Extraterrestrial impact caused Younger Dryas?

[Xnn]

Yes; the problem of deuterium-excess from Greenland ice cores is much more complex than for Antarctica.

Further progress should result from the use of isotopic ocean atmosphere
General Circulation Models to account for the complexity of topographic changes, source conditions and atmospheric circulation. They have, however, up to now, shown a very poor representation of the predicted characteristics of deuterium-excess in precipitation and clearly require additional work.

Nonetheless, these models are our best hope to account for sources of complexity,
such as the shifts of source locations. In addition, they can be used to investigate some of the implicit but important assumptions embedded in the simple models. With significant improvements, isotopic GCMs would be ideal tools to examine the properties of stable isotopes, including excess, in regions such as Greenland.

 

[Andre]

Yes; the problem of deuterium-excess from Greenland ice cores is much more complex than for Antarctica.

Do tell about it.

And perhaps the greenland problem could disappear if somebody brought the two dimensions in, temperature AND humidity

Further progress should result from the use of isotopic ocean atmosphere
General Circulation Models to account for the complexity of topographic changes, source conditions and atmospheric circulation. They have, however, up to now, shown a very poor representation of the predicted characteristics of deuterium-excess in precipitation and clearly require additional work.

Nonetheless, these models are our best hope to account for sources of complexity,
such as the shifts of source locations. In addition, they can be used to investigate some of the implicit but important assumptions embedded in the simple models. With significant improvements, isotopic GCMs would be ideal tools to examine the properties of stable isotopes, including excess, in regions such as Greenland.

If you don't have the basics right, models go nowhere.

 

[Xnn]

It's all part of the continual improvement process!

Make a model, check it out against observations and then make it better.

One always has to keep an open mind that there will be room for improvement.
It's a good reason to write grants and keep unemployment down!

Check out the following for a discussion:

http://pubs.giss.nasa.gov/docs/2006/2006_Hansen_etal_1.pdf

 

[Andre]

It's all part of the continual improvement process!

Make a model, check it out against observations and then make it better.

One always has to keep an open mind that there will be room for improvement.
It's a good reason to write grants and keep unemployment down!

Check out the following for a discussion:

http://pubs.giss.nasa.gov/docs/2006/2006_Hansen_etal_1.pdf

Not really. when you're off on the wrong trail, the only improvement is going back to where you lost track and that's rather ..erm.. counter intuitive. See also http://www.des.emory.edu/mfp/Kuhn.html

 

[Mammo]

Firestone et al 2007 Evidence for an extraterrestrial impact 12,900 years ago that contributed to the megafaunal extinctions and the Younger Dryas cooling, PNAS Vol 104, no 41, 9 Oct, pp16016–16021

I had an inspirational thought recently regarding the above event. Is it not a possibility that a comet ocean impact could be responsible for the observed evidence? I imagined that the ocean could act like a solid due to the extreme impulse of the impact and therefore the ejecta would be forced skyward just like a terrestrial event. It would explain the lack of any cratering and also the increase in seawater in the Greenland ice cores. The cooling phase could be attributed to a direct disruption of the thermohaline circulation, rather than the suggested influx of meltwater into the Gulf Stream (which is complete speculation).

 

[JusDennis]

R.B. Firestone et al. Also described a 10⁹Megaton above ground explosion with a fireball around 10⁷ Deg. C. that set fire to the continent, and reduced it's ecosystem to ashes. But they could only guess at the location.

Here's a good candidate for you:
http://theholocenecomet.spaces.live.com/"

What do you think?

 

[Andre]

I think that an event like that would have left a lot of physical evidence that could be traced back. Actually I know that a research after that by Nilequeen is in it's final stage.

Don't hold your breath

 

[JusDennis]

My problem is that the explanations I get from the geologists I've talked to about it just don't fit what I see. or as my Grandpa would say; "that dog don't hunt!" The thing is' I've seen all of those features before. But on a much smaller scale.

Thanks to the army I know what the ground looks like after a really big explosion. after thirty years my ears have never quit ringing. As for the epicenter; If you go to a large structural steel shop where they have high energy plasma cutting equipment all you need to do is tweak the controls until the cutter head explodes. Imagine a fircracker, but at 10^{5 o}C. you'll get a two inch mark in the surface of the steel just like the one you see in the pictures.

