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New Evidence Supports Cosmic Impact Theory

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Quasar
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« on: June 30, 2012, 04:38:11 pm »


New Evidence Supports Cosmic Impact Theory
by Archaeorama News on Jun 13, 2012 • 18:57 6 Comments



melt-glass
    Melt glass known as trinitite formed at the ground surface from the melting of sediments and rocks by the very high temperatures of the Trinity nuclear airburst in New Mexico in 1945.  This material is very similar to the glassy melt materials now reported from the cosmic impact YDB layer. Credit: UCSB

Melt-glass material found in sedimentary rocks at sites around the world has provided new evidence for an extraterrestrial impact about 13,000 years ago, says a new study published in the current issue of the Proceedings of the National Academy of Sciences.

According to an international team of researchers that includes James Kennett, professor of earth science at UC Santa Barbara, the material, found in  Pennsylvania, South Carolina, and Syria, was formed at temperatures of 1,700 to 2,200 degrees Celsius (3,100 to 3,600 degrees Fahrenheit), and is the result of a cosmic body impacting Earth.

These new data strongly support the controversial Younger Dryas Boundary (YDB) hypothesis, which proposes that a cosmic impact occurred 12,900 years ago at the onset of an unusual cold climatic period called the Younger Dryas.

The episode occurred at or close to the time of major extinction of the North American megafauna, including mammoths and giant ground sloths; and the disappearance of the prehistoric and widely distributed Clovis culture.

Morphological and geochemical evidence of the melt-glass confirms that the material is not cosmic, volcanic, or of human-made origin.

“The very high temperature melt-glass appears identical to that produced in known cosmic impact events such as Meteor Crater in Arizona, and the Australasian tektite field,” said Kennett.

“The melt material also matches melt-glass produced by the Trinity nuclear airburst of 1945 in Socorro, New Mexico. The extreme temperatures required are equal to those of an atomic bomb blast, high enough to make sand melt and boil,” he said.
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Quasar
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« Reply #1 on: June 30, 2012, 04:38:41 pm »



Images of melted quartz from the YDB cosmic impact layer at Abu Hureyra, Syria, showing evidence of burst bubbles and flow textures that resulted from the melting and boiling of rock at very high temperatures. A: Light microscope image; B: scanning electron microscope image. Credit: UCSB
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« Reply #2 on: June 30, 2012, 04:39:06 pm »

The material evidence supporting the YDB cosmic impact hypothesis spans three continents, and covers nearly one-third of the planet, from California to Western Europe, and into the Middle East.

The discovery extends the range of evidence into Germany and Syria, the easternmost site yet identified in the northern hemisphere. The researchers have yet to identify a limit to the debris field of the impact.

“Because these three sites in North America and the Middle East are separated by 1,000 to 10,000 kilometers, there were most likely three or more major impact/airburst epicenters for the YDB impact event, likely caused by a swarm of cosmic objects that were fragments of either a meteorite or comet,” said Kennett.

He added that the archaeological site in Syria where the melt-glass material was found –– Abu Hureyra, in the Euphrates Valley –– is one of the few sites of its kind that record the transition from nomadic hunter-gatherers to farmer-hunters who live in permanent villages.

“Archeologists and anthropologists consider this area the ‘birthplace of agriculture,’ which occurred close to 12,900 years ago,” Kennett said.

“The presence of a thick charcoal layer in the ancient village in Syria indicates a major fire associated with the melt-glass and impact spherules 12,900 years ago. Evidence suggests that the effects on that settlement and its inhabitants would have been severe,” he said.

http://www.archaeorama.com/archaeology/cosmic-impact-theory/
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« Reply #3 on: June 30, 2012, 08:54:26 pm »

Meteorite Crater In Greenland Called World's Oldest, Biggest

Posted: 06/29/2012 5:45 pm Updated: 06/30/2012 9:31 am
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Meteorite Crater



By: Douglas Main, OurAmazingPlanet Staff Writer
Published: 06/29/2012 03:29 PM EDT on OurAmazingPlanet

A study of Greenland's rocks may have turned up something unexpected: the oldest and largest meteorite crater ever found on Earth.

