Pre-Columbian settlement.

[Bruce]

What about the human element? These people were getting blown away by all this melting water, don't you think they would have done something? The drainage flows were going north then south then east all by ice dams? at 10,600 yrs ago all drainage south completely stopped. You would think if the water flow had built up a drainage that it would have taken some kind of event to plug it up.
This is really out ther but at this time there were giant beavers roaming the continent and I've seen what normal beavers can accomplish! they probaly had a heyday in is this enviroment surely causing some of, or contributing to, the blockages that were changing the directions of the drainage flows.
http://en.wikipedia.org/wiki/Driftless_Zone#In_history
This would have been a perfect base camp for humans to manipulate the enviroment as the ice melted. Why was this zone imune from the glaciers? We try to look for natural causes but you have to include biological forces to. This rarely happens but I think they play a tremendous role in nature.

[Minimalist]

The Club tells us that humans at this time were stone-age hunter/gatherers who had no capacity to mold their environment. Their environment molded them!

[War Arrow]

Bruce, as you say yourself, that idea really is out there, but then again the history of the planet is most likely littered with 'out there' occurences and your suggestion is at least on the right side of the probability line. All the same, I personally wouldn't want to be the guy who found himself having to fight the corner for the 'giant beaver hypothesis.'.

[Beagle]

A comment on earth crustal displacement:

There are a number of illustrations about how ECD has never happened but I like the geologic "hot spot" example. There are several places on earth where magma breaks through the tectonic plates and creates volcanoes. One is the Hawaiian island chain. This chain even extends to Midway island and a series of underwater sea mounts.

The tectonic plate has moved over this "hot spot" for many millions of years and it's path can be seen where volcanic islands have been formed.

If the crust of the earth shifted, this linear progression would have been interrupted. So, in my view, no ECD.

[Cognito]

The tectonic plate has moved over this "hot spot" for many millions of years and it's path can be seen where volcanic islands have been formed.

Yellowstone Park has the same "hot spot" that traveled under the crust in a straight line for millions of years taking out at least one mountain chain on its way to its present location.

[Digit]

Yep! Good points all. But we are still left with the original question that we are no nearer resolving. How does an ice sheet several miles thick melt in its centre? Anyone got any ideas on that?

[Minimalist]

How does an ice sheet several miles thick melt in its centre?

I still maintain that it doesn't. It melts on the edge just like a modern glacier and thus retreats in the direction from whence it came.

[Digit]

Can't see it Min. The moraines could hold back the sort of flood that created the 'Badlands' surely? There is evidence for ice melting in the centre in Iceland but that was with heat from beneath. A programme I watched here in the UK (Discovery) was quite explicit on the 'Ice Dam' idea so there must be some evidence to support it.

[Minimalist]

http://www.sciencedaily.com/releases/20 ... 140730.htm

Glaciers and ice streams carry ice from the interior of an even larger ice sheet out to sea, where the ice breaks up into icebergs in a region called the calving front. In the critical region upstream from the calving front, scientists measure the thickness of the ice to gauge conditions within the glacier.

I don't see why this glacier should operate any differently than earlier glaciers.

[Digit]

It probably wasn't any different Min, only the melting seems a bit odd, after all'normal' glaciers don't melt into a wall of water.

[stan]

Here's a little article about a glacial lake with pictures.

http://www.geography-site.co.uk/pages/p ... cecap.html

And yet another:

http://www.esa.int/esaCP/SEM2OFX5WRD_index_1.html

Thing about these is that these glaciers were in valleys, and water flowed onto them from mountains above. Could this have happened in the glaciers we are arguing about? After all, there must have been
dozens or hundreds during the ice age.

[Cognito]

It probably wasn't any different Min, only the melting seems a bit odd, after all'normal' glaciers don't melt into a wall of water.

Rocks and terrain do not retain heat as well as water and as a result all stationary glaciers will begin to melt in the middle. The heat retention difference from sunlight is small, but enough to explain the phenomenon. Just ask anyone who lives on a pond or small lake that freezes over today, same sequence. Ice dams form where there is a blockage in terrain.

[Minimalist]

So how come Greenland isn't a lake with a ring of ice around it?

[Cognito]

So how come Greenland isn't a lake with a ring of ice around it?

Probably for the same reason that the majority of Greenland's ice sheet lies within the Arctic Circle, don't you think?

[Minimalist]

The only man on the planet who doesn't know that it is melting is George W. Bush....arctic circle or no.