It may, or may not, relate to the YD event, but I know blast damage when I see it.

 

[Gokul43201]

Your source does not meet the requirements spelled out in our guidelines. Please provide links to original sources and publications. Also, appeals to authority (~ I know an explosion when I see one) are wasted here.

 

[Gokul43201]

Ooops, I thought we were discussing the PNAS paper.

But the paper by Kennett you are referring to is still making the same claims of megafaunal extinction and an abrupt end to clovis culture.

Missed this post before.

No, the Kennett article does not make this claim.

PS: That the Firestone paper was rejected by Science and Nature before being accepted by PNAS tells you nothing about the quality of the paper or specifically about the validity of certain conclusions. Most scientists will give an arm and a leg to publish in PNAS (it has a higher impact factor than even PRL, which many physicists will give an arm and a few toes to publish in). I think we should stick to discussion of the content of the papers rather than try to score points by asserting that they were rejected by X or Y journal.

 

[JusDennis]

Sorry I didn't intend to hijack this thread. But I've been studying these two papers for weeks.

Evidence for an extraterrestrial impact 12,900 years ago that contributed to the megafaunal extinctions and the Younger Dryas cooling
http://tsun.sscc.ru/hiwg/Activity/Firestone+25_2007.pdf

and:

Younger Dryas ‘‘black mats’’ and the Rancholabrean termination in North America
http://www.georgehoward.net/Haynes (2008)_PNAS_YD.pdf

 

[JusDennis]

Is this the YD impact site?

I am admittedly over my head here but this thing seems to be beyond anything old school geology can describe. Or even acknowledge as possible.

It is my hope that someone here might take a look at it while geology waits in the hall.

http://theholocenecomet.spaces.live.com/"

 

[matthyaouw]

Hello again. I believe we spoke on sciforums.com

In that discussion, I asked you if we see any evidence of thermal alteration of the rocks in that area and I never got an answer.
On your site you say:

The theory is that, if a fireball were higher than the atmosphere, convection would have no room to form a mushroom cloud. And the heat, having no where else to go, would stay and spread out at ground level and be absorbed into the surface. Causing partial thermal metamorphism in the surface materials or sediments

You don't state whether or not we actually see this. Do you have any evidence for this?

 

[JusDennis]

If you had read the thing and the refernces included you may have noticed that I called the epicenter of the blast structure a plasma burn. There is a certain high temp. implication in that word don't you think? And in fact the only reason the site is worthy of any note at all is because it looks like the stuff you see in a war zone. But covering a third of the continent.

I'm afraid if you need me to spell it out any clearer I am at a loss for words.

 

[matthyaouw]

Yes, you do call it a plasma burn and I did notice this. I also noticed you fail to do two things. The first is you fail give a definition of 'plasma burn'. A quick google search tells me that it is a problem with flatscreen TVs, but I have a feeling this isn't what you're talking about. The second is you fail to provide any evidence of any burning or heating going on there. If I have missed this, do point me towards the specific line or paragraph on your site or your references that show evidence of recent thermal alteration of the rocks in the area you describe.

 

[JusDennis]

In the steel industry a high energy plasma cutting machine called a burn table makes a very distintive mark in the steel. Called a plasma burn, or a burn caused by high energy plasma. Very different from a simple oxygen breathing fuel burning fire.

Here's a link to describe the equipment.

http://www.kaliburn.net/products/proline2260/downloads/ProLine-2260-Plasma-Cutter-Family-Brochure.pdf"

I've stated that it is a blast zone. If you see no evidence of a high energy explosion thank you for telling me that.

 

[matthyaouw]

Thanks for the clarification there. Nah, I don't really see any evidence for an explosion, but I watch with interest if you have any to add

 

[JusDennis]

Look I am a layman. nothing more.

If I found a dinosaur bone I'd tell a paleontologist about it. If he wanted me to give a long explanation of why I think it's dinosaur bone. I'd walk away and tell someone else.

