The world’s most complete pygmy mammoth skeleton was excavated on Santa Rosa Island in 1994. This animal was only 5.5 feet tall. NPS photo by Bill Faulkner.
Many archeologists and other scientists have speculated that the abrupt disappearance of numerous animal species in North America about 12,900 years ago, matched with the demise of the Clovis Paleoindian culture at about the same time, can be attributed to massive ecological disruptions caused by a meteorite or comet impact. Until recently, however, evidence supporting the extraterrestrial impact hypothesis has been scanty and inconclusive. Now scientists believe they’ve found the smoking gun in Channel Islands National Park just off the coast of southern California.
Scientists have long been puzzled as to why the Clovis era ended so abruptly 12,900 years ago (+/- 100 years), and why so many animal extinctions occurred at about the same time. The disappearance of the Clovis people closely paralleled the disappearance of 19 bird genera and nearly three dozen mammal species, including megafauna like horses, camels, giant short-faced bears, and the pygmy mammoths of the Channel Islands. Whatever caused this was something more like an event than a process or trend, and it was something that doesn’t happen very often.
The search for an answer narrowed a few years ago when scientists constructed a strong argument for an extraterrestrial impact. The hypothesis seemed plausible enough. If global ecological disruption and the demise of the dinosaurs could be attributed to a colossal asteroid impact about 65 million years ago, why couldn’t continental-scale ecological disruption, the disappearance of numerous megafaunal species, and the demise of the Clovis culture be attributed to a less gargantuan cosmic impact that occurred much more recently?
What was missing was the empirical evidence. You don’t have good science without good proof.
Once scientists were pointed in the right direction and began carefully searching for evidence of an extraterrestrial impact, it didn’t take long to find it. That’s because they knew what to look for and had a pretty good idea where to look for it.
When a good-sized meteorite or comet strikes the earth, an immense amount of kinetic energy is immediately converted to heat and work. One result is extremely hot forest fires, the dispersed organic remains of which end up as a surface layer of soot, ashes, charcoal, carbon spherons, and other fire-signature debris that is subsequently buried by sediments and preserved (as rock, if old enough) for scientists to dig up much later on. If a soot-rich layer of a particular age is distributed on a continental or vast regional scale, it’s prima facie evidence of a rare mega-event.
Among the other things that an extraterrestrial collision yields is the enormous heat and pressure needed to convert graphite (present in meteorites) into diamonds. The diamonds produced in this way are microscopic in size and very distinctive in shape. Properly termed “shock-synthesized hexagonal nanodiamonds,” they go by the mineral name lonsdaleite. An important thing to know about lonsdaleite is that the only place we’ve ever found the naturally-occurring variety is in association with impact craters.
If scientists were to dig into the earth and find a layered deposit rich in soot, lonsdaleite, and perhaps other nano-sized diamond polymorphs (n-diamonds and cubics), they would know that they have uncovered very convincing evidence of a cosmic impact. If they were to find it at the Younger Dryas Boundary (YDB), which is material laid down 12,900 years ago (+/- 100 years), they would have, from the perspective of the Clovis-era extraterrestrial impact hypothesis, the “smoking gun” that they’ve been looking for.
That said, you can imagine the excitement of the researchers (a 17-member team led by University of Oregon archaeologist Douglas Kennett) who recently found such a deposit at the Younger Dryas Boundary while digging about 13 feet down in Arlington Canyon on Santa Rosa Island in Channel Islands National Park.
It wasn’t a random find. Since the Clovis-era megafauna extinction included the Channel Islands pygmy mammoth (Mammuthus exilis) of the Northern Channel Islands, the scientists had deduced that this would be good place to look for evidence of a Clovis-era extraterrestrial impact.
Scientists have found charred debris at the YDB in some 50 other Clovis-era sites around North America, and some sites have yielded small amounts of nanodiamonds as well. Scientists will need to find additional corroborating evidence before the Clovis-era cosmic impact idea can be comfortably moved from the hypothesis category (speculative) to the viable theory category (tested and proved). Meanwhile, you have to admit that the evidence gathered so far is mighty compelling.
Just where the Clovis–era impact may have occurred remains open to speculation, as is the matter of whether it was a surface strike, an airburst, a swarm of airbursts, or some combination. Noting the absence of a crater of the right size and age, some scientists speculate that an extraterrestrial object, possibly a comet, exploded above or within the Laurentide Ice Sheet in the vicinity of the Great Lakes.
Postscript: Somebody has got the date wrong. The caption of the accompanying NPS photo stated that the pygmy mammoth skeleton excavated on Santa Rosa Island in 1994 was determined to be 12,240 years old. The problem is, 12,240 BP is something on the order of 600 to 700 years after the pygmy mammoths in the Northern Channel islands were purportedly wiped out by the Clovis-era impact. Some sources state that Channel Islands mammoths were still around as late as 10,300 years BP.
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Comments
That's not really news as in new: the first publication on findings of synthetic diamonds in a horizon that matches the end of Clovis was published in Nature on May 17, 2007. The following news report in the New Scientist can still be found online: http://space.newscientist.com/article/dn11909-did-a-comet-wipe-out-prehi... - last year the same issue made news again: http://www.spacedaily.com/reports/Exploding_Asteroid_Theory_Strengthened...
