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re: the deccan traps and the bolide
> Bonnie Blackwell writes:
> > i would beg to differ with the recent poster who suggested no
> > between the deccan traps and the chicxulub event. an article in
> > J.geophys.Res last year and a summary in Eos, suggested
> > essentially they suggested that the deccan was at the antipode of
> > which released so much energy it religned the plates somewhat
> > the energy at the deccan. please see the original article for the
> > unfortunately, i have misplaced the reference.
> But it's not anywhere near the antipodes relative to Chicxulub. The
> antipodes is well out in the southern Indian ocean, roughly on a
> parallel with the middle of the island of Madagascar and over 2,000
> miles from the Indian mainland. I'm no geologist, but that article
> sounds to me like a fishing expedition.
Perhaps it was at the time. Someone can look into that if they have
enough time? But that aside, and the physicists will correct me here,
if it was at the antipodes, surely the core would have filtered out the p
and s waves produced by the impact in the same way as it does with
earthquakes today? The shadow zone, I seem to remember is
antipodal to the focus. I know that minor amounts of activity can be
detected, but the vast majority of the waves occur within (approx) 120
degrees or so of the focus. I'm afraid that I don't have my geophysics
crib books beside me so I may have this all wrong.
Curator of Palaeontology
University of Glasgow
Mountains are found in erogenous zones.
(Geological Howlers - ed. WDI Rolfe)