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Is there any new evidence on the environment during the Jurasic period?

  1. Jul 18, 2012 #1
    Two part question:
    1. I keep reading about large dinosaurs having nostrils the size of horses, thus not able to breathe in today's environment. Also, the oxygen content found in petrified amber, being higher than current day. Is there any new evidence or new theories about the environment?

    2. Is the current consensus, volcanic acitvity, methane or oxygen content that killed the dinosaurs? Thanks.
     
  2. jcsd
  3. Jul 18, 2012 #2
  4. Jul 18, 2012 #3
    1. I wonder if these calculations used the respiratory system of extant reptiles or extant mammals. Some dinosaurs may have had a far more efficient respiratory system, similar to birds.
    Extant birds have respiratory system up to tend times as efficient as mammalian respiratory systems. They have compartmentalized lungs connected to their hollow bones. The result is that every separate bird breath uses a higher fraction of the available oxygen then the corresponding breath in an extant reptile or mammal.
    The evidence is that some large dinosaurs had hollow bones. Lungs don't often leave fossils. However, it seems plausible that some dinosaurs with hollow bones may have had a respiratory system analogous to the respiratory system of modern birds.
    You said that dinosaur had nostrils the size of horses. I will make the assumption that you mean dinosaur nostrils were the size of horse nostrils.
    If a dinosaur the size of a horse had a bird-like respiratory system, then it would be using a larger fraction of the oxygen per breath then the horse. I could then imagine that the dinosaur would not need nostrils the size of horse nostrils.
    Dinosaurs are now thought to have been warm-blooded. However, the question is how warm-blooded.
    Our hypothetical dinosaur, the size of a horse, may have had a lower operating temperature than a horse. Then it would require less oxygen than the horse. So if the dinosaur were cooler than the horse, it would need smaller nostrils than the horse.
    2) The Deccan Trappes, in India, were caused by super flow of lava that has been implicated as a possible cause of the KT extinction. The famous asteroid collision that caused the KT occurred during this lava flow. The evidence is very clear that the two occurred at the same time, regardless of which one did more damage.
    The Deccan lava flow may have been the major cause of extinction. If so, then volcanic activity (i.e., the lava flow) in some way killed the dinosaurs. However, the Deccan lava flow took place over an extended period of time (maybe 500 KY). Some evidence indicates that there was a spike in extinctions much smaller than that.
    One view is that while the asteroid may have caused many of the extinctions, the Deccan lava flow couldn't help the dinosaurs. When it rains, it pours! The two disasters probably added in a nonlinear way.
    Scientists aren't completely sure how either the asteroid or the lava flow killed so many species. The killing mechanism is still being discussed, whether or not you believe in asteroids or lava flows.
    The asteroid or lava flow changed the amount of methane and oxygen in the atmosphere. You didn't say what you thought would cause a change in methane or oxygen.
    The lava flow could have released lots of carbon dioxide in the atmosphere. The carbon dioxide causes heating of the oceans and lakes. Heating drives oxygen out of the water, causing the death of sea and lake life. A large asteroid hits, causing sudden heating of the atmosphere. More oxygen is driven out of the oceans. Pretty soon, nothing is left in the water.
    Heating also could have cause melting of those "frozen methane" deposits in the ocean. Either Deccan Trappe or asteroid could have done that.
    Both asteroid and lava flow would have caused acid rain. The asteroid supposedly hit some sulfur deposits. Volcanoes naturally give off sulfur and carbon dioxide. The asteroid started forest fires. Forest fires release carbon dioxide, using acid rain.
    What is clear is that an asteroid strike AND a super lava flow occurred at nearly the same time 65.5 MYA. At about this time, there was a mass extinction. So we have two smoking guns.

    What would Hercules Peroit say?
     
  5. Jul 19, 2012 #4
    -I'm wondering that the status is of the antipodal volcanism of the Deccan traps with the Chicxulub impact.

    The impact date (65.3Ma) appears to be 300,000 years earlier than the extinction It is debated of the impact caused the Deccan traps to erupt in India, which is dated at various times for instance from 69-63 million years or 60.4 - 68.5 million years. Obviously that would refute that antipode hypothesis and also the http://geoweb.princeton.edu/people/keller/chicxpage1.html [Broken] for the extinction.

    Als one would have to identify a large eruption within that ~8 million years period that dates at the K-T boundary to identify the Deccan traps as cause. But there doesn't seem to be evidence for that.

    So the jury is still out, I guess.
     
    Last edited by a moderator: May 6, 2017
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