Guest Post by Dan Johnston
I have been following the proposed collision theory for the onset of the Younger Dryas for a number of years with considerable interest as it explains so much in a relatively straightforward fashion, if true. The academic response to the hypothesis has been, predictably, harsh and unforgiving with accusations flying back and forth as to procedures and interpretations. I did, however, enjoy one researcher’s claim that he could not reproduce the results reported in one peer-reviewed paper on the evidence for an impact. The impact researchers countered with the valid observation that the scornful researcher did not bother to use the same time-consuming methods they employed to extract extremely small microtectite spherules and nanodiamonds from sediments.
Carl Sagan’s “Extraordinary claims require extraordinary evidence” comes to mind with regard to the Younger Dryas claims but I have to admit, based on the global warming “consensus,” that this fundamental principle of science seems to have been trumped by politics and media attention in the past. I do remember the long struggle involved in getting the Alvarez’s theory of a catastrophic asteroid impact causing the end of the Cretaceous and extinction of the dinosaurs accepted. No matter how much physical evidence was gathered from around the world, acceptance (a much stronger word to me than consensus) didn’t happen until the smoking gun of the Cretaceous impact was located at Chicxulub in the Yucatan. Once the crater had been found, resistance to the asteroid theory rapidly crumbled and it is generally accepted as fact by most scientists today, though there is still a small minority of “deniers.”
The Chicxulub impact was a relatively straightforward exercise in science compared to the extraordinary claims being made about the cause of the Younger Dryas. WUWT has been following the Younger Dryas debate closely for a number of years and I won’t belabor the background information on its evolution except to say that resistance to the idea seems overwhelming despite repeated attempts to present more extensive, rigorous and compelling evidence. Just as with the end of the dinosaurs the extinction of mammoths and other North American megafauna requires an air-tight case and this will only happen when a crater or other irrefutable evidence of an impact is discovered and, preferably, dated.
When confronted with the fiery question of where evidence lies of an impact that only occurred some 12,800 years ago, barely time for a deep breath geologically, the Younger Dryas Impact proponents respond with an extremely weak mumbling about “air blasts,” asteroid clusters and ice sheet impacts that left no evidence of a large chunk(s) of space debris hitting the Earth. They point out that the Tunguska Impact (called an impact even though it left no crater) was an air-blast at an altitude of 3-6 miles (5-10 km) above Siberia that yielded the equivalent of 3-30 megatons of TNT in explosive force. The skeptics counter with Meteor Crater in Arizona, a beautiful little 1,200 ft (4,000 m) diameter hole 570 ft (170 m) deep made by a meteorite a mere 54 yds (50 m) in diameter that released 10 megatons of energy upon impact. They reasonably expect that a piece or pieces of space debris able to spread ejecta over half of the northern hemisphere, cause a 1,300 year halt in global warming and lead to the extinction of numerous species that had survived for hundreds of thousands of years had to leave some evidence of its arrival behind. The YD proponents then countered with the fact that the northern half of North America was covered with ice sheets and an impact on a 1 to 2 mile thick layer of ice may have mitigated the expected formation of a crater.
An impact on an ice sheet does seem reasonable as the evidence from the ongoing investigation points at the impact occurring somewhere in north-central North America near what is now the Great Lakes. Unfortunately, there is no crater evident and the projected impact should have left some imprint on the earth, even if it was a cluster of meteorites or an airburst. Let’s take the researchers at their word and look where the evidence points-the Great Lakes.
Water is capable of hiding almost everything beneath its waves but bathymetric maps showing the depths to lakebed of the Great Lakes can give us some idea of what lies beneath. A number of years ago, I looked at bathymetric maps of the Great Lakes because I was curious about alarmists reports of the five Great Lakes drying up due to global warming. I didn’t see any reason for alarm for the foreseeable future but did note what I considered an anomaly in the map for Lake Michigan in the central part of the southern lake. The map can be viewed at http://www.glerl.noaa.gov/data/bathy/ and is shown below.
