From the University of California at Santa Barbara -By Julie Cohen |
Most of North America’s megafauna — mastodons, short-faced bears, giant ground sloths, saber-toothed cats and American camels and horses — disappeared close to 13,000 years ago at the end of the Pleistocene period. The cause of this massive extinction has long been debated by scientists who, until recently, could only speculate as to why.
A group of scientists, including UC Santa Barbara’s James Kennett, professor emeritus in the Department of Earth Science, posited that a comet collision with Earth played a major role in the extinction. Their hypothesis suggests that a cosmic-impact event precipitated the Younger Dryas period of global cooling close to 12,800 years ago. This cosmic impact caused abrupt environmental stress and degradation that contributed to the extinction of most large animal species then inhabiting the Americas. According to Kennett, the catastrophic impact and the subsequent climate change also led to the disappearance of the prehistoric Clovis culture, known for its big game hunting, and to human population decline.
In a new study published this week in the Journal of Geology, Kennett and an international group of scientists have focused on the character and distribution of nanodiamonds, one type of material produced during such an extraterrestrial collision. The researchers found an abundance of these tiny diamonds distributed over 50 million square kilometers across the Northern Hemisphere at the Younger Dryas boundary (YDB). This thin, carbon-rich layer is often visible as a thin black line a few meters below the surface.
Kennett and investigators from 21 universities in six countries investigated nanodiamonds at 32 sites in 11 countries across North America, Europe and the Middle East. Two of the sites are just across the Santa Barbara Channel from UCSB: one at Arlington Canyon on Santa Rosa Island, the other at Daisy Cave on San Miguel Island.
“We conclusively have identified a thin layer over three continents, particularly in North America and Western Europe, that contain a rich assemblage of nanodiamonds, the production of which can be explained only by cosmic impact,” Kennett said. “We have also found YDB glassy and metallic materials formed at temperatures in excess of 2200 degrees Celsius, which could not have resulted from wildfires, volcanism or meteoritic flux, but only from cosmic impact.”
The team found that the YDB layer also contained larger than normal amounts of cosmic impact spherules, high-temperature melt-glass, grapelike soot clusters, charcoal, carbon spherules, osmium, platinum and other materials. But in this paper the researchers focused their multi-analytical approach exclusively on nanodiamonds, which were found in several forms, including cubic (the form of diamonds used in jewelry) and hexagonal crystals.
“Different types of diamonds are found in the YDB assemblages because they are produced as a result of large variations in temperature, pressure and oxygen levels associated with the chaos of an impact,” Kennett explained. “These are exotic conditions that came together to produce the diamonds from terrestrial carbon; the diamonds did not arrive with the incoming meteorite or comet.”
Based on multiple analytical procedures, the researchers determined that the majority of the materials in the YDB samples are nanodiamonds and not some other kinds of minerals. The analysis showed that the nanodiamonds consistently occur in the YDB layer over broad areas.
“There is no known limit to the YDB strewnfield which currently covers more than 10 percent of the planet, indicating that the YDB event was a major cosmic impact,” Kennett said. “The nanodiamond datum recognized in this study gives scientists a snapshot of a moment in time called an isochron.”
To date, scientists know of only two layers in which more than one identification of nanodiamonds has been found: the YDB 12,800 years ago and the well-known Cretaceous-Tertiary boundary 65 million years ago, which is marked by the mass extinction of the dinosaurs, ammonites and many other groups.
“The evidence we present settles the debate about the existence of abundant YDB nanodiamonds,” Kennett said. “Our hypothesis challenges some existing paradigms within several disciplines, including impact dynamics, archaeology, paleontology and paleoceanography/paleoclimatology, all affected by this relatively recent cosmic impact.”
– See more at: http://www.news.ucsb.edu/2014/014368/nanodiamonds-are-forever#sthash.Jz8DHJU3.dpuf
h/t to David Hagen.
The bottom line remains that you cannot explain the multiple, intense temp fluctuations of the late Pleistocene (YD and older) by cosmic impact.
.
Don Easterbrook says which is correct. Cosmic impact is not the cause of the YD a much more realistic cause was the ice dynamics at that time and the initial state of the climate which was near the threshold of glacial versus inter – glacial conditions which made the climate especially vulnerable to changes in solar variability due to primary solar changes and the associated secondary effects. Also at that time the earth’s magnetic field was very weak and under going excursions which made it quite vulnerable to cosmic ray concentrations changes which would be associated with weak solar conditions which evidence points to.
Further the YD event was by no means an isolated or unique event which throws cold water on a comic impact.
http://www.sciencedirect.com/science/article/pii/S1040618200000604
USGS on the 2012 black mat study finds YGIH myth busted:
http://www.usgs.gov/newsroom/article.asp?ID=3180&from=rss#.VAZm36NuowQ
Evidence used to support a possible extraterrestrial impact event is likely the result of natural processes, according to a new collaborative study led by U.S. Geological Survey scientists.
