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.
DaveF says:
March 27, 2013 at 5:46 am
So what killed those dinosaurs that lived in the sea?
###
You have just hurt Nessy’s feelings 🙁
“””””…..jim2 says:
March 27, 2013 at 7:36 pm
“Abstract
For several hours following the Chicxulub impact, the entire Earth was bathed with intense infrared radiation from ballistically reentering ejecta…….”””””
So the orbital period at earth surface is 84 minutes. So how does that “ejecta” re-entry shower last “several hours” ?
Enquiring minds want to know.
John Tillman says:
March 27, 2013 at 8:41 am
###
I was pretty happy that the Gelasian had been moved to the Pleistocene. I had not thought about the position of the Oligocene, but what you opined makes a lot of sense. I tend to think of things in terms of Eocene and post Eocene. It would surely make it easier for me to explain what my interests are which is currently the Oligocene of the Paleogene, the Neogene, and the Quaternary.
In response to: MarkW March 27, 2013 at 10:49 am who responded to wsbriggs March 27, 2013 at 6:49 am . Briggs: “The ionization radiation created from the passage of the object through the atmosphere” – Mark W: “How pray tell does an object plowing through the atmosphere cause atoms to fission?”
__________
How do you get “fission” from Briggs’ statement? Ionization is the stripping of one or more electrons from an atom. As energy is added to an atom, the electrons get more energy (excitation) and if enough energy is gained an electron can escape from the atom (ionization). At some point in both excitation and ionization, the gained (excess) energy will be released. In excitation, the energy is released either by the emission of electromagnetic energy or by transfer to another atom. In ionization, much of the excess energy will be imparted to the escaping electron but usually there is also an emission of electromagnetic radiation. One means of Imparting excess energy into an object’s atoms can be accomplished via frictional forces such as experienced by an object coming from space and entering our atmosphere. If I am following the argument correctly on this thread, then the impact of a large meteor, asteroid or comet would throw material (ejecta) high enough back into the atmosphere to produce further objects subject to frictional heating and which in turn would produce excited/ionized molecules, which in turn would emit harmful electromagnetic radiation (principally IR). The ejecta phenomena would be a one time event, but could (I have no idea) be wide spread. Atom –> add energy —> excitation and/or ionization —> production of electromagnetic radiation (light, IR, radio waves, et cetera) —-> too much bad radiation = dead things.
george e. smith, the ejecta from a major impact comes out at a wide ranges of velocities, from slow to fast, from low to high angles but mostly around 45 degrees. Some is even at greater than escape velocity (thus the few Mars rocks that have been found on Earth). Many pieces will go very high, taking a long time to fall back, with stragglers tailing off over hours, days, even weeks- consider a chunk thrown as far as the moon, but still on an elliptical path that eventually hits the earth again.
A video showing the ejecta from a 2 km/s impact:
A simulation of part of the ejecta from a large impact. The Earth rotates while the crud flies high.
Re: ‘Siberia Rose’
Thank you for all of the comments and links, I did eventualy find some myself. As much as its visual and the geological aspects are remarkable, they are more than matched by its geomagnetic anomaly, I will post some details at a later stage.
Thanks again.
sorry, forgot link to the most recent article:
http://link.springer.com/article/10.1134/S1028334X12080053#page-1
I strongly recommend Richard Muller’s book, ‘Nemesis’. He was closely involved with the Alvarez group which discovered the cause of the death of the dinosaurs. The book tells the story of that discovery and it is a fantastic read, showing science at its best. It was written long before Muller was tainted by the AGW nonsense.
Nemesis refers to his theory that he described towards the end of the book: that comet/asteroid impacts that cause extinctions occur regularly, and are due to a distant companion of the sun. That companion has never been discovered and I assume his Nemesis theory is long dead. His cherished AGW theory also seems to be dying….
Chris
Well actually, I DID think about the trajectories a bit, and I don’t think your scenario is obvious at all. To be honest, it doesn’t seem especially likely either. AFAICS, any ejecta that is travelling at less than orbital velocity (roughly 8km/sec) and most that is “launched” at angles below about 45 degrees will impact in the “impact hemisphere”. As will any material launched more or less straight up although that will presumably trail out to the West of the impact point as the Earth turns. Unless one assumes that ejecta are mostly traveling very fast and are mostly “launched” at high but not vertical angles, not all that many are coming down on the “back side”. However, I admit that I didn’t give any consideration to the distribution of ejecta velocity and elevations and assumed something sort of random — which is surely wrong. I don’t suppose you have a reference or two?