I'm familiar with these studies, MRC, and I've also seen the Nova and Discovery Channel documentaries (but not the History Channel one). Your point is well taken. I should have taken more time to relate the Channel Islands findings to the extant knowledge. My bad.
This is a very interesting find, although sudden climate shifts are not unusual in the history of our world. Indeed, over the past 700,000 years the earth's climate has experienced rapid and dramatic shifts that substantially affected human development, with the last 44,000 years being particularly unstable. It is only recently that the earth's climate stabilized in a relatively moderate zone condusive to the rise of human civilizations and rapid population growth. It would not take a comet strike to set off a return to climatically interesting times. We may pull the trigger ourselves by changing the chemical makeup of the atmosphere.
The likelihood of the obvservations of an amateur being taken seriously by the academic comunity is inversely proportional to the significance of those observations. So that a really big idea that changes things has about as much chance of being heard as a mouse breaking wind in a huricane.
But once you shake off the unquestioned 19th century assumptions of Sir Charles Lyell, namely the principle of gradual, uniform, geologic change, and the fairy tale that 'The present is the key to the past', the pristine planetary scarring of the most violent extinction level, multiple airburst, impact event in 65 million years isn't hard to recognize out at all.
Keep sight of the fact that the nano-diamonds formed in the atmosphere during violent atmospheric impact explosions. They are a barometer, and pyrometer, in one. The nano-diamonds exist as empirical fact. Therefore, the atmospheric conditions of almost inconcievable heat, and pressure, required for their formation were equally real. Those atmospheric conditions were directed downwards. And they hit the ground as multpile supersonic downblasts of thermal impact plasma hot enough to blast a mountain aside like wax under a high pressure blowtorch.
Those atmospheric conditions left many scars. And here in California, those scars are not craters. It didn't smash the ground. The heat, and pressure, of the multiple downblasts of thermal impact plasma flash melted it. And drove it into frothing waves of melt, like the debris laden foam on a storm tossed beach. The final blast of heat left a black fusion glaze on the outer surfaces of the resulting, non-volcanogenic ignimbrites, melt formations, and mega-breccias of the local component of the YD impacts that is as magnetic as any meteorite.
Think: Multiple airburst, thermal atmospheric, geo-ablative, impact event.
Please read. A Catastrope of Comets, And California Melt
I direct your attention to the recent Proceedings of the National Academy of Sciences paper, "No Evidence of Nanodiamonds in Younger-Dryas Sediments to Support an Impact Event."
http://www.pnas.org/content/early/2010/08/26/1003904107
The Daulton paper is shamefully inept.
From an email from Bunch to Leroy Ellenberger:
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Dear Leroy – not to worry, Daulton is a competent scientist and did what he could do with the materials given to him. The problem lies with Scott and Pinter.
Some brief reasons why the Daulton et al paper is inept:
1.They did not collect from the YDB layer at the Arlington site that was used in the two Kennett et al papers, but from layers that contained “carbonaceous particles”, mostly charcoal – there are no diamonds in charcoal and it is not clear that they even sampled the YDB.
2. They did not collect or at least process the YDB sediment at Murray Springs, which contains most of the nanodiamonds in the YDB as loose nanodiamonds – probably too much work because the work is labor intensive – need to separate kilos of material. The diamonds average about 50 to 100 ppb and you need a lot of diamonds, processed by the correct separation protocol.
3. Yes, we saw graphene, graphane and chaoite, but these are not diamonds.
4. They analyzed microcharcoal and glassy carbon for diamonds and found none, neither did we! These “carbon particles” were made outside the constrains for diamond production and survival.
5. Two reviewers for the Kennett papers are world class shock and diamond experts – they had no problem.
6. One independent stratigrapher who read the Daulton paper was astonished at the “complete ineptness of field protocol and sample characterization”. Of course, you and others can judge for yourselves.
7. The Greenland paper reporting the Discovery of a nandiamond-rich layer in the Greenland Ice Sheet is in the September issue of the Journal of Glaciology and there are sufficient diamond data in this paper (STEM, HRTEM, RAMAN, EELS, etc.) to prove once and for all that diamonds do, indeed, occur in the YDB.
More later, Ted
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The simple reason the Daulton gang couldn't find nanodiamonds is because they didn't duplicate the experiment.
The Greenland evidence pretty much trumps the nay sayers. The NDs are there. Nuff said.
That whole a debate is more than little frustrating,from the perspective of one who has been studying the emplacement motions of the airburst impact melt full time for two years now, like studying a choreographic dance chart. And has who already identified a few hundred thousand cubic miles of pristine geo-ablative impact melt from the event. Debating whether or not it happened is starting to feel like debating wheter, or not the sun came up yesterday.
It’s a little like playing follow the leader with the big kids. Only this time they’re the ones who are having a hard time catching up. And I have many questions of the materials I’ve found, that won’t get answered untill they do.
In the interest of leaving some crumbs at the trailhead,and showing the way, I put together a little Airburst Scarring Demonstration.
Dennis Cox,
A Catastrophe of Comets
P.S. since we are talking about an extinction level impact event for california, it should be noted that significant airburst scarring can be identified. And these burnt facies are pristine. See California Melt