Where Lies the Younger Dryas Smoking Gun?

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.

clip_image001

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 .

clip_image002

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.

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One of the main problems is that the isotope signature, ie d18O, dD AND deuterium excess, and accummulation rates of the Greenland ice cores during the Younger Dryas are identical to the Dansgaard Oescher events. http://en.wikipedia.org/wiki/Dansgaard%E2%80%93Oeschger_event
Therefore one should wonder why the Younger Dryas needed an impact and 25 similar events did not.

Mike Bromley the Canucklehead

“Meteor Crater in Arizona, a beautiful little 1,200 ft (4,000 m) diameter hole 570 ft (170 m) deep….”
Methinks the 1200 ft should be meters, & the 4000 m should be feet….?

alex

Offtopic.
I believe, everybody MUST read this:
http://www.welt.de/debatte/henryk-m-broder/article116332834/Eine-Behoerde-erklaert-die-Klimadebatte-fuer-beendet.html
German Ecology Ministry claims any “climate debate” as finished and publishes a list of persons who deny climate change.
According to the Ministry, these persons should not publish anything in official newspapers.
Did not expect such things were possible 70 years after Nazi Germany.
[Best to post this into the “Tips and Notes” thread.
Note: The new (just anointed (er, appointed) US Dept of Energy king (er, head) ALSO said equivalent statements in his coronation speech in front of his adoring audience of DOE serfs (er, employees) and lackeys. Mod]

Matt

“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.”
No, they do not respond with an extremely weak mumbling regarding to what happened, instead, they have this to say:
http://wattsupwiththat.com/2012/06/13/new-evidence-of-younger-dryas-extraterrestrial-impact/

Pedantic old Fart

Have you thought much about the profile? The South Chippewa Basin, although fairly circular, has very even slopes all the way to a central deepest point–not typical. The northern ‘basin’ is twice as deep and very precipitous outer sides even if it is not circular. Dunno.

dearieme

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. What extraordinary evidence did Clerk-Maxwell’s field theory, or Planck’s quantum notion, need? Come to that, Newton’s claims about gravitation, the greatest advance in the history of physics, needed no new evidence to persuade people: it just cast a fresh and compelling light on heaps of old evidence.

Peter Miller

A large stony meteorite, as opposed to the much rarer metallic sort, exploding in the atmosphere above 1-2 kms of ice, would leave no sign of impact, but there should be dust/ash/something in the ice core records.

Matt

“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. 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. – Of course Einstein has been put to the test in many, many experiments and observations and a hundred years on, it has been confirmed time and time again with very high precision. – Actually extraordinary claims DO require extraordinay evidence, which is precisely why Einstein is being put to the test up to this day. you have a distorted understanding of what is going on 🙂

Keith

Have to say that the South Chippewa Basin looks like a pretty normal depression. Worthwhile someone having a dig, but I wouldn’t be holding my breath (I’d use SCUBA gear…).
On the more general point of asteroid/comet or not as the cause of the YD, our ancient texts/drawings/carvings might point towards the former. Ancient civilisations the world over, from China, India, the Middle East, Europe, Africa and the Americas, feature dragons as the bringers of disaster. Firebreathers with long, fiery tales coming from the sky. If you start from the premise that they weren’t real creatures, the best explanation for the ‘dragon’ featuring across the world is that they were meteors of some description. There’s some (though not compelling) evidence dating many of these civilisations to at least 10-12K years ago. I wouldn’t say that this means “Yes, an impact caused the YD”, but it seems to me more likely than not that some fireballs from the skies scared the bejesus out of our ancestors so much that the legend was depicted for millennia afterwards. Exactly when this event or these events occurred is another matter.
It certainly merits having an open mind to the impact hypothesis, rather than writing it off completely. We might not find The Crater, but the evidence is building.

