Labels:text | screenshot | font | document OCR: Geologists believe that the Earth's surface is fragmented into 20 or so moving pieces, called tectonic plates. For millions of years the continents have drifted around on top of some of these plates as they slide and collide with one another. The continual movement of the plates creates earthquakes and causes volcanoes to erupt, builds and destroys mountains, and makes and breaks continents. INSIDE THE EARTH The movement happens because inside the Earth, a layer called the mantle is hot and turbulent. Its motion disturbs the Earth's cool, rocky surface, or crust, and makes its huge plates move around. This slow movement of the plates - about 1 cm (less than 1/2 in) a year - has been going on for billions of years.
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