also  accumulates  to  form  fossil  fuels  that humans have
learned  to use.  Such burning of the carbon in these fuels releases
additional   CO2  into  the  atmosphere,  causing  an  unbalance  or
destabilization     in    the    natural    equilibrium    of    the
atmosphere/biosphere dynamic relationship.

Cutting down forests or plants also creates a destabilization of the
environment,  because  it  results  in  less  photosynthesis.   As a
result, less CO2 is consumed and less oxygen is produced.

The  highest  reservoir  of  carbon is found in rocks, especially in
limestone.   The  carbon  is  trapped  in  the limestone when marine
organisms,  whose  shells  are  made  of calcUe, die and fall to the
bottom  of  the  ocean  and  accumulate into thick layers.  When the
layers compact and harden they become limestone.  Most of the carbon
stays  there  until  the  ocean floor, and the limestone with it, is
consumed   through  earthquake  and  volcanic  activity.   Then  the
limestone melts and the

                > 162 <


carbon  in  the  form  of  CO2  gas is released through volcanos and
returned to the atmosphere.

The  processes of weathering and erosion cause many elements trapped
in  minerals  to  be  transported  back  to  the  oceans, where they
interact with both the oceanic water and rocks.

For  the  purposes  of studying the Earth, we need to know how these
elements  are  transported  back  to  the  oceans  and how long they
interact with water before being trapped in minerals.  This helps us
understand mountain-building activity, the measure of erosion rates,
and  how  rock/water  interactions  and  basalt composition form the
oceans.

For  environmental  reasons, knowledge of these processes is equally
important.  It teaches us about the behaviour of toxic or radioactive
elements  in  the  ocean  that  occur,  for  example, as a result of
disasters such as major oil spills.  It also helps us understand the
effects of increased CO2 in the atmosphere, which occurs as a result
of the burning of fossil fuels by an ever-increasing population.

INTERNAL HEAT ENGINE-PLATE TECTONICS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The  most  outstanding  achievement of the Earth sciences in all its
history  was  the  advent  of  the  theory of plate tectonics in the
1960s, which, with a few simple geometrical arguments, has organised
and explained the large-scale processes of the surface of the Earth.

Plate tectonics is the work done by the internal heat engine.

HISTORY
~~~~~~
Early  in  the  1600s  Sir  Francis  Bacon  had  already noticed the
jigsaw-puzzle  features  of the early maps produced by the explorers
of  the New World.  Later, Antonio Snider and Edouard Suess proposed
the  existence of a giant super-continent, but it was not until the
late  1920s,  100  years  after  their  first  publication,  that  a
hypothesis explaining these features was proposed.

In  1929,  Alfred Wegener, a meteorologist, proposed the Continental
Drift  hypothesis.  Wegener collected paleontological data on fossil
plants  and  animals  in  the  Old  and New worlds, as well as other
geological  evidence  (structures,  rock  types  and ages across the
equatorial   Atlantic)   and  proposed  the  existence  of  a  giant
supercontinent  that  broke  into the present continents 200 million
years ago.  He named this continent Pangaea.

                > 163 <

Wegener's  hypothesis was dismissed after 10 years because he failed
to  present  a valid mechanism that would satisfy the physicists and
geophysicists  of the time.  Ironically, 60 years later, continental
drift and plate tectonics are accepted as the ruling paradigm of the
earth  sciences, but there still isn't a clear idea of the mechanism
that causes it.

Continental  drift  and plate tectonics were finally accepted in the
1960s   after   several   geologists   and  geophysicists  presented
incontrovertible  evidence of sea-floor spreading, ocean consumption
and transform motions.

PLATE TECTONICS
~~~~~~~~~~~~~~~
In  simple  terms, the earth's surface is not continuous and static,
but broken into pieces like a giant jigsaw puzzle.  Those pieces can
be  continental  or  oceanic.   They  move due to flow in the mantle
underneath   the  surface.   With  this  simple  explanation,  plate
tectonics  was  used  to  explain  the  distribution  and  nature of
volcanos  around  the Pacific Ring of Fire and also the distribution
of earthquakes all around the world.

Plate  tectonics  is the theory that explains how the lithosphere is
broken  into  pieces called spherical caps that are internally rigid
and  change  in  limited amounts only at boundaries.  Three types of
boundaries   exist:    divergent  (mid-ocean  ridges),  convergent
(subduction  zones),  and  transform  (faults).   The  caps  move at
constant  velocities  which  are continually being determined by the
convection in the mantle.

Before  we  explain  the  three  different  types  of boundaries, or
margins, what follows is an explanation of volcanos and earthquakes.

VOLCANOS
~~~~~~~~
A  volcano is a land edifice that is slowly built up by the eruption
of hot molten rock (magma) on the surface of the Earth.  The erupted
rocks,  made  up  of  many different compositions (cooled magma) are
called  volcanic.   If the molten rocks don't reach the surface, but
cool under the volcano, they are called plutonic.

The  hot  magma flowing on the surface is called lava.  Volcanos can
be  of  very  different  types  depending  on the composition of the
rocks.   The  composition  determines  if  the  volcanos  will erupt
quietly  (Kilauea,   Hawaii)   or   violently  (Mt. Saint  Helens,
Washington).

Volcanos  occur  at  two  plate boundaries and also in the middle of
plates.   When  associated  with  convergent  boundaries,  they  are
usually  violent;  when  divergent  they  are  under water and erupt
quietly.  Intra-plate volcanos are often associated

                > 164 <

with  hot-spots  in  the bottom of the mantle that produce chains of
volcanos  such  as  we  find  in  Hawaii.   These  are usually quiet
volcanos.

Knowing  the  plate boundaries is important in predicting which type
of  eruption  will  occur  so  that volcanic hazards can be properly
evaluated.   Big,  violent  eruptions can send so much material into
the  atmosphere that it will change the color of sunsets or cool the
global  temperature  by  a  few degrees.  This happened in the 1880s
when  Krakatoa erupted in Indonesia.  The sunsets were intensely red
for a year and England did not have a summer for two years.

EARTHQUAKES
~~~~~~~~~~~
An earthquake is the result of the sudden release of energy that has
been  accumulating  between  two  parts  of  the  Earth divided by a
fracture  we  know  as a fault.  The energy accumulates because the
two  sides of the fault cannot slide past each other easily; rather,
they  find  a lot of resistance to sliding and this resistance locks
the fault.  When the resistance is higher than the blocks can stand,
the fault snaps and an earthquake occurs.

Earthquake  magnitude  is  measured by the Richter scale, which is a
measure  of  the energy released by the earthquake.  What we feel is
measured  by  a  subjective  scale  of intensity called the Mercalli
scale.  Earthquakes occur at all three plate boundaries because they
all  divide  blocks  of  the  Earth,  where  there  is resistance to
sliding.

Earthquakes  occur below the surface of the earth but are located by
latitude  and  longitude measurements.  Such measurements, which act
like  a  grid  around  the  entire surface of the Earth, are used to
define  an  earthquake  epicenter.   The  depth of the earthquake is
called  a focu-s or hypocenter.  Earthquakes are classified by their
depths  into  shallow  (0-70  km), intermediate (70-300 km) and deep
(300-  700  km).   Big,  shallow  earthquakes  like those on the San
Andreas fault are highly destructive.

DIVERGENT MARGINS
~~~~~~~~~~~~~~~~~~
In  the  1950s  it  was  discovered that in the middle of the oceans
there  were  very  long  mountain chains emitting volcanic material.
These  chains,  known  as  Mid-Ocean Ridges, are where new oceanic
floor (basalt) is constantly being created.  The material builds up
symmetrically on both sides of the ridge with a deep central valley.
There  are  volcanos  and  shallow  earthquakes there.  This type of
boundary  is  called  a  constructive  boundaRy  because  sea-floor
material is generated here.

                > 165 <

Mid-ocean ridges can be followed for a continuous 40,000 km from the
Atlantic to the Pacific, the Indian Ocean and so on.

TRANSFORM MARGINS
~~~~~~~~~~~~~~~~~
The  ridges  are  offset by faults known as transform faults.  These
faults  are  plate  boundaries that join ridges to ridges, ridges to
trenches,  faults  to  trenches, and so on.  Material is not created
nor  destroyed  at  transform faults.  They are vertical faults that
generate  shallow  earthquakes.  The best example is the San Andreas
fault.

CONVERGENT MARGINS
~~~~~~~~~~~~~~~~~~
If  material  is  created at the ridges and the Earth is not getting
bigger,  ocean  crust  must  be destroyed somewhere.  This occurs at
convergent  margins, also known as subduction zones.  Here an oceanic
plate  dives  into  the  mantle  under  another  younger and lighter
oceanic plate or continental plate, such as with the Pacific oceanic
plate  under  the  continental  South  America.  A continental plate
cannot  subduct, so when two continents converge they crash together
in  what  is  known  as  a  continental  collision, generating large
mountain chains, such as the Himalayas.

Subduction  of  an  oceanic plate generates magma, which rises under
the  overriding  plate and builds a volcanic line such as what takes
place  in the Andes.  Subduction generates 99% of the seismic energy
released every year, in shallow, intermediate, and deep earthquakes.
It  also generates the biggest earthquakes (9.5 on the Richter scale
in  Chile,  1960;  9.0  in  Alaska,  1964).

                > 166 <



                   CLIMATE
                   =======

The  study  of atmospheric and hydrospheric systems (air and oceans)
explains the climate of the planet.  The greenhouse effect and other
present-day  environmental problems are related to climate.  Climate
is part of the external heat engine and is driven by the radiational
energy of the Sun.

        --------------------------------------------


The  composition  of  our  atmosphere  is  shown  in Table 1.  It is
composed of 78% nitrogen gas (N2), 21% oxygen (O2) about .93% argon
(A),  and  minor  amounts  of  carbon dioxide (CO2).  There are also
traces  of  nitrous  oxide  (NO2),  methane (CH4) and sulfur dioxide
(SO2).

The atmosphere did not always have this composition--free oxygen was
not  available  until  the  first photosynthetic organisms appeared.
This will be covered later in the chapter on "Life."

The   atmosphere   is   divided   into  four  layers:   troposphere,
stratosphere,  mesosphere  and  thermosphere.
Ozone (03) is a compound of  oxygen  that  absorbs  and  repels
a  large  percentage  of the ultraviolet radiation in solar energy.

The  ozone  layer  protects  us from the deadly UV rays of the Sun's
radiation.   Our use of chlorofluorocarbons enlarges the hole in the
ozone layer, which reduces this protection.



GAS            CHEMICAL     CONTENT
            SYMBOL      (% by volume)
Nitrogen          N2        78.09
Oxygen              O2        20.95
Argon              A         0.93
Carbon dioxide         CO2         0.03
  Total                       100.00

Table 1 Principal Components of Dry Air

                > 167 <


OCEANS
~~~~~~
Not  just  composed  of  water,  oceans  have many other elements in
solution  such  as sodium, potassium, and calcium, and gases such as
carbon  dioxide  (see  Table  2).  All of the dissolved elements are
critical for the survival of marine plants and animals.


Life  in  the  deep oceans is limited greatly by the availability of
food and light. The zone of the ocean that is well-lighted is called
the euphotic zone (upper 200 meters)  and  the darker, deeper layers
are called the aphotic zone.  The amount  of oxygen available in the
oceans also decreases sharply at deeper levels.

The  structure of the oceans detailed in the figure below shows that
water  temperature  decreases  to  4C at a depth of 2000 meters in
tropical  and  temperate  regions.


