Asteroid likely caused global fires, which led to extinctions

From the AGU:

Global fires after the asteroid impact probably caused the K-Pg extinction

example graphic

Chicxulub Crater, Yucatán Peninsula, Mexico – Artist’s Impression Image: University of Colorado

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.

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Jimmy Haigh.

What’s the chances of the big one hitting right on the Cretaceous /Tertiary boundary, eh?

Bill_W

And what do you get when you burn things? CO2!!! The demon gas strikes again.

Steve Keohane

Interesting coincidence isn’t it Jimmy Haigh! This site is the only known source of blue pectolite, usually a grayish material. The blue makes a fine semi-precious stone, a mix of translucent blue and white. It is pretty hard and works and polishes similarly to jade.

Mark

Jimmy, you’ve hit the nail on the head. Proof, as if more were needed, that greedy corporate American interests will do *anything* to ruin the environment…

pokerguy

NOw that’s what I call global warming…

Mike Bromley the Canucklehead in Switzerland

Jimmy Haigh. says:
March 27, 2013 at 4:33 am
What’s the chances of the big one hitting right on the Cretaceous /Tertiary boundary, eh?
A case of the Egg hitting the Chicken, eh?

Theresa

I have heard that it was the Dekkan traps volcano eruption that killed them. Does that create Co2 as well?

AleaJactaEst

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. The related extinction event took several million years and this is shown in the fossil record. Global wildfires would have caused an immediate (in geological terms) fingerprint. One that does not exist in the said record.

TG McCoy

We are now capable of stopping such an event-with adequate warning. but we must spend money for the prevention of a Chimera outbreak….

I await any follow up papers.

darwin

I think they’re wrong. Recently scientists have uncovered fossilized SUV’s and coal fired power plants. The evidence is mounting that Global Warming controls everything.

jim2

You can see a CO2 spike ~ 66 million years ago in this stomata study. This study shows CO2 much higher in the past than now.
http://www.sonoma.edu/users/c/crocker/516-2011/300myr%20profile.pdf

DaveF

So what killed those dinosaurs that lived in the sea?

Micula

A layer rich in carbon was recorded from the classic K/T (K/Pg) site at Stevn’s Klint in Denmark. It was referred to by Hans Joergen Hansen (Univ. Copenhagen) as the “grey chalk” and has been used by some researchers as evidence of the post impact fire storm. Detailed sedimentological analysis shows that the carbon content includes 1-2 micro diameter hollow graphite spheres, known only from volcanic glasses. The depositional period of the “grey chalk” has been calculated by H.J. Hansen as approximately 600 thousand years. As he once said on a field excursion, “If we could find the wood that burns that long, then the energy problems of the world would be solved.”

Steve from Rockwood

A meteorite created the Sudbury Basin 1.85 billion years ago in Northern Ontario, Canada. A second meteorite struck the eastern edge of the same area about 40 million years ago in what is now Lake Wanapitie. This led one geologist to conclude that God has a very good aim but a very poor memory.

Luther Wu

Somehow, I feel it’s all my fault.

pokerguy

“So what killed those dinosaurs that lived in the sea?”
Salty diet. They all got hypertension.

darwin

DaveF,
Any disruption in the food chain will eventually find it’s way to the larger animals.

Ceri Phipps

Most of our fossil record comes from sea creatures and especially shell fish. They also became extinct in vast numbers which is how we know of the extinction, not from land based animals which are very rarely fossilised. I think therefore that fires are unlikely to be the cause.

I thought it was a flood.

Hypothermania

DaveF says:
March 27, 2013 at 5:46 am
So what killed those dinosaurs that lived in the sea?

Burning trees caused CO2 levels to increase, which caused sea levels to rise dramatically and they all died from vertigo.

CodeTech

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.

