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Originally Posted by Martian
The Earth is flatter at the poles because it spins. Centrifugal force cause the equator to 'bulge,' creating an oblate spheroid. This is backed up by the other observable planets; the faster the rotation, the more oblate the body. No expansion necessary.
As to accretion.. well, as I said earlier, I don't know a whole lot about geology; however, I was under the impression that this is adequately explained via tectonics.
Wiki goodness. |
Cosmic material, multiplication of life + perpetual decay, and the gravitational bulge are factors. Subduction alone promotes the Earth will remain in volumous homeostasis. The same arguement is being applied now to mars and venus. They (scietific community) are especially looking at Europa because of its theoretical likeness to a once ocean covered Earth.