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mrmitchell
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Question: Would an endless rain of nuclear holocaust seriously effect any of the geologic factors that shape the world?
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Oerdin
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of Internet Music.
Sep 2001
time: 21:30
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quote:
The Yellowstone tread gave me the Idea for this thread, how will the continents move in the future. I have heard many conlflicting ideas. here is my ideas:
North America: rotates clockwise, California moves up the coast, continent starts to move generally SW, Greenland rotates counter-clockwise and moves NW.
South America: moves NW, continues to subduct Nazca plate, crashes into S. Mexico forming mountains.
Eurasia: rotates counter-clockwise, moves SE, collides with N. America and forms mountains, India finishes penitration of Eurasia.
Africa: Moves N, collides with Eurasia, Mediterrainean Sea closes, Alps grow enourmously, E. Africa rifts from continent and closes the Arabian sea, Red Sea expands to form new ocean basin.
Australia: moves N at fast clip, eventually collides with NW Asia, forming mountains
Antarctica: ???
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Have you ever heard of a German mathematician named Euler? He came up with a way to compute "Euler poles" which allow us to figure out how flat objects rotate on the surface of a sphere. Without that we would be hard pressed to computer the exact tectonic movements of the Earth's many plates.
Now, why are contents moving? To understand the why you have to know that the Earth's crust is broken up into Oceanic crust, which is relatively thin and dense (because it is "mafic" i.e. it contains a large proportion of metals especially iron and aluminum), where as the continental crust is relatively thick and low density (that's because it is "felsic" or contains much more silicates (SiO4) and much less metals). Because the contential crust is so much less dense it ends up "floating" upon the Earth's mantle (the subdivision of the earth directly below the crust) and when the continental crust crashes into the oceanic crust it almost always ends up with the oceanic crust sinking beneath the continental crust (how fast it sinks depends on the oceanic crust's temperature; the colder the faster it sinks) and we call this subduction. The opposite of subduction is spreading and spreading occurs when the earth’s crust is stressed so much that giant cracks appear; at these cracking points magma wells up and new crust is formed.
So which direction are each of the continents going today? 100 million years ago North America & Europe formed the continent of Laurentia, however, North America rifted (that means broke off of) Europe and began moving westward. Rifting of contents normally occurs when the continental landmass is so large that it acts like an insolating blanket and heat builds up underneath the continent. North America has been heading westward ever since and it is just now beginning to crash into Siberia (the eastern most part of Siberia is actually on the North American plate). 63 million years ago South America, Africa, Antarctica, the Indian subcontinent, and Australia formed Gondwanaland which is essentially the southern part of Pangea (Pangea was formed when Laurentia and Gondwanaland briefly merged together). Gondwanaland broke up with India rapidly heading northeast (where it eventually hit Asia and formed the Himalayas) while slowly rotating counter clock wise, South America rifted off of Africa heading westward, Africa is very slowly heading northward (thus closing off the straight of Gibraltar and eventually crashing into Europe), Antarctica is rotating slowly clock wise almost exactly around the south pole, and Australia rifted off of Antarica and is now rapidly (Australia is moving the fastest of any continent) northward. Asia forms a special case because it is the youngest of all the continents. Asia is actually an acresionary mass of volcanic arches and old island chains.
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Comrade Tassadar
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Care to draw us a really crude map, Oerdin?
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CerberusIV
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Supercontinents are believed to form on a regular cycle ~ 500Ma or so. The thought is that the Pacific Ocean is more or less permanent whilst the Atlantic will eventually close up again. Once the oceanic crust flooring the Atlantic gets cold enough it will start to sink beneath Europe/Africa and the Americas, the continents will start to move together again and the ocean will close up.
As the earth cools, the rate of tectonic drift is slowing down.
By the time anything noticeable happens none of us will be around. Of more immediate interest is the likelihood of a magnetic polarity reversal during the next few hundred years. That is going to be very interesting indeed!
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22-09-2003 06:46
Looking at those maps.....
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