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Plate Tectonics

plates

Plate Tectonics is a theory scientists have about the earth's surface. Scientists think that the earth's outer surface consists of 12 rigid plates. Some of these plates do not follow continental boundaries, and some include both continents and oceans. They are all different shapes and sizes and are in continual motion. The plates slowly slide on a soft plastic layer of molten rock called the mantle and move from 1.3 to 10 centimeters a year. This tectonic activity occurs along the edges of the plates. When plates collide or push against each other, over periods of millions of years, one plate will either slide on top of the other, which creates a fault movement generating earthquakes and volcanoes, or crumples and forms mountains.

plates Scientists believe that about 250 million years ago, the plates were positioned so that all plates were joined together to form a super continent called Pangaea. They also thought that about 200 million years ago, the super continent Pangaea separated into 2 large continents called Laurasia and Gondwanaland. Over periods of millions of years the plates continued to collide and separate to eventually form seven continents. This plate tectonic theory became real to scientists in the 1960s when they and map makers noticed how well South America and Africa fit together, even though the continents are far apart. All seven continents are moving farther apart or closer together because of plate tectonic activity. North America and northern Asia are moving closer together, as well as South America and southern Asia, but North America and Europe are moving farther part, as well as South America and Africa. In another 100 million years or so, another super continent will form where the Pacific Ocean used to be.



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