Plate Tectonics

[JohnB]

Possibly a stupid question, but here goes.

 

I was looking at a .jpg posted in another thread showing plate movements over the millennia. (Right hand side of picture.)

http://departments.oxy.edu/biology/bbraker/courses/bio105/images/15.3A,B%20Earth's%20crustal%20plat.JPG

 

I realised that in all the depictions I've ever seen, Antarctica doesn't move. Every other plate happily wanders all over the place, but not that one. I"m not saying it's wrong, it just seems "funny". Does anyone out there know why one plate doesn't move?

 

A secondary question. If Antarctica was in the same place for the last 150 million odd years, (and therefore covered with ice since the time of the dinosaurs) then shouldn't ice cores allow us to view the atmosphere all the way back to that time?

 

That's assuming that there wasn't a more recent time when all ice on the planet melted.

[inquisitive]

If you find a map of north and south magnetics poles plotted over time, you will notice that they move around the surface of the globe quite a lot. If you then compare the plate movements with this pole movement, you will see that what moves where (moving north, moving south) is relevent to where (which plate you are watching it from).

 

when you are shown plate movement, it is always mapped from our present day perpective of our rotating globe and like most spinning things, the outer areas are effected more than anything that is at the 'top' or 'bottom' of the spinning object (forget north and south pole)

 

The only thing left to notice is that there has never been a land mass at the 'top', if solid it is floating ice so wont move with plates anyway. The antarctic is a land mass and is (always has been?) at the 'bottom' of the spinning planet, so least effected....... and least moved.

 

just a thought.... open to other thoughts/knowledge (errr or it could be the penquins anchored it)

 

[Mokele]

If Antarctica was in the same place for the last 150 million odd years, (and therefore covered with ice since the time of the dinosaurs) then shouldn't ice cores allow us to view the atmosphere all the way back to that time?

 

Actually, polar ice is far from a constant. For a lot of good-sized chunks of the earth's history, there have been either no or only seasonal polar ice caps.

 

Back in the Paleocene (just after the dinosaurs died), the arctic was almost sub-tropical. There were palm trees with gigantic leaves (an adaptation to the low light levels, and even alligators. Many ecothermic species have migrated across the Bering land bridge (when it's existed) and across Antarctica.

 

Mokele

[TimeTraveler]

Many ecothermic species have migrated across the Bering land bridge (when it's existed) and across Antarctica.

 

Really? How did they get to Antartica?

[Mokele]

Antarctica used to be connected to both South America and Australia. This is why SA has marsupials like the possum (which only came to North america during the last 3 million years, when the Ithsmus of Panama arose).

 

Mokele

[coquina]

Look here:

 

http://www.scotese.com/earth.htm

 

You can click on each geolocic time period and see where the present continents were at the time.

 

For example, in Precambrian time Antartica was at the equator:

http://www.scotese.com/precambr.htm

 

You can also click on the climate section, and see what the temperatures were for each time period.

[TimeTraveler]

Wow excellent links sandi, thanks. I remember reading a little about pangea in highschool, Very interesting.