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| marnixR |
 Posted: Fri Mar 21, 2008 1:30 pm Post subject: dispersal of Gondwana |
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Forum Isotope
Joined: 10 Apr 2007
Posts: 2584
Location: Cardiff, Wales
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came across the following site showing the break-up of Gondwana
the animation's a bit fast, but still neat
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| KALSTER |
| Posted: Sat Mar 22, 2008 2:08 am Post subject: |
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Forum Cosmic Wizard
Joined: 08 Sep 2007
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Location: South Africa
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Wow, look how India shoots off! Pretty cool. 
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| thacheezinator |
| Posted: Sat Mar 22, 2008 10:27 am Post subject: |
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Forum Freshman
Joined: 18 Feb 2008
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Location: Texas
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that is pretty darn cool...
i wish that they could do it a litle slower...
I AM GOING TO SHOW THAT TO ALL THE PEOPLE THAT LIKE SCIENCE THAT I KNOW...
which is unfortunately, only me...
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| Pendragon |
| Posted: Sat Mar 22, 2008 2:21 pm Post subject: |
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| marnixR |
| Posted: Sat Mar 22, 2008 2:46 pm Post subject: |
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Forum Isotope
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Location: Cardiff, Wales
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in our current understanding of plate tectonics, do we actually know enough to predict when a passive continental margin becomes an active one, when mid-ocean ridges become inactive and when new subduction zones form ?
if not, are the images for +100MYA and +250MYA any more than pure guesswork ?
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| The Matt |
| Posted: Sat Mar 22, 2008 3:06 pm Post subject: |
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| I got the impression that it was educated guesswork, but guesswork none the less |
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| Pendragon |
| Posted: Sat Mar 22, 2008 3:58 pm Post subject: |
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| marnixR wrote: |
in our current understanding of plate tectonics, do we actually know enough to predict when a passive continental margin becomes an active one, when mid-ocean ridges become inactive and when new subduction zones form ?
if not, are the images for +100MYA and +250MYA any more than pure guesswork ? |
Guesswork: probably yes, to some extent. It doesn't seem difficult to extrapolate current plate movements, which we can measure very accurately. But when new mid-oceanic ridges form it's very hard to predict what will happen. For example the mid-Atlantic ridge was just one of many candidates to split the Americas from Africa and Europe, it could easily have had a different shape. For example the Mississippi valley was one side-'crack' attached to the mid-Atlantic ridge, but I don't see a reason why it couldn't also have become the main route for the ridge. In that case the Eastern half of the US would've stayed attached to Europe and the Mississippi valley would've been the center of the Atlantic ocean, giving the continents quite different shapes. It's like cracking an egg-shell, it's impossible to tell beforehand how the cracks will run exactly.
On the other hand it doesn't seem a crazy idea that one way or another we'll end up with a new Pangaea. According to one theory we've had several 'pangaeas' already in Earths long history. There's some evidence that the earth has had about 6 or 7 pangaeas already in it's history, so it would almost be strange if there wouldn't be one in the future. |
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| Ophiolite |
| Posted: Sun Mar 23, 2008 10:51 am Post subject: |
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Forum Radioactive Isotope
Joined: 25 Jul 2005
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Location: Scotland
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One of the delights and benefits of predicting what will happen in 100 million years time is that its difficult to prove you wrong.
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| Orleander |
| Posted: Tue Mar 25, 2008 11:53 am Post subject: |
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| How do they know there was nothing on the other side of the planet, just one mass on one side? Could there have been lots of land and it sunk? |
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| marnixR |
| Posted: Tue Mar 25, 2008 1:44 pm Post subject: |
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Forum Isotope
Joined: 10 Apr 2007
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Location: Cardiff, Wales
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clues from geomagnetism and paleobiogeography (oh, and rock formations too, obviously)
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| The Matt |
| Posted: Tue Mar 25, 2008 4:24 pm Post subject: |
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| Orleander wrote: |
| How do they know there was nothing on the other side of the planet, just one mass on one side? Could there have been lots of land and it sunk? |
Sunk to where? continents don't just bob under the surface randomly. They're not dense enough to do that. |
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| Orleander |
| Posted: Wed Mar 26, 2008 9:23 am Post subject: |
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| The Matt wrote: |
| ...Sunk to where? continents don't just bob under the surface randomly. They're not dense enough to do that. |
LOL, I don't mean sink like a boat. I mean sink like New Orleans or Port Royal.
OK, this may be a stupid question, but that never stops me, so here goes.
Hawaiian Islands are basically vents for the earth's core. If the plates over the vents shift, the vents will spring up else where right? The islands will stop growing. Wind/erosion could wear down the islands over millions of years. That land is gone and with it all evidence of civilization. Does that make sense? |
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| KALSTER |
| Posted: Wed Mar 26, 2008 9:46 am Post subject: |
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Forum Cosmic Wizard
Joined: 08 Sep 2007
Posts: 2222
Location: South Africa
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| Quote: |
| Hawaiian Islands are basically vents for the earth's core. If the plates over the vents shift, the vents will spring up else where right? The islands will stop growing. Wind/erosion could wear down the islands over millions of years. That land is gone and with it all evidence of civilization. Does that make sense? |
Actually, this is sort of what happens. There is what is called a hot spot over which the continental plate moves, creating new islands along the way.
See HERE.
Edit: Only thing is, there were no Homo sapiens sapiens millions of years ago. 
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| Orleander |
| Posted: Wed Mar 26, 2008 10:10 am Post subject: |
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| No, I don't think civilizations disappreard during that time, but the land could have. |
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| KALSTER |
| Posted: Wed Mar 26, 2008 10:19 am Post subject: |
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Forum Cosmic Wizard
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Location: South Africa
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| That land is gone and with it all evidence of civilization. |
What did you mean by this? Anyway, I am sure that does happen as you said. Another possibility is landslides. I think ones big enough to plunge a large city into the sea can and do happen from time to time.
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