Actually only debris ejected at a fairly high angle through the “hole” in the atmosphere caused by the entry can get very far. The stuff ejected at low angles is braked by air resistance within several hundred kilometers.
The best reference on the subject is here:
http://onlinelibrary.wiley.com/doi/10.1029/2001JE001532/abstract
Unfortunately it does not seem to be available outside the paywall. However here is a animation showing the calculated impact distribution:
http://www.lpi.usra.edu/science/kring/epo_web/news/chicxulub2.html
“So the orbital period at earth surface is 84 minutes. So how does that “ejecta” re-entry shower last “several hours” ?
Enquiring minds want to know.”
Because most of the re-entering ejecta was ejected at high angles into very excentric elliptic trajectories which only re-enters the Earths atmosphere several hours later. As a matter of fact a fair amount probably went into orbits around the Sun. I would expect that there was a lot of shooting stars for centuries afterwards as the Earth swept up most of the debris.
Luther Wu says:
March 27, 2013 at 6:04 am
No, it’s survivor guilt. And I’m voting to keep KT. Like I vote to keep Pluto. Oh, crap, does that mean a meteor is heading for this neo dinosaur?
tty says:
March 28, 2013 at 4:29 am
“Actually only debris ejected at a fairly high angle through the “hole” in the atmosphere caused by the entry can get very far. …”
Thanks for the response. I think I understand what you’re saying, but I still don’t find the analysis to be overwhelmingly convincing. e.g. I think you (and “they”?) are asuming that the “hole in the atmosphere is vertically above the impact point. But isn’t a lower angle impact creating a low angle directional “tunnel” a lot more likely? etc, etc, etc. (OTOH material that is fairly large and travelling really fast can presumably “punch” its way out vertically or near vertically whereas lower angle material is going to need to be larger and/or faster to get a long distance “downrange”)
I did google the Chixulub impact angle and found some modeling, but no consensus
Anyway, I don’t propose to spend the next six months/years worrying about this.
Thanks Jimmy Haig!
(What is the chances of the big one hitting….)
I just sprayed coffee all over the keyboard and monitor!
But I am a bit dissapointed that not too many tried to correct you. That would have made for more fun morning reading.
“So what killed those dinosaurs that lived in the sea?”…Thanks to all those those who replied to my query, humorously or otherwise. Good comments, DaveF.
Staten-John says:
March 27, 2013 at 3:17 pm
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.
**********************************************************************************************************************
A remarkable amount is known about Cretaceous birds, due in large part to the wonderful EK Lagerstätten of China but also other epochs & regions, such as LK western North America, especially for sea birds. Your hypothesis is falsified by the many non-archaic birds wiped out at the K/T along with their archaic kin. It wasn’t the presence of teeth & claws that determined which avian species survived, but their lifestyles & locales. Those few modern groups which came through the catastrophe lived far from the worst effects of the impact & had feeding behavior that allowed them to live into the post-apocalyptic Cenozoic.
Here you can read up on archaic birds:
http://en.wikipedia.org/wiki/Enantiornithes
And here on Cretaceous birds of modern aspect, with a cutting-edge cladogram:
http://en.wikipedia.org/wiki/Euornithes
___________________________________________________________________________
DesertYote says:
March 27, 2013 at 10:33 pm
John Tillman says:
March 27, 2013 at 8:41 am
###
I was pretty happy that the Gelasian had been moved to the Pleistocene. I had not thought about the position of the Oligocene, but what you opined makes a lot of sense. I tend to think of things in terms of Eocene and post Eocene. It would surely make it easier for me to explain what my interests are which is currently the Oligocene of the Paleogene, the Neogene, and the Quaternary.
**********************************************************************************************************************
Thanks. I would be happy with a still on-going geologic period coincident with your interests, ie a revised Neogene including the Og on one end & the Quaternary on the other. There is not much left of the Pliocene sans Gelasian, but the Miocene is already so long that attaching it at the end of that epoch doesn’t help. If you have pull with the IUGS, please see what you & your colleagues can do about this. The Gelasian move shows there’s hope for more rational geotime ordering.
@TomR,Worc,MA
The sea-going reptiles, not dinosaurs, were wiped out at the K-T interval because an increase in surface gravity would increase water pressure at all depths because water pressure is dependent on depth, water density and “g” (i.e. magnitude of gravity).