Figure 1 Bathymetry of Lake Michigan (Great Lakes Environmental Research Laboratory)
The almost circular feature has a diameter of almost 40 miles (64.5 km) and the topography seems to indicate relatively steep slopes down to a central depression. A higher resolution view of the anomaly is shown in Figure 2 and comes from the Great Lakes Rescue Project at http://www.ngdc.noaa.gov/mgg/greatlakes/lakemich_cdrom/html/images.htm .
Figure 2 High Resolution Bathymetry of Southern Lake Michigan (GLRP)
I am not a geologist but this image definitely suggests the possibility of an impact crater, probably modulated by a considerable thickness of ice lying above the point of impact. A quick check of the assumed conditions at the proposed onset of the Younger Dryas (12900-12800 YBP) shows that at this time Lake Chicago existed as a melt lake with an outlet near Chicago and covered the southernmost tip of the current Lake Michigan. At this time, just north of Lake Chicago, the Michigan Lobe of the Wisconsin Glaciation was in rapid retreat. There is no reason to dismiss the likelihood that the edge of the ice sheet may have lain to the south of the Southern Chippewa Basin (SCB), the location of the anomalous terrain. After the onset of the Younger Dryas, the glacial front advanced for a millennium before the retreat resumed.
A check of the underlying geological explanation for the formation of the SCB is classical geological speculation with no real data. The belief is that easily eroded Devonian shale overlay a more resistant Silurian dolomite (the same or a similar formation to the one that forms Niagara Falls). The glacial front scooped out this almost circular feature by differentially eroding the shale while in doing so leaving behind steep escarpment walls into the basin and a shallow plateau just to the north. The story seems somewhat weak to me and, as far as I can tell, no samples of what lies beneath have ever been obtained from the SCB. I really feel it would be a wonderful idea to find out just what happened to form the SCB.
The Younger Dryas Impact proponents would be well-served by promoting an exploration of the SCB as a starting point while looking for other anomalies further north in the deeper Chippewa Basin and in other Great Lakes. If a smoking gun does exist for their theory, it probably lies under these waters.
As a footnote, an impact with the ice sheet and its catastrophic effects could explain the other primary explanation of the source for the Younger Dryas. An asteroid strike leaving one or more craters in the Great Lakes area could have resulted in a rush of fresh water flowing either north into the Arctic or out the St Lawrence Seaway and shutting down the North Atlantic conveyor transporting heat from the equator. Thus, the two theories would merge into a progressive explanation of the sudden cooling, its long duration and the deaths of the megafauna.
And can that … (Typing on a tablet is trying)
Any cosmic impact of such consequence as to alter global climate drastically will leave an unmistakable crater, no guessing games needed. Micro-sperules rain constantly on the planet. This subject is a corner of geology known as “impact studies” and the would-be climatologists should leave such questions to those who know the subject of cosmic impacts.
dbstealey says:May 24, 2013 at 9:24 am
I remember a ‘Frozen Mammoth’ article in Nat’l Geographic. Could have been in the 50s or early 60s issues. The meat was allegedly flash frozen, and still ‘fresh’, as eaten by a stranded expedition.
@ur momisugly Matt says:
May 24, 2013 at 2:03 am
“I must say that ““Extraordinary claims require extraordinary evidence” is drivel. What extraordinary evidence did Einstein’s claims need for support? One astronomical observation that may anyway not have been precise enough to do the job. ”
This is utter nonsense.
***Sagan’s requirement thus stated is obviously a highly subject demand. What is “extraordinary?” It is better to formulate it: “More fundamental conjectures require more fundamental proofs.”
I have a corroborating bit of evidence supporting a southern Lake Michigan proposed impact site. There are some associated ejecta or fragment impact features with this proposed primary impact location that have no other generally accepted explanation at this time: Carolina Bays — See generally: http://en.wikipedia.org/wiki/Carolina_Bay
Carolina Bays are elliptical depressions that appear anomalously across the Southeastern inland sedimentary landscapes from Alabama to Virginia and predominating in — you guessed it , the Carolinas and the long axes of these features show consistent trends and converge — on southern Lake Michigan.
See here: http://abob.libs.uga.edu/bobk/cbfig5.gif (you can overlay the image on Google Earth to see the extended long axis trend lines at the proposed site in southern Lake Michigan).
