COMET CLASH: James Kennett [left] and son Doug on Santa Rosa Island in California where they discovered more evidence that a comet caused an extinction event 13,000 years ago.
Image: UC SANTA BARBARA
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Researchers have found shock-synthesized hexagonal diamonds on one of California's Channel Islands, which they say is the strongest evidence yet that a comet exploded in the atmosphere above North America, causing widespread extinctions there around 12,900 years ago. Skeptics, however, say the debate is far from over.
In 2007 researchers theorized that a comet set off continental fires that led to the mysterious disappearance of the Clovis people and the extermination of 35 mammal genera, including mammoths, mastodons, ground sloths and camels. The team documented a "black mat" of charcoal throughout North America that contains high levels of iridium, magnetic spheres, and nano-diamonds, which are consistent with such an airburst. The controversial theory also gibes with the 1908 Tunguska atmospheric detonation (also thought to be from a comet or meteorite) that leveled trees in Siberia, and it echoes the extraterrestrial impact widely believed to have wiped out the dinosaurs 65 million years ago.
Today, in Proceedings of the National Academy of Sciences, the same team reports on shock-synthesized hexagonal diamonds, known only from meteorite and other impact events, in a soot layer from Arlington Canyon on Santa Rosa Island in California. The canyon is famous for containing the earliest human remains in North America, dating back to 13,000 years, and the soot layer coincides with the disappearance of the pygmy mammoth from the island. In a documentary shown earlier this year on the Public Broadcasting Service's NOVA science show, the team also claimed that they discovered similar diamonds from the Greenland Ice Sheet dating to the same period.
But the evidence does not convince everyone. "I don't think much of this whole story," says geochemist Christian Koeberl of the University of Vienna in Austria, "Diamonds of any sort are not uniquely characteristic of impact events." He says that the major lines of evidence are still missing, including the presence of shocked minerals, including breccias and tektites as well as an impact crater. "At least three other groups searched for similar evidence in the same or similar samples and found none," he adds.
Briggs Buchanan, an archaeologist from Simon Fraser University in Burnaby, British Columbia, disputes the notion that humans declined following the purported impact. "We have shown that in California, specifically, that there [was] no severe decline in the resident population." He adds that other researchers have shown that the black mat varies in age across the continent and appears to have a variety of geologic origins.
What does the research team have to say about their doubters? "I'm so skeptical about the skeptics," says marine geologist James Kennett of the University of California, Santa Barbara. "We work in a different paradigm where different materials result from different kinds of impacts."
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10 Comments
Add CommentGreat new theory that fits a lot of facts and the skeptics seem a bit threatened. For example, one says that he has shown that the human population of California did not experience a decline in population when, in fact, no one really knows much about populations in California at 13,000 years ago. This seems like it will probably replace the competing megafaunal extinction theories - overhunting, disease, and climate change --- unless we want to consider it one hell of a change in the climate.
Reply | Report Abuse | Link to thisWouldn't it be much more probable that the decline in large species is a result of the growing human population? Wherever else humans have been introduced, there have been mass extinctions of species that couldn't adapt. I think there is a lot of traction on this theory, so to just dismiss objections as the work of "skeptics" is a bit premature.
Reply | Report Abuse | Link to thisI enjoy keeping an open mind (or eye) on past events. I believe that is how we discover things.
Reply | Report Abuse | Link to thisrwilliston, a hypothesis doesn't become a theory simply based on something similar happening someplace else. There needs to be proof. There is no such thing as a "default" theory. We don't just believe something to be true until someone proves otherwise. There are a great deal of unanswered questions regarding an anthropomorphic cause to the North American Mega Fauna Extinction. I somehow doubt that a handful of stone age wonderers wiped-out all the mega fauna of North America shortly after arriving. There weren’t that many of us and we weren’t that great at bringing down the big animals. Ultimately, let the best hypothesis win, and by best I mean most consistent with existing evidence.
Reply | Report Abuse | Link to thisBy the way; I don't know why the term "sceptic" is such a bad thing. Scepticism is not only a good thing; it is essential to good science. Only once a hypothesis has past the scrutiny of informed scepticism can we feel confident that we are on the right track. If only more people were sceptical about what they read or heard we would have a much more enlightened population and fewer tabloids, fewer republican presidencies and certainly no Fox News! The hypothesis you should be most sceptical about is the one you find easiest to believe.
@ robert schmidt: Now now, there. Take an aspirin and get a good nights sleep. You were doing all good and stuff until you went all political our science butts.
Reply | Report Abuse | Link to thisHere it is: Liberal--$32 TRILLION in new debt, spending, loan guarantees, bailouts, and stimulus. Another TRILLION to insure health coverage for a *fraction* of the 47 million currently uninsured. Get that? $32 TRILLION.
Get ready for HYPER inflation. Really, really big time price run-ups. Paying this debt off in today's dollars is inconceivable without devaluation. Do the math--Liberal.
BTW, the Republicans started it. So I'm not beating anything other than YOUR comment. And even then, only the last paragraph. You seem to like skepticism.
