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  #1  
Old 05-12-2012, 04:17 PM
ralph124c ralph124c is offline
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A Question About Climate and Sea Levels

I was reading about the fossil forests of Axel Heiburg Island, in the Canadian Arctic.
A few years back, scientists found the remains of a tropical forest on the island, which is about 500 miles south of the North Pole. According to estimates, this area had a tropical climate (like modern day Florida), about 40 million years ago.
My question: since the planet was so warm back then, it is obvious that the Greenland and Antarctic Icecaps could not exist. Yet, the elevation of the island forests (Axel Heiburg Island) is no more than 100 foot above present day sea level. Where did all the water go? Was it tied up in interior lakes?
Could mankind live in the climate of 40 million years ago?
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Old 05-12-2012, 04:26 PM
Trinopus Trinopus is online now
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Isn't 40 million years more than enough for the land where the island is now to have risen or fallen dramatically? Maybe it was on a shoreline *then* and maybe it is on a shoreline *now* but in between, it might have been upthrust or folded under all sorts of ways.
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Old 05-12-2012, 05:39 PM
Colibri Colibri is online now
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Yes, 40 million years is a very long time. The elevation of the land where the forest is could have been substantially higher at the time it was fossilized. Also, the distribution of land was quite different than today. The Himalayas had not yet formed, and much of Asia was under water.
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Old 05-12-2012, 05:55 PM
Musicat Musicat is offline
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Not only has land risen & fallen as well as the seas, but continents have drifted. Just because the land at 45 degrees north latitude is not in a tropical zone now doesn't mean it wasn't 40 million years ago; the tropics haven't moved, the land has.
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Old 05-12-2012, 06:08 PM
srzss05 srzss05 is offline
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Originally Posted by Musicat View Post
Not only has land risen & fallen as well as the seas, but continents have drifted. Just because the land at 45 degrees north latitude is not in a tropical zone now doesn't mean it wasn't 40 million years ago; the tropics haven't moved, the land has.
This thought crossed my mind as well, but apparently the North American continent hasn't drifted that much in the last 40MY.
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Old 05-12-2012, 06:12 PM
sitchensis sitchensis is offline
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The weight of the ice during the ice ages would have forced the island down.
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Old 05-12-2012, 06:40 PM
GreasyJack GreasyJack is online now
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40 Million years isn't that long in terms of plate tectonics. India hadn't quite collided with Asia yet and North and South America were still separated, but everything was in the same neighborhood of where it is now. What was interesting about the fossil site is that even during the Eocene the island was far enough north that it got months of total darkness and light, but the ecosystem was somehow able to adapt to it.

As for why the forest is above sea level now, it's probably just coincidence. It's likely that most of the region was covered by such forests, but only this one survives and is exposed because through the vagaries of erosion and uplift it just so happened to avoid being eroded by the glaciers and ended up above sea level today. There were many more fossil forests that were obliterated by advancing glaciers and there are likely some that are still underwater today.
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Old 05-13-2012, 08:42 AM
md2000 md2000 is offline
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68M years ago and earlier, the central plains was a shallow sea. Everything was tropical, dinosaurs migrated up and dwn the shoreline of Texas - Colorado- Wyoming-Ablerta - Yukon. Run-off from the nearby mountains eventually created coal, shale oil, and oil fields. The occasional mudslide buried dinosaurs in anaerobic conditions resulting in interesting bone fields too.

Today that land is 2,000 feet or more above sea level.

I remember some science fiction author writing once that one of his stories was set on Santa Catalina island off the California coast in the dinosaur era. Just before he submitted it, he suddenly thought "OMG, did the island exist then?" He said he looked it up, and sure enough, the geology was correct. When the story was published, sure enough, some educated reader wrote in - yes the island existed, but it was 10 miles inland!

Geology happens.

Also, depending on who you listen to, water levels with fluctuate by 3 feet, 12 feet, 30 feet, or more if the ice caps melt. Allegedly archeological sites for the first humans in America are 300 feet down off the coast underwater, because in the middle of the ice age, water levels were painfully lower than today with all that ice tied up in mile-thick glaciers. That was only 14,000 years ago or so.
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Old 05-13-2012, 12:32 PM
Michael63129 Michael63129 is offline
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Originally Posted by md2000 View Post
Also, depending on who you listen to, water levels with fluctuate by 3 feet, 12 feet, 30 feet, or more if the ice caps melt.
Those different estimates consider the effects of only Greenland or Antarctica (partially) melting, or for the first figure, sea level rise in the next century (which, while not explicitly stated, assumes that further rise will occur afterwards; a total loss of all ice would raise sea levels by over 200 feet):

Quote:
If all of the Antarctic ice melted, sea levels around the world would rise about 61 meters (200 feet)...

...There is a significant amount of ice covering Greenland, which would add another 7 meters (20 feet) to the oceans if it melted.
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Old 05-13-2012, 02:04 PM
sitchensis sitchensis is offline
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Quote:
Originally Posted by md2000 View Post
Also, depending on who you listen to, water levels with fluctuate by 3 feet, 12 feet, 30 feet, or more if the ice caps melt. Allegedly archeological sites for the first humans in America are 300 feet down off the coast underwater, because in the middle of the ice age, water levels were painfully lower than today with all that ice tied up in mile-thick glaciers. That was only 14,000 years ago or so.
I agree with your statement, the ice did indeed tie up large amounts of water, lowering sea level.

I believe the current thinking is that as the ice advanced, and the weight of the ice put vast amounts of pressure on the land to the point of lowering it. A fore bulge developed in front of the ice. Like a rolling pin on dough the fore bulge actually raised the land level, the combination of the two is why those archeological sites are so far out to sea.
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