Some 12,800 years ago, when the climate was warming very fast and temperatures had almost reached present day levels... they suddenly plumetted again in a matter of months and remained at Ice Age levels for more than a thousand years before warming again. That period is known as the Younger Dryas.
|The Younger Dryas is the last cold gorge by the left|
There used to be several explanations but since some time ago, the meteorite impact theory has been gaining weight. This evidence would seem to consolidate it.
It was already quite consolidated as a theory because, while some had questioned the earliest evidence, further data had been collected from around the world that reinforced the model by about the same time.
The new evidence comes in form of melted glass (siliceous scoria like objects, SLOs) mineral inclusions from Pennsylvania (USA), which appears to require such an impact to have been produced. This kind of product requires temperatures similar to those of a nuclear explosion.
|The glass-like grains at two different imaging resolutions|
These remains have been found so far in North and South America, Europe and West Asia, suggesting several impacts from an already fragmented meteorite. It is unclear if there could be more such findings elsewhere on Earth.
One of the places directly affected by the impact was the site of Abu Hureyra, at the Mid-Upper Euphrates (Syria), where a layer of ashes followed by an archaeological hiatus mark the boundary between an Epipaleolithic and the more important Neolithic settlement.
The impact and the subsequent sudden cooling probably was a major influence in the extinction of some subarctic megafauna in North America and Northern Eurasia such as the mammoths.
Source: Science Daily.