Reptiles must frequently come to the surface to breathe, therefore, all vertical movement in the water column would be problematic for reptiles and also ammonites, which also became extinct at this time.
@John Tillman,
Not enough is known about the archaic birds to explain why they went extinct and the other group did not including their internal structure.
However, the fact that the birds that did not become extinct at the time of the asteroid impact casts doubt on the severity of the effects of the impact. One would expect birds to be much more susceptible to the alleged environmental effects such as the blistering heat, cold, smoke, lack of food, etc. which would affect the highly active birds.
The above could also be applied to lizards, snakes and other environmentally sensitive species casting further doubt on the impact extinction hypothesis.
Staten-John says:
March 27, 2013 at 1:12 pm
—
Mammals didn’t die out. Dinosaurs did.
Dinosaurs also lay eggs.
The change happened slowley enough that birds could adapt, but no other animals could?
Anyone who thinks that it is possible for the core to shift sufficiently to change gravity a noticeable amount between hemispheres is not thinking clearly. (And that’s being charitable.)
Leg says:
March 27, 2013 at 11:56 pm
—
Now you have to get those low energy electrons from their position miles up, down to the surface with enough energy to do something more than cause a static build up.
Staten-John says:
March 28, 2013 at 10:10 am
—-
An increase in gravity would have no impact on the ability of creatures to move through water.
Drag is determined by density, and density of water does not increase with gravity.
On the other hand, gravity does increase the density of air, which would make it much more difficult to fly. Hence birds would be the first to die as they would have trouble getting into the air, and more difficulty staying there if they did succeed in getting launced.
BTW, even if the core did manage to shift, it would only increase the gravity in one hemisphere compared to the other by at most a few percent. Not enough to impact life.
Staten-John says:
March 28, 2013 at 10:10 am
@TomR,Worc,MA
The sea-going reptiles, not dinosaurs, were wiped out at the K-T interval because an increase in surface gravity would increase water pressure at all depths because water pressure is dependent on depth, water density and “g” (i.e. magnitude of gravity).
Reptiles must frequently come to the surface to breathe, therefore, all vertical movement in the water column would be problematic for reptiles and also ammonites, which also became extinct at this time.
************************************************************************************************************************
How then do you explain the survival of freshwater & marine reptiles like sea snakes & turtles, tuatara ancestors, crocodilians & their relatives?
__________________________________________________________________________
Staten-John says:
March 28, 2013 at 10:24 am
@John Tillman,
Not enough is known about the archaic birds to explain why they went extinct and the other group did not including their internal structure.
However, the fact that the birds that did not become extinct at the time of the asteroid impact casts doubt on the severity of the effects of the impact. One would expect birds to be much more susceptible to the alleged environmental effects such as the blistering heat, cold, smoke, lack of food, etc. which would affect the highly active birds.
The above could also be applied to lizards, snakes and other environmentally sensitive species casting further doubt on the impact extinction hypothesis.
**************************************************************************************************************
It’s clear that you don’t know enough about the opposite birds & their modern relatives to explain their extinction, but ornithologists & paleontologists have good explanations, which have been tested in the fossil & not yet falsified. Vaguely imagining internal structure explanations is not science. Make a falsifiable hypothesis.
Certain types of modern (& possibly one opposite bird line) did indeed have what it took to survive, & had you bothered actually to read the scientific literature, or even Wiki, you’d know what those ways of living were.
The impact extinction hypothesis has by now achieved theory status, since the hypothesis has been rigorously tested under decades of attack by skeptics, God bless them (welcome & encouraged in real science) & not yet been falsified, least of all by an easily shown false gravity change hypothesis, if I may dignify the baseless, WA speculation with that term.
@johnTillman,
Don’t keep it a secret, tell us what those ways of living were. Just a few bullet points would suffice.
@MarkW
I’ll try to address your multiple posts:
“Mammals didn’t die out. Dinosaurs did.
Dinosaurs also lay eggs.”
1. Yes the above is true. However, the mammals were extremely small compared to ost dinosaurs. The smallest dinosaurs might have survived if mammal predation, of the dinosaur’s eggs, didn’t happen.
“The change happened slowley enough that birds could adapt, but no other animals could?”
2. My answer to the first question applies here. Birds were able to avoid mammal predation of their eggs and themselves because they could “hide” in treetops and on cliffs.