Elevated levels of iridium, magnetic spherules, and titanomagnetite grains, collectively called “impact markers,” form the bulk of the evidence for the Younger Dryas impact hypothesis, a hotly contested idea that links climate change, extinctions, and the demise of the Clovis culture.
Scientists found high levels of the reported markers in deposits called black mats, the organic-rich remains of old marshes and swamps, at several sites in the southwestern U.S. and the Atacama Desert of northern Chile. Markers were found in black mats ranging in age from 6,000 to more than 40,000 years in areas far removed from the purported impact location. These findings indicate the markers accumulated naturally in wetlands and are not the result of a catastrophic impact event. The full report is available online.
“Luis and Walter Alvarez’s proposal that an extraterrestrial impact was responsible for extinctions at the Cretaceous-Tertiary boundary eventually moved from unlikely hypothesis to accepted theory, and with its acceptance came the temptation to apply this explanation to any rapid change in Earth’s conditions,” said USGS Director Marcia McNutt. “The results of this study demonstrate the importance of maintaining a healthy skepticism and multiple working hypotheses.”
The controversial Younger Dryas impact hypothesis contends that an extraterrestrial object, possibly a comet, exploded over North America about 12,900 years ago, resulting in dramatic climate change, massive wildfires, and the extinction of many large herbivores and their predators. If true, the recency of such a large impact might have implied a greater risk to humanity than previously imagined.
“When the idea was first promoted in 2007, those of us familiar with black mats suspected that normal depositional processes in wetlands might be responsible,” said Dr. Jeff Pigati, a USGS geologist and lead investigator of the new study. Indeed, this is what Pigati and coauthors now report in this week’s issue of Proceedings of the National Academy of Sciences, USA.
“This is a great object lesson for how scientific hypotheses are done and undone,” said Paul Baker, Professor of Earth and Ocean Sciences at Duke University and a member of National Geographic Society’s Committee for Research and Exploration.
The study was funded cooperatively by the National Geographic Society, the USGS, the Millennium Science Initiative and Chile’s National Commission on Scientific Research and Technology.
Nice page for this study, on USGS.
It’s interesting to see that National Geographic funded it. They often run with ‘pop stories’, and YDIH still gets strong ‘gee-wiz’ coverage in the commercial press, even while the studies that show negative findings are panned.
It’s worth noting, that nobody likes an exciting cosmic-impact story any better than all those reporting here on the hard-science negations, nor indeed the authors & institutions of those published papers. I do not doubt that Hollywood has been sniffing around quite seriously.
Public interest in this general sort of thing is so strong, there has in fact been a steady string of decently-successful movies on photogenic wow-wee science-stories … and this YDIH could be a doozy.
But it has to be “based on Science“, to get cooperation from real scientists and academic and government science institutions. That they won’t touch it is in itself a clear sign that the science says “nah”.
This whole affair has had so many “odd” aspects to it … the knowledge eg that these “black matts” are usually wetland layers, or fluvial deposits (they are very common along the Quaternary bluffs lining the shores of the Olympic Peninsula/Pacific Northwest where I live … I’ve explored & sampled them for many decades) … how could the project leaders pose these layers as conflagration-deposits … these starkly-black layers draw notice & attention, and thus are popular study-specimens. They’re strikingly black, but they aren’t fire-remains. Strange.
It’s all about the funding. The Climate Change Settled Science Team has showed the way forward for corrupting science.
It never ceases to amaze me, how the blind circle the wagons, use circular logic and false assertions along with a liberal dose of defamation and insult to protect an untenable position.
They are the same ones who cry foul when the watermelons use such tactics. But just the same as watermelons they ignore all evidence to the contrary of their deluded dreams and roll on like an extinct mammoth across the pages of blogs, acting just like a lost herd.
Their evidence, wow, temperatures changed suddenly before. Thats it.
Any attempt at debate or discussion or comparison, shouted down by the group think.
They really need to look at WUWT ethos and look in the mirror.
Your position is untenable. There is no valid evidence of an impact, no mechanism by which the nonexistent impact could have caused the YD and no way in which the impact could have caused whatever extinctions might have occurred promptly after the onset of the YD.
That sharp warmings and coolings occurred before in the record is prima facie evidence that your position fails totally to show false the Null Hypothesis. If the YD was nothing special, and it wasn’t, then there is no reason to suppose an imaginary impact to explain the abrupt climate shift or the subsequent and preceding extinctions.
Grey, I haven’t abandoned you. I just know when pearls are exposed to swine…
“They are the same ones who cry foul when the watermelons use such tactics. But just the same as watermelons they ignore all evidence to the contrary of their deluded dreams and roll on like an extinct mammoth across the pages of blogs, acting just like a lost herd.
