>Dan Clemmensen asks
>: [...] why does all the major motion seem to be toward
>: the center of the Pacific, causing the "ring of fire?"
>: Maybe something (antimatter meteor?) took a chunk out
>: there and the earth is now adjusting? (Estimated silliness
>: factor on this is 90%, but what the heck.)
>
>Well, you can't comb the hair on a bowling-ball - if everything is
>moving, at least one convergence and one divergence are inevitable.
>But I believe conventional wisdom says the Pacific Ocean is the scar
>left by a really big collision which ripped out the Moon.
I've heard that theory. The problem is that the moon is about 4by old, while
Pangaea appears and disappears on about a 600 my cycle. The continents move
out (ring of fire) but then they move back (ring of blah?). They've cycled
about 6 time since the moon formed. Also, the current theory of moon
formation is that a *big* rock smacked the earth and knocked the entire crust
into orbit, in little bits. Most of it stayed up there to form the moon.
But as a result, there's no particular place the moon's material came from.
But I've also heard a another theory. Continents, especially large ones,
thin the rock over which they sit, making it easier for magma to pop up,
creating new rifts. Once formed, the rift creates an ocean. However, once
the continent is gone, rifts are more likely to close and eventually do, and
the continents drift back together. So you get a cycle: Pangaea - Pangaea
rifts apart - Atlantic/Pacific/multiple continents - Atlantic rifts close -
New Pangaea.
Supposedly the Atlantic closes rather than the Pacific because it's always
smaller.