ELEMENT        AMOUNT IN OCEAN        RESIDENCE IN TIME.
             (G)            (YR)
Sodium        147*10^20        260,000,000
Magnesium     18*10^20         12,000,000
Potassium       5.3*10^20         11,000,000
Calcium            5.6*10^20          1,000,000
Silicon        5.2*10^18              8,000
Manganese    1.4*10^15                700
Iron        1.4*10^16            140
Aluminium       1.4*10^16            100

          Table 2 Residence Time of Some Elements in Seawater


                > 168 <

SOLAR HEATING - INSOLATION
~~~~~~~~~~~~~~~~~~~~~~~~~
The  energy to carry out processes on the surface of the Earth comes
from  the Sun.  Solar radiation, also known as insolation,  is what
spurs life and geological processes on the Earth.

Since the birth of the Solar System, the Sun has been radiating heat
at a constantly increasing rate.  This is the natural consequence of
the growth of a star.  The life span of a star like the Sun is about
1400  billion  years,  which  means  that  the  Sun  will  last  for
approximately  another  10  billion years.  The solar radiation will
increase  with time and cause the surface temperature of the Earth to
get  higher  and  higher  until  the  Sun  dies.   When this finally
happens,  life  on  the Earth will probably die unless forms of life
not dependent on photosynthesis evolve.

Climate  is  highly  dependent  on solar output variations.  Seasons
(winter  and  summer)  and  climatic  zones  are  dependent on solar
output.   Figure  11  shows the angle of the Earth to the solar rays
with   different   seasons   and  at  different  latitudinal  zones.
Variations  in solar output do not follow just the seasonal cycle of
summer  and  winter.   They also follow other longer cycles that are
directly related to long-period changes in temperature on the Earth,
such as during glaciations.

GLACIATIONS AND CHANGES IN THE ORBIT OF THE EARTH.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Scientists  have  argued  for a long time on the cause of the recent
(10,000  to 15,000 years ago) ice ages since they were discovered by
Louis Agassiz in the 1800s.

In  the  1930s, a mathematically sound hypothesis for glaciation and
long-period  climate changes was proposed by Milutin Milankovitch, a
Yugoslavian  astronomer.   He  proposed  the  astronomical theory of
climate,  which  says that variations in the Earth's orbit influence
climate  by  changing  the  seasonal and latitudinal distribution of
incoming solar radiation.

Incoming  solar  radiation  falls  at  different angles in different
seasons.  The angle of incidence depends on the tilt of the rotation
axis  of  the  Earth  (axial tilt).  This tilt is technically called
obliquity,  and is measured with respect to a plane that crosses the
Sun and contains the orbit of the Earth (plane of the ecliptic).

                > 169 <


Another  factor  that  influences  the  angle  of incidence of solar
radiation  is  the  precession,  or the measure of how the equinoxes
succeed  each  other and how this affects the seasonal configuration
of the Earth.  Precession depends on the longitude of the perihelion
(the point at which the Earth is closer to the Sun).

A  final  factor  that  influences  the  angle of incidence of solar
radiation is eccentricity, which is a measure of how much the orbit
of the Earth around the Sun differs from a perfect circle.

Obliquity,  eccentricity  and precession of the equinoxes are called
the  orbital  parameters and variations in them determine changes in
the   solar   heating  and  therefore  affect  our  climate.   These
parameters cause changes with different period lengths:

Eccentricity   Long-period cycles   95,000;136,000;   413,000years
Obliquity      Medium-period cycles 41,000years
Precession     Short-period cycles  19,000; 23,000years

Changes  in climate are classified according to the lengths of their
cycles:

Tectonic band           more than 400,000 years
Milankovitch band        10,000 to 400,000 years
Millenium band            400 to 10,000 years
Decadal band            10 to 400 years
Interannual band        2.5 to 10 years
Annual band            0.5 to 2.5 years

Changes in the tectonic band are attributed to tectonic effects such
as  mountain  building.   This  is  a  current  topic of research in
paleoclimatology and is known as Tectoclimatology.

Changes  in  the Milankovitch band are due to changes in the orbital
parameters  mentioned above.  These changes are the direct result of
the  gravitational pull of the giant planets (Jupiter and Saturn) on
the Earth.

Changes  in the millenium band are attributed to episodes of flux of
volcanic  gases,  and  expansion and contraction of alpine glaciers.
Changes  in  the  millenium  band  are  due to episodes of explosive
volcanism.

Finally,  changes  in the annual and interannual band are attributed
to  the well- known seasonal fluctuations of solar radiation.  These
are probably due to

                > 170 <


motions  of  the Earth around its own orbit (wobbling of the axis of
rotation,  for  example) and not the geometry of the orbit as in the
orbital parameters.

A variation in the solar output that frequently occurs is related to
sunspot  cycles.   A  sunspot  is  a dark area of the sun's surface,
which  represents a region of lower temperature than the rest of the
sun's  surface.   Sunspot cycles are fluctuations in the ultraviolet
radiation  from  the Sun.  The approximate duration of a cycle is 11
years.   The  influence  of sunspot cycles on the climate is still a
controversial and constantly debated topic.


EARTH`S RESPONDING TO SOLAR HEATING
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The Earth does not just passively absorb the radiation from the Sun,
but  returns  some of the radiation back to space.  It does not emit
it  back  at the same frequency, but at a lower one.  Emissions from
the  Earth are in the infrared spectrum while radiation from the Sun
comes  from  the whole spectrum of light, from UV (ultraviolet) rays
to  visible  to IR (Infrared).

Part  of  the  solar  radiation  (IN  rays) is absorbed by the ozone
layer,  part  is reflected by clouds and solids, part is absorbed by
water  vapour,  dust particles and clouds, and 47% is absorbed by the
ground.

The  overall albedo is the most important process preventing the Sun
from  frying  us.  It is measured by the amount of the Sun's radiant
energy that is reflecting off clouds, water and land surfaces.  This
reflectivity  is called albedo.

                > 171 <

ALBEDO EFFECTS
~~~~~~~~~~~~~~~
Albedo  is  the  ratio  of  light  reflected to light received.  The
combination  of  the  following mechanisms gives the total albedo of
Earth and atmosphere.

Orbiting satellites keep track of the albedo in order to monitor the
rate  at  which  the  earth's surface is heating when exposed to the
sun.   Such  instruments  measure short-wave and infrared radiation,
both  coming  in  from the sun and going out from the atmosphere and
the  earth's  surface  below.   The  earth's average albedo has been
estimated at between 29% and 34%.

There are four major mechanisms for returning radiation to space:

* Reflection from dust, salt, ash and
  smoke particles in the air;
* Reflection from clouds;
* Reflection from the ground; and
* Refraction by air molecules.

If  a  ray reaches the Earth after all these obstacles then it still
has  to  deal with the Earth's albedo.  This varies depending on the
composition  of  the surface.  The average surface albedo is only 4%
but  in  certain areas, for example the poles, the albedo is between
50-70%.

Because of its high albedo, the amount of snow that falls in a year
will affect the climate  and  the average temperature of the Earth.
The presence of more deserts will have the same effect.  Deforestation,
even though its  albedo  is  very low, also affects the weather
because more dry uncovered  land  with a high albedo gets exposed.
The Earth retains this  heat  and  transports  it  from  equatorial
latitudes to polar latitudes.

HEAT TRANSPORT & ATMOSPHERE OCEAN INTERACTIONS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The  heat absorbed by the ground and by the ocean surface waters is
greater at the equator than at the poles because of the higher
amount  of  insolation  at  these regions. This heat is transported
from  the  equator  to  the  poles both by the atmosphere and by the
oceans. In a general sense, the atmosphere does it using winds and
convection  cells (like the mantle in the internal heat engine), and
the oceans using currents, both surface and deep.

                > 172 <

ATMOSPHERIC TRANSPORT
~~~~~~~~~~~~~~~~~~~~~
Atmospheric  transport,  or  global circulation, takes place largely
due to winds.  The pattern of global circulation is characterised by
permanent  anticyclones  and cyclones, called centres of action, and
by persistent wind systems.

At  low latitudes near the Earth's surface, the easterly trade winds
dominate.   At  high  latitudes and aloft, the prevailing westerlies
dominate.    The  occurrence  of  zonal  winds  is  explained  bythe
deflection  of  motions  of the meridians due to the rotation of the
Earth.   This is the Coriolis effect, which also says that particles
in  the  Northern  hemisphere  tend  to  go  to the right and in the
Southern  hemisphere  to  the  left.   The  driving  force  for this
circulation is the variation in solar radiation with latitude.

Near the surface of the Earth the pressure is low at the equator and
high  at  the  poles.   This  gives  rise to a circulation along the
meridians,  with  the heated air rising near the equator and flowing
high  towards  the  pole  and  the  cooled  air  descending  at high
latitudes and flowing towards the equator at the ground.  The stream
of  air  moving  towards  the  pole  is deflected to the east by the
Coriolis  force,  originating  westerly  winds,  and the one flowing
towards  the equator at the ground will be deflected to generate the
easterlies.   Friction  with the surface of the Earth does not allow
the  pressure  and Coriolis force to balance so that the circulation
is not just zonal but also along the meridians.

The  pattern  of  meridional  circulation  was  discovered by George
Hadley in the 1700s and the circulation patterns along the meridians
are called Hadley cells.  Since friction does not allow pressure and
Coriolis  force  to  balance, the pressure force is greater at great
heights  than  the Coriolis force and the air at great heights is
pushed towards the poles.  At high latitude the air tends to Equator
cool  and  descend,  completing  the meridional Hadley cell.

The  Hadley  cells,  one in each hemisphere, perform the function of
transferring  excess  heat  from  the Sun at low latitudes to higher
latitudes.   The  true  circulation pattern is not as simple as just
having  a Hadley cell in each hemisphere because of a law of physics
called  conservation  of  angular momentum.  The results of applying
the  law  show  that  Hadley  cells alone will cause very high-speed
winds,  which  in  turn  will  cause great instability in the global
circulation  pattern.  Friction between the Earth and the atmosphere
also complicates simple Hadley cells.

Heat  is  also  transported  by  waves  and  vortices.  Waves in the
atmosphere  are the result of the breakdown of the zonal flow due to
high-speed winds and lateral

                > 173 <


mixing of the air.  Swirls or vortices and cyclones and anticyclones
also  result  from  the breakdown of the zonal flow.  These are very
effective at transporting the heat in the North-South direction.

OCEANIC TRANSPORT
~~~~~~~~~~~~~~~~~
Heat transport from solar radiation is also accomplished via oceanic
circulation.   Circulation  of the oceans is one of the main factors
in the total heat budget of the Earth.

Oceans  act  as a great reservoir of heat for the planet.  The Sun's
energy  heats up the surface of the ocean, which stores the heat and
transports it via oceanic currents both at the surface and at depth.
Like  the atmosphere, the ocean currents move heat from low latitude
to high latitudes.

HEAT STORAGE
~~~~~~~~~~~~
The oceans are very large reservoirs of water that can hold a lot of
heat  without  changing  their  average  surface temperature by very
much.  This is known as the climatic flywheel.

Oceans  are  better  at holding heat than the ground or the air, and
absorb  more  heat  per unit area at the equators than at the poles.
The  heat  is  transferred  to the colder areas by convection.  This
moderating  effect  on  the  climate is easily observed in temperate
coastal regions where warm air from the seas is transferred to the
land.

SURFACE CURRENTS
~~~~~~~~~~~~~~~~
The  wind-driven  circulation  of  the oceans is strong, but extends
only  within  the  upper  1000 meters of the ocean.  The wind system
described in the previous sections exerts a stress on the surface of
the  ocean,  generating  surface currents.  The easterly trade winds
form the equatorial currents of all oceans.

When  intersected  by  land  these  currents are deflected North and
South,  as  in  the Atlantic and Pacific oceans.  Deflected currents
travel  along the western parts of the oceans and are called western
boundary currents--they are the strongest in all the oceans.  One is
the Gulf Stream.

These currents are driven by the westerly winds across the ocean and
form  currents that flow back into the equatorial region, completing
the   convection   cell,  similar  to  what  occurs  in  atmospheric
circulation.   These  cells or gyres occur in subtropical regions in
the  N and S Pacific, N and S Atlantic and S Indian oceans.  The N
and S gyres are separated by a countercurrent that flows east.

                > 174 <


In  the  N  Indian  Ocean  a similar gyre is found, but this changes
direction   every   six  months  due  to  reversals  in  atmospheric
circulation  called  monsoons.   Some  weaker  gyres  are  found in
northern  subpolar  regions.   In  southern  gyres  the  flow is not
blocked  by  land,  so  the  Antarctic  circumpolar flows completely
around  the  world.   The  circulation  is  driven by differences in
pressures between high and low areas of the sea surface.

The  action  of  the  wind  on  the surface of the ocean also causes
vertical  motion.  These vertical currents are called upwellings and
occur  when  prevailing  winds  blow  parallel  to  a  coast.  These
upwellings  are  in offshore and subsurface waters, which frequently
are  rich  in  nutrients.   When  this  is the case, an area of high
biological productivity may develop.

