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Ice Age blast 'ravaged America'

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Adam Hawthorne
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« on: May 21, 2007, 07:09:05 pm »

Ice Age blast 'ravaged America'



 
A space rock may have exploded in the air over North America

A controversial new idea suggests that a large space rock exploded over North America 13,000 years ago.

The blast may have wiped out one of America's first Stone Age cultures as well as the continent's big mammals such as the mammoth and the mastodon.

The blast, from a comet or asteroid, caused a major bout of climatic cooling which may also have affected human cultures emerging in Europe and Asia.

Scientists will outline their evidence this week at a meeting in Mexico.

  "Their impact theory shouldn't be dismissed; it deserves further investigation."

- Jeff Severinghaus, Scripps Institution of Oceanography


The evidence comes from layers of sediment at more than 20 sites across North America.

These sediments contain exotic materials: tiny spheres of glass and carbon, ultra-small specks of diamond - called nanodiamond - and amounts of the rare element iridium that are too high to have come from Earth.

All, they argue, point to the explosion 12,900 years ago of an extraterrestrial object up to 5km across.

No crater remains, possibly because the Laurentide Ice Sheet, which blanketed thousands of sq km of North America during the last Ice Age, was thick enough to mask the impact.

Another possibility is that it exploded in the air.

Climate cooling

The rocks studied by the researchers have a black layer which, they argue, is the charcoal deposited by wildfires which swept the continent after the explosion.

 

The Clovis people developed an advanced stone tool technology

The blast would not only have generated enormous amounts of heat that could have given rise to wildfires, but also brought about a period of climate cooling that lasted 1,000 years - an event known as the Younger Dryas.

Professor James Kennett, from the University of California in Santa Barbara (UCSB), said the explosion could be to blame for the extinction of several large North American mammals at the end of the last Ice Age.

"All the elephants, including the mastodon and the mammoth, all the ground sloths, including the giant ground sloth - which, when standing on its hind legs, would have been as big as a mammoth," he told the BBC.

"All the horses went out, all the North American camels went out. There were large carnivores like the sabre-toothed cat and an enormous bear called the short-faced bear."

Professor Kennett said this could have had an enormous impact on human populations.

Population decline

According to the traditional view, humans crossed from north-east Asia to America at the end of the last Ice Age, across a land bridge which - at the time - connected Siberia to Alaska.

 

The extinction of large North American beasts is a puzzle

The Clovis culture was one of the earliest known cultures in the continent. These proficient hunter-gatherers developed a distinctive thin, fluted spear head known as the Clovis point, which is regarded as one of the most sophisticated stone tools ever developed.

Archaeologists have found evidence from the Topper site in South Carolina, US, that Clovis populations here went through a population collapse.

But there is no evidence of a similar decline in other parts of the continent. The Clovis culture does vanish from the archaeological record abruptly, but it is replaced by a myriad of different local hunter-gatherer cultures.


 
The Tunguska event devastated parts of Siberia in 1908

Jeff Severinghaus, a palaeoclimatologist at Scripps Institution of Oceanography in California, told Nature magazine: "Their impact theory shouldn't be dismissed; it deserves further investigation."

According to the new idea, the comet would have caused widespread melting of the North American ice sheet. The waters would have poured into the Atlantic, disrupting its currents.

This, they say, could have caused the 1,000 year-long Younger Dryas cold spell, which also affected Asia and Europe.

The Younger Dryas has been linked by some researchers to changes in the living patterns of people living in the Middle East which led to the beginning of farming.

A massive explosion near the Tunguska river, Siberia, in 1908, is also thought to have been caused by a space rock exploding in the atmosphere. It felled 80 million trees over an area of 2,000 sq km.

The new theory will be presented and debated at the American Geophysical Union's Joint Meeting in Acapulco, Mexico, this week.

 http://news.bbc.co.uk/2/hi/science/nature/6676461.stm
« Last Edit: May 21, 2007, 07:12:57 pm by Adam » Report Spam   Logged

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Adam Hawthorne
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« Reply #1 on: May 21, 2007, 07:14:23 pm »

Diamonds tell tale of comet that killed off the cavemen


Fireballs set half the planet ablaze, wiping out the mammoth and America's Stone Age hunters

Robin McKie, science editor
Sunday May 20, 2007
The Observer


Scientists will outline dramatic evidence this week that suggests a comet exploded over the Earth nearly 13,000 years ago, creating a hail of fireballs that set fire to most of the northern hemisphere.
Primitive Stone Age cultures were destroyed and populations of mammoths and other large land animals, such as the mastodon, were wiped out. The blast also caused a major bout of climatic cooling that lasted 1,000 years and seriously disrupted the development of the early human civilisations that were emerging in Europe and Asia.

