About 12,800 years ago, the last Ice Age was coming to an end, the planet was warming up. Then, inexplicably, the planet plunged into a deep freeze, returning to near-glacial temperatures for more than a millennium before getting warm again. The mammoths disappeared at about the same time, as did some Native American cultures that thrived on hunting them. That climatic event is known as The Younger Dryas.
Many explanations for the event point to the impact of a comet or an asteroid, but now there is a new study suggests the driver/trigger was all from terrestrial based events.”
According to the article in Science Magazine, they find no evidence for an impact:
The study “pulls the rug out from under the contrived impact hypothesis quite nicely,” says Christian Koeberl, a geochemist at the University of Vienna. Most evidence for the extraterrestrial impact hypothesis, he says, was conjured up “out of thin air.”
The notion was popularized in television documentaries and other coverage on the National Geographic Channel, History Channel, and the PBS program NOVA.
…
Now comes what some researchers consider the strongest attack yet on the Younger Dryas impact hypothesis. In a paper published online this week in the Proceedings of the National Academy of Sciences, a team led by David Meltzer, an archaeologist at Southern Methodist University, Dallas, in Texas, looks at the dating of 29 different sites in the Americas, Europe, and the Middle East in which impact advocates have reported evidence for a cosmic collision.
Only three of the 29 sites actually fall within the time frame of the Younger Dryas onset
http://news.sciencemag.org/archaeology/2014/05/what-caused-1300-year-deep-freeze
From the publication:
A key element underpinning the controversial hypothesis of a widely destructive extraterrestrial impact at the onset of the Younger Dryas is the claim that 29 sites across four continents yield impact indicators all dated to 12,800 ± 150 years ago. This claim can be rejected: only three of those sites are dated to this window of time. At the remainder, the supposed impact markers are undated or significantly older or younger than 12,800 years ago. Either there were many more impacts than supposed, including one as recently as 5 centuries ago, or, far more likely, these are not extraterrestrial impact markers.
Chronological evidence fails to support claim of an isochronous widespread layer of cosmic impact indicators dated to 12,800 years ago
David J. Meltzer, doi: 10.1073/pnas.1401150111
David J. Meltzera, Vance T. Holliday, Michael D. Cannon, and D. Shane Miller
Abstract
According to the Younger Dryas Impact Hypothesis (YDIH), ∼12,800 calendar years before present, North America experienced an extraterrestrial impact that triggered the Younger Dryas and devastated human populations and biotic communities on this continent and elsewhere. This supposed event is reportedly marked by multiple impact indicators, but critics have challenged this evidence, and considerable controversy now surrounds the YDIH. Proponents of the YDIH state that a key test of the hypothesis is whether those indicators are isochronous and securely dated to the Younger Dryas onset. They are not. We have examined the age basis of the supposed Younger Dryas boundary layer at the 29 sites and regions in North and South America, Europe, and the Middle East in which proponents report its occurrence. Several of the sites lack any age control, others have radiometric ages that are chronologically irrelevant, nearly a dozen have ages inferred by statistically and chronologically flawed age–depth interpolations, and in several the ages directly on the supposed impact layer are older or younger than ∼12,800 calendar years ago. Only 3 of the 29 sites fall within the temporal window of the YD onset as defined by YDIH proponents. The YDIH fails the critical chronological test of an isochronous event at the YD onset, which, coupled with the many published concerns about the extraterrestrial origin of the purported impact markers, renders the YDIH unsupported. There is no reason or compelling evidence to accept the claim that a cosmic impact occurred ∼12,800 y ago and caused the Younger Dryas.
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Maybe it could have been the Vela supernova, a relatively close explosion at 800 lightyears.
The resulting cosmic rays could have enhanced clouds and cooled the Earth.
Vela Supernova Remnant.jpg Vela Supernova 11th–9th millennium BCE ? 800 ? Vela Supernova Remnant
http://en.wikipedia.org/wiki/List_of_supernova_remnants
Sandi says:
May 13, 2014 at 8:26 am
Yes, it would be nice if we had all the answers, but we don’t. See Arthur Conan Doyle:
Beyond impacts and volcanism, what remains to account for the relatively rapid ups and downs of the YD?