Their evidence, wow, temperatures changed suddenly before. That’s it.”
Bingo. It’s like in a trial and the jury is done hearing the prosecutions,case, and someone declares the accused guilty – before hearing one word from the defense counsel’s case. The one loudmouth shill in the jury shouting at the top of his lungs, “We don’t need to hear no other Side! He’s GUILTY!”
Sturgis continues to flail.
Here is more evidence, it needs investigation and study to increase our knowledge, not hand waving.
http://www.livescience.com/30896-stalagmites-climate-clues-blue-holes.html
The YD African dust storm was a major event and resulted in great ecologi8cal changes in the Bahamas. But what caused the event.
Previous sudden changes could also have been caused by similar events. we know the dinosaur extinction was one such.
Why do you ignore that the massive changes recorded make a mockery of catastrophic climate changes now being peddled to extort money and fear from you?
Why do you continue to insult?
What are you afraid of?
Saying that it happened before does not explain why or how at all.
Grey Lensman said @September 2, 2014 at 10:01 pm
Lensman’s reference describes the time frame of their study:
What they were looking at happened before the Younger Dryas, and spanned 18,000 years.
The mention of African dust is:
During the period of the Heinrich events, great dust-storms blew south from the terminus of the North American ice-sheet, transporting vast deposits of soil hundreds of miles across the future United States. These blows would carry more dust & iron to the Bahamas, than dust-storms from Africa.
Certainly interesting work by U Maimi with the Blue Hole stalagmites, even if it’s not about the Younger Dryas.
Impact, you keep repeating impact. As has been said many many times, no actual impact is required, just an air burst.
I’m concerned that yet more pseudoscience is being perpetrated.
It’s called the YD Impact Hypothesis because one of the various versions of the baseless conjecture has a comet actually hitting the Laurentide Ice Sheet. You really ought to read up on the nonsense you purport to support. Besides which even a low airburst which leaves a crater or impact area counts as an impact.
The opening paragraph of the UCSB press release repeats more falsehoods:
“Most of North America’s megafauna — mastodons, short-faced bears, giant ground sloths, saber-toothed cats and American camels and horses — disappeared close to 13,000 years ago at the end of the Pleistocene period. The cause of this massive extinction has long been debated by scientists who, until recently, could only speculate as to why.”
This baseless assertion is blatantly false on its face. Mastodons lived for millennia longer; giant sloths for 6000 years or more after 13 Ka. DNA evidence shows that horses and mammoths both survived at least thousands of years later than their last appearance in the North American fossil record.
http://www.pnas.org/content/106/52/22352.full
There were probably other refugia for mammoths in Beringia besides the area of St. Paul Island. And of course mammoths survived until less than 4000 years ago on Wrangel Island, off eastern Siberia.
There is nothing special about the YD that didn’t happen at prior glacial-interglacial transitions, so no need to posit an ET event. There is no valid evidence for such an event, as every independent analysis has shown, including by the author of the well validated K/T hypothesis, who himself also allows that other causes contributed to the demise of the non-avian dinosaurs besides the Yucatan impact. There is no plausible mechanism for an imaginary ET event to have caused the totally natural YD climatic fluctuation. There is no evidence that “most” North American, let alone Eurasian, megafauna went extinct at the YD boundary. Indeed the more evidence accumulates, it appears that many of the species previously assumed to have been wiped out then died off before or long after the YD.
This completely conjectural “hypothesis” has nothing going for it. Nothing at all.
Your heroes’ press release calls it an impact. Please get your bedtime story or fable straight:
http://www.sciencedaily.com/releases/2014/08/140827163443.htm
Nanodiamonds are forever: Did comet collision leave layer of nanodiamonds across Earth?
Date:
August 27, 2014
Source:
University of California – Santa Barbara
Summary:
A comet collision with Earth caused abrupt environmental stress and degradation that contributed to the extinction of most large animal species then inhabiting the Americas, a group of scientists suggests. The catastrophic impact and the subsequent climate change also led to the disappearance of the prehistoric Clovis culture, and to human population decline. Now focus has turned to the character and distribution of nanodiamonds, one type of material produced during such an extraterrestrial collision. The researchers found an abundance of these tiny diamonds distributed over 50 million square kilometers across the Northern Hemisphere.