Some of the “prairie potholes” in the Midwest have similar features to the Carolina bays. A substantial body of these also have a long axis convergence trend on southern Lake Michigan.
http://cosmictusk.com/wp-content/uploads/Midwest-bays-long-axis-1024×690.jpg
http://cosmictusk.com/perigee-zero-carolina-bays-in-the-midwest/
The nature of these Carolina Bay sites could not have been from solid meteorite impacts as the typical impact characteristcs of those objects at such as site are entirely absent in Carolina Bays. They have fit however some ideas about possibly low velocity prograde orbit cometary fragment impacts. See here: http://abob.libs.uga.edu/bobk/cbayint.html
But if they fit data and concepts about low velocity cometary ice impacts — then they could ALSO very easily fit a theory of secondary ice eject impacts caused by surviving ice thrown clear from a primary impact site on a massive ice sheet.
Food for thought.
G.R. Mead
@Steve Keohane
Flash frozen mammoths is just a rural legend. In the last decades, several mammoth mummies have been found after the legend was created, ie the Jarkov Mammoth, the Fishhook mammoth, the Yukagir mammoth, Luba the baby mammoth. All highly googleable. The common factor with all of them is water, marshes, swamps, bogs, they probably drowned and became naturally mummified due to peat acids.
Dude, don’t quit your day job.
Proelior you left out the following (forgive me for using Wikipedia as a “cringe” scientific source)
Theories of origin Carolina Bays
More than a dozen bays are shown in this photo in southeastern North Carolina. Several are cleared and drained for farming.Theories of the origin of the Carolina bays fall into two major categories: that these features were created by forces within the Earth, or that they were gouged by an astronomical event or set of events.
Geomorphology
Various geomorphological theories have been proposed to account for the bays, including action of sea currents when the area was under the ocean or the upwelling of ground water at a later time. One major theory within the earth sciences academic community is that a combination of processes created the shapes and orientations of these ancient landforms, including climate change, the formation of siliciclastic karst by solution of subsurface material during glacial sealevel lowstands and later modification of these depressions by periodic eolian and lacustrine processes.
Various proposals that they were either directly or indirectly created by a meteorite shower or exploding comet are disputed by many scientists for an apparent lack of extraterrestrial material, absence of shocked quartz and “bedrock” deformation associated with larger bays, and extremely low ratio of depth to diameter of the larger bays. More information on these theories can be found at: Carolina Bays.
Quaternary geologists and geomorphologists argue that the peculiar features of Carolina bays can be readily explained by known terrestrial processes and repeated modification by eolian and lacustrine processes of them over the past 70,000 to 100,000 years. [2]. Also, quaternary geologists and geomorphologists believe to have found a correspondence in time between when the active modification of the rims of Carolina bays most commonly occurred and when adjacent sand dunes were active during the Wisconsin glaciation between 15,000 and 40,000 years and 70,000 to 80,000 years BP [3]. In addition, quaternary geologists and geomorphologists have repeatedly found that the orientations of the Carolina bays are consistent with the wind patterns which existed during the Wisconsin glaciation as reconstructed from Pleistocene parabolic dunes, a time when the shape of the Carolina bays was being modified [4].
Impact event
The cometary impact theory of the origin of the bays was popular among earth scientists of the 1930s and 40s. It said that they were the result of a low density comet exploding above or impacting with the Laurentide ice sheet about 12,900 years ago.[1]
New hypotheses arose again in the 1980s and 1990s, spurred on by various attention to impacts such as the Tunguska event, Cretaceous–Paleogene extinction event and a theorized link to the unsolved scientific mystery of the Younger Dryas event. Impact geologists determined the depressions are too shallow to be impact features. Reports of magnetic anomalies turned out not to show consistency across the sites. There were no meteorite fragments or impact crater geologic structures. None of the necessary evidence for an impact was found. The conclusion was to reject the impact theory at the Carolina bays.[2
http://en.wikipedia.org/wiki/Carolina_Bay
phlogiston says:
May 24, 2013 at 5:35 am
Note the author is not questioning the existence of the D-O events but calls them instead quasi-periodic, and suggests that the very regular 1500 year signal might be an aliasing artefact, not the real D-O events. The many posters here who regularly refer to the 1500 year periodic events needs to address this possibility.