DEEP CURRENTS
~~~~~~~~~~~~~
Variations  in  water  density cause deep water circulation known as
thermohalline  circulation.  These  density differences develop at the
air-sea interface and are the result of differences in the amount of
heat  received  and  the  effects  of dilution and evaporation.  The
dense,  cold  waters  of high latitudes sink and slowly flow towards
the  equator.  This is a convective process, like that of the mantle
inside  the  Earth.   This process occurs principally in two places,
the North Atlantic and the Antarctic.

The  North  Atlantic  Deep  Water  is  very  clearly  defined by its
temperature,  oxygen  content  and  salinity.   The Antarctic Bottom
Water  travels  north along the ocean floor across the equator.  The
bottom  water  path  is  influenced  by  the topography of the ocean
floor.

ATMOSPHERE-OCEAN INTERACTION
~~~~~~~~~~~~~~~~~~~~~~~~~~~~
This cycle can be summarised as follows:
the wind blowing over surface waters generates waves, mixes the surface
waters  and  removes  water  vapour  from the sea surface.  The water
vapour  is taken into the atmosphere by evaporation and transferred
to  land  by  precipitation,  which  returns  it  to  the rivers and
groundwater that eventually return it to the sea.

                > 175 <

GREENHOUSE EFFECT AND CLOUD COVER
AND THEIR INFLUENCE ON CLIMATE.

GREENHOUSE EFFECT
~~~~~~~~~~~~~~~~~
In  recent  years  we  have heard a lot about global warming and the
greenhouse  effect due to increasing consumption of fossil fuels and
continuous   deforestation,   but   few  accurately  know  what  the
greenhouse  effect  is  and how to gauge its delicate balance on the
Earth.   Not  even  the  experts can predict the Earth's behaviour in
terms  of  global warming trends, because we don't know enough about
climatic fluctuations and CO2 levels in the past.

The greenhouse effect can be described as follows:

The  atmosphere  of  the Earth is fairly transparent to the incoming
visible rays of the Sun, but 48% of the radiation is absorbed by the
ground  and  emitted  back as infrared radiation.  The atmosphere is
opaque to infrared because carbon dioxide and water vapour absorb the
radiation  instead  of  allowing  it  to  go  back into space.  This
absorbed radiation heats the atmosphere, which radiates heat back to
the  Earth.   Without  this  effect  the Earth's surface temperature
would be below freezing and the oceans a mass of ice.

                > 176 <


Any  process that alters the delicate balance of CO2 and water vapour
molecules   may   affect  Earth's  climate.   Burning  fossil  fuels
increases  the amount of CO2 in the atmosphere, and deforestation of
the  Amazons prevents plants from taking CO2 and returning oxygen to
the atmosphere.

Since  the  beginning of the Industrial Revolution the amount of CO2
in  the  atmosphere has increased steadily to values that we think
have  never  been  reached before. Some of these CO2 molecules
are taken from the atmosphere and dis solved in the oceans, because
nature  tries  to  reestablish  equilibrium, but we are releasing so
much CO2 that the planet cannot rebalance itself.

Increases  in global temperature caused by the greenhouse effect may
also increase sea levels by 1O meters or more by melting part of the
Antarctic  ice  sheet.   This  could  be devastating to many coastal
cities.

CLOUD COVER
~~~~~~~~~~~
We  have  already  discussed  briefly  the  effect of cloud cover on
albedo  and  therefore  on insolation.  Cloud cover also affects the
reflection of incoming rays from the Sun.  Clouds form as the result
of  the  condensation  of  rising hot air into the lower part of the
atmosphere.   Clear  air  descends to the ground where it is heated,
then  rises  as it warms up; it goes up into the atmosphere where it
cools  and condensates, trapping a lot of water vapour, which in turn
reflects the sunlight, making it less intense.

Global  warming  would evaporate more water and therefore more water
vapour  will  go into the atmosphere and be trapped into clouds which
will  in  turn  cover  more of the sky and decrease the intensity of
sunlight that comes in.  This could balance warming, but water vapour
also traps infrared radiation.

                > 177 <


                LIFE (Get one eh ?)
                ====

ORIGIN OF LIFE
~~~~~~~~~~~~~~
Why does life flourish on the Earth and not on any other planet?  In
this  section  we  will  take  a  look  at  the history of planetary
evolution from the origin of life up to vertebrates and humans.


In the early 1920s a young Russian biochemist, Aleksandr (ivanovitch)
Oparin, theorised that there must have been a beginning of life at a
certain  point in Earth's history and that we could make intelligent
guesses as to when it was and how it occurred.

Oparin  theorised  that  the  atmosphere  of  the early Earth lacked
oxygen  but  contained  gases such as ammonia, methane and hydrogen.
In  that  kind  of  atmosphere  (without  ozone),  UV rays would have
energised the components and generated the first synthetic reactions
of  organic  compounds  such  as  amino acids, the building block of
life.   These  in  turn  would  clump  together  in  long chains and
possibly  take  on  the  characteristics  of the primitive cell.  He
called this early amalgamation of compounds primordial soup.

In  the 1950s Stanley Miller devised an experiment that demonstrated
how  it  may  have  happened.   He  built an apparatus that zapped a
primordial  soup  with electrical jolts comparable to lightning, and
produced  amino acids.  The step from amino acids to actual life and
genetic  coding  is not yet understood.  Other theories suggest that
the  early  atmosphere was primarily carbon dioxide, water vapour and
nitrogen,  as  expected  from  degassing  of  the  Earth.   In  this
environment, amino acids have also been produced.

Others propose that building blocks may have originated in nearby
comets and come to Earth on impacts.  The origin of the nucleic
acids DNA and RNA  that  enable life to replicate and transmit
genetic information to the offspring is not clear, but it is
obvious that this was the final and most crucial step towards
organised life.

If  you  ever  watch the old "Star Trek" series, you may have seen a
couple  of  episodes  in  which they discuss the possibility of life
based  on  silicon  instead  of  carbon  (Si  and  C are of the same
chemical  group  and  possess  many  of  the  same characteristics).
Silicon-based  life  is  highly  unlikely  because  one  of the most
outstanding  properties  of  carbon  is  that  it is gaseous at room
temperature  rather  than solid like silicon.  This property enabled
carbon  to  make  organic  compounds  in  the  fluid  state,  at low
temperatures, with lower energy requirements than that of silicon.
Silicon  is  too heavy and too inert to react at the temperatures at
which life as we know it survives.

                > 178 <

EARLY ORGANISMS
~~~~~~~~~~~~~~~
The  first known organisms on Earth are some carbonaceous remains of
primitive  cells  with  no nucleus that date back 3.5 billion years.
Prokaryotes,  which  still exist today in bacteria, algae, ameba, and
other  simple  organisms,  lack  a  nucleus,  the  central part that
contains all the genetic material, as well as specialised organelles
for  other cellular activities.  These first organisms were probably
anaerobic and fed on methane.

Two billion years ago, organised life--like
algae--were thriving on the planet. One billion years  ago the
eukalyotic cell, the cell with a nucleus,  developed.  One of
the most popular theories on the origin of eukaryotes is that
two prokaryotic cells may have stayed together after mitosis
(cell division) or they may have started a symbiotic
relationship. One  may  have captured the other and from there the
"trapped one" would have developed into a nucleus,  and
also into several different organelles that perform different activities,
such as breathing, metabolizing,  etc. inside the cell.
This is seen in modern eukaryotes in that mitochondria
(the organelles that breathe for us) have  their  own  genetic
material and replicate separately from the rest of the genetic
material in the cell.

Shortly  after  the evolution of eukaryotic cells (In geologic time),
the  first  multicellular  organisms or metazoans evolved.  With the
advent  of  metazoans  a  very  diverse range of life-forms evolved,
including  the  development of soft-bodied organisms as seen in the
Ediacara fauna of Australia and the Burgess shale in Canada.

Six  hundred  million years ago, after the explosion of diversity of
soft-bodied  organisms,  the  first shelled organisms developed in a
period called the Cambrian.

The  rate of evolution between one billion years ago and 600 million
was  so  much  higher  than at earlier times that it could be termed
explosive.  From  a world dominated by algae and bacteria we passed
to a world full of different species that in some form or other
still survive today.  There  were more species alive at that time
than have evolved since.

                > 179 <


EVOLUTION OF OXYGEN RICH ATMOSPHERE AND PHOTOSYNTHESIS.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We  have  already stated that primitive life evolved in an anaerobic
atmosphere  with  little or no oxygen.  Obviously, many changes have
occurred  since.   Even  the  Cambrian  organisms  needed  oxygen to
survive.


Around three billion years ago (with the advent of blue-green algae)
organisms  must  have developed the ability to photosynthesize--take
CO2  from  the  atmosphere  and with the aid of the sun's radiation,
break  it  down  and  use  the  carbon  to  make  the  food, complex
carbohydrates  and  other energy compounds that enabled the organism
to  survive.   In  return the organisms give free oxygen back to the
atmosphere.

The  oxygen  must  have started to accumulate in the atmosphere, and
soon its levels would become high because few organisms were able to
breathe and deplete it.  The accumulation of oxygen was poisonous to
many organisms, which must have died out as a consequence.

                > 180 <


Some  time  just  before  600 million years ago the amount of oxygen
reached   high  enough  levels  to  allow  rapid  evolution  of  the
invertebrates  in the Paleozoic period.  For the rest of the life of
the   planet  the  amount  of  oxygen  has  been  kept  constant  by
photosynthetic organisms.

Life  not only changed the atmosphere, but also changed the geology,
by  originating  new  types  of  sediments,  rocks  and geographical
features such as coral reefs.

        --------------------------------------------

HISTORY AND DIVERSITY OF LIFE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Diversification  of life had already taken place before the Cambrian
explosion.   That  diversification  is hard to describe because of a
lack  of  fossil  evidence,  so we will concentrate on life from the
Cambrian period on.

CAMBRIAN PERIOD--INVASION OF THE SEAS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The  Cambrian  initiation  was  the beginning of organisms with hard
body  parts  or shells.  This provided defence against predators and
also prompted better fossil preservation.  The most common hard body
parts  were  made  of  calcite,  chitin and SiO2.  The fossil record
really  begins  at  the beginning of the Cambrian era because of the
better preservation of hard body parts.

The  first  fossils with hard skeletal parts were the trilobite, an
extinct  group of arthropods related to crabs, lobsters and shrimps.
These  first  trilobites  had  large  eyes,  long  antennae,  and  a
well-developed  nervous  system.   In the early Cambrian over 90% of
all  the  fossils  specimens  were trilobites.  Other common animals
were  the  brachiopods,  similar  to  clams,  and  some  echinoderms
(starfishes  and sand dollars).  Many other organisms became extinct
and  left no descendants.  All these animals were marine and invaded
the  seas  all  around  the  world.   Other marine organisms such as
corals,  mollusks,  fish,  etc.,  developed  during  the rest of the
Paleozoic and also into the Mesozoic and Cenozoic.

INVASION OF LAND: PLANTS AND ANIMALS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The  most outstanding achievement of the post-Cambrian Paleozoic was
the invasion of land by the first plants and animals.  This opened a
lot of new niches (ecological habitats) for animals to evolve.

Organisms  that  lived  underwater  had  gills or special systems to
breathe,  and  in  order to survive on land they needed to develop a
vascular  system  that  enabled them to use oxygen or carbon dioxide
that  was  not dissolved in water.  Plants did it first in the early
Devonian period.

                > 181 <

Transition  from  water  to  land took place in the Devonian and the
mid-to-late  Paleozoic  periods.   One of the reasons why it did not
take  place  earlier  is that there were extensive shallow seas over
the land, so there was not very much dry land available.

Unfortunately the fossil record on land is not as good as the marine
record  because  preservation is a lot worse on land.  The record is
spotty, discontinuous and full of gaps even in younger rocks.

PLANTS DO IT First
-------------------
In the mid-to-late Paleozoic plants developed a vascular system that
allowed  them  to  survive  without  being  underwater.  This system
consisted of very narrow, elongated hollow cells through which water
and  food could circulate.  It was also a way to maintain the needed
water  balance  inside  their bodies.  They also needed to develop a
rooting  system (and plants need to be attached), and a support for
the  body  like  cellulose  or  lignin.  Once these adaptations were
developed,  the  first  land plant could survive far away from water
and depend only on precipitation and groundwater.

Further  into  the  Paleozoic era, larger and more plants developed.
The  first land plants were small grass-like weeds or bushes.  Later
into  the  Carboniferous  period, large ferns took over, and shortly
after  that  came the conifers, which dominated most of the Mesozoic
era.   It was not until the end of the Mesozoic and the beginning of
the  Cenozoic  that  flowering  plants,  with their efficient repro-
ductive system, came along.

LAND ANIMALS AND THE EVOLUTION TO HUMANS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In  this section we will concentrate on the evolution of vertebrates
after  they  reached  the  land, all the way to humans.  We have not
included  a  discussion  on  the  mechanisms  of  evolution  itself,
although  they  will  be  mentioned  in relation to theories of mass
extinctions.   We leave it to the reader to consult more specialised
books on the subject.