Grey –
On that particular point, I will say that I disagree with you. I can be wrong on it, but I am pretty convinced by Tunguska and Chelyabinsk that – Boslough’s work aside – an airburst is not sufficient. That is just my own take on things at this time. Chelyabinsk really taught me quite a bit. About ablation, about the amount of psi, about how deep into the atmosphere an object can get before the stresses prevent it from staying together long enough to hit the ground. But right now I also am strongly leaning toward the idea that almost all entry paths are low angle. Chelyabinsk was at about 20°. EVERY bolide I’ve seen has been low angle. Until I see a high angle entry, I am leaning that way. Ablation ate up about 90% of the mass of the Chelyabinsk object before it flared – and then only about 1 meter was left out of a 17-meter object. I think that other than the size, Tunguska and Chelyabinsk wee very much the same. Tunguska – because of its size (IMHO at this point) – was able to penetrate deeper (closer to the ground), so the amplitude of the shock from its flare was more intense at the surface.
That is my own working premise for now. Subject to alteration with new evidence.
I think that to put enough energy into the atmosphere to ignite the conflagration on that wide of a scale the event needed to be an impact. And no, we don’t have a crater.
But Luis and Walter Alvarez’s crater took 10 years to find. And had those two counted on academic scientists to find their crater, they might STILL be looking. Chixculub was only found because a perceptive oil industry field geologist became aware that people were looking for a crater.
The YDB hypothesis has only been around for 7 years, and the object envisioned is much smaller than the K-T impactor. Not only that, but right now the “impact specialist community” only looks at one kind of impact evidence – ones that look like Barringer Crater, made by clear cut stony or iron/nickel asteroids-turned-meteorites. But with the density range of about, say 0.25 g cm^-2 to about 3 or 4 g cm^-2, the variation may deliver something quite unrecognizable if people are looking for Barringer everywhere. What those impacts of low density-high velocity comets might look like, no one has a CLUE.
I invite you also to look at something called the Rio Cuarto craters. Google that and take a look at what ARE considered craters – in spite of the conservatives arguing otherwise! – down in Argentina, on the pampas. VERY big and VERY elongated craters – and QUITE deep. VERY much different. Very low angle impacts. On Google Earth, also pan SSW of the recognize ones NNE of the city of Rio Cuarto. Some of those craters are several miles long, and as I said quite elongated. Not Barringer at all.
We have found about 1400 Near Earth Objects (NEOs), using – FINALLY – satellites to get a clearer view of the space around Earth’s orbit. Only a very few percent are we currently aware of – mostly Apollos and Atens. None of the ones we know about are in orbits threatening us in the next several decades. But, as Chelyabinsk showed us, we can get blindsided at just about any time. NOBODY saw Chelyabinsk’s meteor coming at all.
A good deal of the interest in the YDB is at least peripherally about our current and future risk from such objects that might come out of nowhere.
Tunguska’s object came out of the Sun, in the early morning, just like Chelyabinsk did. It came in on June 30th, 1908. Tunguska, however, came right at the perfect time of the year to have been a Taurid comet/meteor. The Taurids are remnants of the very large comet which spawned the comet Encke (google “Encke Napier Clube”). That big one is referred to as the “Encke progenitor”. It is calculated to have been about 30 km across (shoot me if I don’t recall that precisely correct). Encke itself is only a very small percentage of that mass, so the smaller fragments are mostly still buzzing us annually – producing the Taurid meteor shower around the end of June every year. And that is exactly the time of year when the Tunguska object came down. Because of the differences in orbits – using Earth vs Encke as a guide – and the pertinent velocities, we see a different part of the Taurids every time they adorn our night skies. 90%+ of the mass of the Encke progentior is probably still out there W(We can’t know for sure), and some of the fragments are in all likelihood as big as the big fragments of Shoemaker-Levy 9 which smacked into Jupiter 20 years and about 6 weeks ago. (We need to use Encke as a guide because there are so many tiny fragments that none of them are able to be tagged/identified and tracked.)
The reason we don’t know how much of the Encke progenitor is still out there is because some of them may have already smacked Earth in the 30,000 years or so since it broke up. Whatever hasn’t hit us yet is a good candidate to hit us in the future.
So, basically, the reason we need to identify things that hit Earth in the past is to get an idea what kind of risk we are under. If all this was ancient history and that is all, nobody would give a damn, really. But since objects DO come at us out mof nowhere, we need to assess what our risk is and hopefully that risk is low.
To hear the Gradualists tell it, Earth hasn’t been hit by anything we need to worry about in a VERY long time – hundreds of thousands of years. But not long ago at all, that value was several MILLIONS of years. As times has gone by with new and better information, that time between Earth impacts has ALWAYS gone down, not up. At the present we don’t even know for sure if the timing we have is correct or will continue to get smaller.
The real truth right now is that if a 1-km object was coming at us,
1. It is 90% that we don’t know about it yet
2. Even if we see it coming, we don’t have the capacity to divert it or destroy it. We KIND OF have some capabilities – but all of those are maybes.