William Astley

70% of the Younger Dryas cooling occurred in less than a decade. The abrupt cooling is the reason for the extinction. The magnitude and rapidity of the cooling is unimaginable. The regions of the planet affected, cool from interglacial warm to glacial cold with 70% of the cooling occurring in less than a decade. There is for example 15C cooling on the Greenland Ice sheet during the 1300 interval of cooling. Britain had a year average temperature of 5C during this cold interval compared to its current average temperature of 13.5C.
There are cycles of abrupt cooling captured in the Greenland Ice sheet record. When the planet cools there is an increase in desertification and an increase in zonal winds. There is a 10 fold increase in dust from the Sahara desert that is deposited on the Greenland Ice sheet during these cyclic abrupt climate change cooling intervals. The increase in dust in the Greenland ice sheet cores is a signature of this special cyclic event.
The duration of the Younger Dryas abrupt cooling period is 1300 years. Extraterrestrial impacts are not capable of cooling the planet for 1300 years.
The cooling due to a comet or a meteoroid impact is similar to a large volcanic eruption. The duration of cooling for that type of forcing mechanism is less than a decade. Insolation at N65 was at maximum for the duration of the Younger Dryas abrupt cooling interval. A very power forcing mechanism is required to cause the cyclic abrupt cooling.
The analysis indicates the Younger Dryas burn marks have been heated to a temperature in excess of 2200 C at 18 different locations at different latitudes and longitudes on two different continents.
That would require 12 to 18 separate extraterrestrial objects. It is physically impossible for a single object to breakup and cause the observed pattern of burn marks due to the distribution of the burn marks on the planet.
The Younger Dryas researchers have not involved astrophysicists when they formulated the impact hypothesis to explain the burn marks. An astrophysicist would unequivocally rule out extraterrestrial objects as the cause of the burn marks. PBS had a special on the Younger Dryas Impact theory and interviewed an astrophysicist who made that statement. It is astonishing that the researchers did not include astrophysical analysis (orbital paths and so on) as part of their hypothesis analysis.
It is unlikely to the point of being close to physically impossible for there to be 12 to 18 separate naturally occurring extraterrestrial objects all of the goldilocks size to heat the planet to greater than 2200C at the locations, without leaving impacts marks, as based on the locations of the burn marks on the planet’s surface, would require that multiple objects with different orbital paths have struck the earth.
Impacts on the earth of the objects of the goldilocks size are very, very, rare. Multiple independent source bodies all striking the earth within a few years, is not a viable explanation for the burn marks.
The Younger Dryas abrupt cooling was caused by an abrupt geomagnetic excursion. There are cycles of geomagnetic excursions. There is a geomagnetic excursion, the Gothenburg geomagnetic excursion that is dated to have occurred at the same time as the Younger Dryas. There are other geomagnetic excursions at other abrupt cooling periods. The special type of Dansgaard-Oeschger cycle cooling – the very, very rapid extreme cooling that sometimes follows the D-O warming phase, is called a Heinrich event. Geomagnetic excursions have been found at the termination of past interglacial periods.
http://en.wikipedia.org/wiki/Younger_Dryas
http://www.sciencedirect.com/science/article/pii/003358947790031X
The Gothenburg Magnetic Excursion
http://sciences.blogs.liberation.fr/home/files/Courtillot07EPSL.pdf
http://www.vvkuz.ru/books/Kuznetsov_and_Kuznetsova.pdf
The Earth Palaeoclimate Response to Cosmic Rays Exposure During Geomagnetic Field Excursions
http://earthobservatory.nasa.gov/Newsroom/view.php?id=24476
Glacial Records Depict Ice Age Climate (William: abrupt cooling periods) In Synch Worldwide
Is the geodynamo process intrinsically unstable?
http://eprints.whiterose.ac.uk/416/

ralfellis

Most holes in the ground tend to end up as circular. Its the way of nature. Turn an hour-glass upside-down and see what happens. Subduction can and will do the same.
.

Another problem is when exactly did then the Younger Dryas start? There are two main ideas. 12.7 and 12.9 thousand kalendar years ago. There is some convincing evidence, duplicated in several independent counted records that it really was 12.7 If the impact was at 12,9 Ka then you’d have an synchronity problem to begin with.

@William Astley
William, The Gothenburg geomagnetic flip was an artifac and has never been reproduced. You won’t find any contemporary publication referring to it. There has never been retractions or refutals, but It’s not there, anywhere. The rumor has it that the sediment core was broken and put together again the wrong way.