Sure. The models show that. However, what other possibilities exist?
First, look at the current understanding of the Chicxulub impactor. It appears to have been about 6 miles in diameter, and left visible rings at 40 miles and 110 miles in diameter. An exceptionally thick layer at 4200 feet deep was part of the discovery, and there is displaced material that indicates a “kilometers high” tsunami, which is to be expected from such a powerful impact. Imagine that volume of water washing away in all directions, and be glad that nothing like this has happened recently. It seems likely that any combustible forest for a long way away would have been stripped bare and carried away.
Second, consider the incredible energy that has just been expended on the crust, sending ringing shock-waves around the planet like a bell had been rung. Any weak spot would soon be volcanic, and who’s to say just how much of the mantle was exposed? Was the crater a gaping, smoking hole for years afterward? We’ve seen just how much material is ejected from a single volcano (Pinatubo comes to mind, and Mt. St. Helens), just multiply that by an unknown but large number. The entire planet was likely blanketed by soot and ash as a direct result, and possibly for decades.
Third, we’ve now seen the Chelyabinsk event, recorded on video from multiple angles. That was a very high relative speed event, and I didn’t see any evidence of ground structures bursting into flames. Ejecta from the Chicxulub impact that cleared the atmosphere and came crashing back would not have the same kind of relative speed, thus less chance of igniting the forests (which were probably washed away).
I like playing “imagine if” games as much as anyone, but the conclusions I’m reading here seem like they’re all on the outside of probability. Nothing seems to take away the most likely current theory, that the extinction event was caused by dramatic and rapid cooling caused by the impact itself, not giant forest fires. Although I don’t doubt there were fires from the impact, and it’s nice that they measured all the soot.
One thing IS certain… we can theorize and hypothesize and imagine all we want, but NOBODY knows for sure exactly what happens when an impact of that magnitude occurs. And if we’re lucky, we never will.

Stacey

@ Dave F
“So what killed those dinosaurs that lived in the sea?”
They died of heatbreak following the death of all their mates on land. 🙂

DaveF says: March 27, 2013 at 5:46 am “So what killed those dinosaurs that lived in the sea?” Ahhh, evolution, they crawled onto land, on their fins/legs that became legs/wings, to occupy vacant niches?

MarkW

DaveF says:
March 27, 2013 at 5:46 am
So what killed those dinosaurs that lived in the sea?

Between the impact and the fires, dust and smoke would have decreased sunlight significantly for months to years. That would have dramatically reduced plankton populations, plus the animals that feed on them. Which is pretty much everything, directily or indirectly.

wsbriggs

The ionization radiation created from the passage of the object through the atmosphere would also be responsible for a wide swath of death. Certainly it wouldn’t reach around the world, but it would have sterilized along its path. The amount would be dependent on its inbound trajectory.

Probably the weak point in this hypothesis is the modeling to determine the amount of radiation from the re-entering ejecta and the global distribution of that ejecta. I think the empact side of the globe should show greater signs of fires than the other side.

Alan

“So what killed those dinosaurs that lived in the sea?”
SPONGE-BOB-SQUARE-PANTS!
(Sorry, couldn’t resist……)

See this presentation for an alternate explanation of what happened…
http://www.threeimpacts-twoevents.com/wp-content/uploads/2013/01/SIMULTANEOUS-IMPACTS-3JAN2013-WEBSITE.pdf

Keith

Mike Bromley says “the egg hitting the chicken”.
Excellent response to Jimmy’s comment. I was thinking something similar.
OT sounds like you were contracting in Kurdistan, a place familiar to this rock doctor.

Don K

DaveF says:
March 27, 2013 at 5:46 am
So what killed those dinosaurs that lived in the sea?
===========================
Strictly speaking, there weren’t any marine dinosaurs that we know of. There were however, a number of large marine reptiles. Crocodiles and turtles survived. icthyosaurs died out before the end of the Cretaceous. Pleisosaurs and Mosasaurs probably were victims of the KT extinction event.

Jeff Alberts

DaveF says:
March 27, 2013 at 5:46 am
So what killed those dinosaurs that lived in the sea?

And why didn’t certain environmentally sensitive amphibian and reptile species die out?

Don K

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. The related extinction event took several million years and this is shown in the fossil record. Global wildfires would have caused an immediate (in geological terms) fingerprint. One that does not exist in the said record.
==================================
Yes.
And, related, massive vulcanism is thought to be a factor in the PT (Siberian traps) and KJ (“Newark Traps”) extinction events. Major vulcanism was also underway in India (Deccan Traps) at the time of the Chixulub impact. An Iridium layer has been found in the middle of the Deccan lava beds — presumably from the Chixulub event.
I’d like to know if the authors of this paper mapped out possible ejecta trajectories. The trajectories vary with the impact velocity and direction of course. My best guess, and it is a guess, is that very little of the ejected material was likely to make it to Australia, South and East Asia as I think that the vast majority of possible trajectories bring the material down rather quickly on the half of the planet centered on the impact site. Fires on that side? Seems quite plausible. Fires of the opposite side? Not so much I’m thinking.

David L.

Something that always concerns me is the total lack of fossils at the boundary, With everything dying at the same time why the lack of fossils?

