From the AGU:
Global fires after the asteroid impact probably caused the K-Pg extinction
About 66 million years ago a mountain-sized asteroid hit what is now the Yucatan in Mexico at exactly the time of the Cretaceous-Paleogene (K-Pg) mass extinction. Evidence for the asteroid impact comes from sediments in the K-Pg boundary layer, but the details of the event, including what precisely caused the mass extinction, are still being debated.
Some scientists have hypothesized that since the ejecta from the impact would have heated up dramatically as it reentered the Earth’s atmosphere, the resulting infrared radiation from the upper atmosphere would have ignited fires around the globe and killed everything except those animals and plants that were sheltered underground or underwater.
Other scientists have challenged the global fire hypothesis on the basis of several lines of evidence, including absence of charcoal-which would be a sign of widespread fires-in the K-Pg boundary sediments. They also suggested that the soot observed in the debris layer actually originated from the impact site itself, not from widespread fires caused by reentering ejecta.
Robertson et al. show that the apparent lack of charcoal in the K-Pg boundary layer resulted from changes in sedimentation rates: When the charcoal data are corrected for the known changes in sedimentation rates, they exhibit an excess of charcoal, not a deficiency. They also show that the mass of soot that could have been released from the impact site itself is far too small to account for the observed soot in the K-Pg layer. In addition, they argue that since the physical models show that the radiant energy reaching the ground from the reentering ejecta would be sufficient to ignite tinder, it would thereby spark widespread fires. The authors also review other evidence for and against the firestorm hypothesis and conclude that all of the data can be explained in ways that are consistent with widespread fires.
Source:
Journal of Geophysical Research-Planets, doi:10.1002/jgrg.20018, 2013
http://onlinelibrary.wiley.com/doi/10.1002/jgrg.20018/abstract
Title:
K/Pg extinction: Reevaluation of the heat/fire hypothesis
Authors:
Douglas S. Robertson: Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, Colorado, USA; William M. Lewis: Department of Ecology and Evolutionary Biology and Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, Colorado, USA; Peter M. Sheehan: Department of Geology, Milwaukee Public Museum, Milwaukee, Wisconsin, USA; Owen B. Toon: Department of Atmospheric and Oceanic Sciences and Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, Colorado, USA.
@ur momisugly Box of Rocks, ouch.
Ban DiHydrogen Monoxide signatory for sure.
vukcevic says:
March 27, 2013 at 9:22 am
Few days ago I was looking at some geomagnetic anomalies across Siberia, then I looked at Google Earth and saw a spectacular feature about 9-10 km across
http://www.vukcevic.talktalk.net/SiberiaRose.htm
I am not aware of any references to it
Geologists, any ideas ?
++++++++++
It’s called the Kondyor Massif.
http://earthobservatory.nasa.gov/IOTD/view.php?id=8773
I agree. Every major biological group survived, except for the dinosaurs. Other large predators such as crocodiles and sharks, survived, and the usual explanation that frogs and crocs were protected by living in an aquatic environment ignores the fact that there were wading dinos. Those discrepancies cry out as the mass extinction being the result of a biological cause, rather than a mechanical cause. Birds could survive because the disease would not reach remote islands only accessible by flying long distances, they would not survive extended global darkening and subsequent famine.
I’m always amazed at the number of people willing to say one specific thing or another “caused” the K-Pg extinctions, when it’s highly likely the blame lies in a combination of things, from the impact itself, to many major stressing events cascading from that impact. Such as the falling hot ejecta and it’s subsequent fires, yes, but also let’s throw in a massive mega-tsunami, a following cold period due to atmospheric dust, leading to loss of sunlight, causing the death of much of the plant material at the bottom of the food chain, including phytoplanton, a long period of volcanism along fault lines around the planet that were jarred into activity by the impact, and then the various ways the oceans and land then behaved on the way to “recovery” (disrupted and, or new ocean currents, “temporary” salinity changes, etc., to which the existing species of that time were not adapted. And it goes on and on.
Why shouldn’t we believe that a vastly complex set of factors is “responsible” and that one particular factor, while awesome and terrifying in it’s global scope, is nevertheless only a single slice of an even greater pie chart of awesome and terrifying effects?
Theresa says:
March 27, 2013 at 5:19 am
I have heard that it was the Dekkan traps volcano eruption that killed them. Does that create Co2 as well?
All vulcanism releases CO2 from the planet. Major volcanic episodes release major amounts of CO2. Volcanic CO2 by and large has never been part of the planetary atmosphere and is “new” in the sense that it became part of the planet during the coalesence of the planet, but never was part of the atmosphere before. Large amounts of water are also released that are “meteoric” water as well. This is water that has not been on the surface before, or not for long geological time spans. Also, when lava flows plants (and animals) burn, which also releases CO2, but that is a trivial amount compared to the volume brought up by the vulcansim.
pokerguy says:
March 27, 2013 at 6:05 am
“So what killed those dinosaurs that lived in the sea?”
