My OperaBreaking News 11000 BC
Tuesday, April 6, 2010 6:26:01 PM
About 13000 years ago a cold climate period began and was to last for about 1000 years. The period is known as the Younger Dryas stadial, but is also also referred to as the Big Freeze - a period between approximately 12,800 to 11,500 years ago (10,800 to 9,500 BCE). It was the time when many big animals, like the mammoth, in North America died out - a rapid extinction of 35 families of North American mammals. The North American clovis culture was also wiped out or at least disrupted around this time. What triggered this cold spell.
For some time a controversial idea claimed it was due to a major extraterrestrial or cosmic impact centered over northern North America. A somewhat similar idea has now been put forward.
New comet hypothesis
It is suggested that the event occurred when the Earth strayed into a dense trail of fragments shed by a large disintegrating comet. Thousands of chunks of material from the comet would have rained down on Earth, each one releasing the energy of a one megaton nuclear bomb. The impacts would have triggered wildfires covering whole continents, filling the atmosphere with smoke and soot and blotting out the Sun. This hypothesis may in many ways seem more plausible than a single meteorite impact.
Lake Agassiz hypothesis
This is my favourite. Lake Agassiz was an immense glacial lake located in the center of North America. It held more water than contained by all lakes in the world today. Around 13,000 years ago the lake came to cover much of Manitoba, western Ontario, northern Minnesota, eastern North Dakota, and Saskatchewan. At its greatest extent, it may have covered as much as 440,000 km2 (about the size of the UK). This lake emptied in a very short time. It has however been debated which way the water flowed.
The Saint Lawrence Seaway has previously seemed a likely route. A route southwards along Missouri- Mississippi has also been in the picture. A study from 2007 pointed to the Hudson Strait as the outlet.
According to a new study published in Nature the melt-water however passed through what is now the Mackenzie River into the Arctic Ocean. A large flood into the Arctic Ocean at the start of the Younger Dryas lead the research team to reject the widespread view that Agassiz overflow at this time was solely eastward into the North Atlantic Ocean.
The huge amount of freshwater dumped into the Arctic Ocean led to the shutting down of the Gulf Stream with cooling effect for North Western Europe. The sea level rose enough for Mediterranean sea water to flow over into the Black Sea.
In Norwegian:
Now of course if a moraine damming Lake Agassiz decided to burst at approximately the same time as a meteorite committed suicide in the Hudson River, or wherever it was, and a comet swept its tail through our atmosphere - wouldn’t that be cool?
Note:
Younger Dryas is named after an indicator genus, the alpine/tundra wildflower Dryas octopetala.
Related posts:
For some time a controversial idea claimed it was due to a major extraterrestrial or cosmic impact centered over northern North America. A somewhat similar idea has now been put forward.
New comet hypothesis
It is suggested that the event occurred when the Earth strayed into a dense trail of fragments shed by a large disintegrating comet. Thousands of chunks of material from the comet would have rained down on Earth, each one releasing the energy of a one megaton nuclear bomb. The impacts would have triggered wildfires covering whole continents, filling the atmosphere with smoke and soot and blotting out the Sun. This hypothesis may in many ways seem more plausible than a single meteorite impact.
- http://www.telegraph.co.uk/science/space/7545993/Hour-long-hailstorm-may-have-caused-1000-year-freeze-say-scientists.html
- http://www.terradaily.com/reports/Comet_trail_may_have_caused_last_ice_age_999.html
Lake Agassiz hypothesis
This is my favourite. Lake Agassiz was an immense glacial lake located in the center of North America. It held more water than contained by all lakes in the world today. Around 13,000 years ago the lake came to cover much of Manitoba, western Ontario, northern Minnesota, eastern North Dakota, and Saskatchewan. At its greatest extent, it may have covered as much as 440,000 km2 (about the size of the UK). This lake emptied in a very short time. It has however been debated which way the water flowed.
