Breaking News 11000 BC
Tuesday, April 6, 2010 6:26:01 PM
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.
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?
Younger Dryas is named after an indicator genus, the alpine/tundra wildflower Dryas octopetala.