Taphonomic

Luther Wu says:
“Somehow, I feel it’s all my fault.”
Don’t worry about it, Luther. I have it on good authority that it is Bush’s fault.

The meteor didn’t find the K/Pg boundary, it defined it. A well defined spike in 12C after the event indicates lots of things were dead. Dead things burn. These guys are just Carbon wags working every angle of their failed model, in this case downwelling Ir, for PR.

M Wagner

@ Jeff Alberts: Ah, the frog problem. Yes, environmentally sensitive species survived. You could make the argument that they were “wet” and thus spared from the fires. However, it’s more difficult to continue the argument in the face of loss of vegitation, which is necessary for the reproduction of their primary food source: bugs.
One thing that frogs do not have in common with dinosaurs is migration. Large species move around and interact with lots of other species. Frogs don’t. I’ve always felt that the demise of the dinosaurs was something more akin to a plague than a natural disaster.

Asteroid likely caused global fires, which led to extinctions

Complete nonsense, as is expected from AGU, a lost cause of a group. What this is an example of is the popular science mentality of career under-achievers who never miss an opportunity to take a dump on hard science. Sounds to me like yet another Omni magazine dramatization of true science, in this case the groundbreaking KT discoveries of Alvarez.
Yes, there were fires, perhaps even global fires, but plants and animals have evolved in a world where fire is a common occurrence and adapted to survive. What they didn’t adapt to survive was the shutting down of the food chain, attacked from below with photosynthesis being taken out of play from months or years of no sunshine. What few plants managed to survive in a low sunlight environment would have been picked clean by starving animals until they were completely gone. As this crept up the food chain extinctions occurred. Eventually the sun would shine, seeds would again germinate, but the higher order animals are already gone, for good.
It must kill these amateur pop-sci pretenders at AGU that all the real groundbreaking discoveries of the last century by actual scientists, such as Milankovic, Wegener and team Alvarez were initially scoffed at but later vindicated, and I’d bet AGU was part of that peanut gallery in each and every case.
NASA and AGU and their peers like Sagan, Hansen and Mann always try to take hard science and divert us with science fiction.

Jimmy Haigh.

When I was doing geological mapping in Eastern Venezuela in 1995 I mapped the Cretaceous/Tertiary boundary. There was nothing there – just a deepwater shale on shale contact. I think the theory is that the asteroid came in from the south east over the top of paleo-Venezuela and landed in the Paleo-Yucatan.
A few years later I was working with some geophysicists in Aberdeen who had identified a possible meteor crater in the North Sea which, as close as it can be dated, is also right at the Cretaceous/Tertiary boundary.
http://en.wikipedia.org/wiki/Silverpit_crater

Gerry

Luther, we’re big on apologies here in Oz …would you feel better if you apologised to the descendants of the dinosaurs ….?

Doug Proctor

No central uplift peak?
Okay, I’m fussy about the painting. It’s science. We’re supposed to be fussy.
An impact that big would send a tsunami up the Cretaceous continental sea from the Gulf of Mexico to the Arctic, one would think. I live in Alberta; out at Drumheller, you can see the Cret-Tertiary boundary in the valley wall (just above the last dark line of a coal stringer). It holds, apparently, the Iridium layer of Alvarez. However, no tsunamic debris OR (more signficantly) an erosive surface.
A “small” seaquake has a tsunami that crosses the Pacific. A global ‘quake stays where it is.
Something is off. Again.