3. We can pretty much kiss our collective arses goodbye – because
4. The three 1-km+ fragments of Shoemaker-Levy 9 that hit Jupiter in 1994 created plumes LARGER THAN THE PLANET EARTH, even in the heavier gravity of Jupiter. Which means
5. That such impacts on Earth would have even LARGER plumes.
J. Hills and M.P. Goda calculated long ago that if a 300-m iron meteor hits in the OCEAN – not even on land, mind you – the coastlines 1000-km away will see a tsunami with run-up of about 1.7 km (more than 1 mile high)..
Working with Peter Leonard determined that
So, we would have all of 10 days warning.
But we don’t need to worry. After all, we have the attack dogs to police our thinking and to inform us of everything we need to know, and diverting and harassing the FEW people who are trying to assess an earlier impact possibility. The harassers are trying to make sure no one takes any of this seriously – telling us the THE SCIENCE IS SETTLED – that those who are researching all of this are a bunch of stumble-bums that can’t read a ruler or a lab report properly.
But the science is not settled at all. Where those harassers are trying to convince people on WUWT that their side is the only side to this, some sober and serious scientists are slowly coming to realize there is something there – that the lab tests don’t lie, and that this is something to look VERY seriously at..
Now what effect any of this has, relative to the ice core readings (which seems to be the only bullet in the opposition’s rifle) – and which will be dealt with in its turn, is this: We do not know what our risk is. And yet, HOW many objects coming out of nowhere have set off the NORAD alerts?
Some people seem to think this is an acceptable risk situation – that we shouldn’t look into our past and do the best science we have to ascertain our risk level. Personally, I am not one of the ostriches. I’d rather tackle this on both fronts – look for objects “out there”, and also look into our past.
I have NO idea why anyone would think that these are not worth doing. BOTH.
No one is suggesting a global-warming-like panic. There is time to look at this calmly and patiently. And if the risk is non-existent, we can all go back to living our lives.
But if we don’t at least assess both ends of this risk – aren’t we kind of really, REALLY stupid? The joke about the ostrich is always that his arse is still sticking out. And that he may not get to kiss it goodbye.
Oh, and Grey, take much of what this yokel is saying about pseudoscience with a grain of sand.
Be aware that science new articles are basically “Science for Dummies” articles.
An important Rule of Thumb: Always go to the source for your information – never to popular articles. Otherwise, we should all go to the Daily Mail or the St Louis Post Dispatch to learn our science.
In this day and age, we don’t need journalists summarizing and paraphrasing for us.
I recommend Google Scholar. Often you only get Abstracts, I admit, which are the scientist’s summaries. But should you use THEIR summaries in their own words, or some journalist’s summaries? Guys who are scared for their jobs, since the internet let’s people go straight to the source and news organizations are all on their last legs and hyperventilating about how to keep their jobs. And that leads to sensationalizing a LOT of what they write.
What you will often enough find is that the popular articles exaggerate – especially in their headlines. And even when they aren’t – how can you be expected to know the difference? You don’t.
So, go straight to the source. I promise – it will not be as much over your head as you may think. You will understand it every bit as well as that journalist. Trust me on that.
And TRUST BUT VERIFY.
Oh, and Grey – in case you need it spelled out for you:
There ARE two sides to this.
Two sides – regardless of what the thought police are trying to shove down your throat – and the throat of everyone here at WUWT.
Go inform yourself. Then make up your own mind.
Hey, my side MAY be wrong. So far the lab tests don’t say so, but maybe some empirical evidence down the road will falsify all of this. THAT is what the scientific method is all about — not some yayhoos getting all shrill on a blog.
Remember – the scientists will figure this out.
That’s what we pay them the big bucks for… LOL
Every independent lab test says you’re wrong, including those analyzed by Dr. Alvarez.
I was looking for the Bahamas source for a while to check it. The experts could easily calculate the winds required to transport that dust that far.
Agree about the two sides, but its sad when one clearly steps way out of line.
For what its worth, reading what they say, does not convince me that they have a real answer. The cosmic event makes sense but is not yet totally proven but time will tell.
Exactly. It has some evidence pointing that way, and they have the right to pursue it. Which they are doing.
It is QUITE obvious that some people won’t buy it, even if a meteor and crater are found. Some people have no capacity to admit being wrong. So what if they don’t? As in other science developments, the wrong ones eventually will die off and the next generation will treat them like they do the now forgotten people who locked up Galileo and threatened Copernicus so much he had to publish after his death.
There is opposition to every development in science. “NO! NO! Please don’t change anything I learned in junior high!”
Who are these people whom you imagine would not be convinced by a crater? At the K/T boundary, there was not only clear evidence of an impact but eventually a crater found.
Your delusions are paranoid.
Those who object to this baseless conjecture do so on the basis of science, ie evidence, for which there is none to support this assertion, and all the evidence in the world against it.
Sockpuppet at Wikipedia:
In the WUWT Policy page (under About):
Steve Garcia and Grey Lensman sound like the same person.
