Arguments
So what did-in the dinosaurs? A murder mystery…
Posted on 12 March 2015 by howardlee
Scientists have assembled a slew of new forensic evidence – from high-resolution dates to microscopic fossils – to prosecute the dino-killer. Their indictment has worrying implications for us.
Everyone knows that the dinosaurs were wiped out - along with about 70% of all species - by a massive asteroid slamming into Mexico, right? Well, not so fast. Like a good murder-mystery, a steady drip of evidence and some major new revelations have implicated another suspect – were they in it together or is one innocent?
Suspect A – the impact
Our first suspect is the asteroid impact at a place called Chicxulub, in Mexico.
This one is not a serial killer. In all the episodes of mass extinction through deep time, it has only credibly been implicated in the end-Cretaceous catastrophe. It’s weapons of death include a violent blast that destroys everything for thousands of miles around the impact, a heat flash from the blast that incinerates everything in a similar radius, followed by a near-global rain of red-hot ejecta that turns the sky into a broiler (“grill” if you are outside the US) inflicting fatal burns and igniting a global conflagration. The blast, centered in shallow ocean, generates a colossal tsunami across the juvenile Atlantic and the shock wave triggers earthquakes and tsunamis around the world far more violent than the 2011 magnitude 9 T?huku earthquake in Japan. Finally, the great quantity of dust and incinerated debris flung into the upper atmosphere blocks out the sun, turning the world dark and the climate frigid for years.
That should do it.
Except lately the idea that the impact’s heat flash could ignite everything has been challenged by experiments, which show: “any fires ignited by impact-induced thermal radiation cannot be directly responsible for plant extinctions, implying that heat stress is only part of the end-Cretaceous story.” Plant fossils around the world also show no sign that fire was above normal levels at the time. So that’s one weapon that probably didn’t cause global extinction. Neither the blast, nor the extreme earthquakes would have been enough to cause a global extinction by themselves. What about the tsunami? Tsunami deposits have been identified around the Gulf of Mexico and into the Atlantic, but further afield the deposits are elusive. Even those in Mexico and in Texas can be interpreted, with convincing detail, as just normal sediments rather than tsunami deposits. So the tsunami was of doubtful reach, its rock evidence questionable, and it can’t have caused global extinction alone.
How about blanketing the planet in hot fallout? While it is true that tell-tale traces of apparent impact fallout (high concentrations of iridium, “shocked” quartz crystals, and tiny glass droplets called “spherules” or “tektites”) have been found in many parts of the world, the physical layer of impact deposits dwindles from a thickness of 2 meters (6 feet) around the Gulf of Mexico, to 3 to 5cm (1 to 2 inches) in Europe, and is apparently absent in China, Alaska, Japan and New Zealand. An iridium-rich layer has been detected across North America, Europe and North Africa, and as far afield as the India-Bangladesh border, but has not been reported from China, Alaska and Japan. So the fallout by itself does not seem convincing as a worldwide killer, and there has even been a suggestion that some of those fallout traces may be from volcanic eruptions rather than an impact.
Was the impact capable of causing the ocean acidification that bumped-off so many marine species?
Professor Toby Tyrrell of the University of Southampton, England, and his coauthors tested this. At the American Geophysical Union conference in December they revealed their dramatic answer: “no.”
The impact cannot feasibly have generated the ocean acidification that killed off calcifying marine species in the mass extinction.
They looked at a number of possible ways the impact might have acidified the ocean. Did the impact’s pressure wave turn nitrogen to nitric acid? If it did, it didn’t generate enough to acidify the ocean. Vaporization of carbon from limestones at the impact site? Not enough. Liberation of carbon from terrestrial decay, soil respiration, wild fires, hydrocarbons? Nope. Tsunami stirring the oceans? No. All of the above together. Still no. Sulfur vaporized from the sulfur-rich rocks at Chicxulub and sucked into the atmosphere? It would take 800 billion tonnes of sulfate to achieve the acidification observed, but to get that number you have to max-out every assumption in the calculation to a ridiculous extent. So no, not even close. The impact cannot feasibly have generated the ocean acidification that killed off calcifying marine species in the mass extinction.
That just leaves the “impact winter” as our suspect’s last remaining, potentially globally-fatal weapon. But plant fossils around the world show that any impact winter severe enough to prevent plant growth can’t have lasted more than a couple of years. Maybe a couple of years was enough? Sediments in Texas and New Jersey do show a strong cooling spike thought to represent the transfer of cold impact winter atmospheric temperatures into the ocean, within months to decades after the impact. But it takes many decades for the ocean to cool or warm significantly, due to its great volume and thermal inertia. Such a brief climate blip is unlikely to have cooled oceans globally fast enough to produce the rapid, sharp cooling spike observed in the sediments. In any case, large eruptions are known to cause temporary climate cooling too. In the absence of any other corroborating evidence, the impact winter seems busted as an effective cause of global extinction by itself.
So, despite its murderous image, the Chicxulub impact seems to lack WMEs (Weapons of Mass Extinction). What about our other suspect?
Suspect B – climate change caused by massive volcanic eruptions
This one has a rap sheet as long as your arm. Unlike asteroid impacts, this suspect is a known serial killer, linked to four of the “big five” mass extinctions, as well as many other global extinctions and global warming events. Still, we should presume innocence until guilt is proven.
The Deccan eruptions in India were in a rare and exotic league of hyperactive eruptions known as a “Large Igneous Provinces” not seen on the planet in the last 16 million years. They inundated an area of India 3 times the size of Texas (or France) in superhot rivers and lakes of lava, including the longest lava flow ever measured (over 1500 km/930 miles) that only stopped when it reached well out into the ocean. Around 3 kilometers (2 miles) thickness of lava built up episodically in around 750,000 years, but at the time of the mass extinction there were four especially massive mega-eruptions packed into just a few millennia.
But it’s not the lava that kills on a global scale, it’s the gasses.
Artist’s impression of a Large Igneous Province mega-eruption such as the Deccan eruptions. Horizontal scale is approximately 1,500 km (930 miles). Vertical scale is exaggerated - the top of the box is the stratosphere (about 15 km above the ground). The modern world’s largest volcano – Hawai’i’s Big Island - is shown for approximate scale.
At the cataclysmic onset of each mega-eruption, towering columns of ash and gasses (including steam, CO2, sulfur dioxide (SO2), chlorine and fluorine) rose to stratospheric levels, where they spread around the planet. The SO2 became sulfate aerosols, just as it does in large eruptions today, which acted as sunscreen to cool the planet for a few years (much like the impact winter), while the chlorine and fluorine may have decimated the ozone layer causing a dramatic increase in harmful UV radiation reaching the ground.
If any of this sounds familiar, it’s because we’re projected to do something very similar to ourselves if we continue CO2 emissions at the same rate as today
The Deccan gas emissions were so massive and rapid they outstripped the ability of the ocean and other feedbacks to absorb them – causing CO2 to build sharply in the atmosphere over a few millennia. As the short-term volcanic winter diminished, it unmasked the really lethal weapons of abrupt global warming and ocean acidification. The planet warmed by 8°C (14°F) on land and 4°C (7°F) in the oceans, while the excess CO2 dissolved in ocean water, turning it increasingly acidic. The sulfur gradually rained down as sulfuric acid, which pickled land and sea alike until oceans were acid enough to dissolve shelly sea life alive.
If any of this sounds familiar, it’s because we’re projected to do something very similar to ourselves if we continue CO2 emissions at the same rate as today (our CO2 emission rate is comparable to that from the Deccan eruptions).
So yes, the eruptions had effective WMEs (Weapons of Mass Extinction), and Large Igneous Provinces have a record of doing all of this before, such as in the end-Triassic and end-Permian mass extinctions.
Placing the suspects at the scene of the crime.
Since we are talking global mass extinction this isn’t so much a problem of where, as when. At the scale of many millions of years that geologists are used to working with, the dates calculated from radioactive element decay (“radiometric dates”) for the mass extinction, the eruptions, and the impact are near identical. But not quite near enough to rule our defendants either in or out.
To tease out which of our suspects caused the mass extinction, we need to refine the dates to within a few tens of millennia. Zooming up to that level of detail puts us in the blur of radiometric dating uncertainty, so scientists have to resort to forensic sleuthing using fossils, traces of orbital wobbles, and magnetic field reversals to narrow the timeframes. The inevitable discrepancies between different studies, locations, and between marine and non-marine rocks, make establishing definitive timelines like trying to find a level line across small boats bobbing up and down on high seas.