I'm skeptical that O'bammmmmma has a clue. We found out the Bush didn't. But at least he only squandered $1 Trillion.
widespread Carolina Bay type craters from Clovis comet 12,900 Ya BP? -- 0.7 M long NS crater with fractured red sandstone on SW rim, CR C 53A, 20 miles E of Las Vegas, NM: Rich Murray 2009.06.08
Reply | Report Abuse | Link to thishttp://rmforall.blogspot.com/2009_06_01_archive.htm
Monday, June 8, 2009
http://groups.yahoo.com/group/AstroDeep/27
This post throughly presents mainstream research, worthy media accounts, and valuable links for open-minded exploration.
To illustrate, I herein quote the whole abstracts for the Richard B. Firestone et al seminal report and a C. Vance Haynes, Jr. review.
As well as evidence for the probable time and cause of the extinction of Clovis culture in the Americas, many sites are also in Europe.
The connection with Carolina Bays confirms a continental disaster, which may have retarded the evolution of urban culture in the Americas, despite generally favorable landscape, climate, water, and lack of large competing
mammals.
As a conscientious scientific amateur, I want to open up evidence and reason based dialogue re evidence I readily found for widespread fields of very similar craters in the Northern Hemisphere, starting with a specific,
convenient, accessible crater near Las Vegas, New Mexico.
Others can join in quickly locating similar fields in almost every state.
There is opportunity for amateurs to make very helpful contributions in exploring multiple research opportunities.
In mutual service, Rich Murray, MA
Google Maps Satellite image link:
http://maps.google.com/maps?f=q&source=s_q&hl=en&geocode=&q=Las+Vegas,+New+Mexico&sll=35.587894,-105.919641&sspn=0.000612,0.001608&ie=UTF8&ll=35.614186,-104.827251&spn=0.078289,0.205822&t=h&z=13
Quinn: First, I want to say that I agree with Robert Schmidt's comment on hypotheses and skepticism. Second, I want to say I agree with yours also. In the next few months we will see the extinction of the U.S. middle class, a man-made catastrophe visited on us by Republicans and Democrats who are supposed to represent us but are actually in the pockets of the big global corporations. Third, I want to go on record as believing that a comet took out the North American megafauna, and the Clovis culture along with them.
Reply | Report Abuse | Link to thisRich: I was unable to access either of the links that you give at the top, but I did look at the Google Map view of the Carolina Bays near Las Vegas New Mexico. Very impressive, but I have two questions. How can you be sure that some or all of these features aren't volcanic, and how can you be sure of these features' ages? I suspect that the second question could be answered by getting someone to determine cosmic-ray exposure ages of the sandstone outcrops exposed inside the bays.
Reply | Report Abuse | Link to thisOtherwise, I'm kind of pushing the impact-origin hypothesis for the original Carolina Bays of N Carolina and Virginia:
http://impactglassheretic.blogspot.com/
Eminence Grise: These kind of fields of round, oval, and irregular shallow craters, sometimes in durable bedrock, usually without connected drainage, with a fractal distribution of sizes, are simply too common to be volcanic in general -- take a look on Google Earth or Maps at the region about 40 miles from Amarillo to its southeast. With Google Maps set to Terrain, many of these 0.1 to 10 km features will show up a blue lakes, making it easy to find clusters. Where there are big craters, there are small ones.
Reply | Report Abuse | Link to thisStart from Las Vegas, NM and follow 104 east to take the NE fork of CR CR53A -- in a mile, directly on the left, is the NS crater that I have walked directly, a mile long and 0.2 mile wide, showing the horizontal red sandstone beds on its rim, especially on the west, and a flat bottom. The rim is not raised. There are two parallel small ridges in the lower center, with a muddy cow wallow between. The south end of the crater is by a small road quarry about 200 feet wide and 16 feet deep of white mineral material, common in the region, completely distinct from the typical red sandstone bedrock. The west rim shows progressive color changes and disruption as I walk along it by to and by the center, including 6 foot chunks tossed over in place, looking to my amateur eyes obviously scorched. Fragments up to 3 foot size abound in and around the crater.
I imagine that the explosion was on the surface, not buried as in typical iron or stone meteors. There is no sign of shocked or vaporized material, so it seems the impact was about 5 km/sec, from a low-impact angle for an mostly ice object falling out of a low orbital trajectory, with enough energy to create a superheated steam explosion, dispersing the surface rock, and depositing its mineral contents as the white deposits locally, which, being water based, would easily moved about by subsequent erosion by water and wind.
The minor degree of erosion indicates a recent Holocene age.
Very similar is McAllister Lake, in a federal wild bird park, 8 miles SE of Las Vegas, NM, and Crane Lake just to its NE.
This overall pattern shows up everywhere. I suggest you survey your own region with Google Maps, or give me the location, so I can scout out some prospects.
Rich Murray, Santa Fe, NM 505-501-2298
Lets not forget that the end of the Ice Age covered up alot of evidence with the rising sea levels.
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