The  oldest  known  land animals including freshwater organisms were
invertebrates  or  arthropods.  A land scorpion and a millipede were
found in early Devonian rocks.  Insect-like fossils of this age have
also  been  found.   Snails  and  slugs do not appear until the late
Paleozoic, after the tetrapods or four-legged vertebrates.

                > 182 <


Apart  from  a few anomalous organisms, vertebrates evolved straight
into  fishes  and  from there into amphibians, reptiles, mammals and
birds.   Fishes  will  not be discussed except for their link to the
invasion of land.  Freshwater Devonian fishes, crossopterygians, had
both  lungs  and  gills  for breathing, so they developed the most
important  adaptation for living on land:  being able to breathe air
and  not water.  They also had thick fleshy fins, which enabled them
to walk.  The fins gradually changed to short stubby legs.  The bone
structure of these fishes matches those of the early amphibians.

These  adaptations,  which  undoubtedly  were meant at first only to
help  them  survive  as  successful  freshwater  fishes, then became
useful to transfer completely to land.  They were probably forced to
transfer to land by changes in climate in the Devonian that dried up
freshwater niches.  There must have also been more food available on
land as freshwater areas dried out.

After these fishes, the first real land animals in the fossil record
are  amphibians,  the  ancestors  to toads and frogs.  These animals
lived  on  land  near  the water since they often had to go into the
water  to  breathe and breed.  As evolution proceeded the amphibians
became  better  adapted  to  living  on  land by developing stronger
limbs.

From  one  of  the  amphibian  lineages  the first reptiles evolved.
Reptiles  started  appearing  in  the Carboniferous period and began
dominating  the  environment  up  until the end of the Mesozoic era.
The  reptiles  had  a big advantage over the amphibians--they didn't
need  to  go to the water to breed.  Reptiles developed the amniotic
egg,  an  egg  with  a  hard, porous shell, which allowed the egg to
survive  without  the  constant  presence  of  water  for breathing.
Unlike  the  amphibians, the reptile youngsters developed right from
the egg without a larval or tadpole stage.

Several  types  of  reptile lineages developed in the Paleozoic, but
the  two  most important and interesting to us are the Synapsida, or
mammal-like  reptiles, from which mammals developed in the Mesozoic,
and  the Diapsida, or ruling reptiles, which included the dinosaurs.
The  end  of  the  Paleozoic  saw the development of many species of
reptiles,   especially   the  dinosaurs,  which  also  proliferated,
may be even more, throughout the Mesozoic. There were many kinds
of dinosaurs: herbivores, carnivores, flying, aquatic, etc.

Mammal-like reptiles developed in the Triassic (the beginning of the
Mesozoic).   These  reptiles  had longer and stronger limbs than the
other  reptiles  and  their brain cases became progressively larger.
Their dental structure approached that of modern mammals.

                > 183 <


The  ruling  reptiles had one important group, the thecodonts, which
then  became the dinosaurs.  These animals were bipedal and had tiny
skulls.   The front limbs were not used for walking but for handling
food. Two main groups of dinosaurs became important: those with a
pelvic bone similar to other reptiles (saurischians) and those with
a pelvic girdle similar to birds (ornitischians). Saurischians were
small and from them developed the large predators of the late Mesozoic
such as Tyrannosaurus rex.  Most dinosaurs nonetheless were herbivores,
not carnivores.

From dinosaurs developed the first bird-like reptiles, and from them,
birds. A very famous bird-like reptile is Archaeopteryx, which had
feathers and a wing structure very similar to modern-day birds.

As mentioned before, mammals evolved from the Synapsida, the mammal-like
reptiles.  The first mammals were small, with small brain  apacity;
most of them were probably rodents (mice, etc.). Mammals were not
very common in the Mesozoic, except for rodents and monotremes
(duck-bill platypus).  Not until after the demise of the dinosaurs
at the end of the Cretaceous did they start taking over the land,
especially  with the evolution of placental and marsupial mammals.

Marsupials  (kangaroos  and  opossums, for example) are animals that
give  birth to young incapable of fending for themselves; the mother
keeps  them  in a pouch outside her body until they are fit for life
on  their own.  Many types of marsupials are only found in Australia
and  New Zealand.  This is because early during their speciation the
continents  separated  (the  breakup of Pangaea), isolating Australia
from the rest of the world.

Placentals  give  birth  to completely developed offspring that feed
from  the  milk  produced  by  the mother's mammary glands.  After a
short period of milking they are ready to start life on their own.

Mammals are very familiar to us:  rodents, canines and felines (dogs
and  cats),  ruminants  (cows), and others.  Those most important in
human evolution are the primates.

Primates  originated  in the Early Tertiary period, after the demise
of  the  dinosaurs.   They  were omnivores rather than insectivores.
They adapted to life in trees, one of their fundamental evolutionary
steps was the development of a grasping hand with an opposable thumb.
Another adaptation was the forward migration of the eyes, which
provides stereoscopic or three dimensional vision.

Primates known to us are the simians (monkeys) and anthropoideans
(man-like).

                > 184 <


Simians  were  preceded  by  prosimians, which gave rise to the true
monkeys  and  apes  of the simians.  In the anthropoideans there are
three  groups:   New World monkeys, old World monkeys and Hominoids,
which  includes  human  beings  and apes.  The only one we will talk
about in some detail is the Hominoids.

HOMINOIDS AND HUMAN EVOLUTION
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The  hominoids  include  the chimpanzee, the orangutan, the gorilla,
the  gibbon  and  human beings.  It isn't until the Oligocene
(-35-24 million  years ago) that these groups start differentiating.
Of all these  groups, one genus dating back to the late Miocene (-5 million
years ago) is apparently the direct ancestor to modern human beings.
This  is the so-called Ramapitbfecus.  Homo sapiens developed in the
Pleistocene  about 4 million years ago during the glaciation epochs.
The  upright posture and ground-dwelling habits of human beings were
already  established  in  Ramapithecus.   This is also true of other
apes.   Grasping  hands  are  common  to all primates and the use of
tools  is  observed  in  chimpanzees.   Language  has been taught to
chimpanzees  and gorillas, although their vocal chords are different
than  ours.   They can also teach it to their offspring as proven in
some recent experiments.

What  makes  human  beings strikingly different than the rest of the
primates  is their brain capacity--much larger with respect to their
size than  any other primate.The development of a complete, complex
language is also a characteristic of human beings.

Human  beings  are  the  only  animals  that  are capable of totally
modifying  their environment, for better or for worse.  They are the
only  animal  capable  of creating new niches and modifying existing
ones.

Another  characteristic  that  distinguishes  a  human being from an
animal  is  the  ability  to  think  of the long-term future.  Human
beings  and  animals  share the memory of the past and the living in
thepresent, but  human beings are unique in predicting the future
and also in questioning their existence.

There are  three  principal stages in the evolution of early human
beings: Australopithecus,  Homo  erectus, and Homo sapiens.  The first
stageis the one to which the famous Lucy, discovered by Donald Johannsen,
belongs.   The  Australopithecines  were  similar  to  modern  human
beings, but although they used tools and weapons, they

                > 185 <

had  very  small brains.  Homo erectus lived at the same time as the
Australopithecines,  and  may  have  developed  independently.   The
species  was  more  advanced  than  the Australopithecines and had a
higher  brain  capacity.   They used stone tools, such as hand axes,
made  from flint.  This specles became widely distributed and is the
direct ancestor of modern human beings.

Fossils  of  Homo erectus range in age from 700,000 to 200,000 years
old.   Homo  sapiens  is  contemporaneous  in age with Homo erectus,
appearing  for  the first time 500,000 years ago.  The first example
of  sapiens  is  Neanderthal  Man,  a  large-boned race that lived
100,000  years  ago.  After sapiens originated, different historical
ages developed, such as the Paleolithic and Neollthic.

        --------------------------------------------

FOOD CHAINS
~~~~~~~~~~~
A  subject  of  great  importance  in  a  world with an ever-growing
population  is  the  availability  of  food.   The  food chain is an
organisational  scheme that describes which organisms feed on which,
and  which ones are essential for the survival of the others.  It is
like a pyramid because the organisms at the base are most abundant.

At  the  base of our food chain are organisms that produce their own
food:   photosynthetic  organisms  such  as  bacteria,  plants,  and
plankton   in   the  oceans.   Upon  these  feed  higher  organisms,
herbivores  (plant-eaters)  and  omnivores  (eating  both animal and
vegetable  matter).  If the plants were to die, all cows will die as
a consequence--there would be no food left for them.

On  top  of  herbivores at the peak of the food chain are carnivores
(animal-eaters)  and  omnivores.   Good  examples are lions, tigers,
cats, dogs and humans.

If  we kill photosynthetic organisms by deforestation, polluting the
oceans or by other environmental problems, we affect the base of the
food  chain  and  decrease the possibility of survival of the top of
the chain--including ourselves.

        --------------------------------------------

MASS EXTINCTIONS
~~~~~~~~~~~~~~~~

Mass  extinctions  are very important events that affect the rates at
which  evolution  occurs.  A mass extinction is defined as the death
of 70% or more of the total biomass of the planet at any given time.
Biomass  is  the  total  weight  of all living matter on the planet.
Mass  extinctions  have occurred at least five times in the geologic
past  within  the  Phanerozoic alone.  Extinctions during and before
the Cambrian are difficult to document.

The  most massive extinction known occurred 225 million years ago at
the  Permian-Triassic  boundary.   Another  one occurred at the next
boundary, Tria-

                > 186 <

ssic-Jurassic,  about  190 million years ago.  During the Cretaceous
another important extinction occurred around 100 million years ago.

The   second  largest  extinction  was  at  the  Cretaceous-Tertiary
boundary,   when   all  the  dinosaurs  became  extinct.   The  mass
extinction  of the dinosaurs has become very famous partially due to
the   hypothesis   that   the   cause   of  the  extinction  was  an
extraterrestrial object:  a meteorite.

Mass extinctions are important because even though a large sector of
the  population  was  wiped  out,  niches  were  left  available for
newcomers  that  could  adapt very fast and evolve rapidly into many
new  species.   This  seems to be the case after every extinction--a
new  group of living organisms takes over and evolves at a very high
rate.  During periods of time without mass extinctions, species also
become  extinct,  but  at a low rate, an event known as a background
extinction.   Evolution  also  takes  place  very slowly during such
periods.

Are  mass  extinctions catastrophic or are they gradual events?  The
debate  continues.   It was generally believed that mass extinctions
were  a  slow,  gradual  process  like  evolution  but more and more
evidence is being uncovered concerning the sudden disappearance of
many  unrelated  species  at the same time.  This has been proven at
the  Cretaceous-Tertiary  boundary, where within one cen- timeter of
rock  (which  corresponds  to a relatively short period of time) all
evidence  of Cretaceous fossils disappears and Tertiary fossils come
into  play.   This  kind  of  boundary  impact  layer can be seen in
Gubbio, Italy.

NEMESIS AND THE IMPACT THEORY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We  have  mentioned  the  extinction  65  million  years  ago at the
Cretaceous- Tertiary boundary of dinosaurs.  Dinosaurs were not the
only  animals  that died:  ammonites very important marine fossils,
also went extinct, as well as many other land and marine animals and
plants.

One  of  the  marine groups that went extinct is the planktic forams
(small,  calcareous,  floating  unicellular  organisms that lived in
Cretaceous  seas).   These  organisms are found in limestones in the
Apennines  of  Italy.   The last bed of the Cretaceous limestone has
bi~  planktic  forams;  the  first bed of the Tertiary has one small
planktic  foram  and  nothing  else.   In between is a layer of clay
about 3 cm thick known as the "boundary clay."

In  1980,  Luis  and Walter Alvarez from UC Berkeley took samples of
that  clay to measure the amount of an element called irldium, which
is  not  very  abundant  on the Earth's surface but more abundant in
extraterrestrial  objects.   Iridium rains at a constant rate, which
made it very useful for measuring the amount of

                > 187 <


time  it took to deposit the layer of clay and therefore how long it
took  for  the extinction to happen.  When they measured the samples
of  boundary  clay,  they  found  that  the  levels  were low in the
limestone above and below the clay, but within the clay, iridium was
at a high peak--at the same level as that in meteorites and comets.