So it helps to have one fixed point to refer to. The official end of the Cretaceous is defined in northern Tunisia at the level of the mass extinction recorded by marine rocks. A kind of tiny shelly sea life called foraminifera (“forams” for short) frequently evolved new species with different shell shapes, so they can be used to establish “level” time zones. The Tunisian rocks show a changeover from the “CF1” to the “P0” fossil time zones at the end-Cretaceous as a marker of the mass extinction, which can be traced in marine rocks around the world, along with a distinct layer of clay with a red layer at its base and a spike in iridium levels, and a kick in carbon isotopes that shows a big upset in the global carbon cycle at that time.
But the best date of the end-Cretaceous so far is defined in non-marine rocks from Montana, sandwiched between the last appearance of Cretaceous pollen and the first post-Cretaceous pollen fossils, dated to 66.043 million years ago, with an uncertainty of 43,000 years in either direction. That date is within 5,000 years (effectively identical) to a date for tektites – traces of the impact – found in Haiti. That would seem to put the impact conclusively at the time of the mass extinction, but the marine fossils associated with those Haitian tektites are from a time zone at least 100,000 years younger, showing that those tektites must have been recycled by later sedimentary processes, and cannot give the true date of the impact.
The plot thickens.
Chicxulub wrongly convicted?
You might expect that the impact fallout would generate a clear global signal, a time “level” against which all other events can be compared, but sadly that is not the case. It turns out that the spherules, shocked quartz, and the iridium spike can all be moved by sedimentary processes and groundwater. Just as we saw in Haiti, a number of locations from New Jersey to the Caribbean, where the signs of impact were considered proof that the impact coincided with the mass extinction, have large gaps lasting several hundred thousand years up to 3 million years, spanning the crucial time period at the end Cretaceous! They can’t be used to narrow down the date of the impact either.
And what if there was a doppelganger – another impact that occurred around the same time generating some of the same signals, potentially throwing us of the scent? It turns out there was.
A smaller asteroid blasted a crater at Boltysh in the Ukraine, dated at 65.59 million years ago, with an uncertainty of more than half a million years in either direction, amply overlapping the events we’re investigating. It appears to have inflicted negligible ecological trauma beyond its local neighborhood, and fossils inside the crater show the Boltysh impact happened a few thousand years before the end of the Cretaceous. The Earth Impact Database shows that there are an additional 3 known (small) impacts that might possibly have occurred in this timeframe, but which are very imprecisely dated. In other words Chicxulub may have been the largest by far, but it wasn’t the only impact broadly at that time capable of generating similar tell-tale impact traces.
Sediments drilled from within the Chicxulub crater itself tell a remarkably similar story to that at Boltysh. Once thought to be the settlings from the immediate aftermath of the impact and tsunami, they have since been shown to include a regular marine limestone containing the distinct late-Cretaceous CF1 fossils - so the crater must have been formed before the end-Cretaceous mass extinction! Corroborating that, rocks from Texas and Mexico show that the impact fallout (in the form of the oldest layer of impact spherules) predates the mass extinction by more than 100,000 years!
So – amazingly - it looks like the Chicxulub impact has an alibi. It wasn’t at the scene of the crime during the mass killing, but what about our other suspect?
The impact’s alibi – it was about 100,000 years before the end-Cretaceous mass extinction. Left: oldest spherule layer at El Peñon in Mexico (formed in the early part of the CF1 fossil time zone). Center: close-up of the spherule layer. Right: microscopic view of spherules bent round each other showing they were still hot and soft when they settled. Photo credit: Gerta Keller, Princeton University.
Incriminating volcanic-induced climate change.
At the end of last year some new radiometric dates were published for the Deccan eruptions that were 10 to 100 times more precise than previously-published dates, placing the start of the main phase of Deccan eruptions within 250,000 years of the mass extinction and showing that the eruptions continued through the extinction event. For a finer-grained link to the mass extinction we need those marine fossils – but the Deccan lavas were erupted on land. Fortunately at the fringes of the lava flows near the Bay of Bengal, sediments between and below the longest mega-flows are characteristic of the latest Cretaceous, and sediments immediately above the lavas have the distinct fossils of the very first post-Cretaceous time zones, showing that the marine mass extinction occurred during the mega-eruptions.
The isotopic makeup of marine fossils varies with temperature and changes in the ocean carbon cycle, giving scientists a picture of the fluctuating climate leading up to the extinction. There were 4 distinct global warming phases punctuated by cooler episodes. Sea levels rose and fell, while some land areas suffered severe drought. This “global weirding” tortured life through wild climate instability, culling biodiversity in mega-eruption steps, culminating in the most abrupt climate change and ocean acidification during the 4th mega-eruption. By its end most Cretaceous life was rubbed-out.
Most shelly creatures make their shells from calcium carbonate – chemistry that only works in alkali water with sufficient carbonate (a throwback to the Cambrian Explosion when seawater first turned alkali and animals had to evolve ways to deal with this new ocean chemistry). Ocean acidification was deadly for these creatures, to the extent that more than 90% of calcareous nanoplankton were wiped out, along with many more well-known, photogenic species like belemnites and ammonites.
On land, forests died across most of the world, moldered, and gave way to open land covered in ferns, although eastern Russian and Antarctic vegetation doesn’t seem to have been so severely affected. Fluctuating climate and drought prevented the return of forests for many thousands of years.
Gotcha!
new dates... do not support an impact as the cause of the environmental changes
An incredibly detailed set of dates has just been published for end-Cretaceous sediments, which contain dinosaur fossils, in Montana. What they reveal is a sequence that is “not obviously consistent with an instantaneous forcing mechanism.” In other words, they do not support an impact as the cause of the environmental changes recorded by the sediments! In fact the new dates fit very well with the rest of the evidence incriminating the Deccan eruptions.
In North America and Europe the dinosaurs were healthy and diverse right up to within about 200,000 years of the end-Cretaceous, at which point they disappeared. Mammals and amphibians continued but declined markedly through the final 200,000 years of the Cretaceous, coinciding with the Deccan eruptions. A very similar story is told by the fossils of India, where you see fossils of flourishing vegetation and abundant animals, including nesting dinosaurs, right up to the Deccan eruptions. Once the eruptions start, sediments between the lava flows capture life dwindling away like a tragic stop-motion film. Dinosaurs and forests are decimated by the onset of the eruptions about 250,000 years before the end of the Cretaceous. The few that survive don’t make it past the next eruption, disappearing from the Indian fossil record well before other reptiles like turtles and snakes. During the final 18,000 years or so of the Cretaceous, terrestrial plant life in North America declines up to the end-Cretaceous boundary, matching the timing of the marine extinction and the Deccan mega-eruptions.
So it seems that the eruptions, not the Chicxulub impact, did-in the dinos, just as they dispatched so much other life on land and in the seas.
Verdict
So we have reached a verdict. All rise.
Deccan eruptions - for the Cretaceous global warming, ocean acidification, and extinction in the marine realm: guilty! For the terrestrial extinction including the dinosaurs: also guilty – but some may still claim reasonable doubt.
Chicxulub impact – for the Cretaceous global warming, ocean acidification, and extinction in the marine realm: not guilty! For the terrestrial extinction and doing-in the dinos: not guilty - It has an alibi, and there’s insufficient evidence of its ability to kill on a global scale to prosecute. After 30 years it’s time to let this one go. It has done its time.
Case closed? Probably not. There’s room for appeals and fresh evidence in the years ahead – perhaps even a “Serial” podcast. But the many strong strands of scientific evidence that global warming and ocean acidification was behind the demise of so much life, including the dinosaurs, should give us pause.
____________________
Hat tip to the Geological Society of America Special Paper 505, the Geological Society of America October 2014 meeting in Vancouver, the American Geophysical Union December 2014 Conference, to NPR’s “Serial” podcast, and to Professors Toby Tyrrell and Gerta Keller for several clarifications, corrections, and explanations.
Howard Lee’s latest book is “Your Life as Planet Earth,” an account of past climate changes, how they affected life, and how Earth and life affected climate.
The theory that the end-Cretaceous mass extinction was due to global warming and ocean acidification goes all the way back to 1978 with the publication of a paper by Dewey McLean in Science. Even back then Dewey saw the parallels to modern climate change. When Alvarez et al published their theory that an impact was the cause, this captured the public’s imagination, but debate continued and became rancorous enough to make the newspapers. When the previously identified Chicxulub crater was linked to the extinction in 1994 the impact theory became mainstream, yet it didn't completely match the observations. So a new theory that combined the Deccan eruptions and the Chicxulub impact was developed, which has been generally accepted since 2008 (the Press-Pulse theory of mass extinction, where the eruptions pressed ecosystems to the brink before the impact pulse finished the job). In 2010, responding to papers by Keller, Schulte et al concluded that the impact was indeed the ultimate cause of the extinction, but the debate continued. The environmental data combined with the slew of high-precision dates since 2013 linking LIPs to mass extinctions in general, and the Deccan LIP to the end-Cretaceous specifically, has now shown the dominant role of the eruptions. But it’s fair to say that the timing and ecological trauma inflicted by the Chicxulub impact will continue to be debated and refined alongside the effects of the eruptions.