Hell_Is_Like_Newark

This guy (see link) put together a pretty comprehensive hypothesis on the same subject. He proposes multiple impacts and air-blasts from a broken up comet. I haven’t read the entire post yet, but what I have read so far seems pretty interesting.
http://cometstorm.wordpress.com/2011/04/27/a-different-kind-of-climate-catastrophe-2/

DSW

I have read that some are not convinced that the meteor strike at Yucatan was not responsible for the dinosaurs extinction primarily because of the lack of fossils found in the KT boundary. If it had wiped them out, shouldn’t there be a lot of fossils at that level? Just shows that what is settled may not be.

mortis88

errr, *was* responsible – ack, need coffee,…

Stephen Wilde

William Astley said:
“There are cycles of abrupt cooling captured in the Greenland Ice sheet record. When the planet cools there is an increase in desertification and an increase in zonal winds. There is a 10 fold increase in dust from the Sahara desert that is deposited on the Greenland Ice sheet during these cyclic abrupt climate change cooling intervals. The increase in dust in the Greenland ice sheet cores is a signature of this special cyclic event.”
Should that be an increase in meridional rather than zonal winds during a cooling phase ?
One would need more meridional winds to carry more dust from North Africa to Greenland.
If so, that would accord with my general hypothesis and that we are currently in a more meridional and slightly cooling regime than we were when the sun was more active.

Nastapoka Arc, Hudson Bay, could be also a serious candidate.
http://www.vukcevic.talktalk.net/NArc.htm
Distinct coincidence between magnetic and gravity anomalies indicates something extraordinary.
Impact was likely to be from a huge ‘iron’ meteorite, since slowly sinking into the crust, with sections of it reaching the Curie temperature of iron around 770 degrees C, judging by the decline in the magnetic intensity of the area.

phlogiston

leftturnandre says:
May 24, 2013 at 12:27 am
I agree with leftturnandre that the YD does not need to appeal to an atmospheric event, since other more plausible explanations exist. Several have been advanced here, such as the Dansgaard Oescher events as you propose. William Astley is no doubt correct that an impact cannot affect climate for a millenium. My own penny-worth theory is that the YD is just part of the “bipolar seesaw” of interhemispheric climate oscillation preceding the Holocene.
I have always felt that there is “no case to answer” with the Younger Dryas (YD). Glacial periods – in contrast to interglacials such as (and especially) the Holocene, are characterised by rapid, even violent, climate temperature swings up and down, as William Astley again points out, in the context of which the YD is not very exceptional. (Glacial epochs are punctuated by “micro-interglacials” lasting less than a century.)
This view is reinforced even more by literature on the bipolar seesaw (reciprocal oscillation between north and south hemispheres) around the time of the YD and before, leading up to the Holocene. One of the most important such papers is Blunier et al 1997 who show that the YD was just the NH reacting to a warming southern ocean. It was proposed by Tzedakis et al 2012 that sharpened bipolar seesawing marked both the beginning and the end of interglacials. Thus in Blunier we see – in fig. 2 – first a warming in the southern ocean about 16 kYa, then the “Antarctic cold reversal”, a cooling oscillation in the SH, coinciding with sharp NH warming prior to the YD. Then a warming upswing in the SH ending the cold reversal coincides with the abrupt YD. It is noted by Barker et al 2009 that the seesaw is characterised by smooth sinusoidal oscillation in the SH but more abrupt changes in the NH, caused in the latter case by Atlantic meridional overturning circuation (AMOC) regime changes. Then at the Holocene inception both NH (abruptly) and the SH (smoothy) rise in temperature, but the SH again cools slightly in advance of the Holocene optimum.
One thing that is clear is how Jeremy Shakun, holder of the chair in climate fraud at Oregon SU, has shamelessly exploited the end-glacial bipolar seesaw to concoct a spurious proof of CO2 leading the temperature rise out of the last glacial. Southern ocean temperatures had been rising since 16 kYa and continued to rise during the YD, resulting in a small CO2 increase in anticipation of the Holocene, on the condition that you take the Holocene to begin after the YD. But CO2 was not driving the start of the Holocene, it was merely following the southern ocean established warming. (There is more ocean in the SH than NH.)
If we demand an atmospheric deus ex machina to explain every upward and downward wiggle of climate history we are falling into the trap of AGW believers, who are unable to accept any cause of temperature change other than atmospheric input by humans and are in denial of the existence of the world’s oceans.

eco-geek

Having been cursed with seeing a stony asteroid three times now by eye and in Earth’s atmosphere I think there are more important things to worry about than what caused the Younger Dryas. This one is >1.75 miles in diameter, mostly dark with some ruddy orange plasma and flickers. I call it “Itys” (Son of Tereus) for obvious reasons. YHBW.

