From the University of California – Santa Barbara some paleoclimatology without the need to see hockey sticks.
Comprehensive analysis of impact spherules supports theory of cosmic impact 12,800 years ago
(Santa Barbara, California) –– About 12,800 years ago when the Earth was warming and emerging from the last ice age, a dramatic and anomalous event occurred that abruptly reversed climatic conditions back to near-glacial state. According to James Kennett, UC Santa Barbara emeritus professor in earth sciences, this climate switch fundamentally –– and remarkably –– occurred in only one year, heralding the onset of the Younger Dryas cool episode.
The cause of this cooling has been much debated, especially because it closely coincided with the abrupt extinction of the majority of the large animals then inhabiting the Americas, as well as the disappearance of the prehistoric Clovis culture, known for its big game hunting.
“What then did cause the extinction of most of these big animals, including mammoths, mastodons, giant ground sloths, American camel and horse, and saber- toothed cats?” asked Kennett, pointing to Charles Darwin’s 1845 assessment of the significance of climate change. “Did these extinctions result from human overkill, climatic change or some catastrophic event?” The long debate that has followed, Kennett noted, has recently been stimulated by a growing body of evidence in support of a theory that a major cosmic impact event was involved, a theory proposed by the scientific team that includes Kennett himself.
Now, in one of the most comprehensive related investigations ever, the group has documented a wide distribution of microspherules widely distributed in a layer over 50 million square kilometers on four continents, including North America, including Arlington Canyon on Santa Rosa Island in the Channel Islands. This layer –– the Younger Dryas Boundary (YDB) layer –– also contains peak abundances of other exotic materials, including nanodiamonds and other unusual forms of carbon such as fullerenes, as well as melt-glass and iridium. This new evidence in support of the cosmic impact theory appeared recently in a paper in the Proceedings of the National Academy of the Sciences.
This cosmic impact, said Kennett, caused major environmental degradation over wide areas through numerous processes that include continent-wide wildfires and a major increase in atmospheric dust load that blocked the sun long enough to cause starvation of larger animals.
Investigating 18 sites across North America, Europe and the Middle East, Kennett and 28 colleagues from 24 institutions analyzed the spherules, tiny spheres formed by the high temperature melting of rocks and soils that then cooled or quenched rapidly in the atmosphere. The process results from enormous heat and pressures in blasts generated by the cosmic impact, somewhat similar to those produced during atomic explosions, Kennett explained.
But spherules do not form from cosmic collisions alone. Volcanic activity, lightning strikes, and coal seam fires all can create the tiny spheres. So to differentiate between impact spherules and those formed by other processes, the research team utilized scanning electron microscopy and energy dispersive spectrometry on nearly 700 spherule samples collected from the YDB layer. The YDB layer also corresponds with the end of the Clovis age, and is commonly associated with other features such as an overlying “black mat” –– a thin, dark carbon-rich sedimentary layer –– as well as the youngest known Clovis archeological material and megafaunal remains, and abundant charcoal that indicates massive biomass burning resulting from impact.
The results, according to Kennett, are compelling. Examinations of the YDB spherules revealed that while they are consistent with the type of sediment found on the surface of the earth in their areas at the time of impact, they are geochemically dissimilar from volcanic materials. Tests on their remanent magnetism –– the remaining magnetism after the removal of an electric or magnetic influence –– also demonstrated that the spherules could not have formed naturally during lightning strikes.
“Because requisite formation temperatures for the impact spherules are greater than 2,200 degrees Celsius, this finding precludes all but a high temperature cosmic impact event as a natural formation mechanism for melted silica and other minerals,” Kennett explained. Experiments by the group have for the first time demonstrated that silica-rich spherules can also form through high temperature incineration of plants, such as oaks, pines, and reeds, because these are known to contain biologically formed silica.
Additionally, according to the study, the surface textures of these spherules are consistent with high temperatures and high-velocity impacts, and they are often fused to other spherules. An estimated 10 million metric tons of impact spherules were deposited across nine countries in the four continents studied. However, the true breadth of the YDB strewnfield is unknown, indicating an impact of major proportions.
“Based on geochemical measurements and morphological observations, this paper offers compelling evidence to reject alternate hypotheses that YDB spherules formed by volcanic or human activity; from the ongoing natural accumulation of space dust; lightning strikes; or by slow geochemical accumulation in sediments,” said Kennett.
“This evidence continues to point to a major cosmic impact as the primary cause for the tragic loss of nearly all of the remarkable American large animals that had survived the stresses of many ice age periods only to be knocked out quite recently by this catastrophic event.”