'This comet set off a shock wave that changed Earth profoundly,' said Arizona geophysicist Allen West. 'It was about 2km-3km in diameter and broke up just before impact, setting off a series of explosions, each the equivalent of an atomic bomb blast. The result would have been hell on Earth. Most of the northern hemisphere would have been left on fire.'

The theory is to be outlined at the American Geophysical Union meeting in Acapulco, Mexico. A group of US scientists that include West will report that they have found a layer of microscopic diamonds at 26 different sites in Europe, Canada and America. These are the remains of a giant carbon-rich comet that crashed in pieces on our planet 12,900 years ago, they say. The huge pressures and heat triggered by the fragments crashing to Earth turned the comet's carbon into diamond dust. 'The shock waves and the heat would have been tremendous,' said West. 'It would have set fire to animals' fur and to the clothing worn by men and women. The searing heat would have also set fire to the grasslands of the northern hemisphere. Great grazing animals like the mammoth that had survived the original blast would later have died in their thousands from starvation. Only animals, including humans, that had a wide range of food would have survived the aftermath.'

The scientists point out that archaeological evidence shows that early Stone Age cultures clearly suffered serious setbacks at this time. In particular, American Stone Age hunters, descendants of the hunter-gatherers who had migrated to the continent from Asia, vanished around this time.

These people were some of the fiercest hunters on Earth, men and women who made magnificent stone spearheads which they used to hunt animals including the mammoth. Their disappearance at this time has been a cause of intense debate, with climate change being put forward as a key explanation. Now there is a new idea: the first Americans were killed by a comet.

It was not just America that bore the brunt of the comet crash. At this time, the Earth was emerging from the last Ice Age. The climate was slowly warming, though extensive ice fields still covered higher latitudes. The disintegrating comet would have plunged into these ice sheets, causing widespread melting. These waters would have poured into the Atlantic, disrupting its currents, including the Gulf stream. The long-term effect was a 1,000-year cold spell that hit Europe and Asia.

The comet theory, backed by observational evidence collected by the team, has excited considerable attention from other researchers, following publication of an outline report of the work in Nature

'The magnitude of this discovery is so important,' team member James Kennett, of the University of California, Santa Barbara, told the journal. 'It explains three of the highest-debated controversies of recent decades.'

These are the sudden disappearance of the first Stone Age people of America, the disappearance of mammoths throughout much of Europe and America and the sudden cooling of the planet, an event known as the Younger-Dryas period. Various theories have been put forward to explain these occurrences, but now scientists believe they have found a common cause in a comet crash. However, the idea is still controversial and the theory is bedevilled by problems in obtaining accurate dates for the different events.

'We still have a long way to go,' admitted West. 'But we have a great deal of evidence, from many sites, so this is quite a powerful case that we are making.'

http://www.guardian.co.uk/science/story/0,,2083785,00.html

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Adam Hawthorne
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« Reply #2 on: May 24, 2007, 02:38:38 am »

New Clovis-Age Comet Impact Theory
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Science News   Keywords
ARCHAEOLOGY, ANTHROPOLOGY, GEOLOGY, CLOVIS, COMET, EXINCTION, PLEISTOCENE, OREGON, AGU 
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Two University of Oregon researchers are on a multi-institutional 26-member team proposing a startling new theory: that an extraterrestrial impact, possibly a comet, set off a 1,000-year-long cold spell and wiped out or fragmented the prehistoric Clovis culture and a variety of animal genera across North America almost 13,000 years ago. 

 
 
 
 
 

Newswise — Two University of Oregon researchers are on a multi-institutional 26-member team proposing a startling new theory: that an extraterrestrial impact, possibly a comet, set off a 1,000-year-long cold spell and wiped out or fragmented the prehistoric Clovis culture and a variety of animal genera across North America almost 13,000 years ago.

Driving the theory is a carbon-rich layer of soil that has been found, but not definitively explained, at some 50 Clovis-age sites in North America that date to the onset of a cooling period known as the Younger Dryas Event. The sites include several on the Channel Islands off California where UO archaeologists Douglas J. Kennett and Jon M. Erlandson have conducted research.

The theory is being discussed publicly, for the first time, Wednesday, May 23, at the 2007 Joint Assembly of the American Geophysical Union in Acapulco, Mexico. Kennett is among the attendees who will be available to discuss the theory with their peers. The British journal Nature first addressed the theory in a news-section story in its May 18 issue.