Citations:
Mateo, P., Keller, G., Adatte, T., & Spangenberg, J. E. (2015). Mass wasting and hiatuses during the Cretaceous-Tertiary transition in the North Atlantic: Relationship to the Chicxulub impact?. Palaeogeography, Palaeoclimatology, Palaeoecology.
Tyrrell, T, Merico, A, & McKay (2014) Model Calculations of Ocean Acidification at the End Cretaceous presentation PP54B-03 12/19 In AGU Fall Meeting in San Francisco, California PNAS paper in press.
Global Boundary Stratotype Section and Point (GSSP) of the Danian Stage as defined by International Commission on Stratigraphy http://www.stratigraphy.org/gssp/danian.html Accessed on 3/10/15
Earth Impact Database maintained by the Planetary and Space Science Centre, University of New Brunswick Fredericton, New Brunswick, Canada http://www.passc.net/EarthImpactDatabase/Agesort.html Accessed on 3/10/15.
Keller, G. (2014) Website: Gerta Keller, Professor of Geosciences. Volcanism, Impacts and Mass Extinctions. http://massextinction.princeton.edu/ Princeton University.
Apology for duplicate post. A view of the Earth-Globes from 65MYA and Today can give a better sense of continental separation than a flat map. Note how continental separation of 65MYA are not overly dissimilar to Today's continental separation. As Tom Curtis pointed out with respect to the angle of Chicxulub's impact, the Chicxulub & Deccan Traps events do not have to be axial through Earth's center.
Watchdog,
Many people attribute the Deccan Traps volcanism to the Chicxulub impact. They view a current Earth map and erroneously assume that the near-antipodal relationship between the two locations existed 66 mya. I believe their logic is that the bolide impact traveled through the core(s) and disturbed the mantle/crust on the Indian sub-continent causing the eruptions. This could not have happened because the two locations were not antipodally positioned 66mya. I don’t believe there is any scientific evidence, based on the apparent latitudinal symmetry to the equator 66 mya, that this would be a feasible explanation.
Also, it is well known that the Deccan Traps began erupting long before the bolide impact occurred.
Returning to the question of whether flood basalt volcanism was responsible for prior mass extinctions, my belief is that the volcanism was the result of the core elements rapidly moving back toward Earth-centricity, and therefore were secondary causes of mass extinction, second to gravitational changes. It is interesting that there is little attention given to the cause of flood basalt volcanism. Specifically, why the greatest outpouring of flood basalt eruptions was greatest when all the continents were massed together and has diminished as the continents continued to separate. This aspect is readily explained by the GTME.
"Sediments drilled from within the Chicxulub crater itself tell a remarkably similar story to that at Boltysh. Once thought to be the settlings from the immediate aftermath of the impact and tsunami, they have since been shown to include a regular marine limestone containing the distinct late-Cretaceous CF1 fossils - so the crater must have been formed before the end-Cretaceous mass extinction! Corroborating that, rocks from Texas and Mexico show that the impact fallout (in the form of the oldest layer of impact spherules) predates the mass extinction by more than 100,000 years"
100,000years seems a long while really to be premature by.
"Deccan eruptions - for the Cretaceous global warming, ocean acidification, and extinction in the marine realm: guilty! For the terrestrial extinction including the dinosaurs: also guilty – but some may still claim reasonable doubt.
Chicxulub impact – for the Cretaceous global warming, ocean acidification, and extinction in the marine realm: not guilty! For the terrestrial extinction and doing-in the dinos: not guilty - It has an alibi, and there’s insufficient evidence of its ability to kill on a global scale to prosecute. After 30 years it’s time to let this one go. It has done its time."
Well drawn conclusions.
And if the bullet did start the eruption, still the CO2 heating and acidificatiom that are the murder weapons found present at the scene of the crime, rather than a historical impact which clearly caused major issues just not the extinction of the dinosaurs.
Given the evidence as well as that from other mass extinctions it seems a sudden release of CO2 can change climatic zones and transforms oceans rapidly enough for the global ecosystem to essentially reset itself to the new conditions, that is why there is always a boom after the bust; sometines after such a huge event it goes bbust, boom, bust, boom until it resettles in a more stable state again.
Watchdog,
As howardlee's research is extensive and the evidence convinving,
What is it about CO2 being the primary murder weapon that makes you feel that this possibility is in error?
I urge everyone here not to take the "Gravity Theory of Mass Extinctions" or GTME seriously at all. It is physically impossible and is completely unsupported by any peer-reviewed research.
If you are curious to know more read this, but please bear in mind that it is bunk.
There are indeed small gravity variations on the present Earth, due principally to the planet's rotation and changes in altitude of the surface. This means that the lowest gravity on Earth is to be found at the summit of Huarascan in Peru and the lowest near the North Pole. These differences are approximately 0.7%.
In other words, an average man weighing 80 kg, standing at the North Pole, would be about 600 grams heavier than the same guy perched on top of a peak in the Andes. If the chap at the pole emptied his bladder, they would then be about the same weight.
Andy Skuce @54, agreed. If the GTME held any water (pun intended), there would be a consistent difference in the gravitational field such that continental areas has a stronger field than oceanic areas. That turns out not to be the case:
(Source, see also )
The strongest gravitational field, as it turns out, is not just (vaguely) near the North Pole, but along the mid oceanic ridge in the North Atlantic where active volcanism brings magma to the surface, with the second strongest being in the Indonesian archipelago.
Nor should this be a surprise. Continental crust floats on the asthenosphere, ie, the semi solid magma beneath the surface. Ergo it has a lower density and is, overall gravitationally neutral. Ergo the basic premise of GTME is false. We need not bother to follow through to its (sometimes very bizarre) conclusions to know the theory fails.
@Andy Skuce .54 and Tom Curtis .55
As I stated in a prior posting, current gravity anomalies found around the globe are due to variations in crust/upper mantle densities, usually from compression by ice. These are minor and not related to core movement.
There is much evidence to support the GTME. If you viewed the Youtube video referenced earlier, you understand the basic concept:
When the continents, coalesced into larger masses, e.g., Pangea, and especially when that consolidated mass moved latitudinally, the law of conservation of angular momentum comes into play in the same way that it does when a spinning skater moves their outstretched arms close to the body or away from the body. In the case of the skater, their rotational velocity must change. For the Earth, when the coalesced mass moves latitudindally, the distance to the Earth’s axis changes in a comparable manner. Therefore, either the Earth’s rotational velocity changes or something else compensates to conserve angular momentum. GTME posits a movement of the core elements to compensate because there is no rotational change known. The movement of the core elements creates a gravitational gradient around the Earth.
Based on the above, some of the results are:
1. Terrestrial and marine life exhibited a much wider range in physical size than is possible today when the core elements moved away from Earth-centricity.
2. When the core elements moved rapidly toward Earth-centricity, surface gravity increased, flood basalt volcanism began and a massive drop in sea level occurred. The latitudinal movement is supported by a scientific study mentioned in the video which illustrates the latitudinal movement of Pangea over the last 300my.
3.When (2) above happens, methane is disassociated from the sea bottom because of the drop in sea level coupled with the (still) relatively low surface gravity. The volcanism further increases the disassociation because it raises the ocean temperature. In fact, the experts claim that the carbon isotope excursion at the P-T boundary was too large to be accounted for by the Siberian Traps alone.
4. At the Cretaceous-Triassic boundary, marsupials in N.America were almost completely wiped out in contrast to other small mammals.
http://phenomena.nationalgeographic.com/2014/12/24/the-opossums-tale/
This can be explained by a rapid increase in surface gravity. If you have an alternate explanation, I would be interested.
5. The reduction in size and complexity of the forams at the Cretaceous-Triassic transition can be explained by an increase in surface gravity, not only by a change in ocean chemistry. Smaller, less dense forams would be more buoyant and more likely survive if surface gravity increased.
[PS] This discussion is now far offtopic and as far as I can see well away from the realms of peer-reviewed science. If proponents wish to continue this, then please find another forum. Further on-topic discussion can continue provided any assertion is first backed by peer-reviewed literature.
ranyl -
I'm placing the question of a chicxulub -> deccan traps connection, and Sulphur Trioxide and other gasses - including CO2 - on the side burner - for the sake of maintaining attention upon both events being self-evident causal factors of widespread catastrophic extinction of life.