They  hypothesized  that the extra iridium was from extraterrestrial
sources,  and that at the time of the Cretaceous-Tertiary extinction
there  had  been  a large meteorite (10 km in diameter) that had hit
the  Earth.   The  dust  from  the  impact  would have gone into the
atmosphere,  causing  total  darkness for several months, inhibiting
photosynthesis  and  cutting  the  food  chain  at  the base.  Other
effects  of  the  impact would have been extreme cold, heat and also
acid rain.  Other evidence for impact, such as shocked minerals, was
found in Italy and in another 100 sites around the world, which made
plausible the global mass extinctions.

Against  this  hypothesis  is the fact that the crater of the impact
has not been found, which may mean that it occurred in the ocean and
that part of the ocean has been subducted--it has moved underneath a
ridge in plate tectonic activity.

This  hypothesis  led to findings of many impact craters and also of
other   boundaries  associated  with  iridium  anomalies.   It  also
generated  interest  in extinctions that seemed to repeat themselves
periodically.

A  study by two paleontologists from Chicago showed that there was a
certain cyclicity to extinctions occurring every 26-28 million years.
This  led  Rich  Muller,  an  astrophysicist  at  U.C.  Berkeley, to
hypothesize that the Sun has a companion star, Nemesis, which orbits
around  the Sun in a tulip orbit with a period of 26-28 million years
and  that  at  its  perihelion  it  disturbed  a  belt of comets and
asteroids  outside the Solar System.  This sent comets and asteroids
into the inner Solar System and caused periodic comet showers on the
Earth, and as a consequence, periodic extinctions.

The   original   statistical   data   showing  periodicity  in  mass
extinctions were sketchy and poorly constrained.  To base Nemesis on
it  was an exercise in creativity--the search for Nemesis has so far
been unsuccessful.

VOLCANISM
~~~~~~~~~
For  many  a  geologist,  accepting  a catastrophic extraterrestrial
event  has  been  difficult, so, two Earth scientists from Dartmouth
University  proposed  that  the extra iridium came from big volcanic
eruptions  occurring  at the same time as the extinctions.  This was
hypothesised because iridium was found in the gases


                > 188 <

emitted  by  Kilauea.   A  candidate for the big volcanic event that
would  have  sent  the  iridium  and  dust in the atmosphere to stop
photosynthesis  and  kill the dinosaurs would be the Deccan Traps of
India,  a big basaltic eruption dated at 66 million years.  However,
no  evidence  of iridium has been found in the Deccan Traps, and the
type of volcanic eruption of these basalts was quiet and not violent
enough  to  send  material into the stratosphere to orbit around the
Earth  (as required by the global distribution of iridium).  It also
would not produce impact minerals, although some scientists claim it
does  (no evidence has been uncovered as to this effect).  Volcanism
may  have  had  something to do with local extinctions, but not at a
global level.

GLACIATIONS
~~~~~~~~~~~
Finally,  many  argue  that climatic fluctuations and changes in sea
level could have caused sudden extinctions.  Although there are data
to  support  contemporaneous extinctions and climatic changes, it is
hard to see how gradual changes in the climate, changes in sea level
and  slow  glaciation, and interglaciation periods could have caused
sudden  mass  extinction of all types of animals, even those used to
living in cold climates.

                > 189 <


HUMAN CIVILISATIONS AND TECHNOLOGY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The   developments--and   disintegrations--of   civilisations   span
thousands  of  years, encompassing spectacular advances in knowledge
and  sharply  disruptive  disturbances  on  the  human and planetary
scale.   This  section  will  encapsulate  the  development of human
endeavour  from  the  Paleolithic  to  the Atomic Ages, outlining the
technological  movements  that  have  accompanied  and  spurred  the
advance of culture.

Civilisation is generally regarded as culture with a relatively high
degree of elaboration and technical development, often demarcated by
the  complex  of  cultural  elements  that  first  appeared in human
history  6,000  to  8,000  years ago.  At that time, on the basis of
agriculture,  stock-raising  and  metallurgy, intensive occupational
specialisation  began  to  appear  in  the river valleys of SW Asia.
However,  the  roots of those circumstances long predate that period
in  several  parts  of  the  prehistoric world:  Mesopotamia, Egypt,
China, Greece, India, Highland Peru, and elsewhere.

The specific characteristics of civilisation--food production, plant
and  animal domestication, metallurgy, a high degree of occupational
specialisation,  writing and the growth of cities--had their origins
in  the Old Stone Age, the earliest period of human development
and the longest phase of humanity's history.

The  Old Stone Age is approximately coextensive with the Pleistocene
geologic period, beginning about two million years ago and ending in
various  places  between  40,000  and  10,000 years ago, when it was
succeeded by the Mesolithic Period.

By  far  the  most outstanding feature of the Paleolithic period was
the  evolution of humans from an apelike creature, or near human, to
true  Homo  sapiens.   This  development  was  exceedingly  slow and
continued  through the three successive divisions of the period, the
Lower, Middle and Upper Paleolithic.

The  most  abundant remains of Paleolithic cultures are a variety of
stone  tools  whose distinct characteristics provide the basis for a
system of classification containing several toolmaking traditions or
industries.   The  oldest  recognisable tools made by members of the
family  of  humankind  are  simple  stone  choppers,  such  as those
discovered  at Olduvai Corge in Tanzania.  These tools may have been
made  over  one  million  years  ago  by Australopithecus or by Homo
habilis.    Fractured   stone   "tools"  called  eoliths  have  been
considered  the  earliest  tools,  but  it  has  been  difficult  to
distinguish human-made from naturally produced modifications in such
stones.


                > 190 <


THE LOWER PALEOLITHIC
~~~~~~~~~~~~~~~~~~~~~
Lower  Paleolithic  stone industries of Homo erectus have been found
at  various  sites  in  China,  Europe,  Africa and Asia dating from
100,000 to 500,000 years ago.  The stone tools of this period are of
the core type, made by chipping the stone to form a cutting edge, or
of  the  flake  type,  fashioned  from fragments struck off a stone.
Hand  axes  were  the  typical  tool of these early people, who were
hunters and food gatherers.

THE MIDDLE PALEOLITHIC
~~~~~~~~~~~~~~~~~~~~~~
The Middle Paleolithic period is often associated with Neanderthals,
living  between  40,000  and 100,000 years ago.  Neanderthal remains
are  often  found  in  caves  with  evidence  of  the  use  of fire.
Neanderthals  were hunters of prehistoric mammals and their cultural
remains, though unearthed chiefly in Europe, have also been found in
N Africa, Palestine and Siberia.

Stone  tools  of  this  period  are of the flake tradition, and bone
implements,  such  as  needles,  indicate that crudely sewn furs and
skins were used as body covering.

THE UPPER PALEOLITHIC
~~~~~~~~~~~~~~~~~~~~~
The  Upper Paleolithic saw the disappearance of Neanderthal in favour
of  other  Homo  sapiens  such  as  Cro-Magnon.   The  beginnings of
communal  hunting  and  fishing  are  found  here,  as  is the first
conclusive  evidence  of  belief  systems centering on magic and the
supernatural.  Pit houses, the first human-made shelters were built,
sewn  clothing  was  worn,  and  sculpture  and painting originated.
Tools were of great variety, including flint and obsidian blades and
projectile points.

The  final  and  perhaps  most  impressive  phase of the Paleolithic
period  is the Magdalenian period, in which communities of fisherman
and  reindeer  hunters  used  highly  refined  and  varied tools and
weapons, and left an impressive array of cave paintings.

        --------------------------------------------

THE MESSOLITHIC PERIOD
~~~~~~~~~~~~~~~~~~~~~~
This  period  began  with  the  end  of  the last glacial period and
involved  the  gradual  domestication  of plants and animals and the
formation  of  settled communities at various times and places, some
overlapping  into  the  considerable  development  of  the Neolithic
period.

Characteristic  of  the  period were hunting and fishing settlements
along  rivers  and  on  lake shores.  Pottery and the use of the bow
began  to  develop.   Hafted  axes  and bone tools were found in the
Baltic  region  and  N  England,  demonstrating strong advances over
Paleolithic crudity.

                > 191 <


The  Mesolithic  period  in several areas shows a gradual transition
from a food- collecting to a food-producing culture.

        --------------------------------------------

THE NEOLITHIC REVOLUTION
~~~~~~~~~~~~~~~~~~~~~~~~~
Toward  the  end  of  that last ice age, some 15,000 to 20,000 years
ago,  a  few  of  the  human  communities  that were most favoured by
geography  and  climate  began  to make the transition from the long
period  of  Paleolithic  savagery  to  a  more  settled  way of life
depending on animal husbandry and agriculture.

This  period  of transition led to a marked rise in population, to a
growth  in  the  size  of communities, and to the beginnings of town
life.   It  is  sometimes  referred  to  as the Neolithic Revolution
because the speed of technological innovation increased so greatly
and  the social and political organisation of human groups underwent
a corresponding increase in complexity.

The  earliest  known development of Neolithic culture was in SW Asia
between  8000  B.C.   and  6000  B.C.   Settled villages cultivating
wheat,  barley  and millet and raising cattle, sheep, goats and pigs
expanded.   Neolithic  culture  and  its  innovations spread through
Europe,  the  Nile  valley,  the  Indus valley ~ndia) and the Yellow
River valley (China).

By  1500 B.C., Neolithic cultures based on the cultivation of maize,
beans,  squash  and  other  plants  were present in Mexico and South
America, leading to the rise of the Inca and Aztec civilisations and
spreading  to  other  parts  of the Americas by the time of European
contact.

        --------------------------------------------

THE BRONZE AGE
~~~~~~~~~~~~~~
This is the period in the development of technology when metals were
first  used regularly in the manufacture of tools and weapons.  Pure
copper   and   bronze,  an  alloy  of  copper  and  tin,  were  used
indiscriminately at first; this early period is sometimes called the
Copper Age.


The  earliest  use  of cast metal can be deduced from clay models of
weapons;  casting  was  certainly  established in the Middle East by
3500 B.C.  In the New World, the earliest bronze was cast in Bolivia
A.D.   c.11O0.   The Inca civilisation used bronze tools and weapons
but never mastered iron.

                > 192 <


The  development of a metallurgical industry coincided with the rise
of  urbanization.  The organised operations of mining, smelting, and
casting  undoubtedly  required  the  specialisation of labour and the
production of surplus food to support a class of artisans, while the
search for raw materials stimulated the exploration and colonisation
of new territories.