phlogiston
Bill Illis

There was also an Older Dryas event that started at 14,300 years ago where temperatures dropped by more than they did in the Younger event at 12,800 years ago.
The issue is the Greenland ice core scientists have never really been clear about the record. It’s all been about global warming scare for them, of which the Younger Dryas was just the one they focused on.
If an asteroid caused the event, then there were about 23 of them during the last ice age because that is how many rapid cooling events there were. More likely is that there are many periods of glacial advance from accumulation at central load points on the ice-sheets in the far north, interspersed with periods when the glaciers melted back just as rapidly. Even in the downturns of the Milankovitch Cycles, solar insolation at 65N was more than strong enough in the summer to melt the ice. The ice-sheets had no business getting down to Chicago and New York. The summer sun is too strong.
The megafauna were mostly mega-grass-herbivores (and then mega-carnivores that fed on them). When the ice age was ending, the extensive grassland habitat that covered most of North America because of low CO2 and low precipitation during the ice ages, was replaced with more C3 bushes and trees. There wasn’t enough grassland left for dozens of giant species.
And giant rivers from the melting ice which flowed south to the Gulf of Mexico would have cut them off into small regions where local extinction became more likely. An entire herd could be wiped out by simply trying to ford one of these rivers in the summer. A few mega species survived, most didn’t.

phlogiston

William Astley says:
May 24, 2013 at 2:17 am
I would be grateful for your comment on the following point quoted from Maslin et al 2001, concerning Dansgaard-Oeschger events with an apparent 1500 year period:
One cautionary note is that Wunsch has suggested a more radical explanation for the pervasive 1500-year cycle seen in both deep-sea and ice core, glacial and interglacial records. Wunsch suggests that the extremely narrow spectral lines (less than two bandwidths) that have been found at about 1500 years in many paleo-records may be due to aliasing. The 1500-year peak appears precisely at the period predicted for a simple alias of the seasonal cycle sampled inadequately (under the Nyquist criterion) at integer multiples of the common year. When Wunsch removes this peak from the Greenland ice core data and deep-sea spectral records, the climate variability appears as expected to be a continuum process in the millennial band. This work suggests that finding a cyclicity of 1500 years in a dataset may not represent the true periodicity of the
millennial-scale events. The Holocene Dansgaard-Oeschger events are quasi periodic, with different and possibly stochastic influences.

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.

Scott

I find this an interesting theory, off of Racine in Lake Michigan (directly west of that hole) there is an underwatwer structure locally known to fishermen as “the hills” three very distinct series of smooth rising/falling hills that rise and fall as you go several miles east into Lake Michigan directly towards that hole. Those hills are not as evident out of Kenosha (to the south) or Milwaukee (to the north). I just started fishing out there and was wondering what could carve out out those hills, Racine onhore is pretty flat, the Silurian rock of this area seems too hard to carve out like that. Perhaps those hills are some sort of remant of a collision, and there are other “hills” out there to find if one were to go more towards the middle of the lake then travel right towards that hole. Anyways something to ponder while trolling this summer, I metal detect the beaches of this area always on the lookout for fossils or ancient stuff including meteorites and have never found nor seen any evidence of a meteor collision.

Phlogiston et al,
I do believe that things are still quite a bit different. Maybe have a peek at this work in progress:
https://dl.dropboxusercontent.com/u/22026080/YD%20working%20paper.pdf

phlogiston

leftturnandre says:
May 24, 2013 at 5:52 am
Phlogiston et al,
I do believe that things are still quite a bit different. Maybe have a peek at this work in progress:
https://dl.dropboxusercontent.com/u/22026080/YD%20working%20paper.pdf

Whoa – that would put the cat among the pidgeons, if correct!

Phlogiston,
scrutinize, try to shoot it down. That’s how science works isn’t it?

beng

Don’t need a crater. Airbursts have already been observed. A meteor or comet “stream” will produce a multitude of airbursts, especially if it comes in at a shallow angle.

beng

***
William Astley says:
May 24, 2013 at 2:17 am
***
Please stop the incessant magnetic cr*p.

wws

regarding the KT boundary: “If it had wiped them out, shouldn’t there be a lot of fossils at that level? Just shows that what is settled may not be.”
Remember that fossilization requires some unique circumstances present, and that vast majority of organisms that have died on earth have left no fossils. Most importantly, a fossil needs almost instant sedimentation after death in order to be preserved from natural processes, which generally means shallow ocean bottoms or swampy areas (ie, the carboniferous period) A disaster as proposed at the KT boundary, which would have resulted in a mostly dead world, may not have produced the kind of conditions which would have led to fossils being quickly buried and preserved.