What is it about their unquestionably individual catastrophic affects upon extinctions of life over millions of square miles of Earth, along with both of their acknowledged causings of known periods of inhospitable Global Freezing - that leads you to feel that they were not - at least - a very large part of the extinction of Dinosaurs?
I don't mind discussing CO2 and other Gasses, but not at the expense of what I perceive to be a possible glossing over the effects of: A) Chicxulub (and theorized additional meteroric impacts). B) Deccan Flats as well as both of the their accompanying C) - Global Freezing — - as if "CO2" somehow minimizes or supplants A, B & C.
Theorist @56, conservation of angular momentum only becomes relevant if the continents generates a significant mass anomaly. As seen above, they do not now and your assumption that they did in the era of Pangaea is entirely evidence free. I am not going to discuss this further. There is no point discussing pseudo-science with pseudo-scientists, and on the pseudo-science scale, yours is right up their with young earth creationism. Right down to the false, unevidenced claims that scientists do not have explanations for phenomenon which are well explained (or for which there are several scientific explanations between which evidence is insufficient to decide).
[PS] Further discussion on these lines will be deemed offtopic and deleted.
The author of this article concludes that the Chicxulub impact was not the cause of the mass extinction. I agree. The author then concludes that the Deccan Traps must therefore be the cause.
I disagree.
Gerta Keller, who has studied the Deccan Traps extensively produced a chart displaying the three main Phases of eruptions of the Deccan Traps, which can be found at the following link:
http://www.princeton.edu/main/news/archive/S32/14/62G75/
The chart in the paper cited above is proof that neither the bolide impact nor the Deccan volcanism was the cause of the foram extinction:
PHASE 1 starting about 67.5 Mya and produced about 8% of the lava.
PHASE 2 starting about 65.3 Mya and produced about 80% of the lava.
PHASE 3 starting about 64.7 Mya and produced about 12% of the lava.
Each of the three Phases are sub-divided into 4 megaflows of lava.
As stated in the research paper and supporting the GTME is the following quote, which describes the foram extinctions:
"After studying microplankton remains in sediment from below, between and above the second-phase lava flows, the researchers observed that the number of living species dropped 50 percent at the onset of eruptions."
Clearly, if this statement is accurate then neither the volcanic eruptions nor the bolide impact could have caused these extinctions. They occurred much too early for the negative environmental effects (specifically sulfur dioxide emissions and carbon dioxide) to have had an effect on forams.
The paper also states:
"The species count plunged by another 50 percent after the first of what would be four lava mega-flows."
This refers to PHASE 2.
This indicates that about 75% of the forams became extinct by the end of the first megaflow within PHASE 2. And, by the end of the fourth megaflow the extinction was complete, which is when the bolide impact occurred.
If neither the bolide impact nor the Deccan volcanism caused the extinctions then what did?
[PS] "the author then concludes that the Deccan Traps must therefore be the cause." Actually he puts forward an alternative scientifically plausible explanation. If you wanted to discuss "GTME", then you need peer-reviewed paper supporting the physical plausibility.
This article was published on this site because it has some relevance to possibilities inherent in rapid climate change. No further offtopic discussion of wild alternatives will be tolerated. Find another forum.
Theorist @59 says:
Below is the chart to which Theorist earlier refers. It's caption reads:
As can be seen from the emphasized statement, the geologists interpretation of their own work directly contradicts the claim Theorist bases on that work. That is, where Theorist concludes from this data that the volcanism of the second phase Deccan traps could not have caused the K/T mass extinction, the geologists interpret the same evidence as the smoking gun showing that it did.
Tom Curtis @60
I agree with your last statement but just to clarify your last statement:
The study makes the point that 50% of the living microplankton disappeared AT THE ONSET of Phase 2 of the Deccan eruptions. Each Phase has four lava mega-flows. Within Phase 2 the magnitude of the four mega-flows increases substantially with time. Therefore, it is reasonable to assume that the Deccan Traps volcanism was not responsible for the extinction.
ranyl @53 - You asked me: "Watchdog, as howardlee's research is extensive and the evidence convinving, what is it about CO2 being the primary murder weapon that makes you feel that this possibility is in error?"
Great Question
All published science research connected with the K/T extinction have also been "extensive with convincing evidences". And as howardlee notes, "The case is probably not closed".
Currently, the answer to the overall question is akin to a jig-saw puzzle; all of whose pieces have neither been clearly identified as yet; nor, therefore, can presently be assembled into a finalized overall picture.
•
Frontnotes concerning the deleterious effects of asteroidal impacts and volcanic particulate and aerosol emissions upon biotic life..
V. Rough Quantification of Chicxulub's Effects upon North America:
Chicxulub's energy is equivalent to 100,000,000 - 1MT HBombs
One 1MT HBomb creates a crater 0.2 miles in diameter and 0.04 miles deep.
It's energy converts to: shockblast, thermal, seismic waves and ejecta debris
Within a circle 3.4 miles in diameter c.98% of life is killed.
Serious damage extends out to a circle c. 10 miles in diameter.
Moderate damage occurs out to a circle c. 20 miles in diameter.
•
Chicxulub's energy of c.10^8 1MT HBombs - created a crater variously estimated to be c. 100 miles in diameter and c. 12 miles in depth.
Its arrival angle is estimated to be 20° to 30° from the horizontal with a general directional heading toward the remainder of North America.
“These asymmetric signatures suggest a trajectory for the Chicxulub bolide from the southeast to the northwest at a 20°–30° angle from the horizontal. As a result, biotic extinctions may have been most severe and catastrophic in the Northern Hemisphere.” [url]http://geology.geoscienceworld.org/content/24/11/963.abstract[/url]
•
Asteroidal Craters and Antipodal Locations:
In addition to Chicxulub (not necessarily connected with Deccan Traps), evidences exist for 2 or more major asteroidal impacts occurring c. 65MYA.
1. Antipodal location of the Deccan Traps is at the Eastern Pacific, whose seafloor evidences a major asteroidal impact.
2. A proposed crater location - 2.5 times the diameter of Chicxulub - lies East and South of Mumbai, India
[url]http://www.dinodatabase.com/dinothry.asp[/url]
[url]https://gsa.confex.com/gsa/2003AM/finalprogram/abstract_58126.htm[/img]
Comparative Volcanic Eruption Effects upon Global Temperature
On June 15, 1991, Mt. Pinatubo erupted, spewing Ash Dust, Smoke and 30 Million Tons of Sulphur Dioxide into the stratosphere. It's ash and aerosols plume was 250 miles wide, reaching an altitude of 34km.
The SO2 formed into sulphuric acid which depleted the Ozone Layer.
From 1991 to 1993, average global temps declined by 0.5°C.
In 1992 the USA experienced its coldest summer in 77 yrs.
A combination of ash particulates, smoke, and aerosol droplets of H2SO4 (see: noted historical “darkening of the skies” events) into the stratosphere lowers Solar Radiation arriving to Earth, thus, historical Lowering of Global Temperatures and ensuing widespread impact upon the biota.
Size Comparison of Historical Ejecta Events
Volume of Ejecta of 1991AD Pinatubo has been estimated at 2 cubic miles
Ejecta from 1883AD Krakatoa was Twice that of Pinatubo.
1815AD Tambora was 10 times larger than Krakatoa.
10,000BCE Toba Ejecta was 2,800 cubic km: 100X larger than Tambora, and coincided with the onset of the last glaciation period. .. Greenland Ice Core data evidences a 1000-year lowering of Temps in Toba's aftermath.
Chicxulub's Crater Volume is c. 28,000 km3 (c.10 times Toba's)
The volume of the basalt lava of Deccan Flats is c. 512,000 km3,
which is 500,000 times as large as that from Mt. St. Helen’s 1km3.
Add in possibilities of theorized additional large asteroidal impacts of 65MYA?
CONCLUSION
Historically and Evidentially, Massive Asteroidal and Massive Volcanic Events can not be deemed as mere “suspects". Taken fully and solely by themselves, the Effects of these Events which are dulely noted above - when taken alone by themselves - are of sufficient intensities to be causal to massive extinctions of life forms.
•••
ranyl — What is it about the colorless gas CO2 that leads you to think that CO2 is the prime suspect in the deaths of dinosaurs?
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Well Watchdog I refer to Howardlee article and references within for CO2 mechanisms and James Mason articles. (http://www.skepticalscience.com/pollution-part-2.html)
However not sure why you feel it necessary to point out CO2 is colourless, so is sarin!
