Having this story make scientific America is certainly welcome. The theory was first published about four years ago and sank like a stone. I have commented a great deal on its importance providing a radical interpretation that I expect few to accept anytime soon.
The comment that the black mat varies in age and has different geological sources is odd. The soot layer is convincingly unique, unless someone is able to show me multiple layers over eons. That argues for a unique causation and additional argues for a critical review of the methods for determining age which we already know is fickle.
An island has less capacity to withstand a shock, while a few human enclaves can repopulate vast tracts in a couple of centuries. Please recall our present population is derived from a fairly modest influx of new settlers. If the resources are there, then a healthy mother can produce several children in a decade and as many more for a total of two decades. Thus a surviving population can increase seven fold in two decades and obviously almost fifty fold in four decades and possibly three hundred fold in a person’s lifetime. Such rapid decline and recovery is so brief as to go unremarked in the geological record.
I would like to see the soot layer mapped and also dated in as many locales as possible so as to use it to act as a dating standard. Just as we know that Hekla blew in 1159 BCE, it is plausible to almost know an exact date for this event. This report tells us that the layer is on a California island. Thus it is now clear that the event affected all of North America.
It has been observed that Tunguska delivered soot into the local environment and a local forest fire is hardly able to create a unique signature. Either heat or shock flash carbonized the local vegetation and this I am skeptical about or the carbon was simply delivered and produced a cloud on passage through the atmosphere.
This last option works best in describing what happened 13,000 years ago. The impact mass came as a comet and impacted on the ice cap with a centre of mass close to the pole itself. It began its targeted orbit a very long ways out and was fairly intact. As it came into close orbit about the sun it broke up somewhat and like all such objects, produced a swarm of carbon rich objects.
These objects exploded in the atmosphere and provided blankets of the observed soot. The continental shock wave was sufficient to kill off animals easily. This model has the advantage of not needing to burn off anything.
This makes it even more survivable. In the meantime the crust cut lose and the present orientation came about.
July 20, 2009
July 20, 2009
Did a Comet Cause a North American Die-Off around 13,000 Years Ago?
Tiny hexagonal diamonds suggest a massive impact during the late Pleistocene that could have wiped out the Clovis people, mastodons and other continental inhabitants--but the geologic evidence falls short for some skeptics
http://www.scientificamerican.com/article.cfm?id=did-a-comet-cause-die-off&sc=DD_20090721
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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