Taphonomic

“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.”
Please. The key word there is “seems”. Just because there are a lot of contour lines does not mean that the slopes are steep. 150 m change in elevation over ~32 km radius? That does not equate to “relatively steep slopes”. That is equivalent to a 4 m rise (or fall) per kilometer (about 5 inches per 100 feet) would be imperceptible to a person walking over the terrain. Even the steepest slope is approximately 70 m over 10 km (7 m over a kilometer; 8 inches over 100 feet).
You admit to not being a geologist, but wish to throw out hundreds of years of geologic investigations in the Lake Michigan area as speculation and replace it with your own speculation which requires that an ice lobe be in place over the SCB at the time instead of Lake Chicago so that you can further speculate on a meteor strike. Speculation heaped on speculation while dismissing all geologic evidence as speculation?

AnonyMoose

If that is a crater, it is both not very deep and not round enough. Craters tend to be very circular, and if the central depression is visible I’d expect more traces of the outer ring. Maybe sediment covered most of it. However, studying Great Lakes sediment is an obvious exercise, and has been going on for some time.
The first sediment study which popped up in a search refers to C14 dates of 13,000 years ago — so one would expect to find some upset in these nearby sediment layers from a more recent impact.
http://deepblue.lib.umich.edu/bitstream/handle/2027.42/22932/0000498.pdf;jsessionid=E6FE4A66B8673CD8A0645A4DA42FB944?sequence=1
And a glance at these sediment sampling locations across the suggested crater shows that there is data which you can look at to see if these sediments hint at their being splattered around about recently.
http://mi.water.usgs.gov/pubs/WRIR/WRIR98-4039/images/fig3.jpg
http://mi.water.usgs.gov/pubs/WRIR/WRIR98-4039/WRIR98-4039TOC.php
Actually, if one wants to look for underwater craters, I suggest Lake Agassiz. It was a bigger target at the time, and maybe a crater got buried by its sediments. It’s a bit north of the center of the identified splash area, but there are few sample areas to the north so it’s possible that the impact is on the north side of the splash area.

@phlogiston:
The “1500 year” cycle is more likely a range of times with 1200 years at the lower band and 1800 years at the longer. It is an average duration, not a fixed period. The most likely causal agent is the lunar tidal cycle that runs a similar duration, matches the historical temperature cycles, and has more effect on ocean mixing (cold deep to surface) than does the wind. See:
The core of it is here:
http://www.pnas.org/content/97/8/3814.full
while I look at it a bit here:
http://chiefio.wordpress.com/2013/01/24/why-weather-has-a-60-year-lunar-beat/
http://chiefio.wordpress.com/2012/12/15/d-o-ride-my-see-saw-mr-bond/
http://chiefio.wordpress.com/2013/01/04/lunar-cycles-more-than-one/
Per the topic of the Y.D.:
The history of Encke matters… it arrived sometime around 20 kya? then proceeded to break up and give periodic meteor storms for generations (decreasing over time as the debris gets consumed). Tunguska Event was likely from one SMALL left over fragment. The orbit of the earth moves into / out of the center of that debris field on a very long cycle (we are presently nearer the edge, so lower level of impacts than in the past). It is a large debris field from a major break up, so arguments of the form “It is unlikely for many to arrive at once” are broken on the face of it due to this existence proof.
http://chiefio.wordpress.com/2011/11/03/lunar-resonance-and-taurid-storms/
http://chiefio.wordpress.com/2011/11/14/meteor-showers/
It think it is likely essential to address Comet Encke and the breakup history of it, along with known cyclical patterns from our drift into and out of that debris field along with the development of that debris field over time, to have any hope of explaining the last 20,000 years patterns. It was a major change in our “context”…
The “1500” year pattern persists over much much longer time scales, so is much more likely tied to a fundamental property of the solar system. (Be it solar dynamics or orbital dynamics – it’s something outside our surface dynamics that are less stable…) IMHO the best candidate is an orbital resonance based “coincidence” of planetary positions with lunar / tidal ocean stirring; and with a “maybe” of a modulation of solar state / sunspot levels (as either coincident event with no climate impact; or a small potential of coincident event with climate impact). Orbital resonance keeps all those things happening in the same interlocked cycles, so “causality” can not be attributed based on showing frequency of coincident occurrence.
For example: IFF the lunar ocean “stirring” is the cause of cyclical 1500-1800 year cooling / warming cycles (as it looks to me) and is held in phase with planetary orbital positions (via orbital resonance) and those same planetary positions modulate sun spot levels: All three will have very high correlation. But it would be seriously wrong to say either “The planets cycles cause the cold” or “The solar sunspot cycle causes the cold”. It’s the lunar tidal stirring the oceans; the other two are non-causal, just coordinated via orbital resonance.
BTW, the lunar orbital tidal effects account for the known cold events other than the Younger Dryas… which further argues for the Younger Dryas to be “special” and suggests unusual causality such as an impact event.

