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Re: Dinosaur Extinction: Impact vs Volcanoes
Hi Bill, Hi List!
William Blair wrote:
> Bernd Pauli wrote:
> >
> > M e t e o r i t i c versus v o l c a n i c events at the Cretaceous /
> > Tertiary boundary - An Australian perspective. F.L. Sutherland. Division
> > of Earth Sciences, The Australian Museum, 6-8 College Street, Sydney,
> > NSW, 2000, Australia.
> >
> > A review of the end Cretaceous extinction debate (Sutherland, 1988)
> > concluded that the cause 'was a coincidence of both impact and volcanic
> > cycles coming together, but not necessarily the first directly causing
> > the other.' New literature expands such views on dual, but uncoupled
> > causes.
>
> Although it's just a guess, couldn't a massive impact somehow trigger
> volcanic eruptions? There would then be no "coincidence" necessary.
> Perhaps _both_ the volcanic and impact theories are correct, but all of
> these environmentally disruptive events were _triggered_ by the impact?
To some this is a plausible explanation for the Deccan Traps in India (a HUGE
flood basalt) and a flood basalt deposit in South America (can't recall the
name). However, I have heard of no real good field evidence nor geochemical
evidence for this. Furthermore, I believe mantle plumes are probably the
best mechanism for creating these large flood basalts.
>
>
> > Coincidental, but independent, northern impacts and largely southern hot
> > spot outbursts seem to fit present data.
>
> I've read somewhere, that the anti-nodal(?) point from the impact would
> experience incredible earthquakes due to the reflected/refracted shock
> waves propagating through the earth from the point of impact. Is this
> true and, if so, has anyone been looking for evidence of this? The
> anti-nodal point of the suspect crater was/is in the southern hemisphere.
This is true, but again, no "hard" evidence.
> Couldn't this explain the southern hotspots?
The hotspots probably were not created by impacts, but are most likely the
manifestation of manle plumes, and are at least a few tens of millions of
years old. To my knowledge no evidence for impact cratering is associated
with these.
>
>
> Bill Blair
>
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Matt Morgan
Mile High Meteorites
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