John Tillman

OK, I’ll play along. The only marine dinosaurs were seabirds, most of which perished along with their terrestrial kin at the K/T boundary. But not all. Modern Aves appears to descend from an unusual group of Cretaceous shorebirds which survived extinction, probably in the southern hemisphere.
And now for something different: geological nomenclature. My opinion doesn’t count, but many geologists share objections to replacing the Tertiary with the Paleogene & Neogene Periods, for various reasons. My problem is more with how the IUGS has split up the Tertiary than to getting rid of it. Reasons for doing so I’ve read are that, at 63 million years (65.5 to 2.6 Ma), the Tertiary was too long, & that finer detail of the geologic record in the Cenozoic Era (65.5 Ma to present) justifies shorter periods.
The Tertiary however was much shorter than the preceding, almost 80 million year-long Cretaceous Period (last of the Mesozoic Era). The Silurian, third period of the Paleozoic Era, lasted only about 24 million years. The following Devonian & Carboniferous Periods were each around 60 million years.
Periods tend to end & begin with mass extinction events & eras with really big ones. The classic Big Five occurred at the Ordovician/Silurian (an ice age under ~4000 to 5000 ppm CO2 with ~96% of present solar luminosity), Devonian/Carboniferous (technically Late Devonian, as it was more drawn out than usual for MEEs), Permian/Triassic, Triassic/Jurassic & Cretaceous/Tertiary (or Paleogene) transitions. The most catastrophic P/Tr (“Great Dying”) & second or third worst K/T (or K/Pg) both ushered in new eras.
The IUGS officially defined the 42.5 million year-long Paleogene Period/System in 1991 & the 20.4 million-year Neogene in ’97. The Pg includes the Paleocene, Eocene & Oligocene Epochs, 65.5 to 23 Ma. The first two epochs continued Hothouse Cretaceous climate, featuring the warmest part of the Cenozoic, the Paleocene/Eocene Thermal Maximum. The Og (~34-23 Ma) however experienced cooling, including initiation of Antarctic glaciation, so seems more akin to the Neogene (23-2.6 Ma) & Quaternary Periods in at least this important respect.
IMO, it would have made more sense to split the Tertiary at the Eocene/Oligocene boundary, about the time that Antarctica was surrounded by the Southern Ocean, separated from South America & Australia by deep channels. The rift with South America has recently been fairly reliably dated to ~41 Ma, with a deep channel opening the Drake Passage to circumpolar circulation in the early Og now favored over a later date.
Another big Og oceanic circulatory event was the closing of the Tethys Sea (nursery of whales) by the collision of the African & Indian Plates with Asia.
Also, quoting Wiki, “The start of the Oligocene is marked by a notable extinction event called the Grande Coupure; it featured the replacement of European fauna with Asian fauna, except for the endemic rodent and marsupial families. By contrast, the Oligocene-Miocene boundary is not set at an easily identified worldwide event but rather at regional boundaries between the warmer late Oligocene and the relatively cooler Miocene.”
Transferring the Og from the Paleogene to Neogene would yield a ~32 million-year (vs. the IUGS’ ~43) Pg composed of the Paleocene & Eocene Epochs, & a ~31 million-year (vs.~20) Neogene (Oligocene, Miocene & Pliocene).
To its credit, the IUGS did a sensible thing in 2009 by lengthening the Quaternary Period & Pleistocene Epoch to include all the Quaternary glaciations (formerly awkwardly called “Pliocene-Pleistocene”). The Quaternary had started only 1.8 Ma but now begins at 2.6 Ma, not long after oceanic circulation was interrupted by the closure of the Isthmus of Panama. The Pliocene is thus a truncated Epoch, but the revision better reflects important geological & climatic change.
Of course our present Holocene is just another warm interglacial phase, but according it Epoch status is justifiable since so many megafaunal species went extinct at the Pleistocene/Holocene transition.
Again, apologies for such length on what’s basically a pet peeve.

tty

A lot of uninformed comments all around here:
“What’s the chances of the big one hitting right on the Cretaceous /Tertiary boundary, eh?”
100 % since the end of the Cretaceous was caused by the impact. Or rather geologists defined the boundary because of the extreme biotic changes at that level.
“I have heard that it was the Dekkan traps volcano eruption that killed them.”
They may have been a contributing factor. But dinosaurs occur in the “intertrappan beds” that formed during breaks in the volcanic eruptions so the certainly weren’t immediately fatal, even for dinosaur living in India (which was an isolated island at that time).
“So what killed those dinosaurs that lived in the sea?”
Strangely enough no dinosaurs ever lived in the sea. There were other marine reptiles (mosasaurs, plesiosaurs) that became extinct at the K/T boundary though. That is not hard to explain as there was a complete ecological collapse in the ocean, probably due to phytoplankton failing to grow during the darkness immediately after the impact.
“I think the empact side of the globe should show greater signs of fires than the other side.”
“I’d like to know if the authors of this paper mapped out possible ejecta trajectories. The trajectories vary with the impact velocity and direction of course. My best guess, and it is a guess, is that very little of the ejected material was likely to make it to Australia, South and East Asia as I think that the vast majority of possible trajectories bring the material down rather quickly on the half of the planet centered on the impact site. Fires on that side? Seems quite plausible. Fires of the opposite side? Not so much I’m thinking.”