        --------------------------------------------

THE IRON AGE
~~~~~~~~~~~~
This  period  begins with the general use of iron and continues into
modern  times.   The  use  of  smelted iron ornaments and ceremonial
weapons  became common during the period extending from 1900 to 1400
B.C.  About this time, the invention of tempering, the strengthening
of  a  metal  by the application of heat or by alternate heating and
cooling, was made in the Hittite empire.  After its downfall in 1200
B.C., the great waves of migrants spreading through S Europe and the
Middle East ensured the rapid transmission of iron technology.


The  casting  of  iron  did  not become technically useful until the
Industrial  Revolution.   The  people  of the Iron Age developed the
basic  economic  innovations  of  the  Bronze  Age  and  laid the
foundations  for  feudal  organization.  Ox-drawn plows and wheeled
vehicles  acquired  a  new  importance  and changed the agricultural
patterns.    For   the  first  time  humans  were  able  to  exploit
efficiently  the temperate forest.  Villages were fortified, warfare
was  conducted  on  horse-  back  and  in  horse-drawn chariots, and
alphabetic   writing   based  on  the  Phoenician  script  became
widespread.

        --------------------------------------------

CLASHES, CONQUESTS AND CHANGE.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Technical  advances  in weaponry and warfare helped an insignificant
pastoral  settlement  in  Rome  to  become  perhaps the world's most
successful  empire supreme  as  a lawgiver and organiser, holding
sway over virtually all the then- known world.

From  the  establishment  of  the  Roman  republic  around  500 B.C.
successive  generations  of  Roman rulers expanded their territorial
acquisitions,  and  thus absorbed and exported the leading material,
social and intellectual advances of the day.

From the age of Caesar, (60 B.C.) Rome was foremost as the civiliser
of  barbarians  and  the  ruler  of  the  older  world.   The empire
promulgated   the  ideals  of  Greek  literature,  architecture  and
thought.   The  extensive  system of Roman roads made transportation
easier  than it was again to be until the development of railroads A
postal service was organised; commerce and industry, particularly by
sea, were greatly developed.

                > 193 <

At   its  height,  imperial  Rome  counted  well  over  one  million
inhabitants.   It  was  well-policed,  sanitation was excellent, and
among  the  rich, such luxuries as central heating and running water
were  not  unknown.  Decline came quickly, however.  In 476 the last
emperor  of  the  West,  appropriately  called Romulus Augustus, was
deposed  by  the Goths; this date is commonly accepted as the end of
the West Roman Empire, or Western Empire.

The  so-called  Dark  Ages that followed in Western Europe could not
eradicate the profound imprint left by Roman civilisation.


This term is usually applied to the social and economic changes that
marked  the  transition  from  a  stable agricultural and commercial
society  to a modern industrial society relying on complex machinery
rather  than tools.  Historically, it refers primarily to the period
in British history from the middle of the 18th century to the middle
of  the  19th  century.  Dramatic changes in the social and economic
structure took place:  inventions and technological innovations cre-
ated  the  factory system of large-scale machine production, greater
economic   specialisation   emerged  and  the  labouring  population,
formerly  employed  pre- dominantly in agriculture (where production
was  also  on  the  rise),  increasingly  gathered in great urban
factory  centres.   The  same process occurred at later times and in
changed tempo in other countries.

There  has  been  much  objection  to  the  term  because  the  word
"revolution"  suggests sudden, violent, unparalleled change, whereas
the transformation was, to a great extent, gradual.  Some historians
argue  that  the  13th  and  16th  centuries  were  also  periods of
revolutionary  economic  change.   The  ground  was  prepared by the
voyages  of  discovery  from  Western  Europe  in  the 15th and 16th
centuries,  which  led  to a vast influx of precious metals from the
New  World,  raising  prices,  stimulating industry, and fostering a
money  economy.  Expansion of trade and the money economy stimulated
the development of new institutions of finance and credit.

In  Britain's  productive process, coal came to replace wood.  Early
model  steam  engines  were introduced to drain water and raise coal
from  the  mines.  Factories and industrial towns sprang up.  Canals
and  roads  were  built,  and  the  advent  of  the railroad and the
steamship  widened  the market for manufactured goods.  The Bessemer
Process made a gigantic contribution, for it was largely responsible
for  the  extension  of the use of steam and steel that were the two
chief  features  of industry in the middle of the 19th century.  The
transformation  of  the United States into an industrial nation took
place  largely  after  the  Civil War and on the British model.  The
Industrial Revolution was introduced by Europeans into Asia,

                > 194 <

and  the  last  years of the 19th and the early 20th century saw the
development of industries in India, China and Japan.

The  Industrial  Revolution created a specialised and interdependent
economic  life  and  made urban workers more completely dependent on
the  will  of  their  employers  than  the  rural  workers had been.
Relations between capital and labour were aggravated, and Marxism was
one product of this unrest.

The  Industrial  Revolution changed the face of nations, giving rise
to  urban centres requiring vast municipal services.  Technology was
praised  by  some  factions as the mainspring of social progress and
the  development  of democracy, and criticised by others as the bane
of  modern  man,  responsible for the tyranny of the machine and the
squalor of urban life.

Machines  had  vastly increased production, eased the toils of labour
and  raised  living  standards, but often at a cost of environmental
pollution,  depletion  of  natural  resources,  and  the creation of
unsatisfying jobs.

        --------------------------------------------

THE ATOMIC AGE
~~~~~~~~~~~~~~
With  the  advent  of  the  Atomic Age we must face the contemporary
dilemma   of   a  highly  technological  society  contemplating  the
possibility  that it could use its sophisticated techniques in order
to  accomplish  its own destruction.  It is not a firm assumption to
identify  technology  with  the "progressive" forces in contemporary
civilisation.    The   forces  of  technology  will  continue  their
seemingly  inexorable  advance, bringing us in vitro fertilizations,
global   satellite  communications,  genetic  manipulations  and  B2
bombers,  but  the  wisdom  to  manage  these  innovations  is not a
guaranteed part of the package.

                > 196 <


THEORIES OF THE EARTH - THE GAIA HYPOTHESIS.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
SimEarth  is  centered  around  a hypothesis of the evolution of the
Earth,  life and atmosphere known as the GAIA HYPOTHESIS, proposed by
James  Lovelock.   The  Gaia  hypothesis  is  a holistic approach to
understanding   life   and   natural   phenomena   as   teleological
circumstances,  that is, as existing because they fill a purpose and
not  just  because  of happenstance.  Here is a brief explanation of
what  the  Gaia  hypothesis  is  and  a few of the examples given by
Lovelock.

SYSTEMS
~~~~~~~
Before  we  start  talking  about  Gaia  we  need to define what the
feedback  mechanisms  "positive"  and  "negative"  mean.  A positive
feedback loop is also known in systems theory as a vicious circle or
catastrophic  loop.  As illustrated in Figure 20, a positive loop is
the  one  that  causes  continuous increase or decrease of a certain
condition resulting in a catastrophe.  A negative feedback loop is a
self-regulating  feedback loop or virtuous circle:  a mechanism like
a  thermostat,  where  if  a  certain  condition increases, the next
decreases, resulting in equilibrium or self-regulation.

Most  of  Earth's systems, like the carbon cycle and the atmospheric
hydrologic  cycle,  are self-regulatory and tend toward equilibrium.
Nonetheless,  most  systems  can  be  driven over the edge and would
never be able to self-regulate again if a certain critical threshold
of  one  of  the  conditions  is  reached.   This  could happen with
atmospheric CO2.


GAIA
~~~~
The  Gaia  hypothesis  comes in two versions:  the weak Gaia and the
strong  Gaia.   The  strong  Gaia says that the Earth is alive.  The
weak  Gaia says that life may have some regulatory effect on some of
the  dynamic  systems of the planet.  We will explore in this manual
only  the strong Gaia version.  Please understand that although this
hypothesis  is controversial and therefore not generally accepted in
the  scientific  community,  it  provides  a  useful  framework  for
understanding the Earth.


Gaia  was  developed  by Lovelock during the time NASA was preparing
the   Viking  explorer  for  a  trip  to  Mars.   He  was  designing
instrumentation  to  test  if there was life there.  But in order to
test  for  life,  Lovelock  had to ask the question, "What is life?"
This  work  provided  Lovelock  the  opportunity  to reevaluate this
fundamental question.

                > 196 <


Lovelock  realised  that  we needn't go to Mars to find out if there
was  life,  because if there were, we would see changes reflected in
its  atmospheric composition and other planetary features like those
we  see on the Earth, which has a very peculiar atmosphere.  Life as
we know it would affect the planet's atmosphere, as shown in Table 5.


GAS        VENUS         EARTH        MARS        EARTH
------    ----------    --------    -----------    ----------
CO2(%)    96.5        98        95        0.03
N2(%)    3.5        1.9        2.7        79
O2    trace        0.0        0.13        2.1
Ar    70.ppm        0.1        1.6        1
Methane    0.0        0.0        0.0        1.7 ppm

Surf.Temp 459C        240-340C    -53C        13C
Total Pressure 90 bars  60 bars          .0064 bars     1.0 bars

Table 5: Origin of atmospheric composition.

DAISYWORLD
~~~~~~~~~~
Lovelock  invented  a  very  simple world model called Daisyworld to
explain   the  tenets  of  the  Gaia  hypothesis.   The  parable  of
Daisyworld  begins  by  explaining that it is a fictitious planet in
which  the  life is represented by different-coloured daisies:  dark,
light and neutral colors.

The planet is at the same distance from the Sun as the Earth, is the
same  size  as  the  Earth  and has a little more land area than the
Earth.   On this planet there is enough CO2 for daisies, but it does
not affect the climate like on the Earth and clouds do not exist.

The Sun increases its heat output with age.  The optimum temperature
for  daisies  is  about 20ø C.  If the planet gets colder than 5C,
daisies will not grow.  If it gets hotter than 40C, they will die.

The  average  temperature of the planet is determined by the albedo,
which  is  determined  by  the  color  of the daisies.  A dark daisy
absorbs  more  heat  and  the  temperature  rises;  a  lighter daisy
reflects more heat and the temperature falls.  This effect will make
white  and  dark  daisies  alternate  in  population size until they
eventually  reach  equilibrium,  a  condition  in  which  all acting
influences  are cancelled by others resulting in a stable, balanced,
or unchanging system.  The

                > 197 <

effect  will  also  control the temperature of the planet.  When the
Sun  gets  hotter the temperature cannot be regulated anymore by the
daisies and they die--the planet becomes barren.

The  Daisyworld  model  illustrates the following tenets of the Gaia
theory:

1. Living organisms grow vigorously, exploiting any environmental
   opportunities that open
2. Organisms are subject to the rules of Darwinian natural selection
3. Organisms affect their physical and chemical environment, by
   breathing, for example
4. Limits of constraints and bounds establish the limits of life

A  version  of  the  Daisyworld  program  is  included as one of the
SimEarth  scenarios.   There is a complete discussion of how and why
Daisyworld works in the "Scenarios" chapter.

        --------------------------------------------


EVIDENCE OF REGULATION BY LIFE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Lovelock's  book,  The  Ages of Gaia, examines the pollution of the
atmosphere by oxygen producers and its consequences.

Many nations are extremely concerned about global warming, but it is
not  clearly understood how the Earth regulates the amount of CO2 in
the  atmosphere.   From  the  very  beginning  of life, CO2 has been
important  in  providing  food  for  photosynthesizers,  and  as the
thermal  cover  to  keep  us  warm.   Biota Qife3 pumps CO2 from the
atmosphere;  its  level has been going down for the last 3.6 billion
years.

The  increase  in CO2 due to the burning of fossil fuels is not much
more  than a minor disturbance to the Earth, but tends to offset the
decline.  Even though the quantities humans add may be small, if the
CO2  regulatory  mechanism is reaching its capacity, then the plants
that  evolved as the CO2 levels declined through Earth's history may
be  affected.   Also,  the  rapid  rise  of  CO2  levels  since  the
Industrial Revolution may indicate that the regulatory pumps are not
working properly to remove the excessive CO2 from the atmosphere.

This  change  in  CO2  is similar to the one that occurred naturally
from  the  last  ice  age,  so  it may affect the climate as much as
between  the  last ice age and now.  We do not know enough about the
CO2 system to predict if the perturbation will self- regulate, cause
oscillations, chaotic changes or total failure.

                > 198 <


The  possible  climactic changes due to the increase in CO2 probably
won't  have  tragic  consequences for the Earth and life as a whole,
but it may wipe out humanity along with many other species of plants
and animals.


GEOLOGY

1. Francis, Peter, 1976, Volcanoes, Penguin Books, England
2. Press, F. and Siever, R., 1986, Earth, fourth edition, Freeman,
   New York
3. Skinner, B.J., and Porter, S.C., 1989, The Dynamic Earth, J. Wiley and Sons,
   New York
4. Uyeda, S1978, The New View of the Earth, Freeman, New York

CLIMATE

1. Iribarne, J.V., and Cho, H., 1980, Atmospheric Physics, Reidel
   Publishing Co.,   Holland
2. Neiburger, M., Edinger, J.G., and Bonner, W.D., 1982, Understanding Our
   atmospheric environment.Freeman, New York
3. Riehl, H., 1978, Introduction to the Atmosphere, McGraw-Hill, New York
4  Ross, D., 1988, Introduction to Oceanography, Prentice-Hall, New Jersey

LIFE

1. Lane, G., 1978, Life of the Past, Charles Merrill Publishing Co., London
2. McAlester, A.L., 1977, The History of Life, Prentice-Hall, New Jersey
3. Muller, R., 1988, Nemesis, the Death Star, Weidenfeld and Nicolson,
   New York

GAIA
1. Lovelock, J., 1988, The Ages of Gaia, Norton, New York
2. Myers, Norman, 1984, Gaia, an Atlas of Planet Management, Anchor Press,
   New York

                > 199 <


PROBLEMS AND SOLUTIONS
~~~~~~~~~~~~~~~~~~~~~~~
Here  is  a listing of common problems and challenges you will face,
their causes, and some suggestions on how to deal with them.