Variation in solar output?
Close passage, sans impact, of a large extraterrestrial body, perhaps causing Earth to wobble on its axis for a bit?
leftturnandre says:
May 13, 2014 at 4:46 am
Sopme of the mamooths found in alaska were from about the 15000 to 18000years ago. A supposed YD period but not the most recent. We have not found a mummy we date to precisely the last YD.
Probably unrelated…. but if you place a line along the long axis of the Carolina Bays, they tend to focus somewhere over the Pacific Northwest. They are dismissed as not being from an exploding impactor as vociferously as those that lightly dismiss the “black mat” research.
http://en.wikipedia.org/wiki/Carolina_bays
Steve from Rockwood says:
May 13, 2014 at 5:46 am
IMO Yuka’s age is not yet well constrained, or if so, a more precise date hasn’t been published. Usual reference is to “at least” or “over” 10,000 years ago.
But clearly, some mammoths did survive past the glacial/interglacial transition, as shown by the finds from Wrangel Island.
Yuka showed signs of having survived lion attack & of being scavenged by humans after death.
http://news.discovery.com/animals/endangered-species/woolly-mammoth-yuka-120404.htm
How about a transient response from the nuclear reaction within the Earth’s core?
vukcevic says:
May 13, 2014 at 4:08 am
Milankovitch cycles aren’t quite that regular, at least as to interglacials. Also, for over half of the past 2.6 million years, the 40,000 year cycle dominated, not the 100,000 year, as lately. The timing & causes of the switch are controversial.
Since the switch in dominant cycle period, interglacials have varied in length from thousands to tens of thousands of years. As has often been discussed on WUWT, the likely duration of the Holocene cannot yet be foretold with any confidence.
The previous interglacial, the Eemian lasted 16,000 years by the most common way of dating its onset & demise. It was also warmer than the Holocene, which, by the same dating system, is about 11,400 years old. The Eemian was preceded by two shorter interglacials, although one had a YD-like interval between two warm spikes. The interglacial before those two shorter ones, MIS 11, was a monster, both warmer & much longer than the subsequent three (MIS 9, 7 & the Eemian). Going farther back in time, before three intervening interglacials, you come to MIS 19, which resembled MIS 11. So based upon only 800,000 years, there appears to be an approximately 400,000 year pattern in interglacial cycles in which orbital mechanical parameters roughly repeat.
If the Holocene proves to last as long as MIS 11 & 19, which showed similar Milankovitch orbital mechanical positions, then “catastrophic” natural global warming could result. There would however be plenty of time to adapt to any sea level rise from melting of the southern dome of the Greenland Ice Sheet (& possibly part of the West Antarctic IS). This might not happen however, even given tens of thousands more years, because the Holocene has been cooler than MIS 11 (& the Eemian) & is liable to remain so. (This dome partially melted during the Eemian, such that Scandinavia became an island.) In any case, the site of NYC under a few meters of water would be preferable to under a kilometer of ice.
Humanity will be lucky if the Holocene lasts tens of thousands of years more, based upon orbital mechanics, rather than the few thousand it appears headed for, based upon the longer-term global cooling trend of the past 3000 years observable in paleoclimatic proxy data. The jury is still out & may remain so for a long time.
Never never never stop asking “QUO BENE?” “Who benefits?”
Think in terms of the Jones/Briffa/Mann “Team”.
Look at the sceince writer on this one. HAHAHAHAHAHA – THE Richard Kerr who still has not acknowledged the pro-impact evidence from YEARS ago.
At http://www.CosmicTusk.com, there is even a widget showing Kerr’s indolence:
HAHAHAHAHAHA, what a JOKE!
Now look at the first name on the paper. MELTZER. Meltzer has spent his career on the mammoth overkill hypothesis, and is totally invested in it. If the impact hypothesis wins, Meltzer loses.
So, with Meltzer, his career is on the line, THREATENED by the YDB impact hypothesis.
Look at the second name on the paper. HOLLIDAY. Holliday is ALSO massively inverted in the Clovs Man DID IT hypothesis. If the impact hypothesis wins, Holliday also loses.
