Thursday, August 2, 2007
Fear of Velikovsky
A new theory tries to explain the Younger Dryas with an extraterrestrial impact. The key evidence for the theory by two Oregon researchers is a carbon-rich layer of soil that has been found at some 50 Clovis-age sites in North America that date to the onset of a cooling period known as the Younger Dryas Event.
Near the end of the last glacial period, North America was covered with huge masses of ice. It is believed that some of the peaks of the Laurentide ice sheet were up to two miles in thickness. After the Last Glacial Maximum, the ice began to melt as North America got warmer. The cause of this warming is generally believed to be the Milankovitch astronomical cycles which gradually alter the amount of solar radiation in the upper latitudes of the northern hemisphere. Then suddenly about 13,000 years ago, North America had another cold period that lasted over 1,000 years. This period is called the Younger Dryas.
The widely accepted theory for the cause of the Younger Dryas has been that glacial melting dumped large quantities of fresh water into the North Atlantic and this altered the Gulf Stream and the worldwide thermohaline circulation.
This new theory perhaps provides an different explanation for the sudden dumping of large quantities of fresh water into the North Atlantic.
We can imagine what might be the effect of a comet or asteroid crashing into a two miles thick glacier. In a matter of seconds, enormous amounts of ice would be vaporized. Much of the water would fall back to Earth within several hundred miles of impact but still substantial amounts would be spread over the Northern Hemisphere. In Siberia, the water might fall in enormous snowstorms depositing dozens of feet of snow in a matter of hours. In the lower latitudes, there could occur deluges and floods even in areas normally dry. Some quantity of the water vapor might be injected into the upper atmosphere where it could condense as ice crystals reflecting solar radiation and possibly dramatically cooling the Earth.
The new theory probably has rough sledding ahead. Scientists generally do not like catastrophism as an explanation. They like the predictable but it is certainly clear that the unpredictable can have a substantial impact in Earth's history.
Near the end of the last glacial period, North America was covered with huge masses of ice. It is believed that some of the peaks of the Laurentide ice sheet were up to two miles in thickness. After the Last Glacial Maximum, the ice began to melt as North America got warmer. The cause of this warming is generally believed to be the Milankovitch astronomical cycles which gradually alter the amount of solar radiation in the upper latitudes of the northern hemisphere. Then suddenly about 13,000 years ago, North America had another cold period that lasted over 1,000 years. This period is called the Younger Dryas.
The widely accepted theory for the cause of the Younger Dryas has been that glacial melting dumped large quantities of fresh water into the North Atlantic and this altered the Gulf Stream and the worldwide thermohaline circulation.
This new theory perhaps provides an different explanation for the sudden dumping of large quantities of fresh water into the North Atlantic.
We can imagine what might be the effect of a comet or asteroid crashing into a two miles thick glacier. In a matter of seconds, enormous amounts of ice would be vaporized. Much of the water would fall back to Earth within several hundred miles of impact but still substantial amounts would be spread over the Northern Hemisphere. In Siberia, the water might fall in enormous snowstorms depositing dozens of feet of snow in a matter of hours. In the lower latitudes, there could occur deluges and floods even in areas normally dry. Some quantity of the water vapor might be injected into the upper atmosphere where it could condense as ice crystals reflecting solar radiation and possibly dramatically cooling the Earth.
The new theory probably has rough sledding ahead. Scientists generally do not like catastrophism as an explanation. They like the predictable but it is certainly clear that the unpredictable can have a substantial impact in Earth's history.
# posted by Jim Cross : 3:36 AM
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