Before today, members of the team – including Kennett’s father, James P. Kennett of the University of California, Santa Barbara, and Richard B. Firestone of Lawrence Berkeley National Laboratory – had been quietly introducing the theory to their professional colleagues.

Douglas Kennett, with Erlandson watching, detailed the theory May 19 to a fully packed UO classroom, where students and faculty members from archaeology, art history, anthropology, biology, geology, geography, political science and psychology, pelted Kennett with questions.

The researchers propose that a known reversal in the world’s ocean currents and associated rapid global cooling, which some scientists blame for the extinction of multiple species of animals and the end of the Clovis Period, was itself the result of a bigger event. While generally accepted theory says glacial melting from the North American interior caused the shift in currents, the new proposal points to a large extraterrestrial object exploding above or even into the Laurentide Ice Sheet north of the Great Lakes.

“Highest concentrations of extraterrestrial impact materials occur in the Great Lakes area and spread out from there,” Kennett said. “It would have had major effects on humans. Immediate effects would have been in the North and East, producing shockwaves, heat, flooding, wildfires, and a reduction and fragmentation of the human population.”

The carbon-rich layer contains metallic microspherules, iridium, carbon spherules, fullerenes, charcoal and soot. Some of those ingredients were found worldwide in soils dating to the K-T Boundary of 65 million years ago.

The K-T layer marks the end of the Cretaceous Period and the beginning of the Tertiary Period, when numerous species were wiped out after a massive asteroid is believed to have struck Mexico’s Yucatan Peninsula and the Gulf of Mexico.

Missing in the new theory is a crater marking an impact, but researchers argue that a strike above or into the Laurentide ice sheet could have absorbed it since it was less intense than the K-T event.

Kennett said that 35 animal genera went extinct at the end of the Pleistocene, with at least 15 clearly being wiped out close to 12,900 years ago. There would have been major ecological shifts, driving Clovis survivors into isolated groups in search of food and warmth. There is evidence, he said, that pockets of Clovis people survived in refugia, especially in the western United States.

“This was a massive continental scale, if not global, event,” Kennett said. He and Erlandson say that they are currently evaluating the existing Paleo-Indian archaeological datasets, which Kennett describes as “suggestive of significant population reduction and fragmentation, but additional work is necessary to test this hypothesis further.” Earlier research efforts need to be re-evaluated using new technologies that can narrow radiocarbon date ranges, and, as funding becomes available, new sites can be located and studied, Erlandson said.

“As we have grown more confident in the theory,” Erlandson said, “we’ve been letting some of it out in informal talks to gage the response to see where we are headed and what the initial objections are, which will help us to maintain our own objectivity.”

The interest in pursuing both old and new leads could ignite a major surge of interdisciplinary questioning and attract a new wave of interested students, Kennett and Erlandson said.


Links: Kennett faculty Web page: http://www.uoregon.edu/~dkennett/Welcome.html;
Erlandson faculty Web page: http://www.uoregon.edu/~dkennett/Welcome.html





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© 2007 Newswise.  All Rights Reserved.
 
http://www.newswise.com/articles/view/530208/
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« Reply #3 on: June 02, 2007, 08:58:08 pm »

Ice Age Ends Smashingly: Did a comet blow up over eastern Canada?
Sid Perkins


Evidence unearthed at more than two dozen sites across North America suggests that an extraterrestrial object exploded in Earth's atmosphere above Canada about 12,900 years ago, just as the climate was warming at the end of the last ice age. The explosion sparked immense wildfires, devastated North America's ecosystems and prehistoric cultures, and triggered a millennium-long cold spell, scientists say.


 
IT'S IN THERE. A layer of carbon-rich sediment (arrow) found here at Murray Springs, Ariz., and elsewhere across North America, provides evidence that an extraterrestrial object blew up over Canada 12,900 years ago. The hallmarks include lumps of glasslike carbon (top), carbon spherules (middle, in cross section), and magnetic grains rich in iridium (bottom).
West; (middle inset): Cannon Microprobe
 


At sites stretching from California to the Carolinas and as far north as Alberta and Saskatchewan—many of which were home to prehistoric people of the Clovis culture—researchers have long noted an enigmatic layer of carbon-rich sediment that was laid down nearly 13 millennia ago. "Clovis artifacts are never found above this black mat," says Allen West, a geophysicist with Geoscience Consulting in Dewey, Ariz. The layer, typically a few millimeters thick, lies between older, underlying strata that are chock-full of mammoth bones and younger, fossilfree sediments immediately above, he notes.