Ted Cayton, no, they are not.
Thank you Anthony Watts!
My apologies to Steve Garcia and Grey Lensman, for accusing them of sockpuppetry.
Ah yes, meteors that specialize in big game, climate change that specializes in big game, disease that specializes in big game, dogs and dire wolves that specialize in big game, versus hunters that specialize in big game. To think that such a question could drag on for decades. –AGF
I am in complete agreement with sturgishooper .
I find this complete insistence “There must be a crater” amusing.
The vast majority of Earth impacts have left no trace as they are atmospheric or water impacts.
Water impacts include ice. As for example, the impact/fireball in Greenland in 1997 that the USAF DSP satellites picked up and classed as “The peak radiated intensity recorded on this event was 9.5E10 watts/sr” and “the total radiated energy of the event was 2.7E11 Joules” AKA roughly a 100 kiloton nuclear detonation equivalent.
See:
http://meteor.uwo.ca/research/fireball/usaf/usaf982.txt
A large cluster of smaller bodies of the Tunguska and Chelyabinsk level could apply heat and blast waves over a huge continent sized area and leave zip, zero, nada in the way of recognizable over 12K(+) years craters. The supply of dead plant mass left over would be the basis for large scale forest fires started by things like lightning.
This neatly gets around a number of energy budget issues people have challenged the YDB hypothesis with.
Now, if you want to talk science, as opposed to argumentum ad nauseam, see this recent YDB impact paper abstract and look closely at _what else_ is showing up with hexagonal nanodiamonds —
Nanodiamond-Rich Layer across Three Continents Consistent with Major Cosmic Impact at 12,800 Cal BP
http://www.jstor.org/stable/10.1086/677046
“Abstract
A major cosmic-impact event has been proposed at the onset of the Younger Dryas (YD) cooling episode at ≈12,800 ± 150 years before present, forming the YD Boundary (YDB) layer, distributed over >50 million km2 on four continents. In 24 dated stratigraphic sections in 10 countries of the Northern Hemisphere, the YDB layer contains a clearly defined abundance peak in nanodiamonds (NDs), a major cosmic-impact proxy. Observed ND polytypes include cubic diamonds, lonsdaleite-like crystals, and diamond-like carbon nanoparticles, called n-diamond and i-carbon. The ND abundances in bulk YDB sediments ranged up to ≈500 ppb (mean: 200 ppb) and that in carbon spherules up to ≈3700 ppb (mean: ≈750 ppb); 138 of 205 sediment samples (67%) contained no detectable NDs. Isotopic evidence indicates that YDB NDs were produced from terrestrial carbon, as with other impact diamonds, and were not derived from the impactor itself. The YDB layer is also marked by abundance peaks in other impact-related proxies, including cosmic-impact spherules, carbon spherules (some containing NDs), iridium, osmium, platinum, charcoal, aciniform carbon (soot), and high-temperature melt-glass. This contribution reviews the debate about the presence, abundance, and origin of the concentration peak in YDB NDs. We describe an updated protocol for the extraction and concentration of NDs from sediment, carbon spherules, and ice, and we describe the basis for identification and classification of YDB ND polytypes, using nine analytical approaches. The large body of evidence now obtained about YDB NDs is strongly consistent with an origin by cosmic impact at ≈12,800 cal BP and is inconsistent with formation of YDB NDs by natural terrestrial processes, including wildfires, anthropogenesis, and/or influx of cosmic dust.”
The “CSI” for the YDB hypothesis is very strong — its more than just nanodiamonds — and thus far I have seen very little, other than outdated or flawed papers by the ‘usual suspects,’ challenging it on the basis of sound science.
There are lots of craters on the ocean floor and under other bodies of water.
Also, your arithmetic is wrong by orders of magnitude: 2.7E11 joules equals 0.06 KT, ie 60 TNT tons equivalent. The proposed YD “impact” would have been at least eight billion times more energetic than the puny strike you cite. Benson doesn’t know if even 474,000 megatons would have done it:
http://www.realclimate.org/index.php/archives/2009/01/the-younger-dryas-comet-impact-hypothesis-gem-of-an-idea-or-fools-gold/comment-page-1/#comment-108750
Somehow it escaped your notice that the paper you linked is the same one which is the subject of this blog post.
Every single one of the alleged evidences of an impact has been repeatedly thoroughly debunked by real scientists. Studies doing so are linked in the comments above.
So far from being “strong”, there is essentially no evidence in support of this falsified hypothesis, if a baseless conjecture can be so dignified.
Tunguska blast estimated at ~500 KT:
http://www.psi.edu/epo/siberia/siberia.html
It is quite amusing (but boring) how your crowd of trolls has basically repelled everyone here on WUWT. Notice how it is basically you four or five, doing your shrill Real-Climate-type thing trying to shut everybody up. That is because people here know what real scientists actually sound like, arguing with reason and not claiming that THEIR scientists are the only real scientists.