Yes, there is no 1500-yr cycle. That value is likely to be an artifact of averaging: http://www.leif.org/EOS/Obrochta2012.pdf “Our new results suggest that the “1500-year cycle” may be a transient phenomenon whose origin could be due, for example, to ice sheet boundary conditions for the interval in which it is observed. We therefore question whether it is necessary to invoke such exotic explanations as heterodyne frequencies or combination tones to explain a phenomenon of such fleeting occurrence that is potentially an artifact of arithmetic averaging.”
Thank you, I have found the extinction of the North American mammals very interesting. I was taught that they were hunted into extinction. I found this strange since there are still elephants in Africa. There must have been much easier prey than a Mammoth or Sabre Tooth. Really.
My theory for the hole in Lake Michigan, the rise to the north served as a small glacier dam or fall. The depression is the same as you would find in a stream or river that flows over a similar embankment. There is always a deep spot. The geology of the area is a major factor of which I know nothing.
My theory on the extinction; large herbivorous mammals were hit by repeated catastrophic flooding on new grasslands (on floodplains) as the glaciers retreated. One of many possible factors. It’s a 12,000 year old mystery. I found the comments very informative.
Love this topic, Thanks
The Carolina bays are now thought to be caused by peat fires. Not to be associated with the Younger Dryas.
http://www.sciencedirect.com/science/article/pii/S0033589411001438
“As a footnote, an impact with the ice sheet and its catastrophic effects could explain the other primary explanation of the source for the Younger Dryas. An asteroid strike leaving one or more craters in the Great Lakes area could have resulted in a rush of fresh water flowing either north into the Arctic or out the St Lawrence Seaway and shutting down the North Atlantic conveyor transporting heat from the equator. Thus, the two theories would merge into a progressive explanation of the sudden cooling, its long duration and the deaths of the megafauna.”
While this can only be the very remote possibility of this scenario supporting the observed ocean circulation change in the North Atlantic. A major problem lies here where an impact big enough to bring down a massive ice sheet would not just melt it and flow down near it’s impact. There would be massive evaporation of the ice sheets which would be thrown miles into the atmosphere all around.Hence, the moisture from the ice would not just flow down into the North Atlantic ocean, but dispersed all over the northern hemisphere.
This wouldn’t cause enough ice melt to be concentrated in just one area of the the North Atlantic for disrupting the conveyor. A rapid natural warm up and melting without an impact would be a much better alternative for this trigger. The flow of melting ice would have flowed in rivers converging into bottlenecks flowing towards the North Atlantic Ocean. A small asteroid strike would keep most of the water from the melt in similar place, but wouldn’t have enough energy to melt most of the ice to have such an ocean conveyor effect..
E.M.Smith says:
May 24, 2013 at 9:02 am
Thanks for the Charles Keeling paper – a less known but much more significant contribution to climate knowledge than his famous CO2 volcano measurements. Yes lunar tidal stirring sounds very plausible as a climate forcing mechanism, I have argued many times that vertical ocean mixing alone is a sufficient and strong cause of climate cooling – due to the obvious fact of sharp thermal stratification. However for this forcing to be strong, and the cooling episodes to follow the 1500-1800 cycle directly, is only one possibility; the other is weak nonlinear forcing, which would cause a much more complex, less predictable temporal pattern. The oceans have their own internal dynamics. Periodic nonlinear forcings can be weak as well as strong.
I was unaware of the comet Encke debris field. There is some scary stuff out there. I dont exclude an impact at the YD, but I feel the ocean is a more plausible factor for millenial scale climate shifts. Do you have any thoughts about the inter-hemispheric bipolar seesaw? Its also a real climate factor, one of many that AGW scientists have sought to misinterpret as CO2 forcing. It is one of a crowded room of proposed YD causative factors, but its the one my money would be on.
Judging from the locations found of the evidence, there is little likelihood of the impact being in the Great Lakes unless prevailing winds during that period were the reverse of what they are today. Most of the debris would form a pattern much like the pattern of tuff left from a volcanic eruption.