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PNAS, uh? Anybody please check for peer review, if any.
This topic is starting to get interesting.
Cosmic collisions! We’re doomed! (Again.)
The crater..
Center in Elko, Nevada..
Diameter form Reno to Salt lake city..
And form Las Vegas to Boise
Too Big?
The PNAS is publishing studies based on empirical data again?
Break out the Champagne!
omnologos said on May 21, 2013 at 3:53 pm:
Ahh, FINALLY found it!
http://www.pnas.org/content/early/2013/05/17/1301760110.abstract
Twenty eight authors?
Edited* by Steven M. Stanley, University of Hawaii, Honolulu, HI, and approved April 9, 2013 (received for review January 28, 2013)
and
*This Direct Submission article had a prearranged editor.
Is that anything like an answer?
What an interesting article. Does the full article give a hint as to where the impact site is?
I suppose Barbara Boxer will now want to increase the carbon tax to stop meteorite impacts.
Since it first came out in 2007, the Younger Dryas impact hypothesis has not been supported by other scientists who tried to replicate or test its conclusions. A 2011 review of the evidence concluded
“In summary, none of the original YD impact signatures have been subsequently corroborated by independent tests. Of the 12 original lines of evidence, seven have so far proven to be non-reproducible. The remaining signatures instead seem to represent either (1) non-catastrophic mechanisms, and/or (2) terrestrial rather than extraterrestrial or impact-related sources. In all of these cases, sparse but ubiquitous materials seem to have been misreported and misinterpreted as singular peaks at the onset of the YD. Throughout the arc of this hypothesis, recognized and expected impact markers were not found, leading to proposed YD impactors and impact processes that were novel, self-contradictory, rapidly changing, and sometimes defying the laws of physics. The YD impact hypothesis provides a cautionary tale for researchers, the scientific community, the press, and the broader public.”
http://www.sciencedirect.com/science/article/pii/S0012825211000262
The Supporting Data makes an interesting read (30 pg PDF):
http://www.pnas.org/content/suppl/2013/05/20/1301760110.DCSupplemental/sapp.pdf
I wonder how much safer we’d be, including Jim Hansen’s grandchildren, if all the $ spent over the last 20 years on climate supercomputers and alternative energy tax subsidies had been spent instead on a near-Earth asteroid (NEA) monitoring system, and research into advanced propulsion.
Pure science makes paleoclimatology very believable and a very interesting read. about 4 years ago I saw a documentary describing this event in detail – The end of the Clovis age, and is commonly associated with other features such as an overlying “black mat” and abundant charcoal that indicates massive biomass burning resulting from impact.
See the Nova Doc: End of the Big Beasts
Who or what killed off North America’s mammoths and other megafauna 13,000 years ago?
By Peter Tyson
Posted 03.01.09
NOVA
The Program explored many possible aspects of this dramatic climate change the most believable was a sudden asteroid impact Witch caused a mass extinction in most of North and South America.
The most recent hypothesis, advanced by Kennett and 25 other scientists in a 2007 Proceedings of the National Academy of Sciences paper, concerns the proposed cosmic impact. Right about the time the Younger Dryas began and at least 15 of those 35 extinct mammals and arguably the Clovis culture itself appear to vanish abruptly from the fossil record—that is, right about 12,900 years ago—Kennett et al see markers of a major catastrophe. The markers lie in a thin layer at the base of a “black mat” of soil that archeologists have identified at over 50 Clovis sites across North America.
Photo of archeologist Vance Haynes, who first discovered the “black mat” in this Arizona riverbed in the 1960s, points it out to geophysicist Allen West. shows the carbon band in the earths layers = Black Mat.
http://www.pbs.org/wgbh/nova/evolution/end-big-beasts.html
Correction: Witch’s nor magic did not change the climate
: A sudden asteroid impact Witch caused a mass extinction in most of North and South America.
Should read a sudden asteroid impact Which caused a mass extinction in most of North and South America.
Full article available at: http://www.scribd.com/doc/142727433/Evidence-for-deposition-of-10-million-tonnes-of-impact-spherules-across-four-continents-12-800-y-ago
“This evidence continues to point to a major cosmic impact as the primary cause for the tragic loss of nearly all of the remarkable American large animals that had survived the stresses of many ice age periods only to be knocked out quite recently by this catastrophic event.”
Not quite so fast.
Scientists in the extinction field should stop using language that is ‘either/or’, ‘primary cause’ ‘nearly all’, and should acknowldge that most extinction events as a result of a combination of processes. This sort of thing has plagued the K-T extinction event, for example, where it is known that rates of extinction before the bolide impact 65Ma were already higher than background, with significant volcanism at the time.