And the publishers pointing out CO2 role are very aware of the effects of eruptions and bolides (although the previaling opinion now is that the global climate effects are more like 5-20years not the 1000 years as you suggest.
e.g. http://www.newscientist.com/article/dn23458-supervolcano-eruptions-may-not-be-so-deadly-after-all.html#.VRAVi2ezWdI
Therefore as I have no problems with accepting all the effects from a volcanic eruption of bollide impact cause major issues, just no mass extinctions, unless a CO2 impulse part of the picture.
Again what is about CO2 the makes you feel it is not involved as a pivotal player?
There must be something for all the scientific evidence and expert opinion is, that a large CO2 impulse can easily cause major prolonged global ecosystem disturbance that can reach the scale of a mass extinction, yet you don't, therefore just wondering how come that is?
ranyl, My "1000 yr Global Cooling period during the last glaciation period",
is also supported by Greenland Ice Core Data.
The following graph is based upon GreenLand Ice Core Data.
NOTE: Multiple significant cyclical Cooling & Warming Temperature periods from Today on back to 17kya, including extreme Cooling & Warming Climate Change from 10kya on back which occurred during the last glaciation.
My focus has obviously been upon obvious negative effects of extreme Global Cooling upon the Biota, of which one known cause is the Atmospheric Blockage of Solar Radiation due to e.g, Volcanic Emissions.
ranyl - Can CO2 - which is said to be the cause of Global Warming - also be the cause of Global Cooling?
The Greenland cited data is only indicative of regional trends over the period you indicate. You need to support your contentions with a global reconstruction.
Daniel @ 65..
Did CO2 cause Earth's cyclical periods of catastrophic Global Cooling, and, the following Warming periods?
You said, "Regional trends". That is "indistinct".
Can you please define And quantify what you meant by "regional"?
During the last period of glaciation, Earth experienced major advances in global (Southern and Northern Hemispheres) glaciation as the result of the Global Cooling leading to a 400' decline in Oceans levels which in turn translates to a Volume of millions of cubic miles of ICE. I repeat that as a means of focussing upon the quantification of the total ICE; whose extent in both hemispheres is shown in a map posted below.
The area of of the ICE CAPS in Both Hemispheres during that recent time period of Global Cooling are not the total areas of both total and major disruptions of the Biota. Disruptions extended well beyond the actual edges of the massive glaciers.
Counter-Intuitively to some, Frigid Temps along with Massive Glaciation - results in a sharp decline of rainfall - even the extent of causing desertification; all of which in turn results in failure in vegetation and food supply. In other words: a catastrophic impact upon the biotic eco-system.
Global extent of ICE glaciation of 20kya
Above - Maximum Glaciation -— 20kya
•••
The 3 graphs below drawn from Antarctic Ice Core Data support the above graph of Greenland Ice Core Temps. The first two graphs of Temperatures show cyclical periods of Global Cooling and Warming which correspond to the third graph of the fluctuatihng ICE Volumes over the past 450,000 years.
Again I ask: Is CO2 the Cause of Global Cooling?
_
[JH] Again, please document the sources of the graphics and data that you include in your posts.
[RH] Adjusted image width.
Watchdog - CO2 is a warming, not cooling, influence. Glacial and interglacial temperatures track with Milankovitch cycle forcings and positive feedbacks including CO2 (lagging the forcings by hundreds of years) and water vapor, plus longer term vegetation and ice albedo changes.
And now we're increasing CO2 on our own, with our increasing greenhouse gases acting as a direct warming forcing - with the predicted warming occurring as expected.
Where do you get 'cooling' from CO2? Reference(s), please.
Watchdog, yes decreasing atmospheric CO2 levels cause cooling. If you look at atmospheric CO2 graphs they line up very well with the temperature and (inverted) ice volume graphs you showed.
I'm familiar with Milankovitch cycles which correlate with, and are proposed to be, causal to extreme abrupt Climate Change cycles. During most of its cycle, temperatures are significantly below our current average.
Global fridid temps occurring, e.g., within the K/T extinction period, were directly caused by Bolidal impact(s) and/or extensive Deccan Traps Volcanism of that time period.
I wanted to establish an agreement that CO2 does not cause abrupt Cooling.
I also look for agreement that extensive periods of Cooling, such as that of our Last Glaciation period which in turn lowered Ocean levels by 400', as well as those longer periods evidenced in Antarctic Ice Core Data, would self-evidently be deadly to _large areas_ of life-forms.
This Vostok data graph shows a correlation between Temperature and CO2.
Source of following graph, labeled:
"Vostok Ice Cores - Temperature and CO2" - is www.climatedata.info
Watchdog wrote: "I wanted to establish an agreement that CO2 does not cause abrupt Cooling."
That is often, but not always, true. Most natural processes (e.g. rock weathering) draw down the atmospheric CO2 level slowly over the course of thousands of years. However, there are exceptions like the Older and Younger Dryas periods... when an explosion of nitrogen fixing plants led to rapid CO2 declines... and corresponding temperature drops.
CBDunderson wrote: "However, there are exceptions like the Older and Younger Dryas periods... when an explosion of nitrogen fixing plants led to rapid CO2 declines... and corresponding temperature drops."
That's a competing hypothesis - concurrent with at least a half-dozen others.
The jury is far from out on that being "settled science".
From Wiki-Younger Dryas - There are prevailing theories of its Cause including several hypotheses replete with evidences; including those connecting the Dryas stadials with both Bolide Impact and Volcanism.
•••
Effects of the Global Cooling period of the Younger Dryas affecting both the Northern and Southern Hemispheres.
Replacement of forest in Scandinavia with glacial tundra (which is the habitat of the plant Dryas octopetala)
Glaciation or increased snow in mountain ranges around the world
Formation of solifluction layers and loess deposits in Northern Europe
More dust in the atmosphere, originating from deserts in Asia
Drought in the Levant, perhaps motivating the Natufian culture to develop agriculture
The Huelmo/Mascardi Cold Reversal in the Southern Hemisphere ended at the same time
Decline of the Clovis Culture and extinction of animal species in North America
•••
References to Hypothesized Causes, Extend and Effects of the Younger Dryas
en.wikipedia.org/wiki/Younger_Dryas
Any time you are talking paleo-anything then "settled science" isnt usually used. Multiple hypothesis are common because we lack the data to constrain them. That is very different to evaluation of climate theory, especially in terms of modern climate where data is so much better.
However, when talking about Milankovich, I take issue with "Milankovitch cycles which correlate with, and are proposed to be, causal to extreme abrupt Climate Change cycles" In terms of global temperature change (not temperate change at the poles), the rate of change is only around 0.15 degrees per century at most. Compare that to 20th century rate of change.
The younger dryas (and Bond/Heinrich events, not milankovich forced) have rates of change which appear to much higher if somewhat localized. Fortunately, it appears that these phenomena only occur as ice age ends.
If this discussion if going to continue on Pleistocene climates, then I suggest it be moved to this thread.
My Point re: 'not settled science' and 'multiple hypotheses' is: ..
CBDunderson's statement, "an explosion of nitrogen fixing plants led to rapid CO2 declines", posited as: the CO2 fact underlying Global Cooling;
- is in fact, not fact.
Since we're discussing events from c.65 MYA - on up to Today,
including several posited Causes of "Mass Extinction (of Dinosaurs",
such as: Bolides, Volcanism, CO2, Global Warming & Global Cooling,
we can't exclude more complete knowledge of recent extinction events
which correlate in time with Global Cooling - replete of evidences of:
Bolide impact and Volcanism..
"Climate Change" encompasses several variable observable parameters.
E.G. - Life, Temperature, Ocean Levels are major factors. We all know that Historical Global Temperatures include periods of constantly fluctuating Cooling and Warming. Do any here deny that?
I've obviously been strongly suggesting - replete with a plethora of varying historical events and evidences - that the extremes of the Global Cooling half of Climate Change - have been very causal to extinctions of Life - and can be argued as being the ultimate cause of the demise of many large hungry non-warm-blooded creatures who directly and indirectly depended upon warm lush environments.
Watchdog,
I'm sure there are good explanations on this website for all the questions you are asking.
The depth of the evidence that CO2 is the primary determinant of the earth's long term temperature is overwhelming and has been very highly scrutinized.
Therefore again what is it about CO2 that inspires you to counter the well presented and explained scientific evidence about CO2's role in mass extinctions?
Watchdog
I would suggest that cooling events have actually been a much smaller cause of extinctions than warming events.
Looking over the period since the start of the Cambrian, there is only one event where a major extinction occurred that apears to be linked to rapid cooling - that is the end-Ordovician event. And that appears to be linked to a geologically rapid draw down in CO2 levels due to some unusual fgeology and possibly the evolution of vascular plants.
We have to go back further than that, to when life on Earth wasn't much more than bacteria to find examples of extreme cooling events - the so-called Snowball Earth Events during the Cryogenian and the earlier Huronian Snowball.