I tend to waste time reading wild-eyed semi-science, just because you come across some interesting data spliced into the refutable theories. Besides reading the semi-science of various climate scientists, I’ve read the semi-science involving lots of ideas regarding the demise of Mammoths. One work was by a guy who I think was named Graham Kendall, but all my links to his paper have failed.
One thing he stated I always wanted to run by a more qualified geologist, (if only to see eyes roll.)
It was the idea that it had to get cold very fast, for the mammoth flesh to not rot in the middle, where food would ordinarily be decomposing and bloating in a dead beast’s guts, (especially a mammoth’s, because they were so large.) He had interesting ideas about a flash-freezing calamity in the north which we can’t imagine, because we have never seen the likes of it.
He also stated the mud beneath the permafrost is not strata in layers, but rather a sort of churned up muck, holding frozen leaves and twigs that are well preserved, and that oil workers run into such well-preserved evidence of a milder, lusher arctic while drilling. Any oil workers care to comment?
I really enjoyed the fellow’s ideas, even if they were science fiction. One thing he stated was that all the frozen mammoths were found clustered in higher places, as if they had struggled up hill through a calamity.
Anyone know what happened to Graham Kendall’s paper?

mandfobob

Two things. 1 – The KT boundary extinction may have something to do with extraterrestrial impact(s) but, by no means, is it the only driver. Megafaunal decline (dino’s) had been ongoing for several million years prior to the impact(s), as were marine vertebrates and invertebrates. Ocean chemistry at the times indicate significant word-wide changes in overall chemistry that started long before the impacts(s). Large volcanic eruptions (Daccan Traps for one) in addition to elevated rates of seafloor spreading (mid-oceanic ridge eruptions) had a role and, with the exception of the impact(s), were long term environmental changes well under way prior to the boundary extinction. Contrary to popular opinion, the K/T extinction event did not happen by one event (impact) no matter how “romantic” the idea.
2 – There has never been any evidence uncovered that Lake Michigan is underlined by an impact crater although the idea that many of the large structural basins (such as the Michigan Basin) in the North American craton may have had a large impact genesis has been a topic of geological discussion. These “genesis” type impacts would be extremely old (Precambrian > 500 MYBP) and not as recent as the late Pleistocene . That would be an “exceptional claim” type of issue. Pleistocene glaciation created and significantly modified many extremely large land forms,the Michigan Basin is one.

G P Hanner

The clues are there. It is a matter of correctly interpreting them. Several decades ago I used to fly over Mellville Island, located in the Canadian Arctic. What appeared to me to be an impact crater on the Sabine peninsula of Mellville Island turns out to be a rather large collapsed salt dome.
You can see the crater using Google Earth at these coordinates: 76.628378N 109.044778W. On radar it appears to have a central rebound rise in the middle of the crater.

Caleb,
There was a very interesting article on mammoths, which I keep losing for some reason. It seems the Wayback Machine changes over time [?!]. I had a much more detailed article bookmarked, but now it is gone.
Here is an abbreviated version of that much longer article, which asks some interesting questions.
One question: what is “muck”? It appears to be some sort of mud, thousands of feet deep in places. At the bottom of the muck is evidence of mammoths, and grasslands, and many other Ice Age mammals. It appears that the mammoths, which numbered in the tens of millions, all disappeared at the same time. When mammoths roamed, the climate in Alaska was much warmer than now.
What caused that mass extinction [which also affected other mammals at the same time]? Some of the mammoths had fresh vegetation in their teeth when they were flash frozen, and their stomach contents were fresh. How did that happen, without putrefication? Many of the mammoths showed signs of being smashed from above, with their legs splayed and broken. Where did the muck suddenly come from? It appears at the same geological time [just prior to the Holocene] over large geographical areas, from Alaska to Siberia and parts of China. A large blob of “muck”, at extremely low temperatures, seems to have descended across vast areas at the same time. How else to explain numerous instantly frozen mammoth carcasses?
The source of the article seems a little wacky, but the questions raised have not been satisfactorily answered, IMHO.