As for how I can know what the ground looks like after a large explosion. Or the effects of a powerful surface compression shock wave, I'm afraid the only diploma I've got are couple of scars, an honorable discharge from the US Army, and ears that are still ringing after thirty years.

 

[GENIERE]

...I'm afraid the only diploma I've got are couple of scars, an honorable discharge from the US Army...

More than good enough for me.

The arc formation is a remnant scar of plate tectonics, the making and breaking of ancient super continents and the birth of the Atlantic Ocean. The arc is a southern fragment of the juncture of what is called the Ouachita (Wichita) Salient and the Tennessee Salient. The junction is a noticeable (salient) deformation of terrain due to these large parts of the Earth’s crust colliding.

(information from William A. Thomas - Uv Kentucky)

 

[JusDennis]

Every other arc shaped landform on Earth that is the product of such a continental collision; The Hymalayas, island arks like the Aleutians, the roots go all the way down through the basement bedrock beneath.

But on a map available from the USGS, and Titled Preliminary Precambrian Basement Structure Map of Continental United States http://pubs.usgs.gov/of/2005/1029/downloads/plate1.pdf" There is no hint of them at all in the geologic and aeromagnetic data. The Appalachians are there, and every other ancient continental collision. But not the arks. They exist only in the surface material.

Perhaps you would be so kind as to explain how this can be?

 

[matthyaouw]

Can I ask you what exactly you expect to see by examining the precambrian basement? What do you expect the map should look like for this to be a feature of tectonic origin?

Looking at the map, I see the southern end of a long major thrust fault. Thrust faults cause uplift. This still suggests tectonic origin to me.

 

[JusDennis]

I don't buy it.

I expect those features to be evident in the precambrian basement structure like everywhere else on Earth a continental collision has occured.

Whenever I hear the words "Most geologists agree that those rings are the result of an ancient tectonic collision." it gives me pause. That's pure dogma, right up there with "Most scholars and scribes agree that the Earth is a flat plate, carried on the back of a turtle at the center of the universe"

I'm sorry but "most______agree" is not good science. No matter how old and firmly held the opinion might be.

Show me the data.

 

[matthyaouw]

I will ask again. exactly what do you expect to see? What do you think evidence for uplift would look like? If you don't know what you're looking for, chances are you won't see it.


It is rather hypocritical of you do demand evidence when you yourself can provide none.
Unless you can, your speculation is wholely useless.

 

[JusDennis]

Thank you for your opinion. In fact I see no evidence of any uplift whatsoever. I do, however, see compelling visual evidence of massive surface compression shock waves. That, judging by their dimensions, are from a surface explosion which would have been large enough to devastate most of the continent. And to kill and incinerate everything for hundreds of miles. The "Black Mat" at the YD boundary layer is the biomass of half a continent reduced to ashes. Furthermore, note the location, and direction that most of the heat would have flowed down-range from the site; It would have melted thousands of square miles of the Laurentide ice sheet in seconds. The sudden inflow of fresh water into the North Atlantic would have shut down the thermal haline cycle like turning a switch.

The evidence is virtually conclusive that just such an explosion did indeed happen somewhere over North America at the beginning of the Younger Dryas cooling. To say that it did so without trace is much more of a stretch than pointing to the obvious epicenter of a giant blast zone and saying it happened right there.

I have stated my qualitifacations for recognizing a blast zone. I haven't heard anything from you on that account. What do you know of the ground effects of powerful explosions? Did you learn it in a classroom? Or on a battlefield?

You, my good man are starting to sound a bit strident. Like the Wizard of Oz. Frantically trying to cover while shouting into the microphone "Pay no attention to the old man behind the curtain." And since you clearly have no idea what a blast zone looks like your opinion in this matter is wholely useless.

 

[Evo]

I suggest that you read this paper.

