Comet Impact Theory Challenged

This one of those items where the headline promises more than it actually delivers. Once again lack of evidence is hardly evidence of lack. This is about evidence supporting an increase in fires as a result of an improving climate. That is all well and good. It does not disprove the existence of a comet explosion, or an asteroid impact leading to the initiation of the climatic change.

That headline writers were extrapolating fires from the shock wave was optimistic. In fact, what evidence that existed was in the form of charcoal, and that is not evidence of burning so much as a blast of heat that toasted large areas.

If significant charcoal survived wildfires then all our soils would be terra preta. The reality is that the charcoal succumbs to fire sooner or later.

The evidence of a blast is in the rock scatter throughout the Ohio Valley. That others have suggested that a Tunguska like event would have ignited a continental wildfire is purely a speculation and as suggested, not supported. There are related charcoal deposits that are not lake sediment related and likely need to be understood.

A charring event following a shock wave passing over grassland is likely to produce a carbon layer if it did not ignite, except it would be consumed during the next season’s grassfire. The same event passing over a forest might just leave enough carbon buried in fallen trees to protect the fresh carbon layer. This tells us that a lot more data is needed, in order to put the early claims in proper perspective.

That a cosmological event took place is not in dispute although this headline claims that. The event put a lot of dust, rock and ice on a trajectory toward the Carolinas from just west of Hudson Bay. It created a shock front that flattened exposed ground but likely left huge tracts untouched.

It was a large object whose energy was largely absorbed by the crust. Much of the shock was absorbed by the ice. And it may have broken up just before impact.

It would be nice if the continent was probably burned over also, but really begs the question of why? It is amazing how a good tale runs ahead of the facts that are dramatic enough.

They did prove that a warmer climate produces more biomass and that this produces more fuel which produces more fire.


Comet Impact Theory Disproved

http://www.spacedaily.com/reports/Comet_Impact_Theory_Disproved_999.html

by Staff Writers
Bristol, UK (SPX) Jan 28, 2009

New data disproves the recent theory that a large comet exploded over North America 12,900 years ago, causing a shock wave that travelled across North America at hundreds of kilometres per hour and triggering continent-wide wildfires.

Dr Sandy Harrison from the University of Bristol and colleagues tested the theory by examining charcoal and pollen records to assess how fire regimes in North America changed between 15 and 10,000 years ago, a time of large and rapid climate changes.

Their results provide no evidence for continental-scale fires, but support the fact that the increase in large-scale wildfires in all regions of the world during the past decade is related to an increase in global warming.

Fire is the most ubiquitous form of landscape disturbance and has important effects on climate through the global carbon cycle and changing atmospheric chemistry. This has triggered an interest in knowing how fire has changed in the past, and particularly how fire regimes respond to periods of major warming.

The end of the Younger Dryas, about 11,700 years ago, was an interval when the temperature of Greenland warmed by over 5 degrees C in less than a few decades. The team used 35 records of charcoal accumulation in lake sediments from sites across North America to see whether fire regimes across the continent showed any response to such rapid warming.

They found clear changes in biomass burning and fire frequency whenever climate changed abruptly, and most particularly when temperatures increased at the end of the Younger Dryas cold phase. The results published, January 26, in the Proceedings of the National Academy of Science.

Understanding whether rapid changes in climate have caused wild fires in the past will help understand whether current changes in global temperatures will cause more frequent fires at the present time. Such fires have a major impact on the economy and health of the population, as well as feeding into the increase in global warming.

Major Meteor Blast 12900 BCE

Those of you who have read my article on the Pleistocene nonconformity will understand my interest in the attached article. My article was posted last July and since published in Viewzone.

In Pleistocene Nonconformity we argue that the Ice age was ended by a crustal movement of thirty degrees south along longitudes passing through Hudson Bay. See my article for all your immediate objections. This put the polar icecap into latitudes wherein it would obviously chill the atmosphere. This chilling lasted for two thousand years until the ice was removed and is known as the Younger Dryas. All this coincides with the worldwide climate, sea level and geological record although the exact timing of each may not yet be precisely synchronized.

The point I am making is that the earth's crust moved. Once this is accepted, all the unexplainable features in the record of conflicting geology disappear. Remember that an icecap at the latitude of New York or at least close by, means a huge global climate impact into the tropics, which is contradicted by the record. Again, read my article to work through the details.

My own suggestion for the motive impulse was the advent of a fast moving very dense meteorite close enough to the pole to impart sufficient power to get the crust moving. The other option was that an excess of ice was inherently unstable, except the icecap had been stable for a million years. A good blow would change that. It just seemed far less probable. Perhaps it was an accident that waited a million years to happen.

Now we have extremely tangible evidence of a major meteorite event that appears to have been explosive, causing a major burn off at the correct time slot. The extensive presence of soot and charcoal strongly suggests that the explosion itself released huge amounts of direct heat to produce the elemental carbon form.