“Anyone who thinks that it is possible for the core to shift sufficiently to change gravity a noticeable amount between hemispheres is not thinking clearly. (And that’s being charitable.)”
3. This opinion has no scientific basis.
“An increase in gravity would have no impact on the ability of creatures to move through water.
Drag is determined by density, and density of water does not increase with gravity.”
4. Please reread my earlier post. Water pressure is directly proportional to “g” (gravitational strength). Any creature (including all sea-going reptiles) must move vertically in the water column to get to the surface to breathe. Vertical movement is hampered by an increase in water pressure per unit depth.
“On the other hand, gravity does increase the density of air, which would make it much more difficult to fly. Hence birds would be the first to die as they would have trouble getting into the air, and more difficulty staying there if they did succeed in getting launced.”
5. The increased air pressure would be insignificant compared to that of water. And, as pointed out earlier, birds has tens of thousand of years to evolve flight compensation for differences in air pressure.
“BTW, even if the core did manage to shift, it would only increase the gravity in one hemisphere compared to the other by at most a few percent. Not enough to impact life.”
6. If you reread the theory you will understand this concept. The amount of core shift is directly determined by the size of the mass that moves latitudinally and the distance it moved. That mass was all of Pangea.
@John Tillman
“How then do you explain the survival of freshwater & marine reptiles like sea snakes & turtles, tuatara ancestors, crocodilians & their relatives?”
1. See my response to MarkW about water pressure increasing per unit depth with an increase in surface gravity. Freshwater depth is insignificant compared to that of sea-going fauna. Most of those you mentioned can live in a few feet of water.
Staten-John says:
March 28, 2013 at 1:36 pm
@johnTillman,
Don’t keep it a secret, tell us what those ways of living were. Just a few bullet points would suffice.
**************************************************************************************************************************
Would it kill you to Google “k/t extinction birds”? Or to read the links I posted?
Contrary to your unresearched assertion, birds were, as I replied, almost wiped out at the K/T. All birds except some neornitheans became extinct (although one non-neornithine, Qinornis paleocenica, has been claimed to show up in the Cenozoic). Groups thriving right up to the impact (or within about 300K years, which is current resolution ability), like the opposite birds (enantiornithines) & flightless hesperornithiform divers, suddenly disappear from practically all ecological niches on all continents & seas.
That lots of opposite bird fossils have been found from the latest Maastrichtian Age supports their mass extinction from effects of the Chicxulub impact. Very few Cretaceous bird species, genera, families & orders survived the hit. Cretaceous ancestors of modern bird lineages like waterfowl, barnyard fowl & ratites did survive, since assignable remains of these basal groups have been found in the Paleogene Period. However to date just a single bird species, in the US & Canadian West, has been with some confidence dated from both above & below the K/T boundary:
http://www.pnas.org/content/108/37/15253
A putative waterfowl has been claimed for Cretaceous Antarctica, & another from Texas.
The paper linked below suggests that neornithine birds may have survived the extinction thanks to their ability to dive, swim or shelter in aquatic & marshy habitats. Many neornithine species burrow, nest in holes in trees (which did not all burn up) or termite mounds, which refugia could have protected them from catastrophic effects of the K/T strike. Their descendents not only survived but thrived during the Paleogene by filling ecological niches vacated by extinct non-avian dinosaurs. This includes the top predator niche in some environments.
http://www.ugcs.caltech.edu/~presto/cenozoic.pdf
___________________________________________________________________________
Staten-John says:
March 28, 2013 at 2:12 pm
@John Tillman
“How then do you explain the survival of freshwater & marine reptiles like sea snakes & turtles, tuatara ancestors, crocodilians & their relatives?”
1. See my response to MarkW about water pressure increasing per unit depth with an increase in surface gravity. Freshwater depth is insignificant compared to that of sea-going fauna. Most of those you mentioned can live in a few feet of water.
*******************************************************************************************************************
How deep do you suppose that mosasaurs & plesiosaurs hunted?
Some plesiosaurs may have been bottom feeders. They’ve been discovered with belemnite & ammonite fossils apparently in their stomachs. Their jaws were probably powerful enough to bite through the hard internal skeletons or shells of such prey. They may also have eaten bony fish inhabiting shallow waters.
Mosasaurs of course ate plesiosaurs. Did you really imagine that the epicontinental Seas of Kansas, for instance, were abysmal in their profundity? (There’s a great maritime Mesozoic Web site by that name. I’d urge you to visit it & learn before speculating wildly.)