Re: Pangaea

[@lepomis.psych.upenn.edu:murphy!acmcr!vr@uunet.uu.net (Vicki Rosenzweig)]

I'm not a geologist either, just an interested amateur. But
here are a couple of points. First, it's not just the shape
of continents that match, but the actual geological strata.
Second, yes, as far as we can tell it _is_ feasible for the plates
to move all over the planet: they have a _lot_ of time to do it
in. As I understand it, continental rock is too light (this is a
relative term, obviously) to sink into the earth when plates meet,
so it's thrust up (as in the Himalayas, where the Indian plate is
moving north against the Asian) or slides along (a la California).
And no, California is not "sliding into the ocean." It seems to have
come from what is now Asia and been attached to North America (in
several distinct pieces), and it could break off again and become
an island (like Taiwan), but it will mostly remain above water.

The plates vary widely in size: one reaches from California to
Iceland (I'm not sure of the northern and southern boundaries
of the North American plate). One is basically the Pacific Ocean.
Another is a little piece off the coast of Washington State (the
Juan de Fuca plate). I don't _think_ the number of plates is fixed
over geological time, either.

Finally, Earth's surface didn't _form_ with all the land in one
place. It reached that state after a number of other configurations,
then drifted away again.

Would a geologist or geophysicist please elaborate, and correct any
errors in this post? Thanks.

Vicki Rosenzweig
vr%acmcr.uucp@murphy.com
New York, NY