This hollering down everyone you disagree with – it’s not science. It’s shock radio.
No one is here on this thread anymore, not because of you having convinced them of anything. The folks here at WattsUpWithThat have heard such shrillness before, and it’s boring. So they’ve left your group to feed off each other. You all haven’t won anything but the echo chamber of your own certainty.
Actually, they’ve won a free trip to the troll bin.
WOW, Anthony. So you saw it, too. So it wasn’t just me seeing it… Nice to know you were paying attention.
Trent Telenko said @September 4, 2014 at 1:19 pm
Firstly, this is the “cometary impact theory of the origin of the [Carolina] bays”, dusted off and reapplied – to wit:
Supporters of the old Carolina Bays ‘soft shotgun blast’ hypothesis never abandoned the idea, although mainstream science discredited it decades ago. The parallels & connection with the new Younger Dryas impact suggestion have been plain since its inception, and can be found spelled out explicitly, as here.
Secondly, although a continental-scale pattern of Tunguska-like airburst objects could deliver the necessary energy, properly-developing the mechanism by which the necessarily large original object is divided into sufficiently-small (but not-too-small) objects to be air-bursts, has the earmarks of a meaningful undertaking in itself.
Third, comets are defined by their primarily icy (water) makeup, and as such would have a great deal less iridium etc (at best) than would a metallic-rich asteroid-type body … but which has greater strength and resistance to fragmentation, and far better penetration-characteristics.
We do see ‘meteor-swarms’, which are sometimes very striking, but projecting these mostly sand & pebble ensembles up to a ‘fresh’ comet that has disintegrated in a particular manner … is a calculus that involves some large, unaccounted-for conditions & steps.
AGU monograph from 2012 makes mincemeat of this preposterous conjecture, and studies since then hammer even more nails into its coffin, some linked above:
http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=5&ved=0CEwQFjAE&url=http%3A%2F%2Fwww.agu.org%2Fbooks%2Fgm%2Fv198%2F2012gm001209%2F2012gm001209.pdf&ei=YzsJVOK8AemejAKL2oCYDA&usg=AFQjCNERJCPDRNT01nhPsMC2B8Sf36JVQg&sig2=1C0UnZzPCzZjBliqWZrRSw&bvm=bv.74649129,d.cGE
Arguments and Evidence Against a Younger Dryas Impact Event
M. Boslough,1 K. Nicoll,2 V. Holliday,3 T. L. Daulton,4 D. Meltzer,5 N. Pinter,6 A. C. Scott,7 T. Surovell,8
P. Claeys,9 J. Gill,10 F. Paquay,11 J. Marlon,10 P. Bartlein,12 C. Whitlock,13 D. Grayson,14 and A. J. T. Jull15
We present arguments and evidence against the hypothesis that a large impact or airburst caused a significant abrupt climate change, extinction event, and termination of the Clovis culture at 12.9 ka. It should be noted that there is not one single Younger Dryas (YD) impact hypothesis but several that conflict with one another regarding many significant details. Fragmentation and explosion mechanisms proposed for some of the versions do not conserve energy or momentum, no physics-based model has been presented to support the various concepts, and existing physical models contradict them. In addition, the a priori odds of the impact of a >4 km comet in the prescribed configuration on the Laurentide Ice Sheet during the specified time period are infinitesimal, about one in 1015. There are three broad classes of counterarguments. First, evidence for an impact is lacking.
No impact craters of the appropriate size and age are known, and no unambiguously shocked material or other features diagnostic of impact have been found in YD sediments. Second, the climatological, paleontological, and archeological events that the YD impact proponents are attempting to explain are not unique, are arguably misinterpreted by the proponents, have large chronological uncertainties, are not necessarily coupled, and do not require an impact. Third, we believe that proponents have misinterpreted some of the evidence used to argue for an impact, and several independent researchers have been unable to reproduce reported results. This is compounded by the observation of contamination in a purported YD sample with modern carbon…
4. CONCLUSIONS
An impact event as proposed by Firestone et al. [2007] is
not consistent with conventional understanding of the physics
of impacts and airbursts. We conclude that the YD
impact hypothesis is not supportable, either physically or
statistically. Much of the putative evidence for a YD impact
is irreproducible. It is highly improbable that a significant
impact event happened during YD, as conceived by Firestone
et al. [2007]. Although the works published by the
proponents of an impact event vary in description about the
impactor, consideration of basic laws of physics indicate
that such a fragmentation or high-altitude airburst event
would not conserve momentum or energy, would lie outside
any realistic range of probability, and therefore did not
occur during the YD as described by Firestone et al.