In contrast from the Cambrian onwards major extinctions appear substantially to be linked to major CO2 driven warming and major disruptions to ocean circulation and chemistry.
The glacial cycles during the more recent Ice Age period over the last 800,000 year or so have not been extreme enough or rapid enough to trigger major extinctions. Life moved and adapted, may have declined in numbers, but wasn't devastated.
Watchdog - I agree Younger Dryas is not settled science. However, with due respect to CBDunderson, I dont think there are scientists who are claiming it is settled science. I will admit to a certain wariness about strawman claims about what is "settled" and "unsettled".
Watchbog, ok... sure, there is debate about all of this. However, a claim that CO2 changes cannot cause abrupt cooling is simply false. Even a claim that CO2 changes have not caused abrupt cooling is not "settled science", and indeed would be disputed by many paleoclimate scientists.
Ergo, your statement that, "...CO2 does not cause abrupt Cooling", falls somewhere between unsubstantiated and certainly false.
CBDunderson - I’ve more to say, but first:
My “Is CO2 the Cause of Global Cooling? ” is intended to be construed as a much better phrased: “Does a Rise in CO2 Cause Global Cooling?”
Perhaps KR@67 intended the same understanding when he responded:
“CO2 is a warming, not cooling, influence”
Solar Radiation is the Primary Cause of Temps in the Solar System
What can Cause Abrupt Major Cooling?
IF - by whatever mechanisms, including Milankovitch cycles, Solar Radiation were reduced to (for the sake of discussion) Zero, that would respresent the maximum possible Solar-Cooling effect upon the entire Solar System: Atmosphere’s or Not.
What mechanisms can reduce Solar Radiation received by Earth?
One known occurring mechanism of blockage of Solar Radiation is: smoke, smog, ash, aerosols and other particulates - caused by, e.g., Volcanic Emissions.
How fast could or would Temps fall or rise?
The GreenLand and Antarctic ICE Core graphs show
-> very “rapid” decreases and increases in temperatures.
The Greenland Ice Core Data directly correlates Temperatures with rapid advances and recessions of Glaciations (Solid H2O) - as would be expected.
These events also directly correlate with rapid Ocean Water Levels
What is “rapid”?
We’ve strong evidences from:
1 Graphs — 2 Ocean Levels Fluctuations and — 3 Published papers (plural) — that Abrupt Climate Temperature Changes have occurred in periods of time - far shorter than as someone(s) suggested, 1000 years. I’ve read “in as little as 10 years. Also, “over a few decades”
This Frontnote to the following online paper mentions:
“This represents an earlier version of our text. Some changes have been made since we stopped modifying this web version: e.g. we have added a discussion of the role of volcanic aerosols in sudden climate changes...evidence suggests the rapid cooling at the end of the Eemian interglacial was due to a big explosive volcanic event. Other 'volcanic' cooling events occurred during the Holocene.”
ref: Sudden climate transitions during the Quaternary
http://www.esd.ornl.gov/projects/qen/transit.html
[JH] Link activated.
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Watchdog,
Thank you for providing a citation for your data so it can be checked.
Looking at your citation I noticed this at the start: "Last modified 14th March 1998". The format of this cite matches your previous posts, so I presume this is what you have been citing all along.
It strikes me that the references in the OP from 2014 are likely to reflect current scientific thought better than your reference from 1998. Perhaps you can cite more recent data to support your claims.
I am not expert on this subject. If I see one person citing references from 2014 and another citing references from 1998 I generally think the more recent references support the argument better. In this case, the OP claims that recent data has contributed to a change in scientific thought. Your old posts cannot help us evaluate recent changes in thought.
Watchdog - The article you linked to (published version here) is from 1999 - I dare say we've learned a bit in the last 16 years, in particular details about CO2 feedbacks and lags in glacial/interglacial temperature changes.
And yes, that was my understanding of your post - that you are claiming rising CO2 causes global cooling. If that's indeed your claim, I would consider it quite wrong, contradicted by basically all of known spectroscopy.
If it's not your claim, I would ask that you be a bit more clear about what you are saying. It's been quite difficult to identify what you are arguing.
Also note that while Younger dryas is indeed associated with rapid cooling, the area of rapid cooling is geographically restricted (and absolutely not caused by Milankovich cycles - this can be catagorically ruled out). Volcanic cooling does not persist very long after an event because aerosols are rapidly removed from the atmosphere. Extra CO2 emitted however is very persistant.
I should also point out that the hypothesis that rapid climate change was responsible megafauna extinction is also far from settled science.
"The evidence points to a distinct warming of the southern mid-latitude atmosphere during the Younger Dryas and a close coupling between New Zealand’s cryosphere and southern high-latitude climate. These findings support the hypothesis that extensive winter sea ice and curtailed meridional
ocean overturning in the North Atlantic led to a strong interhemispheric thermal gradient8 during late-glacial times, in turn leading to increased upwelling and CO2 release from the Southern Ocean9, thereby triggering Southern Hemisphere warming during the northern Younger Dryas."
Kaplan M.R. et al (2010), Glacier retreat in New Zealand during the Younger
Dryas stadial, NATURE| Vol 467|9 September 2010
http://geology.gsapubs.org/content/early/2013/10/30/G34867.1.abstract
Those guys feel it was the thermohaline stopping that cuased the cooling as well...in 2013 with improved proxies etc...and the evidence for an impact causing it is slimer as each new study is published, check the abstracts here,
LINK
YD was most likely due a fresh water lake burst in the North Atlantic, and therefore was akin to Hienrich event, causing SH warming and another outgasing burst in CO2 from the southern ocean which firstly increased the temperature of SH then globally.
http://www.nature.com/ncomms/2015/150106/ncomms6916/full/ncomms6916.html
The rapid warming in Greenland when the meridional circulation turned on again was10C in decades (similair to the cooling rate), and a tad worrying for those arround the North Atlantic really as it also induced quite marked changes in weather patterns and ecosystem dispersions across Europe, Asian (Monsoons), and North America, however it was not a global cooling event for the SH warmed. Although these abrupt changes in the NH climate, combined with the hand of man, does seems most likely scenario for the loss of the Sabre tooths etc.
As for the science being settled about mass extinction. Well it does seem very suggestive that rapid global warming, induced ocean stratification and acidfication do have marked ecosystem impacts (that aspect is settled), however no one says these are the only factors in the major mass extinctions (just an essential one, it seems) for each mass extinction seems to also to have been associated with other climatic disturbances, ozone depletions and an input into the global ecosystem of an array of toxic substances (to release such large amounts of CO2 melting coal filled rock desposits is often part of the volcanic activity, so very toxic stuff being released as you can imagine).
However this is of no comfort for humanity has already induced an extinction rate in keeping with a mass extinction levels, at least, with many estimates that rates are far greater, with current rates being between 100-1000 times the baseline fossil levels.
Therefore we have already induced a totally unprecendented rate of global warming (I stress globally for those still in regional camps), which is at the very least only half complete having had already introduced a vast arrray of toxins, waste and poisons, disturbed the ozone layer, cleared vast areas of land of natural ecosystems, etc, etc etc,.....
Therefore we have a very sick global ecosystem and the additional blow of the combination of CO2 warming and ocean acidification that has a long rap sheet for mass extinction involvement has only just begun in earnest really.
Last time CO2 was 400ppm consistently at 400-450ppm (COe2 ~465ppm) was the Miocene, totally different climatic world back then.
[RH] Shortened link.
John Mason:
More grist for the mill...
Fact or Fiction?: Dark Matter Killed the Dinosaurs by Lee Billings, Scientific American, Mar 25, 2015
KR@80 - My Apology for my sometimes opaque grammar.
No.. I am not saying CO2 causes Cooling
Nor do I agree with this following:
"Long declines in CO2 causes Cooling."
I am saying that Extended Periods of Extreme Cold
are most definitely injurious to the Biota.
I am also saying that Blockages of Solar Radiation from e.g., Volcanism,
will directly cause Lowering of Temps.
With that above statement said,
I'm not saying that COLD is the only cause of injury to the Biota.
Nor am I saying: Volcanism is the only cause of Lowered Solar Radiation.
I am saying: Volcanism indeed reduces Solar Radiation / Temperature.
Which brings me to CO2.
CO2 certainly correlates with Temps
- as does Black Carbon aka Soot,
- as does other Climatic parameters.
Refer again to the Vostok Graph of Temp & CO2 @69
and take close note of their correlation...
CO2 is presented as being the cause of Global Warming.
Which brings me to Global Warming
Earth's Temperature is oft-presented as being too Warm for the Biota.
