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Lithosphere
Wow! That's the lithosphere! See how uneven
the surface of the lithosphere is. There
are high mountains ranges like the Rockies
and Andes (in reds), huge plains like
those in Texas, Iowa and Brazil (in greens),
and the deep valleys of the ocean floor
(in blues). We walk and climb on this
part of the lithosphere.
But the surface of Earth
is only the very top of the lithosphere. If you look at the cut-away
globe above, you can see the rest of the lithosphere with its many
layers like an onion. The very thin crust on top, the thick mantle
underneath, and the huge core of liquid iron at the center.
You must be careful with
the word "lithosphere," though. It is tricky! "Lithosphere"
has different meanings. As we are using it here, it means both the
rocky surface and the whole inside of Earth. But the deep interior
of Earth is very hot, and even though the rocks there are mostly
solid, they can flow over long periods of geologic
time like soft butter. This flow on the inside causes the cold,
hard surface layer of Earth to break into pieces and move around.
This movement causes earthquakes and mountain ranges and is called
"plate tectonics." When talking
about plate tectonics, geologists use the word "lithosphere"
to mean only the cold, hard part at the surface, and not the whole
inside of the Earth.
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