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K-T and terminal Permian vulcanism



Michel remarked that the Deccan Traps started several million 
years before the K-T.  Not so!  Some time before the K-T, but the
whole volca nic epidosde only lasted a billion years.  Obviously,
there was pre-existing hot spot  in India, producing lava  well
before the K-T, but the spherical interference waves from Chicxolub
would have e xploited this pre-existing weak spot (for "hot spot"
read "weak spot") and greatly increased the flow of lava.  The
Sib erian episode lasted longer, perhaps 5 million years.  AGain,
the mostd likely scenario is a hot/weak spot made wo rse by 
an impact.
        The rate of release of lava by either of these volcanic
episodes is not really all th at extreme.  Deccan released about
100 cubic kilometers a century, the Siberian Traps maybe 350.  If
we add up the rate of production of lava by taday's volcanoes,
chiefly Hawaai and Iceland, but also others we obtain comparable
figures, even without taking into account any eruptions b elow
one cubic km.  If Deccan could  produce a mass extinction then
we are living through one now!
        Dinogeorge wonders where Siberia was 250 Ma ago.  Ungortunately,
Unfortunately, we have l ittle knowledge of the detailed movement 
of the plates thqt far back.  WE can trace the formation and breakup
of supercontinentss, but the precise location is more difficult.
In any  case, the end of the P ermian was a time of a supercontinet,
so the antipodes were almostd certainly ocean floor, in which
case any crater would long since have been subducted.
David

--
>From: David Brez Carlisle
bk090@Freenet Carleton.CA