Pre-Columbian settlement.

stan · Post by **stan** » Wed Nov 22, 2006 12:53 pm

I am enjoying this discussion.
But I don't understand your point here, Bob.

And are you saying that a 450-ft morraine would help to
create an ice dam?

Digit · Post by **Digit** » Wed Nov 22, 2006 12:53 pm

Good point Min. Point taken. So where do we stand on non continuous Moraines? Could shorter Moraines have been an effective barrier or are we back to an 'ice dam'?
My head aches!

Digit · Post by **Digit** » Wed Nov 22, 2006 12:58 pm

I'm getting out of step here. Just to muddy the water further on the subject of river flows, apparently the Nile at one time flowed West, towards the Niger. So along come idiot politicians and use rivers as boundaries then want us to fight when the river changes its course.
I need some tea!

Post by **Minimalist** » Wed Nov 22, 2006 1:00 pm

stan wrote:I am enjoying this discussion.
But I don't understand your point here, Bob.

And are you saying that a 450-ft morraine would help to
create an ice dam?

No. The whole "ice dam" concept seems bizarre to me. It would virtually mean that the glacier started melting in the middle and worked its way to the edge. That seems illogical.

However, it is known that a glacier pushes dirt and stone ahead of it into a mound called a moraine. ( I used to live on Long Island which was the terminal moraine for the last glacier.) That moraine could serve as an earthen dam for melting glacial water. As more and more water melts the lake behind the moraine gets deeper. Sooner or later the pressure of all that water would get to be too much and bingo...superflood.

Digit · Post by **Digit** » Wed Nov 22, 2006 1:07 pm

Which brings me back to my original question Min, why the Hell would several miles depth of ice melt in the middle. I suspect the easiest answer is that the 32 degree line moved in relation to the ice and left the leading edge in a frigid zone. All other alternatives seem even more implausible.

Post by **Minimalist** » Wed Nov 22, 2006 1:08 pm

Digit wrote:Good point Min. Point taken. So where do we stand on non continuous Moraines? Could shorter Moraines have been an effective barrier or are we back to an 'ice dam'?
My head aches!

NO I think there is more to it. There has to be some depression which allows the lake to form in the first place. Until I read Hancock's book I never gave much thought to the mechanism for glacial meltdown. From what I have read since it seems that the process was not steady and there were temporary advances and retreats of the ice during the period until the final meltdown. But as I discussed with Charlie the notion for these superfloods when these glacial lakes drained is not really a question. It happened. And the effect must have been devastating for anyone nearby.

Of course, The Club says that the Americas were not populated at all until after the ice had already melted for the most part so how can this be?

Post by **Minimalist** » Wed Nov 22, 2006 1:11 pm

I suspect the easiest answer is that the 32 degree line moved in relation to the ice and left the leading edge in a frigid zone.

Earth Crust Displacement?

Post by **Minimalist** » Wed Nov 22, 2006 1:13 pm

why the Hell would several miles depth of ice melt in the middle.

I don't think it did.....I think it began melting on the edges just like glaciers melt today....and will keep melting no matter how many times that moron in the White House keeps saying that global warming needs more study.

Digit · Post by **Digit** » Wed Nov 22, 2006 1:33 pm

Surely Min I have to accept that the Earth's crust might be depressed under the weight of that much ice and so be lower in the centre. But come on Min, that doesn't mean liquid water!
That far north of the 32 degree thermocline it would have been b---dy cold.

Post by **Minimalist** » Wed Nov 22, 2006 1:39 pm

http://www.newswise.com/articles/view/?id=FLOODS.UAZ

Around 15,000 years ago, as the last ice age was melting down, you didn't want to be standing in Idaho's Clark Fork River Valley. Giant glacial Lake Missoula stretched 174 miles behind an ice dam ready to burst.

When the 2,000-foot-high ice dam did go, the lake surged downstream with a flow ten times greater than the flow from all the world's present rivers combined. The massive flood cut deep canyons, stripped away soils, and carried boulders all the way from Idaho to what is now Portland, Ore. In 48 hours, it transformed the landscape of the Pacific Northwest.

I don't know but it still seems illogical that there would be 174 miles worth of water...which had all melted from receding glaciers...but this "ice dam" somehow remained intact.

Digit · Post by **Digit** » Wed Nov 22, 2006 1:54 pm

It seems more than odd. If I was a member of the club I would fall back on the usual 'we can't explain it so it didn't happen!'
What about the Yellowstone magma dome as a candidate? There's enough enegy there to melt the ice, is/was it far enough North? Is there any evidence of activity anywhere in North America at a suitable date?

Post by **Minimalist** » Wed Nov 22, 2006 2:02 pm

There's a whole string of volcanos in Washington/Oregon but volcanic activity throwing millions of tons of ash into the air tends to lower temperatures not raise them by blocking sunlight, doesn't it?

Digit · Post by **Digit** » Wed Nov 22, 2006 2:19 pm

True Min, but I wasn't working on that basis. As I understand it, at the moment the Yellowstone plume is making one of its periodic moves towards the surface. Logic says that radiant heat from the ground must increase as the plume moves nearer to the surface, and several miles of ice would have been a pretty good heat trap. Following logically from there the ice would have begun to melt from the bottom upwards. As the ice melted there would have been a collapse of the surface ice as the volume of melt water would have been less than the volume of ice that produced it.
Thermal currents in the water would have spread the heat then towards the edges and promoted further melting. But as I said, is there any evidense to support the idea?
A similar, much smaller, event occurred recently in Iceland.

Post by **Minimalist** » Wed Nov 22, 2006 2:28 pm

I just checked it on Mapquest and its about 250 miles SE from the Clark Ford River Valley to Yellowstone. Since the water was north of the 'dam' it seems a bit far.

Digit · Post by **Digit** » Wed Nov 22, 2006 2:41 pm

Well Min, I'll call it a day and hope someone can come up with an answer. I must cofess I love it when the experts pass all this information to us, explaining what this flood must have been like, complete nowadays with computer animation, but then dodge the awkward bit. Like what makes an ice filed melt from the centre outwards. Usually it's 'at the moment the reasons are not fully understood', i,e, 'we don't know but we're not going to admit it'.
Admitting that you don't know is the first step towards understanding.