http://www.geo.lsa.umich.edu/~crlb/COURSES/270/gs270.html
Comparative planetology: Plate tectonics.
On Earth, we have plate tectonics. This means
that continental plates move over, under, around,
and next to each other, floating over the mantle
of the Earth.
http://www.geo.lsa.umich.edu/~crlb/COURSES/270/gs270.html
There are some wicked cool movies at Tanya Atwater's animations site.