@dbstealey:
One proposal is that the same impact into the ice sheet that caused the Y.D. also kicked up a load of frozen “ejecta” and sent a tidal wave of frozen mixed with mud / slush over the pole to land on top of the Siberian Mammoths. It explains all those odd things in the muck, the ‘flash freeze’, and more. (The only part that bothers me about it still is the question of how to get that much stuff moved in a tidal wave of muck – clay mud and ice – and not heat it enough to melt fully…)

Jean Parisot

If the strike hit ice, then where would the ejecta originate?

jorgekafkazar

eco-geek says: “…I think there are more important things to worry about than what caused the Younger Dryas….”
Yes. It’s the sun, sagacious.

@Jean Parisot:
As I understand it (which is ‘not well’ – since it’s not my theory and I’m only ‘channeling’ someone else on it 😉 the impact causes a significant vaporization / jet of hot crap downward. This large gas pocket (think minor nuclear explosive force) puts lots of pressure / force on the surrounding ice sheet as the shock wave fractures it. Then the whole mass gets moving from that impact overpressure event. “Steam explosion under ice” writ large… very large…

William Astley

In reply to:
leftturnandre says:
May 24, 2013 at 3:19 am
@William Astley
William, The Gothenburg geomagnetic flip was an artifac and has never been reproduced. You won’t find any contemporary publication referring to it. There has never been retractions or refutals, but It’s not there, anywhere.
William:
See the contemporary reference below to the Gothenburg geomagnetic anomaly.
There is evidence of a very large increase in C14 that correlates with the Younger Dryas cooling event. There are papers that assert a reduction in ocean circulation cannot result in an increase in C14 of the magnitude observed.
I believe is other evidence to support the existence of the Gothenburg geomagnetic excursion.
The discovery of cyclic and rapid changes to the geomagnetic field is recent. What is missing is a mechanism that explains what causes the geomagnetic excursions. One hypothesis proposed is that growth or change of the ice sheets causes results in a change to the earth’s rotational speed which in turn causes the geomagnetic excursion.
There is a question in terms of ice sheet growth what is the dog and what is the tail. If there is an external forcing function that can cause an abrupt change in the geomagnetic field then the geomagnetic excursion causes the cooling and the ice sheet growth. In the last 10 years there has been the discovery of archeomagentic jerks (spacing roughly 400 years) at which time the geomagnetic field orientation changes abruptly by 10 to 15 degrees. Planetary temperature changes correlate with these changes. The acheomagnetic jerks are captured in fired pottery. The French have thousands upon thousands of pieces of pottery that they have examined.
A geomagnetic excursion is capable (assuming Svensmark’s mechanism is real) of cooling the planet for 1300 years. As noted above a meteoroid or comet impact is not. There still needs to a physical explanation for the 18, plus 2200C burn marks.
http://link.springer.com/article/10.1134%2FS0001433812080063#page-1
The Gothenburg geomagnetic excursion as a chronological marker for the Allerød interstadial in the Central Russian Upland
http://cio.eldoc.ub.rug.nl/FILES/root/2000/QuatIntRenssen/2000QuatIntRenssen.pdf
Estimates for the increase in Delta 14C at the start of the YD all demonstrate a strong and rapid rise: 40-70%/% within 300 years (Goslar et al., 1995), 30-60% in 70 years (BjoK rck et al., 1996), 50} 80&in 200 years (Hughen et al., 1998) and 70& in 200 years (Hajdas et al., 1998). This change is apparently the largest increase of atmospheric 14C known from late glacial and Holocene records (Goslar et al., 1995). Hajdas et al. (1998) used this sharp increase of atmospheric 14C at the onset of the YD as a tool for time correlation between sites.
http://www.sciencedaily.com/releases/2012/10/121016084936.htm
http://www.mendeley.com/research/paleoclimatic-context-geomagnetic-dipole-lows-excursions-brunhes-clue-orbital-influence-geodynamo/

