re: the deccan traps and the bolide

[NEIL CLARK <NCLARK@museum.gla.ac.uk>]

> Bonnie Blackwell writes:
> 
> > i would beg to differ with the recent poster who suggested no 
relationship
> > between the deccan traps and the chicxulub event.  an article in 
> > J.geophys.Res last year and a summary in Eos, suggested 
otherwise.
> > essentially they suggested that the deccan was at the antipode of 
the impact
> > which released so much energy it religned the plates somewhat 
and focused
> > the energy at the deccan.  please see the original article for the 
details,
> > 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.
> 
> -dick

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.

Neil


Neil Clark
Curator of Palaeontology
Hunterian Museum
University of Glasgow
email: NCLARK@museum.gla.ac.uk

Mountains are found in erogenous zones.
(Geological Howlers - ed. WDI Rolfe)