Exploring abrupt climate change induced by comets and asteroids during human history

But seriously, folks: Harvard bangs a big fat Platinum nail in YDB critic coffin

Restored from the library fire 1/11/20


The Mail 



Stein B. Jacobsen? and here and here

Program Note: More recent posts can be found below

Large Pt anomaly in the Greenland ice core points to a cataclysm at the onset of Younger Dryas

The impact hypothesis (11), once declared dead (1213), recently gained new support from the discovery of siliceous scoria-like objects (SLOs) with global distribution, which provide strong evidence for processing at high temperatures and pressures consistent with a cosmic impact (14)….

…Until the question about the nature of Pt-rich material and the means of its delivery to the ice is resolved, an extraterrestrial source of Pt appears likely…..

 Sarcasm aside, we have a profound development here from Harvard. An enlightening team from that fabled university has provided arguably the best independent evidence yet that something very powerful — from space — went down ~12,876 years ago which dramatically changed climate, led to the elimination of 35 or so genera, and altered our course forever.

In the finest spirit of Thomas Kuhn their work is the best public indication so far that the paradigm is cracking and the paleo-worm is turning.

A convenient aspect of the YDB hypothesis is that the evidence is at hand for most earth science researchers with the curiosity, equipment and skill to contribute. These gentleman did so and they will be rewarded in years to come with deserved accolades. But most important for the propagation of our understanding was their work with — they term it encouragement from — Dr. Wallace “Wally” Broecker of Columbia University.

Wally Broecker is the kind of guy you pick first for your team in the science fair. And if he ain’t available, you wait hopeful that he will someday join.

Broecker originally authored the Thermohaline Circulation Shutdown theory in the early 1970’s and many call him the father — or grandfather — of climate science itself. Having devoted that much time to defining the Younger Dryas it should be no surprise that he is slow to come around to a cosmic impact as the cause (what’cha bet he never considered it prior to 2007?).


mark twicklerPhoto: Dr. Mark Twickler, GISP2

And indeed there is no confirmation that Wally agrees that a disintegrating comet induced his cold time. But “encouraging” a look for evidence — finding it — and lending his name to the credits is certainly reason to rejoice.

(I should add that Jim Kennett, the grise eminence of the YDB team, is a peer of Broecker’s and they have a long, long history of fruitful collaboration. That’s even more reason for hope that we will get a fair shake from here out from granddad.)

As far as the substance of the paper is concerned, what thrills me most is the match of the platinum spike with the YD initiation. If you are too far off in this game you are cave bear meat.


11 Responses

  1. Platinum…I wonder if there is a mine-able quantity associated with the layer?

    IF there is a dollar to be made with the YDB hypothesis-turned-theory, that will do more than anything else to mow down the academic opposition.

  2. The only thing that comes immediately to my mind is Corossol, as it’s near enough to Greenland and upwind of it.

    It doesn’t quite jibe with a kilometer sized body, but if it was straight down and hypervelocity that might work, as the crater wouldn’t be as large as one would expect from an ordinary impact. One could presumably now do some seismic work on the crater to determine if it has the required deep tunneling structure required for this scenario. Superficially at the surface it looks right, though, but certainly it’s not a Younger Dryas creation event as it’s simply not large enough and most people (like me) are convinced the YD is a hydraulic phenomenon.

  3. TLE: “…but if it was straight down and hypervelocity that might work, as the crater wouldn’t be as large as one would expect from an ordinary impact.”

    Just a thought…

    Is Corrosol on the Canadian Shield? Does the Canadian Shield represent a different target than “normal” terra firma? If so, would the crater be smaller because of the target material?

    It’s honestly a question I hadn’t thought of before, though it seems reasonable. Reasonable doesn’t make it true, though, so I am asking.

    Ed? TH?

  4. Lots of heat applied to tundra gives you mud.

    That mud would flow back into any crater carved out of tundra by a hyper velocity impact during the time the mud was above freezing.

    If there were thick glacial layers above the tundra, before or after impact, the impact structure isn’t going to be readily identifiable as such.

  5. Maybe this’ll help.

    Firestone 2007 stated that:

    “Hypervelocity oblique impact experiments (P.H.Schultz, unpublished data) indicate that a low-impedance surface layer, such as an ice sheet, can markedly reduce modification of the underlying substrate if the layer is equal to the projectile’s diameter. These results suggest that if multiple 2-km objects struck the 2-km-thick Laurentide Ice Sheet at 30°, they may have left negligible traces after deglaciation. Thus, lasting evidence may have been limited to enigmatic depressions or disturbances in the Canadian Shield (e.g., under the Great Lakes or Hudson Bay), while producing marginal or no shock effects and dispersing fine debris composed of the impactor, ice-sheet detritus, and the underlying crust."

    Some of the hypervelocity impact experiments done by Pete Schultz at the HVGR at NASA’s Ames Research center can be seen in this YouTube video. Please pay particular attention to the experiment about halfway through that simulates an oblique angle hypervelocity impact into an ice covered surface. Those ice sheet impact simulations of his are the experiments that produced the “unpublished data” mentioned in Firestone 2007.

  6. Hi Dennis –

    The evidence would be isostatic rebound (an uplift) where the ice was removed.

    The Lloydminster structure in Canada may be an example of this process. But whether it is, and whether it dates from the Holocene Start Impact Event are unknown right now.

  7. Or as Dr Schultz proposed Firestone 2007, evidence of ET chemistry and isotopes in "fine debris of the impactor" found in "enigmatic depressions or disturbances in the Canadian Shield".

    Isostatic rebound never produced an “enigmatic depression”

    Evidence of Post-glacial rebound only proves that an immense weight was lifted from the continent. It would’ve happened in any case after the weight of all the ice of the Laurentide, and Cordilleran ice sheets was removed.

    And in fact it did.</p

  8. Actually though,

    Once it was recognized that the process of loading and unloading of the Earth’s surface during, and after an ice age, and the resulting readjustments to the Earth’s crust and mantle involved more than just up and down movements of the crust, but side to side movements too, as well as movements of the Earth’s mantle, and that those adjustments were in fact a global process, the terms “Isostatic rebound”, or “Post-glacial rebound” have recently fell out of favor with most geologists, and are gradually being replaced by the use of the more accurately descriptive term that’s referred to as Glacial Isostatic Adjustment.

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