Holliday and Meltzer have been carping on the YDB impact hypothesis since it came out, they and a very small cadre of gradualists who basically do not do any original work themselves regarding the impact evidence but just run around and try to poke holes in the pro-impact papers, which are loaded with ORIGINAL research and TONS AND TONS of forensic data on several fronts.
Do you think I am kidding? EVEN THIS PAPER – look at the Abstract. It’s a JOKE. All they do is KIBITZ:
Do you SEE? All it is is a COMMENTARY paper.
WHERE IS THEIR ORIGINAL SCIENCE, folks?
There ISN’T any.
This crowd – being mainstream (meaning uniformitarian-gradualist) – has the ear of similarly gradualist science editors. Richard Kerr is only one. ThePro-impct people have a tough time getting published – and every time they do, one of the Meltzer crowd is interviewed to “give balance”.
But where is the
So, every LITTLE PUNY point in refutation they can make is heralded from the rooftops – even if it doesn’t amount to anything. Names on the YDB skeptical “Team” are Daulton, Pinter, van Hoesel, Boslough, and Surovell. Their work is SHODDY and proven to be shoddy.
At the same time, Surovell, though a died-in-the-wool gradualist, pokes big holes in the Mammoth Overkill hypothesis with some of his papers. I point to Surovell’s 2007 paper, “How Many Mammoth Kills Are 14?…” (http://www.uwyo.edu/nmwhomepage/pdfs/qi%202008.pdf) Which craps all over the PUNY amount of evidence that Clovis Man was the “extinction event” for Meltzer’s Overkill hypothesis.
I ALSO point to my blog entry of two days ago: “Mapping Clovis Man vs Mammoths – Just Asking” at http://feet2thefire.wordpress.com/2014/05/10/mapping-clovis-man-vs-mammoths-just-asking/ The theme of that blog entry is that whenever we here of CLovis Man did this sand CLovis Man did that, they talk about CLovis out WEST.
You wanna know something? Google Image “Clovis Sites Map”. You will SEE where Clovis Man REALLY was – and, Baby, it wasn’t out WEST! Clovis Man was primarily – VASTLY SO – east of the Misssissippi River.
And here is the kicker:
In the region where Clovis was greatly populated, THERE WERE NO MAMMOTHS.
So, the great Mammoth devourers, Clovis Man, was eating OTHER animals!
You won’t hear Meltzer or Holliday
The skeptics always get the science journalists to state something like the one here: “Now comes what some researchers consider the strongest attack yet on the Younger Dryas impact hypothesis.” They have counted it dead and buried (if you listen to THEM tell it) several times over. AND ALWAYS PREMATURELY AND AMATEURISHLY.
They are fighting to save their careers. They have a VESTED INTEREST in the impact hypothesis failing, and they are doing everything – EXCEPT ORIGINAL SCIENCE – to shoot it down.
This so-called “paper” and its contents are – as usual – WEAK and adding nothing to the discussion but WORDS. WHERE IS THEIR ORIGINAL SCIENCE? NEW ORIGINAL LAB DATA?
As one last blast at them, I will agree with Richard Fireston’s comment, ““Radiocarbon dating is a perilous process.” And it IS. Only recently did the Carbon14 IntCal calibration curves get changed – FOR THE THIRD TIME IN NINE YEARS. In one of the changes, the of the YDB impact radiocarbon dates moved by 100 years – from 12,900 years ago down to 12,800 years ago. And that will not be the last such change. So the skeptics picking nits about a few scores of years is a tempest in a teapot. The pro-impact realize this uncertainty in dating, and put down the best dates they can – but realize that those may change down the road.
Melzer and Holliday act like all that dating is written in stone (no pun intended), and jump on any 5-year anomaly.
Like I said, amateurish.
Sorry about that editing. The sloppiest comment I’ve ever posted here.
At lest 2 sentences started and not finished. BAD. Typos galore.
Mea culpa.