Just as close scrutiny of the Holocene impacts belies an extraterrestrial source, an impact on the southeastern Laurentide ice sheet at 12.9 ka proposed at the 2007 American Geophysical Union Joint Assembly (Firestone et al., 2007a, 2007b) engenders similar doubts. This purported impact is cited as a trigger for the Younger Dryas climate event, extinction of Pleistocene mega-fauna, demise of the Clovis culture, the dawn of agriculture, and other events (Firestone et al., 2007a, 2007b). Evidence of the 12.9-ka impact includes magnetic grains, microspherules, iridium, glass-like carbon, carbonaceous deposits draped over mammoth bones, fullerenes enriched in 3He (Becker et al., 2007), and micron-scale “nanodiamonds” (Firestone et al., 2007c). We suggest that the data are not consistent with the 4–5-km-diameter impactor that has been proposed, but rather with the constant and certainly noncatastrophic rain of sand-sized micrometeorites into Earth's atmosphere.

The 12.9-ka impact story has struggled to bring its disparate evidence under a single umbrella. The impact story originated in Firestone and Topping (2001) and the Firestone et al. (2006) book, both of which contain observations and claims so wild that other work by these authors invites careful scrutiny. The nature of the 12.9-ka event changes radically with each iteration, from a supernova-generated “cosmic ray jet” (Firestone et al., 2006) to a massive atmospheric airburst (Firestone et al., 2007a, 2007b) to “multiple ET airbursts along with surface impacts” (Firestone et al., 2007c). Airbursts are a convenient explanation, given the lack of an impact crater, tektites, shocked quartz, or high-pressure minerals. Airburst events are associated with small impactors, perhaps <160 m diameter (e.g., Chapman and Morrison, 1994). Furthermore, the 12.9-ka event is identified as an oblique strike with “high-speed projectile material” (Firestone et al., 2007a) creating the elliptical “Carolina Bays” of the southeastern United States. Yet, of all impacts in the solar system, only a handful represent strikes capable of generating visibly elliptical forms (Pierazzo and Melosh, 2000). No meteorite material has ever previously been recovered from the Carolina Bays. Firestone and colleagues return to an impact origin for the Bays, ignoring a half-century of mainstream research focused on geomorphic mechanisms and age control documenting formation over extended time (Grant et al., 1998; Ivester et al., 2007). Similar elliptical depressions in Argentina, once claimed as an oblique impact swarm, were recently debunked and are now recognized as eolian (Bland et al., 2002).

http://www.gsajournals.org/perlserv/?request=get-document&doi=10.1130%2FGSAT01801GW.1&ct=1

I have merged the two threads.

 

[JusDennis]

Ok, I read the mans paper. I don't agree.

Time will tell

 

[Evo]

Here is another paper that disputes the extraterrestrial impact theory.

Abstract - Paleoindian demography and the extraterrestrial
impact hypothesis

Briggs Buchanan*, Mark Collard, and Kevan Edinborough

Recently it has been suggested that one or more large extraterrestrial
(ET) objects struck northern North America 12,900 100
calendar years before present (calBP) [Firestone RB, et al. (2007)
Proc Natl Acad Sci USA 104: 16016–16021]. This impact is claimed to
have triggered the Younger Dryas major cooling event and resulted
in the extinction of the North American megafauna. The
impact is also claimed to have caused major cultural changes and
population decline among the Paleoindians. Here, we report a
study in which 1,500 radiocarbon dates from archaeological sites
in Canada and the United States were used to test the hypothesis
that the ET resulted in population decline among the Paleoindians.
Following recent studies [e.g., Gamble C, Davies W, Pettitt P,
Hazelwood L, Richards M (2005) Camb Archaeol J 15:193–223), the
summed probability distribution of the calibrated dates was used
to identify probable changes in human population size between
15,000 and 9,000 calBP. Subsequently, potential biases were evaluated
by modeling and spatial analysis of the dated occupations.
The results of the analyses were not consistent with the predictions
of extraterrestrial impact hypothesis. No evidence of a population
decline among the Paleoindians at 12,900 100 calBP was found.
Thus, minimally, the study suggests the extraterrestrial impact
hypothesis should be amended.

http://www.hecc.ubc.ca/pdf/PaleoDem_PNAS2008.pdf

 

[JusDennis]

Ok

Buchanon et al. disagrees with Firestone et al.

I am not qualified to be the arbiter in that debate. I'm an old ex GI who still knows his place in the firing line. I ‘m not sure how it fits into all of the different scientists pet theories, or research. I think, after all of the fur stops flying, it will turn out that they are all absolutely correct. But each holding a different part of the elephant.