The Saint Lawrence Seaway has previously seemed a likely route. A route southwards along Missouri- Mississippi has also been in the picture. A study from 2007 pointed to the Hudson Strait as the outlet.
According to a new study published in Nature the melt-water however passed through what is now the Mackenzie River into the Arctic Ocean. A large flood into the Arctic Ocean at the start of the Younger Dryas lead the research team to reject the widespread view that Agassiz overflow at this time was solely eastward into the North Atlantic Ocean.
The huge amount of freshwater dumped into the Arctic Ocean led to the shutting down of the Gulf Stream with cooling effect for North Western Europe. The sea level rose enough for Mediterranean sea water to flow over into the Black Sea.
- http://www.nature.com/nature/journal/v464/n7289/full/nature08954.html
- http://www.nature.com/news/2010/100331/full/464657a.html
- http://umanitoba.ca/news/blogs/blog/2010/04/01/news-release-lake-agassiz-drained-into-arctic-ocean/
- http://www.sheffield.ac.uk/mediacentre/2010/1583.html
- http://www.dailymail.co.uk/sciencetech/article-1262750/Mega-flood-triggered-Europes-big-freeze--global-warming-plunge-cold-warn-scientists.html#ixzz0k7cfmjkv
- http://www.montrealgazette.com/technology/Ancient+flood+path+that+sparked+cold+snap+traced/2754098/story.html
- http://www.sciencemag.org/cgi/content/abstract/1148924v1?etoc
In Norwegian:
Now of course if a moraine damming Lake Agassiz decided to burst at approximately the same time as a meteorite committed suicide in the Hudson River, or wherever it was, and a comet swept its tail through our atmosphere - wouldn’t that be cool?
Note:
Younger Dryas is named after an indicator genus, the alpine/tundra wildflower Dryas octopetala.
Related posts:
- http://my.opera.com/nielsol/blog/who-or-what-was-the-north-american-mammoth-killer
- http://my.opera.com/nielsol/blog/2007/06/11/belgium-iridum-and-clovis
- http://my.opera.com/nielsol/blog/2007/12/10/lake-agassiz
simoncito # Wednesday, April 7, 2010 10:28:30 AM
It's a mind-boggling scenario, indeed, a lake of that size bursting and draining to the sea in a very short time. But is it realistic? Could something like that happen as a cataclysmic event lasting, say, a few days rather than a matter of years or decades? Wouldn't such a catastrophe leave more tracks?
The gulf stream shutdown scenario would still be consistent with a slower drain of the melt water into the ocean, I suppose?
And one way or the other: this scenario would imply that a warming of the contintents around the Northern Atlantic means there is a big chance of sudden reversals into very cold snaps (if a thousand years can be called a "snap"), is that correct?
Ole Nielsennielsol # Wednesday, April 7, 2010 1:24:37 PM
As to the second point. There is no glacial lake that size today, so a repeat of the same scenario is out of the question. There has been a lot of speculation in the possibility of a sudden transition into an "icehouse world". I don't think this will happen in the "near future", but after a certain "tipping point", whatever that is, it could maybe happen from one year to the next.
simoncito # Friday, April 30, 2010 7:45:58 AM
This is not a glacial lake held back by a moraine, but a small river dam being demolished - but it's an impressive show of what water can do with a heap of dirt and stones in a few hours.
I thought this might be of interest. I also post this because it's such a cool thing to watch, in my opinion. :-)
Ole Nielsennielsol # Friday, April 30, 2010 8:54:39 AM
simoncito # Monday, June 28, 2010 9:12:40 PM
If these guys are right,
http://bit.ly/aLKqOr
then the sudden draining of Lake Agassiz didn't just cause the Younger Dryas cool period, it also had a much persistent effect - not on the atmosphere, but by changing the flow dynamics of the Atlantic.
What do you think about that? Does that sound convincing, or at least a possible account of things?
Ole Nielsennielsol # Tuesday, June 29, 2010 7:33:41 AM
An interesting link !
As these kind of stories usually concludes: more research is needed !