Salty diet. They all got hypertension.
*
I really – REALLY – must stop having my morning coffee at my desk when reading WUWT.
This one is going on my wall. No, people, the words by Pokerguy, not my coffee (my coffee is already there).
Paul Westhaver says:
March 27, 2013 at 11:25 am
John Tillman, thank-you for the citation. You made me very happy.
When I look at the Gulf of Mexico, it looks like the superposition of an ancient double hit, then the later Yucatan hit.
The Island of Cuba appears, to me, to be impact zone ejecta, as if the asteroid hit traveling south east obliquely to the planet. The impact would push up most of Florida and leave Cuba behind in the splatter zone.
That is complete speculation on my part.
If an approaching asteroid broke apart as it approached earth, then you could get a double hit effect. Again, mere speculation on my part and I do not possess the tools or expertise to test the idea.
When I learned of Pangaea as a child and tried to fit the continents together like puzzle pieces, the Gulf of Mexico always proved to me that a piece was missing.
Thanks
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You’re welcome, but there are many problems with Stanton’s hypothesis. The GoM is satisfactorily explained by plate tectonics.
Staten-John says:
March 27, 2013 at 11:37 am
Neither the Chicxulub impact nor the Deccan Traps volcanism were the primary extinction mechanism at the K-T boundary.
The fact that birds were little affected discounts the impact causation. The fact that all marsupials went extinct in N. America is another bit of evidence.
However, the marsupial extinction supports the theory that surface gravity increased rapidly at the K-T interval as well as the extinction of all marine reptiles and ammonites. Dinosaurs were diminishing in numbers as well as size millions of years prior to the K-T interval.
The Gravity Theory of Mass Extinction (http://www.dinoextinct.com/page13.pdf) is the only viable theory.
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It is so far from the only viable “theory” that it’s about as invalid as possible, IMO.
Nor is it a “fact” that birds were little affected. They were almost all wiped out.
Nothing about marsupial survival or extirpation suggests an increase in gravity, but is well explained by bolide collision at the K/T in the Yucatan.
Sorry, but no credible evidence supports this notion. By contrast, abundant evidence from many separate lines of inquiry support a role, arguably predominant, for the impact. The formation of the Deccan Traps as the Indian Plate passed over the Reunion Hotspot may not have helped.
vukcevic says:
March 27, 2013 at 9:22 am
Few days ago I was looking at some geomagnetic anomalies across Siberia, then I looked at Google Earth and saw a spectacular feature about 9-10 km across
http://www.vukcevic.talktalk.net/SiberiaRose.htm
I am not aware of any references to it
Geologists, any ideas ?
******************************************************
Just looking at the picture, my WAG is that looks like a volcanic eruption with a lava flow that came out to the bottom left.
Staten-John says:
March 27, 2013 at 11:37 am
—
If gravitational changes killed the Dinos, how did the birds survive? Presumably a big increase in gravity would have rendered them unable to fly.
BTW, changes in gravity would not have any impact on sea level.
Every time I see a documentary or read an article about this, some major detail changes. Large animals were already dying. Large animals died because of cold. Large animals died because of fire. Large animals didn’t die until several thousand years later. Large animals died because of disease. Large animals died because oxygen percentages decreased. Large animals were kidnapped by aliens. Large animals went out for a pack of cigarettes and never came back.
Of course, the first lesson here is to not trust documentaries and articles, which are primarily speculative (speculative means “made up”).
Luckily we’re not currently facing the choice of whether or not to allow a large asteroid to strike Earth, so I can shelve the subject for the moment.
MarkW,
Birds were able to avoid extinction for several reasons:
1. They were able to adapt to changing surface gravity better than mammals because they did not give live birth. This is contrast to marsupials which went extinct in N. America.
2. They could evolve changes, wing area to mass ratio, etc.
3. They were able to nest in high places making them less vulnerable to predation, just as they do today.
Note that the change in surface gravity took place over tens of thousands of years, not instantaneously.
Sea level would definitely be affected by changes in surface gravity. If you read the theory, shifting of the cores away from Earth-centricity would have lowered surface gravity in one hemisphere (i.e., on Pangea) and raised it on the other hemisphere (i.e., antipodal to Pangea).
This is confirmed, see Wiki Sea level chart.