I've several questions - and I'll begin with this one:
Has Warm Climate ever been the Cause of mass extinctions?
Watchdog,
"Earth's Temperature is oft-presented as being too Warm for the Biota."
Citation for the above please.
Mass extinctions are associated with rapid change - change too fast for adaptation. As other commentators have pointed out, change from cool to warm is indeed implicated in previous mass extinctions. Extinctions from change to cold (eg YD) are more controversial. The objection to the YD for megafauna extinction has been that it doesnt fit well with species that disappeared compared to those that survived.
CO2 can be released very rapidly but it is harder to reduce it quickly so it is natural to look at its effects. Volcanism warms in long run - it only cools in very short term.
We dont blame climate change on CO2 because of correlation but from basic physics. If the sun suddenly put out an extra energy to tune 4W/m2 received at surface, then noone would be even slightly surprized at temperature change. Why the surprize when you get 4W/m2 from extra CO2 and a frantic search for alternative explanations?
"CO2 is presented as being the cause of Global Warming."
Umm... No It's Not!
It is 'presented' as the most significant (but not only) driver of warming in our current context.
Musings:
The minor Cold Climate "blip" aka the Maunder Minimum, caused widespread Famine, and Forced Migrations of Peoples - including, forcing Vikings to abandon their colonies in the Land which became labeled "Green" due to the immediately prior Global Warming blip oft-referred to as, The Medieval Warming Anomaly.
This Website discusses the Medieval Warming Period and its Causes.
How does the Medieval Warm Period compare to current global temperatures?
" It has now become clear to scientists that the Medieval Warm Period occurred during a time which had higher than average solar radiation and less volcanic activity (both resulting in warming). "
Yes. Papers exist supporting its contention that: "warming would occur due to less volcanic activity resulting in higher solar radiation" - and I concur.
The article also presents a graph showing Temps surpassing the higher Temps of the MWP at some point in the 20th century due to AGW..
ref: www.skepticalscience.com/medieval-warm-period.htm
_
So that I'm clear:
I've never said: "Global Warming does not exist."
Neither have I denied, "Periods of Global Cooling have existed".
Nor have I denied, "Climate Change occurs with or without Man's input."
Please Show Me Temp Data - where Warmth Itself (which is "presented" as being predominately caused by its "predominate driver" - CO2, Yes? ) is the Climate- Parameter cause of Mass Extinctions?
Watchkog, one of the primary suspected causes of "The Great Dying" (i.e. the P-T extinction event) is rapid CO2 increase/global warming. You will no doubt revert to, 'there are other theories!' again... but that is true about all of the 'evidence' you have been citing as well. Evidence about past events is often inconclusive.
There is no question that rapid changes in atmospheric CO2 levels can cause corresponding rapid changes in global temperatures OR that such rapid temperature changes can cause extinctions. Further, there is very little question that such changes have occured in the past... only debate over which precise events were due to these vs other kinds of changes.
One way to minimize uncertainty is to look at regional shifts in the more recent past... as you do with the 'Little Ice Age'. Taking the same approach for 'recent' warm events we find the collapse of the Chaco culture ~900 years ago, the Maya ~1200 year ago, the Khmer ~600 years ago, California the past three years, et cetera. Maybe next you'll say, 'those events were not all caused by rising CO2'... but that's irrelevant. The cold events you cite weren't all caused by the same factor either. You've conceded that "CO2 certainly correlates with Temps"... leaving your only apparent argument, 'warming does not cause extinction'... but there is overwhelming evidence to the contrary.
CBD -
"CO2 certainly correlates with Temps." — I say, "Yes, it does."
So do: SO2, Sky Darkenings, Volcanic Emissions, Crop Failures, Etc,
- correlate with Global Temps.
Without anyone reverting to "CO2 levels" and only "CO2 levels",
I still await science data or data-generated graphs
which quantify Temps (not CO2 levels) versus Dates,
which in turn show correlation with historical Mass Extinctions!
This topic is "So what did-in the dinosaurs? A murder mystery…"
The Moderator @56 stated that the discussion was far offtopic, which I disagree with, yet does not seem to think it is true here. Why not?
[PS] I agree it is far offtopic and latest post from watchdog has been deleted.
Apology for unintended duplicate post above.
In my quest of seeking confirmation on historical WARMING Data, I re-examined the Graph derived from Vostok, Antarctica Ice Core Data;
which examined both Temperature levels, And, CO2 levels - vs TimeBP.
The quantifications of the Climate Parameters (Temp levels and CO2 levels)
are Not based on each other: rather, their levels are directly derived independently from each other - from the data measured in the ICE core.
The cause of the obvious repeating and abrupt up and down cycles shown in the Vostok Ice Core are attributed to - as others here have advised me - Milankovitch Cycles - which in turn are all unconnected with, e.g., CO2.
Taking a re-look at the Vostok Ice Core, what jumped out to me in looking at the two graphs (Temp and CO2) is that a Rise in Temps drives the Rise in CO2 - with the lag time of CO2 being somewhere in the vicinity of 800 years!
One might quickly argue:
"Then how do you explain the current parallel-in-time correlation
of Rise in Temps - with Rise in CO2?"
My response:
"IF as the Vostok graph clearly shows - Temps drive CO2 - and not the other way around, THEN, the current rises in CO2 would have to have been driven by rises in Temps 800 years ago.
The only c.800 TimeBP rise in Temperature Anomaly that I can find which would correspond to the recent CO2 rise - is the Medieval Warm Period - previously mentioned by this website."
Note: The CO2 ppm concentration is indicated by the pink graph
[PS] This is now completely offtopic. Take it here but read the article first before regurgitating a myth.
I disagree with "a near-global rain of red-hot ejecta" in the posting. I'd like to see the physics in the paper about that. I'm assuming that "ejecta" means lava, if it means ash or gas then it really should say that. I scale Earth 5,000,000:1 in my ponderings because it's a handy 100" dia. that fits my kitchen and bashes only a modest hole to 4" about drywall ceiling. Ocean lithosphere 0-3/8" thick around that liquid interior rock an iron core. Land plates to 2-1/4" thick but almost all <3/4" thick. Ocean water 1/20" thick. Troposphere 1/8" thick at equator.
Chicxulub rock 1/13" dia. (a Tapioca grain) hits my Earth ball that's filling half my kitchen. How on Earth (I mean literally) does that cause a "rain of red-hot ejecta" tapioca bits to land way around the other side unless they fly our to my fridge (which is near the Moon) and bounce back ? I think this whole raining of this and that has become wildly exaggerated beyond the vaporous cloud of ash & nasty gases thaht doubtless drift in a very leasurely fashion around my kitchen Earth ball towards my sink.
grindupBaker @92, the "ejecta" consists of the rock ejected from the crater by the impact. Viewed logically, and given the size of the impact, at least some of the ejecta must have escaped to space, ie, achieve orbital velocity. That being the case, then some portion of the ejecta must have acheived a just suborbital velocity with the result that it would have been deposited very distant from the crator, and hence logically, ejecta should be found world wide.
In fact, geologically, the Cretaceous-Tertiary (K-T) boundary is characterized an iridium enriched layer containing micro-tektites:
If I remember correctly, this K-T layer was first found in Italy, but has been found world wide:
I had not thought about the red-hot aspect of the ejecta before. Certainly while following a sub-orbital trajectory the micro-tektites would not have significantly cooled (radiative cooling being fairly inefficient), but I had mostly assumed they would be quenched by the atmosphere. Turns out that is not so. This paper, for example, suggests previous estimates of the associated heat pulse to have been overstated, the pulse only being "... >5 kW/m2 for a few minutes" which "... may have been sufficient to ignite localized fires and kill fauna lacking temporary shelter". So red hot ejecta, and very unpleasant is a best case. I do not know where the consensus on that debate has settled (if it has formed at all).
I was a doctoral student in Ecology and Evolution when the bolide-impact theory for the K-P extinction event was gaining currency. Since then I'd come to consider the matter "settled", but Howard Lee's argument is convincing, on a preponderance of the evidence he presents.
Now, on the "red-hot ejecta" question:
The photo in the OP, credited to Gerta Keller, is from a site in NE Mexico, several hundred miles from the Chicxulub site. It shows "spherules bent round each other showing they were still hot and soft when they settled."
One imagines that where those spherules landed, falling thickly enough to bend round each other, ambient temperatures might well rise to levels lethal to most or all above-ground organisms.
I'm leaning towards the climate change theory rather than the asteroid impact. Dinosaurs have been found in many different continents and not a single one survived. The planet needed to be literally destroyed by meteors in order to have such a brutal effect and extinguish an entire species spread around the territory1!
