I am posting this news story because it establishes a couple of dates rather more closely than previously. I think readers could read my postings back in July of last year to understand my ideas on the Pleistocene nonconformity. This has also been published in Viewzone (Google it).
The reduction of the Laurentide ice sheet was the final act in the total collapse of the Northern Ice Cap. The first act was the swift collapse of the Scandinavian sheet. What this makes very clear is that the final collapse was an escapement of a huge amount of pent up lake water a mere 8200 years ago.
The drop in global temperatures may have lasted a couple of hundred years, but the reduction of the balance of the ice would be then steady and uneventful. This means that the global climate finally stabilized only 7800 years ago. This all coincides with the rise of agricultural man in the Northern Hemisphere. Mind you conditions had been improving during the previous 5000 years as the climate regime of the Holocene established itself.
This also means that the sea would have swiftly risen a total of 45 feet, almost certainly driving out coastal populations from fertile deltas in particular. This is keeping in mind that the loss of the Northern Ice Cap over the past 5,000 years had driven all populations off the continental shelf itself. We know that the total rise in sea levels was around 300 feet.
I find this late date for the collapse of the Laurentide to be intriguing. The actual climate became warm through to about 3,000 years ago ending with the demise of the Bronze Age.
In any event the apparent settling of the temperate zones appears to have happened hot on the heels of any climatic improvement. It is as if we were ready and waiting to go. Cattle culture in particular was established in
as early as 9,000 years ago. Obviously the England Gulf Stream was hard at work.
I cannot emphasize strongly enough how utterly recent the rise of man in the temperate climes is. In the meantime, the possible antiquity of man in the tropics is not even been truly investigated if it can be. Did some form of agricultural man arise, say thirty thousand years ago? The sea has covered the traces of maritime man in those same waters.
How it happened: The catastrophic flood that cooled the Earth
PARIS (AFP) — Canadian geologists say they can shed light on how a vast lake, trapped under the ice sheet that once smothered much of North America, drained into the sea, an event that cooled Earth's climate for hundreds of years.
During the last ice age, the Laurentide Ice Sheet once covered most of Canada and parts of the northern United States with a frozen crust that in some places was three kilometres (two miles) thick.
As the temperature gradually rose some 10,000 years ago, the ice receded, gouging out the hollows that would be called the
Beneath the ice's thinning surface, an extraordinary mass of water built up -- the glacial lake Agassiz-Ojibway, a body so vast that it covered parts of Manitoba, Saskatchewan, North Dakota, Ontario and Minnesota.
And then, around 8,200 years ago, Agassiz-Ojibway massively drained, sending a flow of water into the
By some estimates, sea levels rose 14 metres (45 feet) as a result.
How the great flood was unleashed has been a matter of debate.
Some experts suggest an ice dam was smashed down, or the gushing water spewed out over the top of the icy lid.
Quebec researchers Patrick Lajeunesse and Guillaume Saint-Onge believe, though, that the outburst happened under the ice sheet, rather than above it or through it.
In a study appearing on Sunday in the journal Nature Geoscience, the pair describe how they criss-crossed Hudson Bay on a research vessel, using sonar to scan more than 10,500 kilometres (6,000 miles) to get a picture of the bay floor.
In the south of the bay, they found lines of deep waves in the sandy bed, stretching more than 900 kilometres (562 miles) in length and some 1.7 metres (5.5 feet) deep.
These are signs that the bay's floor, protected by the mighty lid of ice, was swept by a mighty current many years ago but has been still ever since, they say.
In the west of the bay, they found curious marks in the shape of parabolas twisting around to the northeast.
The arcs were chiselled as much as three metres (10 feet) into the sea bed and found at depths of between 80 and 205 metres (260 and 666 feet).
The duo believe that this part of the bay had icebergs that were swept by the massive current.
The bergs' jagged tips were trapped in the sea bed and acted like a pivot. As the icebergs swung around, other protruding tips ripped arc-like tracks on the bay floor.
Also presented as evidence are deep submarine channels and deposits of red sediment that stretch from land west of Hudson Bay right across the northwestern floor of the bay itself -- both point to a current that swept all before it.
"Laurentide ice was lifted buoyantly, enabling the flood to traverse southern Hudson Bay under the ice sheet," the study suggests.
Previous work suggests the flood was so huge that it affected climate around the world.
The influx of freshwater into the
Temperatures dropped by more than three degrees Celsius (5.4 degrees Fahrenheit) in