CONTINENTS THROUGH THE AGES
Geologists have learned that the inside of the Earth
has many layers. The outermost Earth layer is composed of rocks. It is
called the lithosphere. The lithosphere is about 100 kilometers
(a bit more than 60 miles) thick. The lithosphere is not a solid shell
of rock, but broken into large plates. Imagine a hard boiled eggshell
that has been cracked on a table top, but the size of the Earth. Unlike
an eggshell, the plates of the lithosphere are not stationary. They are
all in constant motion. Plate movement is slow.
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