Correlation is not causation. The problem with volcanic activity theory is that heat and CO2 are known to facilitate life, not destroy it. To harm plants, CO2 has to be above 7,000-10,000 ppm, which is way above what the volcanic acitivty would produce. While some organisms may do better than others, improved high CO2 and high temperatures is going to produce better living conditions for plants and is hardly a condition for mass extinction. It makes no sense.
From a biochemistry standpoint, it makes more sense that a lack of CO2 killed the dinosaurs. The carbon fixing enzyme RuBisco doesn't work well below 800-1000 ppm. The evolution of coccolithophores at the start of the crestaceous period must have cause CO2 levels to drop throughout that period. It's called the crestaceous period because its a massive chalk layer and chalk is calcium carbonate (i.e., sequestered carbon dioxide). The loss of CO2 should have had a catestrophic effect on the carbon fixing enzme Rubisco, which loses a lot of its activity below 600-800 ppm CO2. RuBisco is the universal enzyme for carbon fixation and sustain almost all life on earth. To make matters worse, flowering plants evolved during crestaceous. These plants dominate earth today. They flower in May when CO2 is at its peak. They have open stomata which allows them to hog all the CO2. They then die and come back the next year. Their ability to selectively take up CO2 in May when CO2 is high would decrease the CO2 concentration even further, eventually dropping atmospheric CO2 below the concentration needed for Rubisco to fix sufficient carbon in the then predominantly C3 pathway. Any plants that couldn't bloom and come back the next year would have died off along with organisms that ate those plants. This is true for ocean life and terrestrial life (e.g., algea blooms in the ocean).
It is hard to explain how this situation wouldn't have happened. We know the activity rates of RuBisco and that almost all life on earth is sustained by carbon fixed through Rubisco. We know the earth went from 4000 ppm CO2 to 180 ppm CO2. Even if you disagree about when it happened, logically we can agree that it did happen. As a biochemist, it seems all but impossible to think that crossing the activity threshold of RuBisco didn't have a catastrophic effect on life. How does the earth sustain life if THE carbon fixation enzyme isn't working? Over time, volcanic activity and weathering rocks would restore the CO2 and the earth would thrive. After enough cycles of mass extinctions, plants evolved mechanisms to cope with low CO2 (e.g., seeds, flowering, and the C4 pathway). It is almost certain that most mass extinctions were caused from plants fighting over CO2 and just like all populations, when they consume all of their food (CO2 is plant food) there is a catastrophic collapse in the population, along with everything that lives off it.
It seems really obvious to me that low CO2 (i.e., lack of food) killed the dinosaurs. How is it that nobody has proposed this or studied it? But yet they believe an astroid from space did it. LOL. The lack of sophistication in our species is shocking.
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[RH] Being there was little of substance in this comment it was an easy decision to snip. If you genuinely wish to contribute to discussions on Skeptical Science you're going to have to substantiate your statements with actual scientific references. If you continue with comments like this one we will have no choice but to rescind posting privileges.
Question for a geologist: Is it possible that the irridium layer was formed from volcanism? It seems to me that the most likely way irridium would cover the earth is if a commet hit the earth billions of years ago and was incorporated into the earth's crust and then melted and spewed out through volcanism that spewed the irridum into the atmosphere. Has anyone proposed this? Is there anything in the geological record that would distinguish between irridium upon impact and irridium through volcanism?
[RH] I would suggest you use google scholar to do a little bit of research so that you can form intelligent questions. After that, if you have a question that pertains specifically to a topic on SkS, post it there.
Andrew1776, paleologically speaking, it is difficult to determine which of your alternatives is the correct one.
From a purely teleological analysis, it seems appropriate that volcanism would spew iridium, but commet impact would disperse irridium.
Andrew, you have frequently mentioned the crestaceous period — but not defined when it occurred. The very name suggests it was the period when the cockatoo evolved — and when there was a high level of sulphur in the air?
Or were you meaning the cretinaceous period? — being the new (post-Holocene) period, when the climate-science denier evolved.
[PS] Attacks on grammar and spelling are not conducive to a constructive discussion and you run perilously close to ad hominem and inflammatory tone.
A constructive response would answer the question with appropriate references to back the answer.
My apologies to moderators.
My post was a response to two posts [one now snipped] where the "author" was being obnoxiously disingenuous and "gish-gallopingly" time-wasting.
Humorous quips seemed the only worthy response to them — and his persistent and frequent spelling errors counted as "icing on the cack".
Why did you snip Q96? The quesiton of whether falling CO2 concentrations could cause mass extinction is a very legitimate scientific quesiton. The scientific literature shows CO2 dropping from 2000ppm to 180ppm betwee K and Pg (see phanerozoic carbon dioxide graph on wikipedia ). My question relates to how this drop in CO2 affected plant life on earth?
The most fundamental enzymatic reaction on earth for sustaining life is the fixation of carbon dioxide by the enzyme RuBisCO. (see wikipedia entry for RuBisCO). RuBisCO's activity is very slow and depends on the concentration of CO2. Indeed, RuBisCO is rate limiting for photosynethesis on earth. It has single digit turnover per second as compared to most enzymes which are in the 1000s/second (see wikipedia). It also makes up 50% of the soluble proteins in leaves (Id.). And despite it's slow activity, billions of years of evolution have failed to produce anthing better. Instead, plants have evolved mechanisms to deal with the low activity rate (e.g., C4 pathway). Since RuBisCO is rate limiting to life on earth and CO2 concentration determines the rate of RuBisCO, competition amongst plants for CO2 must be a driver of evolution, especially in a low CO2 environment.
My hypothesis is that flowering plants were more fit for low CO2 and outcompeted plants that relied on high CO2. The plants that thrived in high CO2 fixed carbon faster and could support large animals like the dinosaurs. The dinosaurs could not survive on the flowering plants and died off. A similar event occured in the ocean. Plankton that was more fit for lower CO2 (i.e., higher ocean pH and less availability of CO2) out competed existing plankton species.
Also note that the total caloric output of the earth's plants should be lower with lower CO2 since CO2 fixation is the rate limiting step. Lower CO2 concentrations therefore create a scarcity of food, which would increase competition amongst populations and should drive evolution (less food means more competition for the food and the fittest survive).
My hypothesis is not "gish-gallpingly time-wasting". Rather it is a hypothesis based on the scientific principle of evolution (e.g., flowering plants out competed their contemporaneous plants by being more fit to survive lower CO2 concentrations). What isn't science is the use of correlation to prove causation. The correlation of an impact event or massive volcanic activity is not proof that either of these things did or could cause mass extinction. These are just theories and the science supporting them are for the most part theories. In contrast, evolution by competition has been proven through scientific observation. The activity rates of RuBisCO are measured using repeatable biochemical assays. The rate limiting effects of low CO2 on RuBisCO are testable and repeatable. The ubiquety and utilization of RuBisCO by plants has been measured. In short, my hypothesis that low CO2 killed the dinosaurs, is a legit hypothesis because it is based on scientific data, not correlations.
If I were to speculate, I'd say low CO2 was probably the cause of the majority of mass extinctions on earth. CO2 is a gas and therefore equilabrates throughout the whole earth, including the oceans and the air on land. It sustains all life on earth. Its fixation is for the most part limited by a single enzyme, RuBisCO. And CO2's concentration has fluxuated by over an order of magnitude (4000-180ppm) during the earth's history (or at least we think it has).
A drop in CO2 from 4000 ppm to 180 ppm would be more catestrophic than a 6 degree change in temperature. Almost all ecosystems on earth experience temperature variations greater than 6 degrees every year (due to rotation of the earth about itself and the sun). Consequently, organisms adapted to relatively large temperature swings long ago. CO2 in contrast, does not vary much from year to year. Cycles of 1000's of ppm allegedly happen with a frequency on the order of millions of years. If so, it would take billions of years to evolve the mechanisms to deal with low CO2. Consequently, we would expect the drop in CO2 to be catestrophic because the plants would not be adapted to it. Note that rising CO2 levels would not be catastrophic because most plants would not need to adapt to it (because they evolved from plants that were adapted to it). Put another way, we expect a catastrophe when we starve a plant of CO2 when the plant has never experienced starving conditions, but giving a plant excess CO2 when it evolved from plants that lived in a high CO2 environment should not produce a catastrophic event, or at least not to the same degree.
I am not suggesting that today's rise in CO2 is a good thing. That's a different debate for a different day. Certainly some plants would do better and others wouldn't in a high CO2 environment. The purpose of this post is to propose the basis for mass extinction of the dinosaurs. The data suggests low CO2 may have been the culprit.
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I'm looking for a scientific based response. No need for ad-hominems.
[RH] Andrew... Your erratic banter has more than run its course.