TSUNAMIS & HOT SPRINGS

TSUNAMIS

Tsunamis are killer waves which are caused by jolting of the ocean floor by an earthquake, volcanic eruption or landslide. Tsunamis, which may initially be less than a metre in height, can race across the ocean at speeds as fast as a jet plane (800 km per hour) and grow to 20 or 30 metres high as they reach shallow water, usually a land mass. A tsunami may even remain underwater for hundreds of kilometres until shallower water acts as a kind of brake, forcing the wave to stop and rush upwards in a wall of water that is capable of continuing for 1 km inland. In 1896, local fishermen returned to harbour on the north eastern coast of Japan to find that a tsunami which had passed beneath their boats undetected had devastated their homes. In 1992, San Juan del Sur in Nicaragua was destroyed by a tsunami. Minutes before its arrival, people flocked to the oceanŐs edge to see that all the water was being sucked out of the harbour by the tidal wave which followed far too soon afterwards for evacuation to take place. Tsunamis occur most frequently in the Pacific Ocean.


HOT SPRINGS AND GEYSERS

Some of the water below the surface of the earth is rainwater that has seeped down into the rocks. When this water comes into contact with rocks that have been heated by magma, it rises back to the surface as a hot spring, mud pot, fumarole or geyser. When mixed with mud as it rises, the spring will become a bubbling mud pot. One type of hot spring which behaves like a volcano is known as a geyser. It erupts hot water, steam and minerals which sometimes form a small cone. Fumaroles erupt steam and gases, some of which are poisonous.