Contrariwise. This has been studied and is fairly well understood. The largest concentration of secondary impacts will actually occur near the antipodal point of the impact (this is pretty obvious if you think about trajectories a bit). An area a few thousand kilometers wide around the impact point would of course have been incinerated/boiled by a shockwave of rock vapor and superheated steam. The area least affected by secondary impacts would probably have been Antarctica.
“And why didn’t certain environmentally sensitive amphibian and reptile species die out?”
Most did, but generally speaking animals and plants in freshwater environment survived best of all. Probably because they were thermally shielded by the water and freshwater food chains are much less immediately dependent on green plants than any other.
“That was a very high relative speed event, and I didn’t see any evidence of ground structures bursting into flames. Ejecta from the Chicxulub impact that cleared the atmosphere and came crashing back would not have the same kind of relative speed, thus less chance of igniting the forests”
A high speed but very small, very brief event. Re-entering secondaries cannot have higher speed than 11 km/s and most will be in the 7-10 km/s range. The stagnation temperature for a body entering at that speed is around 3,000-4,000 degrees, which is white-hot but not quite as bright as the sun. Think a bit about the effect of a large part of the sky having a brightness temperature of 3,000-4,000 degrees for a period of hours instead of just a small spot for a few seconds.

Ryan

Here is a far better paper. Written by Geologists for Geologists in the Journal of Geology.
Fireball Passes and Nothing Burns – The Role of Thermal Radiation in the K – T Event: Evidence from the Charcoal Record of North America
Geology 2003;31;1061-1064
Claire M. Belcher, Margaret E. Collinson, Arthur R. Sweet, Alan R. Hildebrand and Andrew C. Scott
Cretaceous-Tertiary event: Evidence from the charcoal record of North America

klem

This is what I like to see, scientists challenging the accepted theory. The asteroid extinction theory is now 35 years old and it holds up well, but many aspects of it are still being challenged. That’s the practice of science I was taught decades ago.

commieBob

How much of the planet’s atmosphere was blown away by the impact? There is some reason to believe that the atmosphere used to be much thicker. http://www.dinosaurtheory.com/thick_atmosphere.html Could it be that the large dinosaurs suffocated?
I have no clue whether the above conjecture is plausible. A bit of quick googling didn’t seem to produce much evidence one way or the other.

“What’s the chances of the big one hitting right on the Cretaceous /Tertiary boundary, eh?”
I knew a girl once who thought it was amazing that so many American Civil War battles, like Gettysburg, happened to get fought in National Parks.

jim2

These things can cause fire. A mountain-sized one could cause a lot of fire, no?
“Selected eyewitness reports
The Southern swamp—the epicentre of the Tunguska explosion, in 2008Testimony of S. Semenov, as recorded by Leonid Kulik’s expedition in 1930:[16]
At breakfast time I was sitting by the house at Vanavara Trading Post [65 kilometres/40 miles south of the explosion], facing north. […] I suddenly saw that directly to the north, over Onkoul’s Tunguska Road, the sky split in two and fire appeared high and wide over the forest [as Semenov showed, about 50 degrees up—expedition note]. The split in the sky grew larger, and the entire northern side was covered with fire. At that moment I became so hot that I couldn’t bear it, as if my shirt was on fire; from the northern side, where the fire was, came strong heat. I wanted to tear off my shirt and throw it down, but then the sky shut closed, and a strong thump sounded, and I was thrown a few metres. I lost my senses for a moment, but then my wife ran out and led me to the house. After that such noise came, as if rocks were falling or cannons were firing, the earth shook, and when I was on the ground, I pressed my head down, fearing rocks would smash it. When the sky opened up, hot wind raced between the houses, like from cannons, which left traces in the ground like pathways, and it damaged some crops. Later we saw that many windows were shattered, and in the barn a part of the iron lock snapped.

http://en.wikipedia.org/wiki/Tunguska_event

John Tillman

tty says:
March 27, 2013 at 8:45 am
A lot of uninformed comments all around here:
“What’s the chances of the big one hitting right on the Cretaceous /Tertiary boundary, eh?”
100 % since the end of the Cretaceous was caused by the impact. Or rather geologists defined the boundary because of the extreme biotic changes at that level.
***********************************************************************************
I’m pretty sure that part was meant as a joke.
Thanks for the rest of your informative comments.

Jimbo

Just 5 days ago I read this:

BBC 22 March 2013
Dinosaur-killing space rock ‘was a comet’
“You’d need an asteroid of about 5km diameter to contribute that much iridium and osmium. But an asteroid that size would not make a 200km-diameter crater,” said Dr Moore.
“So we said: how do we get something that has enough energy to generate that size of crater, but has much less rocky material? That brings us to comets.”
http://www.bbc.co.uk/news/science-environment-21709229