New analyses of samples taken from 26 of those sites reveal several hallmarks of an extraterrestrial object's impact, West and his colleagues reported at the spring meeting of the American Geophysical Union in Acapulco, Mexico.

Samples from the base of the black mat yield most of the clues to its extraterrestrial origin, says Richard B. Firestone, West's coworker and a nuclear physicist at the Lawrence Berkeley (Calif.) National Laboratory. Some of the particles there are small, magnetic grains of material with higher proportions of iridium than are found in Earth's crust, he notes.

Also in the mat's base are tiny lumps of glasslike carbon that probably formed from molten droplets of the element. These lumps, as well as little spheres of carbon with a different microstructure, contain nanoscale diamonds formed under intense pressure.

A host of unusual geological features, collectively known as Carolina Bays, hints at the cataclysm's location, says team member George A. Howard, a wetland manager at Restoration Systems, an environmental-restoration firm in Raleigh, N.C. Around 1 million of these elliptical, sand-rimmed depressions, measuring between 50 meters and 11 kilometers across, scar the landscape from New Jersey to Florida. In samples taken from 15 of the features, Howard and his colleagues found iridium-rich magnetic grains and carbon spherules with tiny diamond fragments similar to those found at Clovis archaeological sites.

The long axes of the great majority of the Carolina Bays point toward locations near the Great Lakes and in Canada—a hint that the extraterrestrial object disintegrated over those locales, says Howard.

Because scientists "haven't discovered a large, smoking hole" left by the event, the object that blew up in the atmosphere probably was a comet, says West.

Heat from the event would have set off wildfires across the continent, the scientists suggest. The heat and shock from the explosion probably broke up portions of the ice sheet smothering eastern Canada at the time, they add. The flood of fresh water into the North Atlantic that resulted would have interrupted ocean currents that bring warmth to the region, and thick clouds of smoke and soot in the air would have intensified cooling across the Northern Hemisphere.

The inferred date of the event matches the beginning of a 1,200-year-long cold spell that geologists call the Younger Dryas, which in its first few decades saw temperatures in the Northern Hemisphere drop as much as 10°C.



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Adam Hawthorne
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« Reply #4 on: June 02, 2007, 08:59:39 pm »

References:

Firestone, R.B., A. West, et al. 2007. Evidence for a massive extraterrestrial airburst over North America 12.9 ka Ago (Presentation PP41A-01). Joint Assembly of the American Geophysical Union. May 22-25. Acapulco, Mexico. Abstract.

Howard, G.A., A. West, R.B. Firestone, et al. 2007. Evidence for an extraterrestrial impact origin of the Carolina Bays on the Atlantic Coast of North America (Presentation PP42A-05). Joint Assembly of the American Geophysical Union. May 22-25. Acapulco, Mexico. Abstract.

West, A., R.B. Firestone, et al. 2007. Extraterrestrial markers found at Clovis sites across North America (Presentation PP41A-02). Joint Assembly of the American Geophysical Union. May 22-25. Acapulco, Mexico. Abstract.


Further Readings:

Becker, . . . L. A. West, and W. Wolbach. 2007. The end Pleistocene extinction event—what caused it? (Presentation PP41A-03). Joint Assembly of the American Geophysical Union. May 22-25. Acapulco, Mexico. Abstract.

Bower, B. 2007. New age for ancient Americans. Science News 171(March 3):141. Available to subscribers at http://www.sciencenews.org/articles/20070303/note12.asp.

Kennett, J.P., L. Becker, and A. West. 2007. Triggering of the Younger Dryas cooling by extraterrestrial impact (Presentation PP41A-05). Joint Assembly of the American Geophysical Union. May 22-25. Acapulco, Mexico. Abstract.

Kennett, D.J., et al. 2007. Exploring the human ecology of the Younger Dryas extraterrestrial impact event (Presentation PP42A-02). Joint Assembly of the American Geophysical Union. May 22-25. Acapulco, Mexico. Abstract.

Perkins, S. 2002. Presto, change-o! Science News 161(June 15):378-380. Available at http://www.sciencenews.org/articles/20020615/bob9.asp.


Sources:

Richard B. Firestone
Lawrence Berkeley National Laboratory
Nuclear Science Division
Isotopes Project
Berkeley, CA 94720

George A. Howard
Restoration Systems, LLC
1101 Haynes Street, Suite 107
Raleigh, NC 27604

Allen West
GeoScience Consulting
P.O. Box 1636
Dewey, AZ 86327

http://www.sciencenews.org/articles/20070602/fob1.asp

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