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Dino extinction and Chicxulub impactor new evidence

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  • rwatts
    replied
    Originally posted by HMS_Beagle View Post
    It's been firmly established that the extinction of the dinosaurs (save birds) is directly associated with the major asteroid impact event at Chicxulub almost 66 million years ago. The precise mechanism that causes the worldwide extinction has never been firmly established however. A leading hypothesis is the "impact winter" scenario where dust and soot from the impact blocked so much sun that the Earth's temperature plummeted and its ecosystems were devastated.

    A new study on PNAS has provided the first direct evidence of this "impact winter" and the havoc it wreaked immediately following the impact.



    Maybe the board's YEC expert could explain this data in his scenario since he is on record as claiming the Chicxulub impact never happened.
    Actually, this proved a timely post because out on the "Your Origins Matter" facebook page was a link to this:-

    That's a fact

    The thing is that for all its confidence, all the ICR has set up in an hypothesis to explain the ice age, along with the usual "evolutionists cannot explain this and they cannot explain that" assertions.

    Why an hypothesis? Well, aerosols can explain global cooling. Volcanoes could plausibly explain oceanic warming.

    The problem is, the ICR seems to think this is the scientific explanation.

    Is there any evidence for a massive injection of aerosol into the atmosphere 4,000 years ago? No. Is there any evidence for a world wide chain of volcanoes releasing massive amounts of lava into the oceans 4,000 years ago? No.

    In the case of the PNAS paper however, the "nuclear" winter scenario always remains contentious until evidence can be found for this cooling. Well now it has been. But even then, arguments will continue too and fro, perhaps as to how good this evidence really is, or perhaps in relationship to other questions this new data now throws up.

    The video and the PNAS paper reveal a sharp distinction between what creationists find acceptable (a lot of hand waving because the Bible tells us so) and what scientists find acceptable (we always want more evidence, what we have is not enough).
    Last edited by rwatts; 05-18-2014, 05:38 PM.

    Leave a comment:


  • sylas
    replied
    Originally posted by shunyadragon View Post
    The Decan Traps are likely a direct result of the ChicXulub impact. I will look for references, but, like the Permian Extinction impact, the shock waves of the impact converge at point (antipod) on the other side of the globe and shatter the crust. It has been some time since I read about this, but as I remember it is proposed that the Chicxulub was one of several large impact that would result in a shock wave antipod where the Deccan Traps occurred.
    My understanding is that this hypothesis has very little support, and is generally considered unlikely; apart from a few mostly amateur enthusiasts. The idea has been proposed; but has also received a lot of criticism. I’ve briefly exchanged some posts with Shunyadragon on this previously, but not in any detail. I’ll try to do better this time.

    Criticisms of the antipodal idea include:
    • The Deccan traps occurred over a substantial time, in a number of pulses, and mainly before the ChiXulub impact..
    • The Deccan traps are not, and were not at the time either, actually at the antipode of ChicXulub; there is a substantial difference.
    • Early work proposing this idea significantly overestimated the amount of energy delivered to the antiopode of a big impact.


    I think the direct causation link is highly dubious, but on the other hand I do find it credible that the combined effect of events close to each other in time contributed to the magnitude of the extinction event.

    A paper usually cited in criticism of a causal link between ChicXulub and the Deccan traps is:
    Antipodal focusing of seismic waves due to large meteorite impacts on Earth. 2011. M. A. Meschede, et al. Geophysical Journal International 187: 529–537. original paper (paywalled), newssummary at Princeton.

    A paper in support of the idea of antipodal effects in more general terms is the following:
    Antipodal hotspots and bipolar catastrophes: Were oceanic large-body impacts the cause?, J. T. Hagstrum (2005), Earth and Planetary Science Letters Volume 236, Issues 1–2, 30 July 2005, Pages 13–27. 10.1016/j.epsl.2005.02.020 (The lack of citations to this paper also suggests that this really is a minority perspective at present.)

    I can’t find a good peer reviewed reference supporting the causation model specifically between ChicXulub and an eruption at the Deccan traps. It seems to be mainly a view of a few enthusiasts. Here is a major one: an online book by Ben Fishler: Solving the Mass Extinctions. He considers this antipodal vulcanism model to be involved generally in all the major extinctions, and does specifically look the model with respect to ChicXulub and the Deccan traps as a part of this.

    If anyone has better references, I’d like to read them!

    Cheers -- sylas

    Leave a comment:


  • shunyadragon
    replied
    Originally posted by rogue06 View Post
    I still think Chicxulub was only one factor (though most likely the primary one) that caused the mass extinction event at the end of the Cretaceous. I would be surprised if the Deccan Traps flood basalts weren't an important contributing factor. Marine regression may also have played an important role as well.
    The Decan Traps are likely a direct result of the ChicXulub impact. I will look for references, but, like the Permian Extinction impact, the shock waves of the impact converge at point (antipod) on the other side of the globe and shatter the crust. It has been some time since I read about this, but as I remember it is proposed that the Chicxulub was one of several large impact that would result in a shock wave antipod where the Deccan Traps occurred.
    Last edited by shunyadragon; 05-17-2014, 10:19 PM.

    Leave a comment:


  • klaus54
    replied
    Did the Chicxulub impact occur 1) at the beginning of, 2) in the middle of, or 3) just after the raging Mabbul?

    Same question for the Deccan Traps.

    Would a Fludde geologist by so kind as to proffer an answer?

    Thanks in advance!

    K54

    Leave a comment:


  • rogue06
    replied
    I still think Chicxulub was only one factor (though most likely the primary one) that caused the mass extinction event at the end of the Cretaceous. I would be surprised if the Deccan Traps flood basalts weren't an important contributing factor. Marine regression may also have played an important role as well.

    Leave a comment:


  • Dino extinction and Chicxulub impactor new evidence

    It's been firmly established that the extinction of the dinosaurs (save birds) is directly associated with the major asteroid impact event at Chicxulub almost 66 million years ago. The precise mechanism that causes the worldwide extinction has never been firmly established however. A leading hypothesis is the "impact winter" scenario where dust and soot from the impact blocked so much sun that the Earth's temperature plummeted and its ecosystems were devastated.

    A new study on PNAS has provided the first direct evidence of this "impact winter" and the havoc it wreaked immediately following the impact.

    Rapid short-term cooling following the Chicxulub impact at the Cretaceous–Paleogene boundary
    Vellekoop et al
    PNAS May 12, 2014, doi: 10.1073

    Abstract: The mass extinction at the Cretaceous–Paleogene boundary, ∼66 Ma, is thought to be caused by the impact of an asteroid at Chicxulub, present-day Mexico. Although the precise mechanisms that led to this mass extinction remain enigmatic, most postulated scenarios involve a short-lived global cooling, a so-called “impact winter” phase. Here we document a major decline in sea surface temperature during the first months to decades following the impact event, using TEX86 paleothermometry of sediments from the Brazos River section, Texas. We interpret this cold spell to reflect, to our knowledge, the first direct evidence for the effects of the formation of dust and aerosols by the impact and their injection in the stratosphere, blocking incoming solar radiation. This impact winter was likely a major driver of mass extinction because of the resulting global decimation of marine and continental photosynthesis.
    Maybe the board's YEC expert could explain this data in his scenario since he is on record as claiming the Chicxulub impact never happened.

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