Comets damaged 4 continents 12,800 yrs ago

[Ichingcarpenter]

Last edited Tue May 21, 2013, 03:51 PM - Edit history (1)

Evidence for deposition of 10 million tonnes of impact spherules across four continents 12,800 y ago








Significance

We present detailed geochemical and morphological analyses of nearly 700 spherules from 18 sites in support of a major cosmic impact at the onset of the Younger Dryas episode (12.8 ka). The impact distributed ?10 million tonnes of melted spherules over 50 million square kilometers on four continents. Origins of the spherules by volcanism, anthropogenesis, authigenesis, lightning, and meteoritic ablation are rejected on geochemical and morphological grounds. The spherules closely resemble known impact materials derived from surficial sediments melted at temperatures >2,200 °C. The spherules correlate with abundances of associated melt-glass, nanodiamonds, carbon spherules, aciniform carbon, charcoal, and iridium.

http://www.pnas.org/content/early/2013/05/17/1301760110







"We know something came close enough to Earth and it was hot enough that it melted rock – that's what these carbon spherules are. In order to create this type of evidence that we see around the world, it was big," Tankersley says, contrasting the effects of an event so massive with the 1883 volcanic explosion on Krakatoa in Indonesia. "When Krakatoa blew its stack, Cincinnati had no summer. Imagine winter all year-round. That's just one little volcano blowing its top."
Other important findings include:
Micrometeorites: smaller pieces of meteorites or particles of cosmic dust that have made contact with the Earth's surface.
Nanodiamonds: microscopic diamonds formed when a carbon source is subjected to an extreme impact, often found in meteorite craters.
Lonsdaleite: a rare type of diamond, also called a hexagonal diamond, only found in non-terrestrial areas such as meteorite craters.


Read more at: http://phys.org/news/2013-05-mammoth-lament-cosmic-impact-devastating.html#jCp


This would have wiped out any civilization that might have come before.

[Socialistlemur]

1. I don't think all the conclusions are right.

I have serious doubts a near miss led to the extinction wave of macro fauna in North America. This extinction is too closely tied to human migration waves, and we have observed similar extinction events in South America, Australia, Madagascar and New Zealand. We Homo sapiens are a killing machine and have been exterminating other species for a long time. I think we are improving a bit now because we're wealthy enough to avoid killing everything, especially if they are cute creatures. Those spherules are likely material from the meteorite or comet itself, rather than original earth material.

[Ichingcarpenter]

2. No evidence for theory humans wiped out megafauna

The research challenges the claim that humans were primarily responsible for the demise of the megafauna in a proposed "extinction window" between 40,000 and 50,000 years ago, and points the finger instead at climate change.
An international team led by the University of New South Wales, and including researchers at the University of Queensland, the University of New England, and the University of Washington, carried out the study. It is published in the Proceedings of the National Academy of Sciences.
"The interpretation that humans drove the extinction rests on assumptions that increasingly have been shown to be incorrect. Humans may have played some role in the loss of those species that were still surviving when people arrived about 45,000 to 50,000 years ago – but this also needs to be demonstrated," said Associate Professor Stephen Wroe, from UNSW, the lead author of the study.
"There has never been any direct evidence of humans preying on extinct megafauna in Sahul, or even of a tool-kit that was appropriate for big-game hunting," he said.


Read more at: http://phys.org/news/2013-05-evidence-theory-humans-megafauna.html#jCp

[AverageJoe90]

3. TBH, I'd believe there's a more likely solution: instead of just one comet.....

...how about dozens of smaller ones? TBH, one single comet doesn't seem at all likely to cause all that damage, and there probably would have been a mass extinction for sure if one single event did all that on its own....and yet, no mass extinction did occur, from what we know today.

[aquart]

4. One comet trailing a string of pearls?

[Ichingcarpenter]

5. Shoemaker–Levy

BTW the data of the heat caused by the strike would have made me stay in my cave

"The melt material also matches melt-glass produced by the Trinity nuclear airburst of 1945 in Socorro, New Mexico," he continued. "The extreme temperatures required are equal to those of an atomic bomb blast, high enough to make sand melt and boil."





These are photos of 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, consistent with the very high temperature origin of the melt materials in the YDB layer. Credit: UCSB

"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.

Read more at: http://phys.org/news/2012-06-evidence-theory-extraterrestrial-impact.html#jCp

[GeoSpace]

6. Evidence vs. belief, speculation, feelings & ignorance

SocialistLemur,

Your comment "Those spherules are likely material from the meteorite or comet itself, rather than original earth material..." is very disappointing.

It seems you didn't read the paper, or completely missed the message in the evidence it presents in great detail. Clearly, the spherules are a conglomeration of superheated and quench melted geochemical effluent from multiple different target surfaces, combined with superheated and carbonized biomass, most likely from vaporized forest regions of pine, among other species of trees.

The evidence looks most like multiple low altitude airbursts of incoming bolides, whose resulting supersonic fireballs then contacted the surface when carried by their remaining astronomical momentum. The bolide fireball, or fragmentary detonation, is process which has now been modeled in detail by Sandia National Labs in the mid 2000's to further our understanding of the Tunguska event early in the 1900's in remote Siberia, and was shown again to accurately represent such phenomenon after the Chelyabinsk (Russia) fireball detonation of 15 Feb 2013.

The temperatures required to produce some of the geochemical and biomass melt/ablation products referenced in the paper are above 3000 (three thousand) degrees, and don't occur on Earth's surface by any terrestrial process. The spherules and melt products are not of the form of volcanic or any other terrigenous process. The paper clearly and carefully points that out in great detail.

Many people who comment on this topic make the same mistake of imposing their own beliefs or feelings, at the expense of the very detailed, accurately measured and characterized physical evidence within the Geologic imprint. Don't make that mistake. The evidence is very clear, and clearly detailed in the paper. To ignore it is to choose the path of ignorance instead of the path of truth. The choice of ignorance is never beneficial in the long run. To anyone.

It is unclear if the causal cosmic impact event(s) were responsible for extinctions or the long term climate "collapse" of the Younger Dryas. What is clear is that the melt products exist in the same strata in at least 4 continents, at a geologic epoch coincident with some species going away and the beginning of a 1400 year cold snap in the otherwise generally warming trend coming out of the last ice age from ~ 19Ka. The geologic record doesn't lie. The temperatures that produced the melt products were unearthly high. The melt products themselves are of terrestrial origin, both geochemical and biomass. That is the evidence, the truth contained in the Geologic Record.

Looking at the vast body of extremely accurately characterized physical evidence which the paper presents in great detail, it would be both illogical and completely unscientific to disagree with its conclusions. Any statement to the contrary shows a disappointing lack of attention, or retention, on the part of those disagreeing. No offense, but instead of trying to impose your own feelings or beliefs over those of the two dozen plus international expert authors of the paper, you might try reading it again carefully before making such ill-informed and self-detracting comments. Open yourself to the truth that it uncovers. Your enlightenment may actually become a positive experience. To ignore its truths is to give up on a better, more enlightened future.

If your comments are based solely on reading the abstract, which it seems may be the case, you will enjoy the rigorous and detailed presentation of the overwhelming evidence by actually reading the paper.

- GeoSpace