One must also explore the possibility that over thousands of years, air bursts built up a lot of this material in glacial ice. When the glaciers melted, a lot of this was left with the other loess from the glaciers and was blown around with the wind. We could well have a layer of these spherules that were simply accumulated over time in the ice, deposited when the ice melted, and blown with the wind.
Also, think for a moment how much of these would have accumulated in Lake Bonneville and Lake Lahontan sediments over time and then blown around with the wind once those lakes dried up. Also, I would be willing to bet there were some serious fires in the Great Basin once those lakes dried up and the trees/grasses supported by all that water died. In fact, not having that great source of evaporation in the Great Basin likely created a massive change in climate. Most of Northern Nevada was a huge lake. Most of the peaks would have been covered with ice. These lakes and the ice would have accumulated debris from air bursts over time.
Do we know that the age of all of this debris is the same? We know it was DEPOSITED at about the same time, but we don’t know that it was CREATED at the same time.
I think a good test would be something like this:
Check the for the population of spherules going back to the glaciation before the Eemian Interglacial. Now check the populations of them over time. Do we see reduced populations of shperules during a glacial period, a layer of high density of these, and then a generally higher population of them during the interglacial than during glacial periods? I would expect to find that during glacial periods, spherules formed from air bursts would get accumulated in ice. As the ice melts, we have a large population of them that gets spread around and deposited from wind blown glacial loess and then we see the usual deposition rate. Then as we go into a glacial period, the deposition rate would reduce as more of them are trapped in ice again.
100.000 years of ice would get pretty dusty/dirty. A lot of those spherules would make it to the bottom of the glacier but would still be covered with ice until the glaciers melt. As they melt, there are no plants to keep the loess in place so it blows around as it dries out.
http://www.climatestudies.unibe.ch/students/theses/msc/45.pdf
So maybe “Younger Dryas” events are normal coming out of ice ages but I am guessing they can vary wildly. If a glacial lake dam bursts very suddenly, it can certainly have a different impact than if it bursts gradually. By that I mean, where a breakout occurs and the nature of the location probably has a lot to do with how quickly a lake empties. If water overtops an area of rock and gradually cuts down into it, that is probably different from a huge wall of ice suddenly giving way at once. The conditions of each interglacial is somewhat random.
The pre-Younger Dryas development of Lake Michigan, and in particular the “South Chippewa Basin” feature in the south end of it, is reasonably well-known.
This basin, put forward here as a possible crater, tied to the onset of the YD, was one of the early features of the proto-Great Lakes to emerge, as the south edge of the continental icesheet began to recede at the end of the last Ice Age.
This depression, now forming the south end of Lake Michigan, is clearly shown by standard geology to have existed for more than 1,000 years before the Younger Dryas.
See Lake Chicago, and in particular the Stages of development of the Great Lakes graphic.
The hole was already there.
@ur momisugly Matt:
“This is utter nonsense. It’s not like Einstein came up with an outlandish idea, and as soon as the first confirmation came in, everybody took his good word for it ever since.”
Nor did I claim that that’s what happened. Einstein did what Newton did – provided a new way of looking at heaps of old – and therefore not extraordinary – data. Lots of people were converted to his view pretty quickly, and celebrated their relief that Eddington’s data showed no flaw in Einstein’s picture. I’m right and you are wrong: there was no extraordinary data necessary for Einstein’s new ideas to triumph. Nor for Clerk Maxwell’s nor Planck’s nor Newton’s.
Naturally because these have all been routine parts of Physics pretty much since their discoveries, you can argue if you wish that now they are tested each time any experiment is done, but so what? All the canon of theory is tested the whole time. You are so wrong that I suspect you have a reading comprehension deficit.
crosspatch says:
May 25, 2013 at 3:40 pm
…
So maybe “Younger Dryas” events are normal coming out of ice ages but I am guessing they can vary wildly…
If bipolar seesawing characterised the run-up to the latest transition to (the Holocene) interglacial then its not too far-fetched to imagine that it might also characterise the prelude to other interglacials. Maybe its an unstable excursion that pushes the system into a different attractor across a phase-space saddle.
