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Did comet start deadly cold snap?
Canada.com ^
| Monday, May 14, 2007
| Margaret Munro
Posted on 05/16/2007 3:00:33 PM PDT by Mike Darancette
An extraterrestrial impact 13,000 years ago wiped out mammoths and started a mini-ice age, scientists believe
Margaret Munro CanWest News Service
Monday, May 14, 2007
A comet or some other extraterrestrial object appears to have slammed into northern Canada 12,900 years ago and triggered an abrupt and catastrophic climate change that wiped out the mammoths and many other prehistoric creatures, according to a team of U.S. scientists.
Evidence of the ecological disaster exists in a thin layer of sediment that has been found from Alberta to New Mexico, say the researchers, whose work adds a dramatic and provocative twist to the decades-old debate about the demise of the mammoths, mastodons and sloths that once roamed North America.
The sediment layer contains high concentrations of iridium, fullerenes and other compounds associated with space rocks and impacts, says Luann Becker, a geologist at the University of California, Santa Barbara, who has been analyzing the sediments.
"We have evidence for distribution of impact debris over several thousands of miles over the North American continent," says Ms. Becker, whose group will detail the findings at the American Geophysical Union meeting on May 24.
The sediment layer formed 12,900 years ago and coincides with both the extinction of the animals and the onset of a mini-ice age that lasted more than 1,000 years, say Ms. Becker and her colleagues from several U.S. universities and research labs. They say they are increasingly convinced the impact, extinction and cold snap are all related.
According to their scenario, a comet or large meteoroid generated a shock wave and threw massive amounts of debris, heat and gas into the atmosphere. This set off wildfires that raced across grasslands in southern North America, depriving the mammoths and other grazing animals of food.
The impact and heat also destabilized the ice sheet that blanketed Canada at the time, creating a flood of melt water that poured into the North Atlantic, according to their theory. The pulse of fresh water then shut down the ocean currents carrying heat from the tropics to the Northern Hemisphere, leading to an abrupt cooling. The resulting "mini-ice age" in the Northern Hemisphere, known as the Younger Dryas, lasted more than a thousand years.
Until now one of the leading explanations for the disappearance of the mammoths and other animals is that they were hunted to extinction by the people who arrived in North America from Asia at least 13,000 years ago.
But Ms. Becker and her colleagues doubt there could have been enough people to drive the creatures to extinction with spears. "It would have been a real challenge to slaughter all the animals," she says.
The leading explanation for the mini-ice age has been that melt water slowly built up behind the ice dams as the Earth warmed at the end of the last ice age and then suddenly burst, sending fresh water pouring into the North Atlantic.
Skeptics are not convinced an extraterrestrial impact explains either the disappearance of the animals or the mini-ice age, let alone both events.
Climatologist Andrew Weaver of the University of Victoria says the notion that an extraterrestrial impact caused the Younger Dryas "requires an extraordinarily huge leap of faith." He says there were many climate swings during the last glacial cycle; the mini-ice age was simply the last of them and does not require an extraterrestrial explanation.
Geophysicist Jerry Mitrovica at the University of Toronto is also skeptical. "I'll wait to see the published papers," says Mitrovica, who has studied how the melting ice helped trigger the miniice age.
While the idea of a comet impact may seem far-fetched, Mr. Mitrovica notes that it took almost a decade before scientists accepted geologist Walter Alvarez's evidence that the iridiumrich layer he found pointed to the asteroid impact that killed off the dinosaurs 65 million years ago.
Ms. Becker says the details of their findings will likely be published in the science journals this summer. Meantime, she and her colleagues are expecting a "spirited" debate at next week's AGU meeting.
She says the concentration of the iridium in the sediment layer dating back to 12,900 years is several times higher than normal. It also contains compounds called "fullerenes" with extraterrestrial gases in them, as well as glasslike carbons that require extraordinarily high temperatures to form. "It's a very discrete, well-defined layer," she says.
As for the crater created by the impact, the scientists say it would have formed on the kilometres-thick ice that covered Canada at the time and melted away with the ice.
TOPICS: News/Current Events
KEYWORDS: acrossatlanticice; brucebradley; catastrophism; clovis; cloviscomet; clovisimpact; comet; dennisstanford; extinction; godsgravesglyphs; iceage; impact; kennethtankersley; preclovis; solutreans
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81
posted on
06/10/2007 9:09:55 PM PDT
by
SunkenCiv
(Time heals all wounds, particularly when they're not yours. Profile updated June 8, 2007.)
82
posted on
06/10/2007 9:37:29 PM PDT
by
SunkenCiv
(Time heals all wounds, particularly when they're not yours. Profile updated June 8, 2007.)
To: muawiyah
I have come to the conclusion based on various inputs that there was something bad that happened about 8,000 years ago. Can you recommend any links?
To: gleeaikin
Genesis ~ oldest story ever about a flood that reached to the mountains.
The Alaskan Earthquake back in the 1960s caused some Tsunamis that reached over 1,000 feet.
There were undoubtedly smaller floods.
84
posted on
12/14/2007 6:35:54 PM PST
by
muawiyah
85
posted on
09/20/2012 4:56:41 PM PDT
by
SunkenCiv
(https://secure.freerepublic.com/donate/)
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