Summary of evidence for the Yucatan impact as main if not sole cause of the K/T MEE:
http://www.sciencemag.org/content/327/5970/1214.abstract
Granted, this looks a lot like consensus science, but the authors IMO do a good job of addressing the arguments & evidence of Chicxu-skeptics like Keller. They consider issues of timing, the case for gradual decline in species diversity, climate change, the Deccan Traps & for multiple impacts, among other alternative hypotheses.
It’s pay-walled, but various articles from 2010 describe its conclusions & methods.
For the effect on birds of the K/T, please read this:
Longrich, N. R., T. T. Tokaryk, et al. (2011). “Mass extinction of birds at the Cretaceous-Paleogene (K-Pg) boundary.” Proceedings of the National Academy of Sciences 108(37): 15253-15257.
Enantiornithes are the “opposite birds”, which were dominant in the Cretaceous, but apparently totally wiped out in the MEE, along with all others except a few modern groups.
Theresa says:
March 27, 2013 at 5:19 am
“I have heard that it was the Dekkan traps volcano eruption that killed them. Does that create Co2 as well?”
It was like this. The Chixulub impact sent shock waves to the opposite side of the earth, which started the Dekkan traps volcanism, which caused the extinction. Dust loading of the stratosphere from extended volcanism is imho the most likely candidate.
We know peat fires can last for decades when large peat bogs slowly dry out.
And IMO this is what happened at the KT Boundary. Large amounts of debris in the atmosphere, solar insolation greatly reduced, and consequently ocean evaporation and precipitation reduced. Peat bogs start to dry out, and fires started by whatever means take hold. Then the smoke from the fires continues the reduced insolation/evaporation/precipitation regime over decades. And if very large peat bogs exist, centuries, even millenia of the peat fires/smoke/reduced precipitation regime seems possible.
The word Probably means nothing. It is like the word Height. The building had a height. The event probably occurred. These are sentences which convey no information. How how was the building? How probable was the event?
Could, would, maybe, probably, might, may. These are all words in any story which tell you that somebody is plucking something out of their ass.
“””””…..AleaJactaEst says:
March 27, 2013 at 5:21 am
Interestingly the only geologist on the paper was the third author. The KT boundary discussion (now I’m showing my age as I prefer the KT monika) is many years old. …….”””””
I’m under the impression that the fossil records show the die off starting long before any impact, and coninuing for eons after the impact. I thought the rise of mammals played a role.
The birds that became extinct at the K-T boundary, or before, were known as archaic birds. Some had teeth and probably had other characteristics which were disadvantages when surface gravity increased. Not a lot is known about them.
DaveF says:
March 27, 2013 at 5:46 am
So what killed those dinosaurs that lived in the sea?
==============================================================
It must have been ………..
The speck on the flea on the tail on the frog on the bump on the log in the hole in the bottom of the sea
“I’ll get my coat” (sorry)
Since the AGW fanatics are now accusing us skeptics of causing the Medieval Warm Period, maybe we dunnit.
What about the Shiva impact site? Is it not a bit larger than Chicxulub?
The Russians always have such cool names. Where we in the US get the incorrectly named “Meteor Crater” near Winslow, AZ.
“Abstract
For several hours following the Chicxulub impact, the entire Earth was bathed with intense infrared radiation from ballistically reentering ejecta. The global heat pulse would have killed unsheltered organisms directly and ignited fires at places where adequate fuel was available. Sheltering underground, within natural cavities, or in water would have been a necessary but not always sufficient condition for survival. Survival through sheltering from an initial thermal pulse is not adequately considered in literature about Cretaceous- Tertiary nonmarine extinctions. We compare predicted intense, short-term, thermal effects with what is known about the fossil record of nonmarine vertebrates and suggest that paleontological evidence of survival is compatible with theoretical results from bolide physics.”
http://gsabulletin.gsapubs.org/content/116/5-6/760.short
Re Vukevic query.
The feature you mentioned is referred to as the Gora Konder crater.
Possibly an impact site but there doesn’t seem to be a lot known about it.
Also some suggestion that it hosts a platinum mining operation
http://below-topsecret.livejournal.com/770802.html
A possibility……Pt deposits are known to have formed at other impact sites
It would have to quite young as it seems well preserved, possibly about the same age as Meteor Crater in Arizona but that’s just a guess.
Whoops, apology. That should be Vukcevic
More Re Vukcevic query
Apparently not a meteorite crater at all. Rather an igneous intrusion.
And not young, but only youngish at around 112Ma
http://www.atlasobscura.com/places/kondyor-massif
http://earthobservatory.nasa.gov/IOTD/view.php?id=8773
http://link.springer.com/article/10.1134%2FS0869591112060033#page-1
CF my earlier comments and changing opinions to fit facts