Pleistocene climate seems to be a bi-stable affair. All, as in 100%, bi-stable systems experience ringing upon state change. If one understands what causes the state changes, one will understand what causes the ringing. The Younger Dryas sure looks like the ringing of a bi-stable systems state change. It is best to try to understand what causes the ice age state changes first before invoking magic meteors
Berényi Péter says:
May 13, 2014 at 5:36 am
A requiem to the Younger Dyras Impact Hypothesis was already announced three years ago.
http://www.sciencedirect.com/science/article/pii/S0012825211000262
Great paper! … from the conclusions of which I extracted this absolute gem of a quote:
Some insight is gained by adding a historical perspective here. Scientific hypotheses are constantly being proposed, tested, confirmed, or cleanly rejected, but a small minority of these stray from this time-proven path. Many scientists are unaware of the surprising number of hypotheses that have gone badly astray, often after widespread initial interest and support (Langmuir and Hall, 1989; Gratzer, 2000; Park, 2000).
Widely applicable!
DesertYote says:
May 13, 2014 at 11:30 am
Some argue there are three Pleistocene states: interglacial, glacial & glacial maximum.
Heinrich Events (iceberg armadas in the North Atlantic) during glacial phases & Dryas Events during deglaciation appear to arise from waxing & waning of ice sheets. The latter events coincide with fresh meltwater pulses.
http://onlinelibrary.wiley.com/doi/10.1029/94PA00032/abstract;jsessionid=292E4DCFA02F926DE23E675A14A6AEB0.f03t03?deniedAccessCustomisedMessage=&userIsAuthenticated=false
Next time someone tells you that any change in glacier melt in Greenland is unprecedented, show them this from the IPCC.
The repetitive mega-floods from glacial Lake Missoula (~ 12,000ya, Montana USA) fall into the Younger Dryas time period. Are there any similar occurence of massive ice dammed glacial lakes from northern europe bursting forth in this time period ?
@Nick Stokes at 4:25 am:
“The AR4 didn’t mention any impact theory 6.4-2-2:
‘Freshwater influx is the likely cause for the cold events at the end of the last ice age (i.e., the Younger Dryas and the 8.2 ka event). Rather than sliding ice, it is the inflow of melt water from melting ice due to the climatic warming at this time that could have interfered with the MOC and heat transport in the Atlantic – a discharge into the Arctic Ocean of the order 0.1 Sv may have triggered the Younger Dryas (Tarasov and Peltier, 2005)’ ”
If you want to see a floundering hypothesis, the “freshwater influx>oceanic conveyor shutdown” is as bad as it gets. Wally Broeker came up with the idead long ago, and it was supposed to have come out of the St Lawrence, a Scablands-like flood from an ice dam failure at the southern end of glacial Lake Agassiz.
THE FLOUNDER BEGINS… Unfortunately, it was found out more than 10 years ago that the ice sheet had not retreated north far enough at 12,800 years ago, so THAT idea had to get dumped. Broeker hismelf admitted it was a lost cause. But then someone came up with the BRILLIANT (/snarc) idea of having the ice dam fail to the NORTH, out via the MacKensie River and north to the western Arctic Ocean north of the Yukon.
Which is THE dumbest idea EVER. That fresh water entering the WESTERN Arctic was going to cause the Gulf Stream to fail? That the fresh water and the fresh water was going to find its way to the east of Iceland, around all those islands north of Canada – and THEN not be diluted as hell? It is amazing how illogical and physics-challenged you can be and still have ANYONE call you a scientist.
It is so dumb that I award them eternal ownership of the Pointed Dunce Cap Award.
leftturnandre at 4:46 am:
“Steven said:
There are huge problems with all the theories about the YD cooling.
No there are no mammoth mummies dated to the Younger Dryas. Most are much older.”
Sorry, lefturnandre, but you are wrong. At Murray Springs, for one, there were found mammoth bones with the “black mat” lying right on the surface of the bones, draped over them. The bones are even permanently STAINED from the black mat.
And what does the black mat have to do with the YD? The underside of the black mat IS the YD.
As to “most” of the mammoths being “much older,” that couldn’t possibly be because MOST mammoths lived in earlier times, could it? And what do their earlier deaths have to do with the extinction of the LAST of the full-sized mammoths? Absolutely nothing. That is like saying that your great-grandparents died before you will have died. So what?
Oh, and lefturnandre, they are not “mammoth mummies.” Sheesh! The ones that aren’t just bones actually have had meat still on them, edible by sled dogs. Frozen? Yes. Desiccated? I’ve been looking into these for decades and can’t recall one account mentioning desiccation, though I could be wrong. Most of the carcasses are quite intact.
