Naked Science Forum
On the Lighter Side => New Theories => Topic started by: Amincd on 24/05/2011 14:42:37
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I've written an amateur scientific paper putting forth the theory that it was a decrease in atmospheric oxygen that was the cause of the extinction of the dinosaurs. Let me know what you think:
http://amincd.tumblr.com/post/5690584281/oxygen-deprivation-caused-dinosaur-extinction
Oxygen Deprivation Caused Dinosaur Extinction
The Cretaceous–Tertiary extinction event, commonly known as the K-T extinction, was the mass-extinction of a large percentage of plant and animal species 65 million years ago, including all non-avian dinosaurs.
It is generally believed that the Chicxulub asteroid impact triggered the K-T extinction due to some combination of the following effects of the impact: global firestorms, infrared radiation, an intense greenhouse effect due to CO2 released by fires, and a reduction in sunlight due to dust released into the atmosphere.
I contend that the primary cause of the mass extinction of animals in the K-T extinction was oxygen deprivation caused by a reduction in atmospheric oxygen due to effects of the Chicxulub asteroid impact.
The support for this theory can be found by looking at which species survived the event, and which did not.
Marine Animals:
Most species of coral close to the surface died out, while those living in oxygen-poor areas below the photic zone survived. 1 (http://www.springerlink.com/content/u650kh4j146565q2/) Species of Echinoderms (the phylum that includes sea urchins) that lived in shallow waters suffered the highest extinction rates while a those that lived in deeper waters had higher survival rates. 2 (http://bsgf.geoscienceworld.org/cgi/content/abstract/168/1/51)
Many species of cold-blooded marine vertebrates like fish and crocodyliforms, though no large members of the crocodilian clade, survived. 3 (http://findarticles.com/p/articles/mi_qa3721/is_199703/ai_n8738406/) No species of mosasaurs or plesiosaurs, which were warm-blooded 4 (http://www.sciencemag.org/content/328/5984/1379), survived.
Terrestrial Animals:
All non-avian dinosaurs died out, while avian dinosaurs (birds) survived. Small burrowing mammals survived. 5 (http://www.ugcs.caltech.edu/~presto/cenozoic.pdf)
Terrestial Plants:
A high percentage of plant species found in North America went extinct 6 (http://www.jstor.org/pss/4096896) while those further from the asteroid impact site, in New Zealand and Antarctica, were less affected. 7 (http://bsgf.geoscienceworld.org/cgi/content/abstract/168/1/51)
For the animal species, the major factors correlating with survival seem to be:
Small size
Cold-bloodedness
Burrowing adaptations
Flight adaptations
Deep-sea adaptations
The biological advantage that all of the above are associated with is lower oxygen requirements. Smaller sized animals have lower environmental oxygen requirements than large one. 8 (http://www.arctic.uoguelph.ca/cpl/arcticnews/updates/goliath/goliath.htm) Cold-blooded animals have slower metabolisms and thus lower oxygen requirements than warm-blooded animals.
Burrowing animals are adapted to survive in low oxygen underground environments. 9 (http://www.livescience.com/5929-naked-mole-rats-survive-extreme-oxygen-deprivation.html) Birds are adapted to survive in low oxygen high altitude environments. 10 (http://icb.oxfordjournals.org/content/46/1/62.full) Deep-sea marine life is adapted to survive in low oxygen aquatic environments. 11 (http://www.interridge.org/files/interridge/Hourdez.pdf)
I contend that the decline in atmospheric O2 of the early Tertiary period which followed the Chicxulub asteroid impact, perhaps due to oxygen combustion in widespread fires or oxygen being used in the oxidation of the massive amounts of sulphur released by the impact 12 (http://books.google.com/books?id=kAup0TOL09gC&lpg=PA137&ots=225_whNvfY&dq=Chicxulub%20H2SO4%20oxygen&pg=PA137#v=onepage&q&f=false), wiped out all species not able to survive in this new low oxygen environment.
Marine animal life adapted to low oxygen deep-sea environments would have been able to ascend to shallow higher oxygen depths.
Burrowing animals could have emerged from their burrows into the more oxygen rich outer environment.
Birds could have stayed at sea level where oxygen levels are higher than high altitudes.
Cold-blooded animals, particularly small ones, could have reduced their activity to slow their metabolism and require less oxygen.
These options didn't exist for animals adapted to live in oxygen rich surface environments and, due to warm-blooded-ness and larger-size, had higher atmospheric oxygen requirements.
