EVIDENCE OF PLATE TECTONICS
If you have ever looked at a map of the world, you may have noticed the
shapes of the continents seem to fit. For example, the east coast of
South America and the west coast of Africa, if you moved them together,
fit like puzzle pieces. Geologists have long noticed these patterns but
until the 1960's did not fully understand their significance. Other
patterns such as the locations of earthquakes, mountain belts, and
volcanoes, the shape of the sea floor, and the distribution of rocks and
fossils can be seen. Geologists have developed the theory of plate
tectonics to explain these features.
According to plate tectonics, the outer part of the Earth is a layer
of rock about 100 kilometers thick. This shell is very thin compared to
the size of the Earth. This shell is divided into at least 25 pieces,
which are called plates. These plates move very slowing on the
partially molten Earth layer (asthenosphere) below them.