The vault.
The sediments at the bottom of the lake in Northen Quebec's Pingualuit Crater hold unmatched clues to North America's climate record.
Credit: Robert Fréchette / ARK; (inset) University of Arkansas
Posted on 12/15/2007 3:43:24 PM PST by neverdem
The vault.
The sediments at the bottom of the lake in Northen Quebec's Pingualuit Crater hold unmatched clues to North America's climate record.
Credit: Robert Fréchette / ARK; (inset) University of Arkansas
SAN FRANCISCO, CALIFORNIA--A million years ago, a large meteorite smashed into what is now northern Quebec and created a crater that may become an unprecedented repository of data with which to study long-term climate change, researchers reported here this week at a meeting of the American Geophysical Union.
Canada and the northern United States are dotted with tens of thousands of lakes, most of them formed by meltwater at the end of the last ice age about 12,000 years ago. Sediments at the bottom of those lakes hold chemical and biological evidence of how the planet's climate has varied for even longer periods, over many ice ages and interglacial cycles, and how those variations have affected the local ecosystems. But almost all of these sediments have been bulldozed repeatedly by glaciers as the giant rivers of ice have advanced and retreated over the last 2 million years, scrambling the geological record.
Pingualuit Crater in northern Quebec seems to have escaped this fate. Its 3.7-kilometer-wide, nearly circular lake not only is deep enough--nearly 270 meters--to have avoided the glacial pummeling but also has remained sequestered from any other body of water during its entire history. So the sediment that has collected on the lake's bottom has preserved a pristine record of the climate and biological activity in the lake for more than a million years--much longer than any similar climate data source currently available. Until recently, however, the technology necessary to retrieve samples from the bottom, without disturbing the samples or contaminating the lake's ultraclear water, did not exist.
So, paleolimnologist Sonja Hausmann of the University of Arkansas, Fayetteville, and colleagues employed a new type of coring rig devised specifically for obtaining delicate samples. Last May, after trekking across the then-frozen lake on foot without the aid of potentially polluting snowmobiles or sled dogs, the team deployed the bottom-dwelling rig, which is suspended from a Kevlar cable, and spent 2 weeks carefully extracting cores from the top 10 meters of Pingualuit's estimated 150 meters of sediment. Those samples are beginning to provide a treasure trove of data going back at least 250,000 years.
"We think the samples span at least two [interglacial] cycles," Hausmann says. They include diatoms--microscopic algae whose silicate shells can provide exquisite historical portraits of the lake's water quality and climatic conditions--as well as trace metals and pollen that have fallen from the atmosphere. Other records can be compiled from sources such as the ice cores in Greenland and the sea beds, she says, but the Pingualuit cores are the only ones available from the North American land that contain the skeletal remains of climate-sensitive algae.
"Collecting this core was no small endeavor," says paleolimnologist John Smol of Queen's University in Kingston, Canada. "Many of us had previously assumed that the last Ice Age had obliterated older sediment records," he says, but Pingualuit's cores show that "there is a remarkable history book still present."
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"Earth's climate is changing rapidly, with the global temperature now rising at a rate unprecedented in modern history. These climate changes are being experienced particularly intensively in the Arctic. Arctic average temperature has risen at almost twice the rate as in the rest of the world in the past few decades........."
It looks like a conclusion in search of evidence to me.
“Wow! What a cool lake!”
Yeah - perfect for some condos, a golf course, and a marina.
Thanks for the ping. Interesting lake, interesting potential results.
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That is a very large above-ground pool!
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Thanks neverdem. |
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Coastal lakes and beach sand grain size are used to track ancient hurricanes on the Gulf Coast. Category five hurricanes decreased substancially about 1,100 years ago...why is unknown,so far.
If you have Google Earth the crater is located at: 61 Degrees 16’ North 73 degrees 40’ West.
kewl!
Lots of permafrost around there where it isn't just bedrock.
If it were a crater, it would be pretty much level with the rest of the terrain. You don't suppose it was impact created with a subsequent volcanic upsurge due to penetration into a magma dome?
Its unusual to see an impact event that would have had to have been at 90 degrees to the surface plane.
If it was soft material as in a crater wall, it would have been glaciated flat, like the rest of the terrain around it.
This is a mysterious formation. I do not believe it is a crater. Its a collapsed cauldera, which has been glaciated. The circumference shows signs of having been rounded on its edges by glaciation, as the ice moved around and over it.It it were soft crater wall material, instead of volcanic rock, it would have been buldozed flatter than a pancake.
I wonder if much geology has been done on the rock matrix surrounding this lake? I doubt it.
It is a strange lookng formation. If there were a mile of ice and the asteroid went through that before hitting dry land what would the result look like and what about when the glacier eventually melted and left along with the regolith? It might look like that.
The top of the lip is kind of flat. This might have been the level of the ice and stuff above that would have been blown all over the landscape. Also, the impact need not have been vertical: note one side is lifted: the remaining mass of the impactor would be under that side.
I wonder if the have done conclusive geology on this?
Its just too regular to be an impact crater, and its too regular in some sense, to be a cauldera either. Very odd.
There are hundreds of impact craters in the Canadian north, in the tundra. They are all flat, without these defined high relief edges,filled with water and organic material, bogs around the edges. Something just doesn't figure here about this formation. If it is indeed an impact crater, it is highly anomalous, and it was not likely created by an ordinary impact like the other hundreds, if not thousands, were in the Canadian North.
Someone should start asking some serious questions about it. If it was an impact crater, there was an explosion "AFTER" the impact object buried itself, with enough extrusive heat and force to create molten rock. Some geologists play with the theory that some impacts can create nuclear chain reactions, if the materials are fortuitously present. Maybe they are right. I can't see this kind of formation ocurring without some major subterranean force being applied from way below. Thats usually volcanic. If its not volcanic, them WTF was it? The walls of this formation likley are as hard as granite.
I agree that the glaciers would seem to have covered the lake as they advanced and retreated, but this is a crater lake (it looks like it is raised above the nearby topography by the crater walls and what’s leftover of the rim) so perhaps the ice wasn’t deep enough here to cover the top of the walls.
The other glacier lakes are scraped out of the flat surrounding rock by the glacier itself, so later glacier advances are going to re-fill the same recess.
The image of a meteor crater jumping up and down the middle of north Canada is NOT what I want to think about ...
Now, how did you guys manage to lose the friggin' North Magnetic pole? It's getting shipped to Siberia right now, and I want it back!
Bush caused it all.
Any results yet?
Another possibility is the most gigantic pingo ever.
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