During an overall ice age (which we are in) inter-glacial periods are innately unstable states. We are on borrowed time.
As much as I dislike Firestone’s impact hypothesis, he has a point about the hazards of 14-C dating. The 14-C production rates are far too variable to rely on without an alternate method to use as a check, especially as you deal with greater time depths. Otherwise, you are using a rubber ruler and need to handle any measurements with great care. One suggestion that Firestone was not interested in pursuing was the possibility that the nanodiamonds and other “cosmogenic” debris might be due to the passage of the solar system through a small dark nebular body. Common estimates of the planetary accumulation of normal meteor dust range from around five to more than 300 metric tons per day! Entry into a nebular cloud could raise that rate considerably, and, thinking about it, the increased interplanetary haze caused by the nebula would reduce insolation triggering cooling (see Sir Fred Hoyle’s “Black Cloud” for a fictional consideration of such an event). That could mean that there was no impact, but there was an increase cosmogenic materials, and that the time span of the onset was also greater.
IMHO the Cosmic Tusk folks have it most right. String of impactors mostly onto the ice sheet. LOTS of detail at their site.
Folks are mixing several different things in comments:
1) What causes glacial / interglacial cycles.
2) What causes instability / wide swings in glacial temperatures
3) What causes period of Ice Age Glacials
4) What caused extinctions / reductions of animals
and a few more….
For most of these there are relatively simple answers IF you keep them separated from each other. For example, the Ice Age Glacial periods. Milankovitch pretty much worked this out. Precession, obliquity and eccentricity. The transition from 41,000 year to 100,000 years, IMHO indicates a continued lower temperature on earth.
The key is realizing that we are only in an interglacial when the north pole melts. During the 40,000 ish thousand year time it was warm enough that that happened when the tilt was changed on the 41,000 year cycle. N.Pole at the sun, ice melted. Once we got even colder, that alone was not enough and we needed it to happen when the eccentricity was enough that summers were a few days longer than the average. (Yes, that still ‘has issues’…)
BTW, we are IN an “Ice Age”, just in an interglacial during it. There are also stadials and interstadials that are not quite as warm / cold as the glacial / interglacial swaps. Ice Ages (not just the glacial / interglacial swapping) seem driven by placement in the galactic arms.
During a glacial, temperatures are more metastable. Swaps of ocean currents cause a switch of the Thermohaline Circulation fairly easily ( there’s a paper that shows the heat backing up in Florida then and summer like rains even in winter here). That ocean current swapping is the biggest trigger of the various swaps. (D.O. and such look tied to Lunar tides and their 1470 -1800 year cycles of extremes).
The extinctions of animals are largely in sync with impact events and occasionally with sudden introductions of other species (continents collide / connect). The idea that humans hunted ALL the megafauna of North America to extinction at exactly the same time is simply stupid. There just were not enough humans to do that.
So, on the thread of this posting, IMHO the impact into the ice theory accounts for all the known facts. Including sending a wall of icy slush over the pole to explain the land form of mixed stuff in Siberia (including the plant and animal inclusions).
BTW, Comet Encke is the likely culprit. Entered about 20,000 years ago and began to break up. LOTS of big chunks “lost”, and likely impacted Earth in many cases. We have regular meteor showers to this day based on the left overs. (Taurids). That pretty much proves we are in the shooting gallery for the break up.
So this paper found some craters that have mildly divergent dates, and the event spans some time. Since we’ve had about 20,000 years of Encke Bits whacking us, I say “So what?”…
Mac the Knife says:
May 13, 2014 at 12:11 pm
The Bretz Floods occurred roughly between 15,000 & 13,000 years ago, so, within dating precision, a little too early for the YD. Other mega-jökulhlaups or Glacial Lake Outburst Floods (GLOFs) are evident from around the world from various times, however.