 

[matthyaouw]

Thank you for your opinion. In fact I see no evidence of any uplift whatsoever.

I have to wonder where (if anywhere) you have looked and if you indeed know what evidence for uplift would look like. On page 2 of http://www.gly.fsu.edu/~holm/Tull and Holm.pdf you will see that there are a series of thrust faults around the area you describe. Take note.

I do, however, see compelling visual evidence of massive surface compression shock waves.

I am still waiting for you to present it, but I have a feeling my wait will be indefinate.

To say that it did so without trace is much more of a stretch than pointing to the obvious epicenter of a giant blast zone and saying it happened right there.

I am not saying there was not an impact. I am not saying there is not an impact site somewhere in the US. I am saying there is no evidence for one wher you claim.

I have stated my qualitifacations for recognizing a blast zone. I haven't heard anything from you on that account. What do you know of the ground effects of powerful explosions? Did you learn it in a classroom? Or on a battlefield?

Classroom, of course. And in the course of my learning I would bet that I learned a hell of a lot more than you about how rock responds to heat, pressure and ET impacts on such large scales.

You, my good man are starting to sound a bit strident. Like the Wizard of Oz. Frantically trying to cover while shouting into the microphone "Pay no attention to the old man behind the curtain." And since you clearly have no idea what a blast zone looks like your opinion in this matter is wholely useless.

And you are starting to sound like every other nutjob that ever brought their own pet theory along to an internet forum. By your own admission you have no evidence beyond what you have gathered from a cursory glance at google earth, yet you are convinced to the point of certainty that you are right and seem to be ready to defend your position to the death. You clearly have no evidence to support your position or refute anyone elses therefore your opinion in the matter is useless.


Seriously, if what you say is true, you will find evidence for it if you look in the right places. Never mind trying to tell everyone else they are wrong. Their being wrong would not automatically make you right. What you need to fucus on is supporting your positon. Go away and find out how rock would respond to the heat and pressure you describe, or what telltale signatures an ET impactor may leave. Then go and look for these things. Come back if you find them. You have already stated your case, and until you have something to add in support of this, the discussion will not progress any further.

 

[Mk]

Evo, I do not quite understand your logic or what you mean by, "the Firestone paper has been thoroughly debunked." How? Do you mean the hypothesis of an extraterrestrial impact impacting the Clovis culture itself, or also the supporting original research published in the paper?

 

[Evo]

Evo, I do not quite understand your logic or what you mean by, "the Firestone paper has been thoroughly debunked." How? Do you mean the hypothesis of an extraterrestrial impact impacting the Clovis culture itself, or also the supporting original research published in the paper?

There are several papers. One was sent to me by the author himself, I will need to check if I can post it. He is an authority on Clovis and has shown why what they propose did not happen, the archeological evidence isn't there.

Here is a good paper.

http://www.gsajournals.org/perlserv/?request=get-document&doi=10.1130%2FGSAT01801GW.1

 

[Andre]

As far as I can see it, there may or may not have been an extraterrestrial event but it can be considered refuted that this hypothetical event had any significant impact on climatological changes and extinctions of species.

 

[Mammo]

As far as I can see it, there may or may not have been an extraterrestrial event but it can be considered refuted that this hypothetical event had any significant impact on climatological changes and extinctions of species.

How do you come to that conclusion? A micrometeorite bombardment which persisted long enough to leave a blanket deposited layer, which is still magnetic enough to deflect a compass (I saw it on TV), must have been a spectacular event. It seems reasonable to assume that it is possible that the event did cause climate change. Here is a paper which discusses this type of subject: Violette 2005 report.

 

[Andre]

How do you come to that conclusion?

Please reread the thread then. Essentially all isotope indications of the start of the Younger Dryas (YD) match the isotope indications of the 20+ Dansgaard-Oeschger (D-O) events in the last ~70 Ka. So the YD can be seen as just another end of a D-O event, which was bound to happen regardless of any extra terrestrial event.

Second, there is no indication of the predicted wild fire spike at 12,900 y BP. (Marlon et al 2009 Wildfire responses to abrupt climate change in North America, PNAS doi10.1073pnas.0808212106 early edition)