I suggested in the article that Iceland sure looks like a good prospect for a meteor event if it were not ruled out for other good reasons. And I really prefer not to penetrate the earth’s crust just to see if it can be done.

The idea of a comet smashing into the icecap and jarring the crust loose is much more acceptable and even survivable in highland earth. The craters in the Carolinas may even be caused by massive chunks of ice been blasted out and crashing back to earth. Having fun yet?

Anyway, the Carolinas would only have been thirty degrees from the poles, so a shock there or further north would have plenty of vector. Once the crust started moving, it seems likely that the icecap mass determined the final thirty degrees off center resting position.

The extent of the event horizon is obviously huge covering the area of Clovis culture. The abrupt extinction of fauna is also strongly indicated. This at least fills in an important blank for the theory presented in my article. There is no reason to look for a bear when a lion is eating the meal. And as usual, it looks more interesting than anything I imagined.

By the way, that event ushered in the incredibly stable Holocene in which we now reside. We are good to go for millions of years without a polar icecap.

Published online before print September 27, 2007
Proc. Natl. Acad. Sci. USA, 10.1073/pnas.0706977104
OPEN ACCESS ARTICLE

Evidence for an extraterrestrial impact 12,900 years ago that contributed to the megafaunal extinctions and the Younger Dryas cooling

R. B. Firestone a,b, A. West c, J. P. Kennett d, L. Becker e, T. E. Bunch f, Z. S. Revay g, P. H. Schultz h, T. Belgya g, D. J. Kennett i, J. M. Erlandson i, O. J. Dickenson j, A. C. Goodyear k, R. S. Harris h, G. A. Howard l, J. B. Kloosterman m, P. Lechler n, P. A. Mayewski o, J. Montgomery j, R. Poreda p, T. Darrah p, S. S. Que Hee q, A. R. Smith a, A. Stich r, W. Topping s, J. H. Wittke f, and W. S. Wolbach r
aLawrence Berkeley National Laboratory, Berkeley, CA 94720; cGeoScience Consulting, Dewey, AZ 86327; dDepartment of Earth Sciences and eInstitute of Crustal Studies, University of California, Santa Barbara, CA 93106; fNorthern Arizona University, Flagstaff, AZ 86011; gInstitute for Isotope and Surface Chemistry, H-1525, Budapest, Hungary; hDepartment of Geological Sciences, Brown University, Providence, RI 02912; iDepartment of Anthropology and Museum of Natural and Cultural History, University of Oregon, Eugene, OR 97403; jEastern New Mexico University, Portales, NM 88130; kSouth Carolina Institute of Archaeology and Anthropology, University of South Carolina, Columbia, SC 29208; lRestoration Systems, LLC, Raleigh, NC 27604; mRozenstraat 85, 1018 NN, Amsterdam, The Netherlands; nBureau of Mines and Geology, University of Nevada, Reno, NV 89557; oClimate Change Institute, University of Maine, Orono, ME 04469; pUniversity of Rochester, Rochester, NY 14627; qDepartment of Environmental Health Sciences, University of California, Los Angeles, CA 90095; sP.O. Box 141, Irons, MI 49644; and rDepartment of Chemistry, DePaul University, Chicago, IL 60614

Communicated by Steven M. Stanley, University of Hawaii at Manoa, Honolulu, HI, July 26, 2007 (received for review March 13, 2007)

A carbon-rich black layer, dating to 12.9 ka, has been previously identified at 50 Clovis-age sites across North America and appears contemporaneous with the abrupt onset of Younger Dryas (YD) cooling. The in situ bones of extinct Pleistocene megafauna, along with Clovis tool assemblages, occur below this black layer but not within or above it. Causes for the extinctions, YD cooling, and termination of Clovis culture have long been controversial. In this paper, we provide evidence for an extraterrestrial (ET) impact event at 12.9 ka, which we hypothesize caused abrupt environmental changes that contributed to YD cooling, major ecological reorganization, broad-scale extinctions, and rapid human behavioral shifts at the end of the Clovis Period. Clovis-age sites in North American are overlain by a thin, discrete layer with varying peak abundances of (i) magnetic grains with iridium, (ii) magnetic microspherules, (iii) charcoal, (iv) soot, (v) carbon spherules, (vi) glass-like carbon containing nanodiamonds, and (vii) fullerenes with ET helium, all of which are evidence for an ET impact and associated biomass burning at 12.9 ka. This layer also extends throughout at least 15 Carolina Bays, which are unique, elliptical depressions, oriented to the northwest across the Atlantic Coastal Plain. We propose that one or more large, low-density ET objects exploded over northern North America, partially destabilizing the Laurentide Ice Sheet and triggering YD cooling. The shock wave, thermal pulse, and event-related environmental effects (e.g., extensive biomass burning and food limitations) contributed to end-Pleistocene megafaunal extinctions and adaptive shifts among PaleoAmericans in