The Strait of Dover & English Channel are thought to have been formed by erosion from two major floods. The first was about 425,000 years ago (onset of interglacial MIS 11), when an ice-dammed lake in the southern North Sea overflowed to break the Weald-Artois (SE England to NW France) chalk range in a catastrophic flood erosion event. After this, the Thames & Scheldt emptied through this gap into the English Channel, but the Meuse & Rhine still flowed northwards. In a second flood about 225,000 years ago (interglacial MIS 7) the ice-dammed Meuse & Rhine formed a lake which broke catastrophically through a high weak barrier (perhaps chalk, or an end-moraine left by the ice sheet). Both floods cut massive flood channels in the dry bed of the English Channel, somewhat like the Channeled Scablands of the Pacific NW or the Wabash River of the Midwest.
It has also been suggested that gigantic jökulhlaups from a Hudson Bay area lake dammed by Laurentide IS ice at the mouth of Hudson Strait could have caused Heinrich events (armadas of icebergs leaving ice-rated debris on the floor of the North Atlantic) during the last glaciation.
Just by coincidence, at middday today I was reading a book ,published about 1975 on AngloSaxon England and the possible effect the prevailing rainfall and temperature had on the successive invasions by Anglo Saxons, Viking and Danes on south East England following the end of Roman occupation.(Our little band of amateur archaeologists had been driven off the excavation site by downpours of freezing rain – which is odd given that we are in early summer and Britain is in the savage grip of unstoppable global warming according to the BBC and the Guardian).
Anyway , with one petrified hand clasping a life giving cup of triple strength espresso , I was leafing through the book and came upon a 2000 year chart of Greenland temperatures from oxygen isotope ratios measurements by a Danish scientist.
The usual variations , the mediaeval “optimum” as the author called it( regarding it as a global effect ) , and the following minimum were there , but the final temperature , ca 1975 was exactly on the longterm mean . No mention of CO2, or hockey sticks and the variations were treated as a natural fluctuation , not related necessarily to human activity or lack of it .
I am sure that later studies are more detailed and accurate but it was such a relief to read a calm and matter – of- fact presentation of scientific data without the shrill screams of imminent doom.
What happened to those happy innocent days of ( largely) impartial , objective and scholarly science .
All gone , gone with the wind? .
@Col Mosby at 5:02 am:
“Get the feeling not much advancement of knowledge here.”
Exactly. This is what I call a “kibitzing paper” – though you COULD call it an Op-Ed paper. It doesn’t DO any new science. All it does is point at REAL work others did and give opinions, with NO new forensics of their own, just trying to pick holes in the work of others.
I am ALWAYS amazed that journals allow Op-Eds. Opinions are not science.
If you look at my long comment here, this small team – I call them “The Daulton Gang” does nothing on the YD except try to undo the work of the pro-impact people. The Daulton Gang only ONCE has gone out in the field (that I know of so far) to get their OWN evidence, and when Surovell did that, he completely FAILED to follow sampling protocol. He diluted the samples by not taking narrow (2 cm or so)samples. So HIS lab results showed WAAAAY too low of impact material levels. His failure has duly been noted. And THEN the bigger didn’t even come back with a response! He just let it lie! What the heck kind of scientist doesn’t even DEFEND his own work?
And HE was the only one who went out in the field and got his own samples. PATHETIC.
So, as you say – no “advancement of knowledge”. The Daulton Gang, in fact, doesn’t WANT any new development – because if the eivdence for an impact at the YDB holds up (and it looks like it will), then their entire careers are garbage.
[“bigger” ? Mod]
What could possibly flash freeze mammoths ? Surely nothing within nature on Earth, the only thing cold enough woud be a ball of ice from outer space. The black mat could be other consequences of the impact.
Or is ice from the arctic or Greenland cold enough to flash freeze an animal well adapted to arctic, or at any rate, Siberian temperatures ? seems unlikely so I can only give credence to the icey comet impact theory.
E.M.Smith says:
May 13, 2014 at 12:38 pm
The Overkill Hypothesis doesn’t maintain that all megafauna were hunted to extinction at the same time. It does however attribute the extirpation or extinction of about 15 genera wholly or in part, directly or indirectly to the Clovis people.
But advocates of the hypothesis also cite genera which survived the alleged Clovis Blitzkrieg as supporting evidence, since most of them were of relatively recent Asian origin, thus adapted to human predation. Among the exceptions is the indigenous American pronghorn, the second fastest land animal on earth.