Comment: Why were the continents once piled in a big clump?

Cecil's Columns/Staff Reports
1

Cecil sez: “The chief engine of plate tectonics, as this process is called, is the seafloor. At the midocean ridges, molten rock pushes up from below, causing the floor to expand laterally.”

My understanding is that plate tectonics is mostly driven by pulling forces rather than pushing forces. That is, heavy slabs of crust sink into trenches (eg, near Japan), pulling the crust away from the mid-ocean ridges. Here’s one cite: Mantle convection in the earth and planets by Gerald Schubert, Donald Lawson Turcotte, Peter Olson (2001), p. 52-53 Mantle Convection in the Earth and Planets - Gerald Schubert, Donald Lawson Turcotte, Peter Olson - Google Books

There’s a third force which involves mantle plumes flowing against the plates, but that apparently tends to slow the process down.

Column: Why were the continents once all piled in a big clump?

2

Actually, I have heard of a hypothesis that ties in the Moon-creating impact with contenental drift. It’s that the impact, by driving so much hot mass deep into the Earth, started the whole thing by literally stirring up the interior of the Earth.

3

A recent poll had A near-majority of Republicans believing that the topic event never happened.

Here we go:

“Do you believe that America and Africa were once part of the same continent?”

[Y/N/unsure]

ALL 42% 26% 32%

DEM 51% 16% 33%
REP 24% 47% 29%
IND 44% 23% 33%
OTH/REF 42% 25% 33%
NON VOTERS 46% 22% 32%

4

I see that there was some regional variation as well:

Do you believe that America and Africa were once part of the same continent?

YES NO NOT SURE

NORTHEAST 50% 18% 32%
SOUTH 32% 37% 31%
MIDWEST 46% 22% 32%
WEST 43% 24% 33%

“Not sure” is pretty much the same across regions. But among those with an opinion, there seems to be a lot of belief in plate tectonics in the northeast, not so much in the south.

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Anyone know of any good - and accurate, as far as we know - online computer animations of how the continents came to be in their present locations, and where they’re likely to end up?

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Hmm, you’d think Google Earth would put something like that in their software.

7

It’s not animated, but here are three views of the future.

50 million years from now: Future World

150 million years from now: Future +100 (note it confusingly says 100M in the title bar and text, but 150 in the graphic)

250 million years from now: Future +250

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Some views of the past are here. Here you can link to some lo-res 1MB gifs, and a 17MB .avi film of the same.

After that, check out the 42MB PLATES 2004 Powerpoint presentation here. You can click individual images from 750 million years ago to the present. After 540 millions years back, it shows increments of 10 million years.

But what I’d like to see is a moving diagram of the plates. I can’t quite work out why there’s a trench fault on the Japanese side of the Pacific ring of fire, but a slip strike fault on the eastern wing.

9

You should see the number of Southerners who don’t believe Obama was born in the US. Mind boggling.

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The crust is what, 10 or 20 miles thick on a ball of molten lava 8000miles in diameter? The best description is, it’s like the solid surface on a cooling bowl of hot mushroom soup. The convection forces of the circulating magma keep things floating around, pulling apart and mushing together.