[2007]. This conclusion is supported by the present work,
as well as a broad review of all the other lines of evidence
critiqued by Pinter and Ishman [2008a, 2008b], Surovell et
al. [2009], and Pinter et al. [2011a, 2011b].
It’s quite laughable that your group of trolls never onc mention the papers that refute these supposed “mincemeat” papers. I don’t even have to link to them, since all of them are mentioned at great length in the paper that is the subject of this post.
Since you haven’t actually READ that paper, though, of course you wouldn’t know. You blow off the lab test – called empirical science – and pretend that any evidence that doesn’t agree with you doesn’t exist.
Here at WUWT that is widely known as cherry-picking the evidence.
Go read the paper. Then refute the refutations therein, if you can.
I will NOT be holding my breath till you get back to us.
This is a hypothesis with two VERY clearly defined groups arguing for and against it. The CON side has:
M. Boslough, K. Nicoll, V. Holliday, T. L. Daulton, D. Meltzer, N. Pinter, A. C. Scott, T. Surovell,
P. Claeys, J. Gill,10 . Paquay, J. Marlon, P. Bartlein, C. Whitlock, D. Grayson, and A. J. T. Jull, as listed above, plus Annelies van Hoevel.
The list just from this one “Kennett” paper is:
Charles R. Kinzie,, Shane S. Que Hee, Adrienne Stich, Kevin A. Tague, Chris Mercer, Joshua J. Razink, Douglas J. Kennett, Paul S. DeCarli (now deceased), Ted E. Bunch, James H. Wittke, Isabel Israde-Alcántara, James L. Bischoff, Albert C. Goodyear, Kenneth B. Tankersley, David R. Kimbel, Brendan J. Culleton, Jon M. Erlandson, Thomas W. Stafford, Johan B. Kloosterman, Andrew M. T. Moore, Richard B. Firestone, J. E. Aura Tortosa, J. F. Jordá Pardo, Allen West, James P. Kennett, and Wendy S. Wolbach.
Notice that Richard Firestone isn’t even listed. Nor is R.
I see a lot of new names in the latter list. It seems they are winning over new scientists. It’s not, of course, the numbers themselves. But it shows that despite the assertions by the Troll Group here, there ARE real scientists on the PRO side. It isn’t just some commenters here on WattsUpWithThat.
The way these things are settled in science is by one group falsifying – proving false – the work of others. Not by insults and ad hominem attacks. Nor by asserting opinions. Opinions don’t count AT ALL as falsification. It takes empirical lab tests, experiments, and empirical field evidence to falsify.
Anyone reading the actual paper will see the numerous failures the CON side has had in falsifying the impact evidence, laid out one after another after another.
So far, not one of the claimed falsifications has held up to later scrutiny.
THAT is the bottom line on the CON side – they still have no shells in their artillery. Every piece of evidence they have come up with has, ITSELF, failed.
READ THE PAPER.
Kevin Trenberth’s compatriot James Kennett of UCSB is also an advocate for the clathrate gun hypothesis.
http://onlinelibrary.wiley.com/book/10.1029/054SP
sturgishopper could you list the cons and pros for the clathrate gun hypothesis to your way of thinking.
I am not impressed by this theory in explaining climate change. It seems if anything to be the result of climate change not the cause.
http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=6&ved=0CEUQFjAF&url=http%3A%2F%2Fgeology.gsapubs.org%2Fcontent%2F32%2F1%2F53.abstract&ei=jawMVM32BYaqyATO0oDoAg&usg=AFQjCNFJ51UbRpxWMCEW2-Vvypo4AQeSZg
This shows the problems with this theory.
Salvatore –
While this paper shows evidence NOT supporting the clathrate gun hypothesis. the clathrate gun certainly should be part of what is considered as the cause of the onset of the Younger Dryas stadial.
One paper does not a sufficient disproof make.
I am highly in favor of the impact hypothesis, as I show above. But scientists should never settle on one hypothesis as mainstream (whatever it is) without considering ALL of the OTHER possible causes.
Right now there are FOUR competing hypotheses for the extinction of the mammoths, and each school of thought is publishinig papers every month or three. They certainly cannot ALL be right, and most of the papers not only try to sell their favorite, but they typically try to shoot down one or more of the other three.
I love the give and take. And I love reading them to see how others are shooting down the ones I don’t favor…LOL
The impact hypothesis is the new kid on the block, so of course it is the target of much dispute.
I find the clathrate phenomenon to be a terrifically fascinating subject.
Thinking out loud, I would also think that in the case of an ocean impact clathrates would be more likely to erupt/be released, as a secondary phenomenon. One thing I have not heard much about is that since water is incompressible, it seems the shock of an ocean impact on the water should be considered as a destructive force, in and of itself, not just the tsunami. This is particularly odd, since in land impacts the shock is seen as such a major destructive force.