The effect of the K-T extinction on plant species supports this theory. If high levels of infrared radiation or reduced photosynthesis due to particles reducing the amount of sunlight reaching the surface of the earth were the cause of the mass-extinction of animals, then plants would have seen a globally uniform reduction in species numbers, as animals did, since they would have been equally affected by these effects.
Instead, plant extinctions occurred at their highest rate near the impact, where the firestorms would have been, and at their lowest rates in the southern hemisphere far from the impact.
(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2F28.media.tumblr.com%2Ftumblr_lljsh4Ls221qk0txfo1_500.jpg&hash=caeb42e6c7573b79a156b7339edf2689)
The ejecta blast created by the Chicxulub impact caused immediate destruction of animal and plant life near the impact site and reduced atmospheric oxygen levels, and the result was a globally uniform extinction of animal species poorly adapted to survive a low oxygen environment, and a more localized mass-extinction of plants that were killed by firestorms caused by the impact.
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Actually, I like this, as it probably happened. But then it may be that such events like this happened on smaller scales, like your event would be a 10 and something that happened at 50 year ago when we suddenly got smart (nobody has any theories of how that happened) and 10,000 y ago when suddenly grain and cow growing commenced. Since science doesn't have a view that 10,000 ya the oceans were sterilized, there is no recognition that the protein on the sea shore fell to slightly above zero as the mussels, clams and other air breathers were the only food to rely on. The Basques, living high in the mountains like almost everyone else for the mineralized spring water, were able to rapidly go after another air breather, the whales. I also propose that eels were already using the surface as they do now so would also be a source of protein.
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Sounds like you covered all the obvious probable causes for declines of the mentioned species with their special adaptation abilities. I think that the possibility for more impacts from the same asteroid may have widened the destruction. The volcanism, which was possibly started by the shock waves from the asteroid with emissions of deadly gasses and large volumes of lava,would have sustained the calamity for decades or much longer. Did the dense magma expand as it surfaced, increasing the radius of the Earth. Increased Angular- momentum could have slowed the days from 20hrs. to 24. The gravity could have increased also with less centrifugal force.
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Interesting Theory.
I assume you could several hits.
Asteroid -->
- Atmospheric Dust
- Loss of sunlight (hard on plant life)
- Cold (hard on both plants and animals)
- Rapid Climatic Shift. While animals can migrate quickly (especially the avians), plants migrate more slowly and may not be able to keep up with climate shifts.
This could cause a loss of both food and oxygen.
It seems to me that food, temperature, and oxygen could be equally likely culprits for many of the phenomenon. For example, Deep Ocean Temperatures likely varied much less and much slower than surface temperatures. Thus, you would expect deep ocean life to be less affected than surface life. It would be hard to differentiate the different effects during such a catastrophic event.
The response to a lack of oxygen in mammals would be an increase in the RBC count & hemoglobin. I'm wondering if there would be a way to detect similar changes in fossils. For example, I assume there is a layer of dust associated with Chicxulub. Would the fossils in the Chicxulub dust layer, or slightly above it have higher Iron content than those below it?
I'm trying to think of what would be expected in Petrified Forests or Coal Deposits dating back to that time.
Another thing to ask is how much oxygen would actually be consumed by fires, decomposers, and animals? If our current CO2 is about 0.04%. And, after 100 years of burning coal and oil, we've managed to change the CO2 concentration by about 0.01%. I assume that actually causes the oxygen concentration to drop by about 0.03% (CnH2n --> nCO2 + nH2O). However, if we burnt every tree, every blade of grass, and 100% of the plankton. How much CO2 would be produced (causing a corresponding drop in O2). Would it be enough to drop the O2 levels from say 20% down to 15%, or even down to 10%?
That might be equivalent to burning more than 100 times (or perhaps 1000 times) as much fossil fuels and forests as we have burnt over the last century, and all done in a very short time period.
I'm not seeing a spike in CO2 as would be necessary for such an Oxygen depletion in the reconstructions.
(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fupload.wikimedia.org%2Fwikipedia%2Fcommons%2F7%2F76%2FPhanerozoic_Carbon_Dioxide.png&hash=9ebd9d24163fadd3cf2b641e047e770d).
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Steve,
Perhaps the volcanism in the Deccan flats contributed. I think the asteroid impact was likely the primary cause of the extinction, as the amount of energy released over a short period of time was massive.
Clifford,
Thanks for the CO2 record. I wonder if there is any thing similar for oxygen levels.
Also, thanks for the analysis of the amounts of combustion that would be necessary to significantly reduce oxygen levels.
It might not have been combustion of biomass that reduced oxygen levels, but oxidation of sulfur. The area where the asteroid impacted was high in sulfur and there is evidence of a large increase in atmospheric sulfur levels after the impact.