@Jean Parisot:
It just occurred to me that we may be using ‘ejecta’ in two different ways. I’m using it to mean “anything ejected – mud, ice, whatever” where I think you might be meaning “solid non-ice matter like clay, rock, dirt”.
Picture a 1 mile wide space rock hitting a 1 mile thick ice sheet. It is coming in at 24,000 mph. That means that the front edge goes from top of ice sheet to touching bedrock in 1/24,000 of an hour. 1/400 th of a minute. 1/6 of a second. It creates a massive explosion as all that energy is liberated in factional second time scale in a ‘solid on solid’ impact. That vaporizes everything (including the rock of the space rock) and makes a giant steam pocket (of intense pressure as everything is still in the same space as the original solids, just very very hot now…)
That is when things can physically start to move as ‘ejecta’. From that 1 mile “spot” of nuclear bomb type pressures and temperatures. Any actual solids will be from significantly outside that “spot”, as that spot is more like plasma / explosive-mid-detonation than solid…
The “thesis” (as I understand it) is that such an impact happened, and the “scouring” marks on the rock level is seen in some areas; but the base rock layers don’t have a ‘crater’ as that 1 mile ‘crater’ event was in the ice (which then made the superheated steam / gasses that scoured the flat rock layer and picked up and tossed more of the surviving soil / ice layers around it)
This would be a lot better as an animation…

@William Astley
Thanks for the Gotheburg flip reference I’ll send that to Prof Langereis, ..
http://www.geo.uu.nl/~forth/people/Corl/corl.htm
…who told me about the failed duplication hunt for the Gothenborg flip. Strange that the thousands of papers about the late glacial oscilllations don’t mention it, whilst routinely researching the magnetic susceptability.
The 14C spike at the beginning of the YD is another artifact caused by a counting error in the grey scale record in the Cariaco basin, which is evident in the INTCAL04 calibration table. However, due to multiple problems in chronology, that record was removed in INTCAL09 with as consequence that this spike also disappeared:comment image
Just plot the delta14C values for INTCAL04 and INTCAL09
http://www.radiocarbon.org/IntCal04.htm
http://www.radiocarbon.org/IntCal09.htm
But of course it will linger on for decades in the Younger Dryas studies.

RE: dbstealey says:
May 24, 2013 at 9:24 am
That’s it!!! Thanks a million!
I had forgotten what good reading it makes. Even if it is balderdash, it is good balderdash, with much more interesting stuff than one lone Yamal larch tree, used to create a world-wide hockey stick.
Now what I have to do is find a chat-room where geologists hang out, and ask a lot of questions about arctic muck, and where it came from.
Either that, or I’ll write an article and submit it here. (I’ve always wanted to be a muckraker.) I’d soon hear from WUWT readers, and learn where I was in error.
From the mammoths to the Vikings, the arctic holds all sorts of mysteries. I wish the politicians would just buzz off, and leave scientists alone to uncover the wonders all around us.

Clearly the only possibility is a non condensing greenhouse gas sucking meteorite because the models can only reproduce such rapid cooling by removing these gasses from the atmosphere.

Caleb,
I would be interested in reading more about “muck”, if you’re thinking about writing an article. It is a mystery. What is it? Where did it come from? Outer space? Did it rain down at ≈3ºK, and freeze everything it covered?
Muck is apparently very widespread on the planet, and forms a deep layer. The Russians drilled through thousands of feet of featureless muck, until they found evidence of prairie-like grasslands underneath.
This event occurred not all that long ago [during the Pliocene, IIRC]. Tens of millions of mammoths, maybe many more, became extinct overnight. What happened?
The climate apparently changed drastically; hippos and rhinos had roamed Alaska and Siberia, in what was a very temperate climate. Now they’re gone, all of them. It’s a mystery, and very interesting.

Steve

There are a number of “prairie pothole” lakes that are quite round and have central islands. There can be other explanations, but if on Mars, the first assumption would be craters. There is a large circular feature on the Minnesota/Wisconsin border roughly between Eau Clare and La Crossethat is reminiscent of a buried and excavated crater, which doesn’t mean that it -is- and certainly would be much older than the Younger Dryas. Just like the arc on Hudson’s Bay and another in the Maritimes, it is interesting.

Jean Parisot

EM Smith, I am considering the ejecta, especially the plant matter and silica, that was formed under pressure into the unique micro-spheres that are a signature of a cosmic event. Does that process happen in a secondary steam blast? A that be duplicated in the lab?