PLANET OVERHEATING
~~~~~~~~~~~~~~~~~~
First,  check  CO2  levels.   If  high,  use Oxygenator, or increase
Biomes to reduce CO2 levels.

You  can  also  turn  down solar input, raise cloud albedo, and turn
down greenhouse effect.

EVOLUTION IN THE WATER SEEMS TO STOP
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Most  advanced  aquatic  life forms live in shallow water.  If there
are  not  enough  shallow  shelves,  you  will  hit  an evolutionary
dead-end.   You can create shelves either by raising the ocean floor
or  lowering  the  land.  You can raise the ocean floor with the SET
ALTITUDE tool or with volcanos.  You can lower the land with the SET
ALTITUDE tool or with meteors.

"... NEEDS ENERGY"
If  you  see  a  message  that  says  that  one  of  the disciplines
(Philosophy,   Science,   Agriculture,  Medicine,  Art/Media)  needs
energy,  increase  their  share  of  energy  in the CIVILISATION MODEL
CONTROL PANEL, or increase the overall level of energy.

Overall  energy  is  increased  by  doing  more  work, by increasing
population,  and  by  concentrating  on  the  most  efficient energy
sources.

METEOR STORM
~~~~~~~~~~~~
This  is  a warning that extinctions are imminent.  There's not much
to  be  done  except  prepare for the worst and get ready to rebuild
your biomass:

MASS EXTINCTIONS
~~~~~~~~~~~~~~~~
Mass  Extinctions  are  caused by too much dust or too little oxygen
(<20%) in the atmosphere.

Dust  is  put  into  the  atmosphere by volcanos and meteor impacts.
Nothing but time removes dust from the atmosphere.

If  oxygen  levels  are  below  20%, use the Oxygenator terraforming
tool, or increase biomes.

                > 202 <



FUELS RUNNING LOW
~~~~~~~~~~~~~~~~~
This is a warning that war is imminent.  Change your energy usage to
conserve fuels.

NUCLEAR DETONATIONS
~~~~~~~~~~~~~~~~~~~
Nuclear  war  is  in  progress.   In  SimEarth,  this  is  caused by
competition for limited nuclear fuels.  Reduce investment in nuclear
energy to halt the wars.

NUCLEAR WINTER
~~~~~~~~~~~~~~
Caused  by  the  radiation  and  dust  in  the  air that result from
numerous   nuclear   explosions.    Cut  back  on  fuel  usage,  and
concentrate on keeping small pockets of your sentient species alive.
Eventually the dust will settle and the radiation zones will vanish.
Tidal  waves  can  help  clean up radiation in the oceans and on the
shores.

POLLUTION
~~~~~~~~~
Pollution  comes from industrial age technologies, as well as fossil
fuel  usage.   The best solution is to invest in science and advance
to the atomic era as quickly as possible.


                > 203 <


Aerobic--Requires  oxygen.   This  can apply to animals, machines or
processes.

Air  Pressure--The  pressure  caused  by  air  molecules
bouncing   against  a  surface.   Vacuum  has  no  air  pressure.

Albedo--The  reflectivity  of a surface.  A surface with high albedo
will  reflect  sunlight.   A  surface  with  low  albedo will absorb
sunlight.   Snow  (high  albedo) reflects sunlight and remains cold.

Anaerobic--Does  not  require  oxygen.   This  can apply to animals,
machines  or processes.

Arctic--Areas that are snow or ice covered.
Cold  and  dry.   See  Tundra.

Arthropod--The phylum of animals which includes insects, crustaceans,
arachnids,  and  myriapods.

Atmosphere--The  blanket  of  gases which envelop a planet.

Atomic Age--This  era  is  characterised by Nuclear Power, Aircraft, Radio,
and Chemical Fertilisers.

Axis--The planetary centre of rotation.  On Earth,  the  axis is
a line passing from the north pole to the south pole.

Biomass--The  total  dry  weight of all living material on a
planet.

Biome--A  major  ecosystem  such  as  temperate grassland,
forest or desert.

Biome Factory--A SimEarth tool which produces the best biome for
the environment it occupies.

Biosphere--The areas of a  planet  which are inhabited by life.  On
Earth this is the crust, hydrosphere,  and  lower  atmosphere.

Boreal--Also  known as Boreal Forest.  Biome designed for cool
regions with airborn moisture. The trees are usually conifers.

Bronze--An alloy of tin and copper that is  stronger than either.

Bronze Age--This era is characterised by bronze  tools,  sail  ships,
clay  tablets  and irrigation.

Carbon Dioxide  (CO2)--A  gas  composed  of  two oxygen atoms and one carbon
atom. This gas is used by plants in photosynthesis and produced by
organisms  as they respirate.

Carnifers--A SimEarth name for mobile, carnivorous plants.The Venus Flytrap
is the precursor to carniferns.

Cetaceans--The  order  of  mammals that is exclusively aquatic.
This includes dolphins and whales.

CO2 Generator--A SimEarth tool that creates carbon dioxide for the
atmosphere.

Class--The  classification  of life under Phylum.  The major classes
of  Chordata  are  fish, amphibian, reptile, avian, and mammal.  See
Order.

                > 204 <

Cloud Albedo--The albedo of clouds. High cloud albedo can keep Earth cool.
See Albedo

Conifer--Cone-bearing trees and shrubs. This includes evergreens, pines and
firs.

Continental drift--The theory that continents have changed position
on Earth. This is a component of Plate Tectonics.

Core--The extremely dense, fluid centre of Earth. It is probably
composed of molten iron. See Mantle.

Crust--This thin outer shell of the Earth is only a few miles
deep. See Mantle.

Clyosphere--The frozen regions such as the icecaps, tundra, and mountain
glaciers.

Desert--An ecosystem suited for hot weather and little water.

Dry Weight--The mass of an organism after the water has been removed.

Dust--In SimEarth, dust refers to airborne dust, ash and detritus. This
can darken a planet, reducing photosynthesis and absorbing heat.

Ecosystem--A group of plant and animal species living together in rough
balance.

Eukaryote--Single-cell microbes with a nucleus.

Evolution--The process by which life has changed and diversified.

Explosive Upwelling--Sometimes hot spots are very hot. This can lead
to a volcano that is a thousand times the size of any seen by
man. These upwellings spew the material for continents and are
possibly Nemesis.

Extinction--The elimination of one species.

Geosphere--See Lithosphere.

Greenhouse Effect--Planetary heating induced by greenhouse gases.

Greenhouse Gases--Certain gases will let solar radiation enter the
atmosphere but not leave. The most common of these are carbon dioxide,
methane, and water vapor.

Hot Spot--Mantle material flows up and down as well as sideways. Hot magma
sometimes rises from the core to the crust creating a Hot Spot. See
Volcano.

Hydrosphere--The water portions of Earth. This includes oceans, lakes,
rivers, and clouds. SimEarth restricts the term to oceans.

Industrial Age--This era is characterised by the use of fossil-fuel
engines, automobiles, telephones, and animal husbandry.

Information Age--This era is characterised by computers, global
communications, robotic labour, and ecologic awareness.

Insolation--Incoming Solar radiation.

                > 205 <

Iron Age--This era is characterised by iron tools, sextants, paper,
the printing press, and horse-drawn plows.

Kingdom--The most general classification of life in Biology. The
five kingdoms are prokaryotae, protoctista (eukaryotes), fungi, plantae
and animalia.

Jungle (Tropical Forest)--A biome that thrives in hot, wet climates.
Lava--The lighter materials of magma that come to the surface via
volcanos and upwellings.

Lithosphere--The rock portions of the planet: Plates, Crust,
Moho, Mantle, and Core.

Magma--Molten rock found beneath the Earth's crust. See Lava.

Mantle--The layer of magma between the crust and core of the Earth.
This area is constantly flowing at a speed measured in centimeters per
year.

Mass Extinctions--At various times in Earth's history large numbers of
species have vanished. Records indicate that at each of these times
between 5% and 50% of the species became extinct. See Nemesis.

Methane (CH4)--A gas composed of one carbon atom and four hydrogen atoms.
It is primarily produced by primitive microbes which currently live in the
intestines of larger organisms.

Microbe--A single-celled organism.

Mollusk--Class of invertebrates that includes snails, mussels and octopus.

Monolith--A SimEarth tool for advancing life. Thank you Arthur C. Clark.

Moho--Also called the Mohorovicic discontinuity. The turbulent region
between the crust and the mantle.

Mutate--When an organism makes an inexact copy of itself. The variability
which allows evolution to occur.

N2 Generator--A SimEarth tool for introducing Nitrogen into the atmosphere.

Nanotech Age--This era is characterised by molecular construction, molecule-
sized machines, and completely automatic production.

Nemesis--The culprit in the periodic mass extinctions (every 25 million
years or so). Identity unknown, the two prime suspects are: Meteors
(caused by a dark star orbiting our Sun) and Explosive Upwellings.

Nitrogen--A gas composed of two nitrogen atoms. It is a heavy, stable gas
comprising 80% of Earth's atmosphere.

Noosphere--"The sphere of mind" which includes society and culture.

Order--The classification of life under Class. The major orders
of mammals are rodents, felines, canines, ruminants, primates and
cetaceans.

Organism--An independent unit of life. All plants, animals and microbes are
organisms.

                > 206 <

Oxygen (O)--A gas composed of two oxygen atoms. This is used by organisms
when they respirate.

Oxygenator--A SimEarth tool that converts carbon dioxide to oxygen.

Photosynthesis--A process that uses light to create energy-storing
chemicals such as sugar. Oxygen is a byproduct of photosynthesis.

Plant--An organism that uses photosynthesis to feed itself.

Plate--A solid piece of the Earth's crust being pushed about by
flowing mantle.

Plate Tectonics--Theory that the Earth's crust is formed of mobile plates
sliding across the mantle. Even the ocean bottoms consist of plates.

Phylum--The classification of life under Kingdom. The major animal phylums
are chordates, arthropods and invertebrates. See Class.

Phytomass--The total dry weight of all plant material on a planet.

Planet--An astral body that orbits a sun.

Planetesimal--An small planet. Small usually means moon-sized or less.

Prokalyote--Primitive single-cell microbes with no nucleus.

Radiate--The class of invertebrates including jellyfish and starfish.

Sapient--An intelligent, tool-using organism.

Stone Age--This era is characterised by stone tools, domestication, fire, and
cultivation.

Surface Albedo--In SimEarth this refers to the albedo of your planetary
surfue.

Swamp--Also known as tropical grasslands. This biome is composed of plants
and animals that thrive in slow shallow water and on muddy shorelines.

Terraform--The process of modifying an entire planet for a particular
purpose.

Trichordate--A SimEarth term for an order of radiates with three radiating
spines.

Tundra--This biome is designed to survive periodic arctic conditions
and year-round cold weather.

Upwelling--When two plates pull apart, lava will flow up between them
forming small rises like the Mid-Atlantic Ridge. See Plate Tectonics.

Vaporator--A SimEarth tool that stimulates global plant growth.

Volcano--When a Hot Spot is over a thin section of crust, a volcano
can erupt. Volcanos spew lava and ash over an area, often forming new
cone-shaped mountains.

Water Vapor (H20)--Water can be a gas with one oxygen atom and two
hydrogen atoms.

Zoomass--The total dry weight of all animal material on a planet.

                > 207 <

                       INDEX
                  =====


Absolute Date     27, 51
Advance Rate         97
Advancement        134
Aerobic 204
Agriculture 47, 88, 99
Air Currents 75, 131
Air Pollution 162
Air Pressure 204
AirSample 49, 91
AirTemperature 74, 81, 91, 131
Air-Sea Thermal Transfer 96, 132
Albedo 171-172, 204
Allocation 87
Alternate Intelligent Species 143
Amphibians 139, 183
Anaerobic 179, 204
Anthropoideans 185
Aquarium 56, 110
Arctic 66, 134, 204
Art/Media 47, 88, 99
Arthropod 137, 181, 204
Asthenosphere 156
Atmosphere 3, 33, 49, 129, 130, 151, 158, 204
Atmosphere Croup 74
ATMOSPHERE MODEL CONTROL
   PANEL 38, 39, 96
Atmosphere-Ocean Interaction 175
ATMOSPHERIC COMPOSITION GRAPH 30, 78, 91
Atmospheric Pressure 130, 132
Atmospheric Transport 173
Atomic Age 143, 195, 204
Atomic Fuel 82
Atomic Test 65, 123
Autoscroll 50
AvailableEnergyDisplay 28, 70, 145
Average Game 55
Avians 140
Axial Tilt 95, 169
Axis 204


Bioenergy 86, 98, 147
Biomass 81, 83-84, 89, 204
Biome 17-18, 49, 65-66, 7S, 134, 204
Biome Factory 62, 204
Biome Preference Chart 66, 135
BIOME PATIO GRAPH 33, 79, 92
Biosphere 3, 49, 151, 204
Biosphere Group 75
BIOSPHERE MODEL CONTROL PANEL 39, 97
Birds 140, 183
Boreal Forest 66, 134, 204
Bronze Age 142, 192, 204

Cambrian Period 181
Cancel 55
Carbon Cycle 162
Carbon Dioxide 81, 91, 129, 162, 204
Carboniferous 182
Carniferns- 60, 141, 204
Cenozoic 182
Cetaceans 138, 204
CH4 81, 91, 129, 206
Cities 61
Civilization 18, 49, 76, 142-144,190
Civilization Group 75
CIVILIZATION MODEL CONTROL PANEL
   40-42, 87, 98
Civilization Time Scale 105-106
Class 204
Climate 131, 132, 167
Climate Overlay Buttons 28, 70
Close Box 21
Cloud Albedo 96, 131, 205
Cloud Cover 177
Cloud Formation 96, 131
CO2 91, 129, 162, 204
CO2 Absorption 97
CO2 Generator 63, 204
Compress Edit Screen 50
Conifer 205
Continental Drift 95, 127, 164, 205
Continental Drift Map 73
Continental Drift Record 77
Convection 158
Convergent Margin 166
Copper Age 192
Core 157, 205
Core Formation 95
Core Heat 95, 127
Coriolis Effect 173
Crust 155, 205
Current Task 31, 83-84, 88-89
Current Tool Display 27, 69


Daisyworld 7, 16, 56, 88, 118-121, 197-198

                > 208 <


Daisyworld Info Box 77
DataLayer Buttons 27 69
DATASOUND MENU 51
Deforestation 172
Deposition 161
Desert 66 134 205
Devonian 181
Dinosaurs 140
Divergent Margin 165
Diversification of Life 181
Diversity 81
Drift Map 32
Dry Weight 205
Dust 205


Earth CambrianEra 56 112
Earth ModernDay 56 114
Earthquake 30 65 124 165
Easy Game 55
Ecosystem 205
Edit 48
EDIT WINDOW 17 23 46 57
EditWindowControl Panel 24 27-28 59
Edit Window Display Area 58
Edit Window Title Bar 57
Efficiency 86
Elevation 58
Empty Space 88
Energy 9 18 86-87 145-147
Energy Ailocation 99
Energy Investment 98
Erosion 95 128 160
Eukaryotes 136 179 205
EventMap 32 73
Event Trigger 64
Events 122-126
Evolution 133 206
Evolution Time Scale 103-104
Examine 34 68
Exodus 126
Experimental Mode 54
Explosive Upwelling 205
External Heat Engine 160
Extinct Function 63
Extinction 205

Fast 51
FiLE MENU 17 48
Fire 65 124
Fish 138 183
Flow Chart 148
Food 82
Food Chain 186
Forest 66 135
Formation of the Oceans 128
Fossil Fuel 86 99 147
Fossil Fuels 82

Gaia 2-3 16 49
GaiaTheory 2-3 6 196
GAIA WINDOW 29 80
Geologic Time Scale 101-102
Geosphere 49 127-128 205
Geosphere Group 72
GEOSPHERE MODEL CONTROL PANEL 25 37-38 95
Glaciation 169 189
glaciers 161
Global Event Map 73
Global Warming 162
Globe 78
Glossary 19 49
GLOSSARY WiNDOW 90
Goal Biomass 89
Goal Population 89
Goto Events 49
GRAPHS 33 91
GRAPHS MENU 25 49 91
Greenhouse Effect 39 96 132 176 205
Greenhouse Gases 205
Growth 84
Gyres 174


H20 (water) 129 207
Habitats 85
Hadley Cells 173
Hard Game 55
Heat Engine 160
Heat Storage 174
Help 19
HELPWiNDOW 20 53
Hide/Show Oceans 73
Highest Technology 85
History 49
HlSTORY WiNDOW 25 40 81
Hominoids 185
Homo Erectus 186
Hot Spot 205
Human Evolution 185
Hurricane 64 122
Hydro/Geo 86 98 147
Hydrologic Cycle 175
Hydrosphere 3 151 205
Hydrosphere Group 73


Ice Meteor 63
Impact Theory 187
Industrial Age 143, 205
Industrial Revolution 194-195
Info Box 22, 76-77
Information Age 143, 205
Input 46
Insects 139
Insolation 169, 205
Intelligence 84
Internal Heat Engine 163
IQ 84
Iron Age 142, 193, 206

J, K, L
Jungle 66, 135, 206
Kingdom 206
Land Life Classes 61
Life 18, 75, 133, 178
LIFE CLASSRATIO GRAPH 33, 79
Life Quality 85
Life-forms 49, 135
Lithosphere 3,151, 156, 206
Load Planet 48
Lovelock, James 2-3

M
Magma 206
Magnetic Field 157
Major Animal 88
Major Daisy 88
Mammals 140, 183, 184
Mantle 155, 206
Map 48
Map Display Icons 72
MAP WiNDOW 21
Map Window Control Panel 21, 72
Map Window Display Area 71
Map Window Title Bar 71
Mars 56, 115-116
Marsupials 184
Mass Extinctions 186, 206
Median Technology 85
Medicine 42, 88-99
Mesozoic 182
Messages 50
Meteor 29, 64, 122
Meteor Impact 95
Methane 81, 91, 129, 206
Microbe 206
Mltochondria 179
MODELCONTROLPANELS 7,17, 37, 46-47, 94
MODELS MENU 25, 49
Moderate 51
Moho 155, 206
Mohorovicic 155
Mollusk 137, 206
Monolith 63, 144, 206
Monsoons 175
Moon 159
Move 36, 67
Moving Tool 67
Music 50
Mutate 206
Mutation Rate 97, 134

N
N2 91, 129, 206
N2 Generator 62, 206
Nanotech Age 143, 206
Nemesis 187, 206
Neolithic 192
New Planet 26, 48
NEW PLANET WiNDOW 26, 54
Niches 181
Nitrogen 91, 129, 206
Nuclear 146-147
Nuclear Energy 86, 99, 146
Nucleic Acids 178


o2 81, 91, 129, 207
Ocean Currents 74, 131
Ocean Temperature 32, 73
Oceanic Transport 174
Oceans 158, 168
OPTIONS MENU 37, 49
Organism 206
Origin of Life 178
Origin of the Earth 153
Oxygen 81, 91, 129, 207
Oxygenator 62, 207
Ozone Layer 171

P, Q
Paleolithic 191
Paleozoic 181-182
Pangaea 163
Pause 51
Phanerozoic 186
Philosophy 42, 88, 99
Photosynthesis 180, 207
Phylum 207
Place Life 34, 59-60, 93
Placentals 184
Plague 65, 82, 125


                > 210 <


Planet 207
Planet Formation 127
Planetary Cooling 127
Plant 207
PlantBiome 35 65
Plate 207
Plate Tectonics 157 163-164 207
Play Data Song 51
Poking Eyes 80
Pollution 82 125
Population 81 85 89
Primates 184
Primordial Soup 178
Print 48
Prokaryotes 136 179

Radiates 137
Radiation 1 23
Fainfall 74 81 96
Ramapithecus 185
Random Planet 55
Relative Date 27 51
Report 49
REPORT WINDOW 31
Reproduction Rate 97
Reptiles 139 183
Rock 66 134


Sapient 207
Save As 48
Save Options + Windows 50
Save Planet 48
Scenarios 7 109-117
Science 42 88 99
Scrolling 58
Sea Life Classes 61
Sea Temperature 81
Sentience 6
Sentlent Type 85
Set Altitude 28 66
Simians 185
Simulatlon Flow Chart 148
Slow 51
Snapshot 48
Software Toy 4
Solar Heating 171
Solar Input 96 131
Solar Nebula Hypothesis 153
Solar Radiation 171
Solar/Wind 86 98 147
Sound Effects 50

SPEED MENU 51
Stag Nation 56 111
Stone Age 142 190 207
Sun 159
Surface Albedo 96 132 207
Surface Currents 174
Swamp 66 135 207
System Simulatlons 5

T
Technology 49
TECHNOLOGYRATIO GRAPH 33 79 93
Technology Time Scale 107-108
Temperate Grasslands 66 135
Terraform 207
Terraformers 62
Terrain 58
Terraln Map 32 72
Tertiary 184
Thermal Tolerance 97
Tidal Wave 64 122
Tlme Scales 17 100-108
Tone Monitor 51
Tool Icons 59
Transform Margin 166
Transportation 160
Triassic 183
Trichordates 138
TriggeringEvents 29-30 64
Trilobites 181
Tutorial 49
TUTORIAL WINDOW 24 90

U, V
UpdateBackground 37 50
Upwelling 207
Vaporator 63 207
Venus 56 117
Vertebrates 182-183
Vlability 83-84 89
Volcanic Actlvity 95 128
Volcanism 188
Volcano 30 64 123 164 207

W,X,Y,Z
War 82 125
Water 161
WaterVapor 129 207
Weathering 160
Wind 161
WINDOWSMENU 29 48
Work 86
Zoomass 207

                > 211 <


PLANET SPECIFICATION SHEET:-
~~~~~~~~~~~~~~~~~~~~~~~~~~~~
MERCURY
Year (Earth Days).................................87.97
Day (Earth Hours)....................................59
Diameter (km)......................................4880
Diameter (miles)...................................3032
Density (water = 1).................................5.5
Moons.................................................0
Surface Gravity (Earth = 1)........................ .38
Mass (x10,000,000,000,000)........................ .332
Distance From Sun (Million km).....................57.9
Distance From Sun (Million Miles).................35.99
Orbital Velocity (km/sec).........................47.73