Researchers think the crater was formed 3 billion years ago, making it the oldest ever found, said Danish researcher Adam Garde. The impact crater currently measures about 62 miles (100 kilometers) from one side to another. But before it eroded, it was likely more than 310 miles (500 km) wide, which would make it the biggest on Earth, Garde told OurAmazingPlanet.

The team has calculated it was caused by a meteorite 19 miles (30 km) wide, which, if it hit Earth today, would wipe out all higher life.

Mystery feature

In the 3 billion years since impact, the land has been eroded down to about 16 miles (25 km) below the original surface. But the effects of the intense shock wave and heat penetrated deep into the Earth, and remain visible today, said Garde, a researcher at the Geological Survey of Denmark and Greenland. [Meteor Mania: How Well Do You Know 'Shooting Stars'?]

Garde had been conducting research on Greenland's geology and noticed several strange features that didn't make sense. One day in September 2009, he came up with the extreme explanation of an impact from a meteorite. His team collected samples over the years and published the results in the July issue of the journal Earth and Planetary Science Letters. He's now "100 percent positive" it's a crater, for several reasons, he said.

For one, he found widespread crushed rocks in a circular shape that seemed to be caused by the shock waves of a massive impact. Second, there are deposits of a melted mineral called K-feldspar (or potassium-feldspar) that could have been liquefied only at extremely high heat, like that caused by an meteorite's crash-landing. There's also widespread evidence of weathering by hot water, which he thinks was caused by the ocean rushing into the crater after it struck the area. The area may have been covered by a shallow ocean at the time, but even if it wasn't, it doesn't matter, Garde said. "The crater from a meteorite that big would have caused the sea to rush in," he said.
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« Reply #4 on: June 30, 2012, 08:55:40 pm »



The black circle on map shows the location of the meteorite impact near the town of Maniitsoq in Greenland.
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« Reply #5 on: June 30, 2012, 08:55:59 pm »

Mining for minerals

John Spray, a meteorite expert at the University of New Brunswick, who wasn't involved in the research, said he thinks it's probably a meteor crater, but points out that it hasn't been proved, and may not be for some time. "It's very interesting and it's good science," he said. "But we don't really know how to recognize very old impact craters, because they are typically so highly modified."

That's because Earth is alive and constantly changing due processes such as erosion, precipitation and plate tectonics. At one time Earth likely had as many craters as the moon, which is essentially geologically dead. But these have mostly been wiped away, destroyed by erosion and the like.

Only around 180 impact craters have ever been discovered on Earth, and nearly one-third of them contain significant minerals deposits such as precious metals. The Canadian mining company, North American Nickel, is exploring the region where the potentially newfound crater is for nickel and other mineral deposits, company geologist John Roozendaal said. They are conducting airborne surveys and will soon do more mapping, small-scale sampling and drilling to see if they can find an area that could be economical to mine.

These impacts are of interest to mining companies not because of the large meteorites themselves — they typically vaporize — but because of the effect upon the Earth's surface. The impact heats rocks so much that metals can melt and then collect toward the bottom of the crater. Craters can also be important sources of oil and gas; the crushed, permeable rocks can act like a sponge, absorbing hydrocarbons.

Before this discovery, the oldest crater was thought to be the Vredefort crater in South Africa, estimated to be 2 billion years old. At 186 miles (300 km) wide, it's also the largest crater that remains visible. Scientists expect that there were many more craters formed around 3-4 billion years ago when Earth lacked a protective atmosphere.

Garde said the most interesting thing about the experience was finding an alternate explanation for something outside of his training. "I had a problem I couldn't solve in a region I knew very well," he said. "A meteor impact was the idea that made everything fall into place — It's not something I was looking for."

Reach Douglas Main at dmain@techmedianetwork.com. Follow him on Twitter @Douglas_Main. Follow OurAmazingPlanet on Twitter @OAPlanet. We're also on Facebook and Google+.

    World's Weirdest Geological Formations
    Meteor Crater: Experience an Ancient Impact
    Earth Quiz: Do You Really Know Your Planet?

Copyright 2012 OurAmazingPlanet, a TechMediaNetwork company. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.
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