I apologize for the intrusion in the conversion but would like any thoughts on underwater explosions as opposed to air burst events and impacts. Would there be any remaining chemical or geologic signature if a large underwater methyl hydrate explosion occurred 13,000 years ago in the Gulf of Mexico or in Lake Michigan?
HI JudyW,
There are features on the ocean floor that clearly represent events that may then have various causes. Some resemble subsidence, and the suggestion/interpretation has been, that these could be due to hydrate outgassing/destabilization.
Release of gasses from hydrate-formations (and collateral/attendant melting of ice) may not be “explosive” in nature, but such events could cause slides, and otherwise generate tsunamis. They might affect the atmosphere, at least briefly. They do/can leave marks on the ocean floor. Dating these features, and tying them to other events in the geologic past, is of course a separate large challenge.
Ocean bathymetry can be obtained. Articles in this general topical area do exist. A Naval Academy instructor is the author of a “MicroDEM” GIS software, with a heavy emphasis on maritime GIS applications, and bathymetry. Other applications, and data are available (NOAA, NASA).
The general idea is not bad. As usual, the devil is in the details. There is some scientific & public policy “concern” with (roughtly) the possibility you allude to, though mainly in terms of contemporary hazards. The general area you are looking at is a bit dominated/skewed by those hoping to use it in pursuit of Climate Change goals, which can muddiy the waters at bit, for straight science-questions.
Ted
As posted recently in WUWT, Santa Barbara’s Emeritus Professor J.P. Kennett’s report of his YDB (“Younger Dryas Boundary”) Research Group seems definitive: Since globally dispersed micro-spherules only form at temperatures exceeding 2,200 degrees Celsius, while nucleo-chemical analysis precludes any lightning-strike, super-volcano, or other terrestrial processes, trans-continental “strewn-fields” of impact-fused/striated nodules can only have resulted from a major series of air-bursts or relatively small-scale chains of cometary/meteorite impacts.
As the contemporaneous “black mat” above Clovis Culture and extinct large-mammal species’ fossil-beds attests, this rain of exo-solar debris –likely originating in disruption of the solar system’s far-distant, spherical Oort Cloud– likely caused continent-wide wildfires whose atmospheric dust and smoke radically reduced plant cover and subsequent re-growth, starving large Mesolithic herbivores and predators alike.
Despite the well-defined Cretaceous/Tertiary (K/T) Boundary, wholesale destruction of late saurian species remained problematic pending Luis and Walter Alvarez’s discovery of Chicxulub’s submerged crater in the Yucatan. Even so, given events such as the Tunguska air-burst of 1908, a Younger Dryas crater in Lake Michigan or elsewhere would only confirm the obvious: That an anomalous 1,500-year “cold shock” radically cooled Earth’s atmosphere in months, coincident with catastrophic global extinctions affecting human socio-cultural milieus.
Certain chronologies indicate that, for whatever reason, Planet Earth risks major geophysical trauma approximately every 3,600 years. Setting exo-planetary Younger Dryas impacts at BC 12,400 – 12,800 readily conforms to this conjecture.
The impact hypothesis leaves unexplained the Oldest Dryas (18-15 Ka) & Older Dryas (~14,050-13,900 BP, but not well constrained) cold snaps. Same goes for stadials in previous deglaciations.
Good information Ted. Thanks for the response and references to pursue.
Judy, there is evidence for methane hydrate destabilization at the Amazon river fan in the period preceeding the Younger Dryas.
http://www.geog.ucl.ac.uk/about-the-department/people/academics/mark-maslin/Maslin%202009%20Amazon.pdf
See table 1 page 136, the mass transport deposit event in the eastern fan at 13,500 or 14,500 years ago, but obviously very tentative.
What an excellent paper and study leftturnandre! It does appear in the Amazon fan study that the outgassing associated with landslides and avulsion events happened when sea levels were falling. Most were prior to the onset of the Younger Dryas. These releases potentially could contribute to restarting the current interglacial period but I will rule out my explosion hypothesis . Thanks for the enlightenment.