To put it another way, if two detrimenetal ecological effects occur at the same time, doesn’t this make their overall effect larger than just one alone? Of course it does. Most viruses for example hit you harder when you are down, ie. they strike harder when you already weakened by something else. This is how people are killed by AIDS, it weakens resistance. Same, goes for extinction periods.
So to claim ‘primary cause’ or ‘nearly all’ requires startling good evidence and time correlation. And yes there was in fact, another major factor that was around at the time-hungry humans. Humans like meat, they have a powerful baseball friendly lever to propel missiles from an arm at a safe distance, and they are already long-trained in how to make sharp hand tools to put on them. The large animals have not evolved to counter projectiles from a distance, in fact if anything their size makes them more vulnerable, a larger target is easier to hit, and gets more bang for buck.
And I dont suppose there were any other minor impacts in all the previous ice ages? Only one thing was different the last time round in America at least-humans.
The supplementary information for the paper is interesting. They found lots of Clovis artefacts when digging for their spherules.
Looks like the evidence for wildfires is stronger than for a cosmic impact event.
The real mystery about the YD is, that once it began, the climate was stable for 1300 years. Why didn’t the climate slowly return to the pre-YD event conditions over decades or even centuries?
bueuf1, I think the region around Elko, NV, that you’re looking at is the Great Basin. Yes, it’s too big, and geologists have other reasons for it.
I’ve lost track of the amount of times I have brought this up. This impact was detailed extensively by German Geologist Otto Muck. His book on the subject should be required reading for everyone on the planet. The reason it’s ignored is it’s title – ‘The Secret of Atlantis’. Yes it existed, yes it was the Bermuda Triangle, yes the impact sunk it completely causing a large magnetic disturbance also that lasted for thousands of years. Check out the mating migration of the Sargasso Sea Eels who still behave as if Atlantis was there. None of this is poppycock. Otto Muck used extensive PROOFS.
Where are the impact sites? Or were all of them structurally weak comet fragments that airburst? Are the spherules composed of material from the ground at impact sites or from cometary material?
Based on earlier research into such an occurrence it was then believed to have resulted from collision with soft core (ice) comets that came in over the North Pole and impacted generally in the area of Hudson Bay and further south.
Those area were completely covered by thousands of feet of thick ice sheets at the time. The theory goes on that the heat of these impacts melted substantial glacial ice and this fresh water proceeded to the Atlantic where is so disturbed the natural conveyor belt currents of the Atlantic that the Gulf Stream shut down.
Impact into the ice sheets concealed all but trace data that indicate potential impact depressions that can be observed today.
I don’t have his book in front of me as I write, but as I recall, the lead author of this original work was a scientist at the Lawrence Berkeley Labs, who with colleagues was investigation a sharp shift in atmospheric C13 at about that time that still gives erroneous dating results, if not properly accounted for.
There is alot more to this current study.
Looks like a pattern I once saw of the Laacher See eruption . If I’m not mistaken that was around the same time frame.
Reminds of the book Stone Spring, they called it the Sky Wolf there.
http://en.wikipedia.org/wiki/Stone_Spring
Comets cannot selectively kill large mammals (Mastodons, Sabre-Tooth Tigers) and leave small mammals (humans) alive.
Humans, OTOH, can selective kill large mammals.
There was also a major impact about 5,300 years ago,
What was in the bible is linked to to that impact..
I know they are not a definitive source but Wikipedia has quite a list of problems that other researchers have raised for this hypothesis. For example, just regarding the extinctions,
“Since it is assumed the effects of the putative impact on Earth’s biota would have been brief, all extinctions caused by the impact should have occurred simultaneously. However, there is much evidence that the megafaunal extinctions that occurred across northern Eurasia, North America and South America at the end of the Pleistocene were not synchronous. The extinctions in South America appear to have occurred at least 400 years after the extinctions in North America.[19][32][33] The extinction of woolly mammoths in Siberia also appears to have occurred later than in North America.[19] A greater disparity in extinction timings is apparent in island megafaunal extinctions that lagged nearby continental extinctions by thousands of years; examples include the survival of woolly mammoths on Wrangel Island, Russia, until 3700 BP,[19][32][34] and the survival of ground sloths in the Antilles,[35] the Caribbean, until 4700 cal BP.[19] The Australian megafaunal extinctions occurred approximately 30,000 years earlier than the hypothetical Younger Dryas event.[36]”
http://en.wikipedia.org/wiki/Younger_Dryas_impact_hypothesis