VENUS
Year (Earth Days).................................224.7
Day (Earth Hours)...................................243
Diameter (km).....................................12100
Diameter (Miles)....................................523
Average Temperature (degrees C).....................477
Density (Water = 1)................................5.24
Moons.................................................0
Surface Gravity (Earth = 1)......................... .9
Mass (x10,000,000,000,000Gigatons).................4.89
Axial Tilt........................................177.3
Volume (Earth = 1)................................. .88
Distance From Sun (Million km)....................108.2
Distance From Sun (Million Miles).................67.24
Orbital Velocity (km/sec)............................35



MARS
Year (Earth Days)...................................687
Day (Earth Hours)...............................24h 37m
Diameter (km)......................................6796
Diameter (Miles)...................................4220
Average Temperature (Degrees C).....................-53
Density (Water = 1)................................3.94
Moons.................................................2
Surface Gravity (Earth = 1)........................ .38
Mass (10,000,000,000,000) Gigatons................ .642
Axial Tilt........................................25.19
Volume (Earth = 1)................................. .15
Distance From Sun (Million km)....................227.9
Distance from Sun (Million Miles)................141.73
Orbital Velocity (km/sec)..........................24.1



SATURN
Year (Earth Days)..............................10760.56
Day (Earth Hours)...............................10h 14m
Diameter (km)....................................120020
Diameter (Miles)..................................74580
Density (Water = 1).................................0.7
Moons................................................17
Surface Gravity (Earth = 1).........................1.3
Mass (10,000,000,000,000) Giagtons).................575
Distance From Sun (Million km)...................1427.7
Distance From Sun (Million Miles.)...............887.13
Orbital Velocity...................................9.45

URANUS
Year (EArth Days)..............................306854.9
DAy (Earth Hours)...............................10h 49m
Diameter (km).....................................50900
Diameter (Miles)..................................31600
Density (Water = 1).................................1.3
Moons.................................................5
Surface Gravity (Earth = 1)........................0.93
Mass (X 10,000,000,000,000 Gigatons)...............88.2
Distance from Sun (Million Km)...................2870.5
Distance from Sun (Million miles)................1783.7
Orbital Velocity (km/sec)..........................6.36

NEPTUNE
~~~~~~~
Year (Earth Days)...............................60191.2
Day (Earth Hours)...............................15h 48m
Diameter (km).....................................48600
Diameter (Miles)..................................30200
Density (WAter = 1).................................1.8
Moons.................................................3
Surface Gravity....................................1.23
Mass (X 10,000,000,000,000 gigatons).............103.89
Distance from Sun (Km)...........................4498.8
Distance from Sun (Miles)........................2795.5
Orbital Velocity (km/sec)..........................4.77

PLUTO
~~~~~
Year (Earth Days)...............................90474.9
Day (Earth Hours)..............................159h 19m
Diameter..........................................2400
Diameter (Miles)..................................1500
Density (Water = 1)...............................0.7(?)
Moons................................................1
Surface Gravity...................................0.03 (?)
Mass (X 10,000,000,000,000 Gigatons)..............0.06
Distance From Sun..(Million KM).................5902.8
Distance from Sun (Million Miles)...............3667.9
Orbital Velocity..................................4.77


            -=-=-=-=- THE END -=-=-=-=-

-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
GREETS TO THE WORLDS BEST DOC TYPERS AND FIXERS (IN NO SPECIFIC ORDER) -
2tuff/CRYSTAL, LOONS, BRYNN ROGERS, MUNCHIE, PAZZA/LSD,  SCOOTER/SKID ROW,
BRYNN ROGERS, AND RYGAR.
-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=