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Re: extinction




On Tue, 13 Jan 2004 12:19:57 -0500 "Dewey M. McLean" <dmclean@vt.edu>
writes:
> Response to Phil Bigelow's Sun, 11 Jan 2004 12:34:18 post.
> 
> Hi Phil, your first two questions are fundamental to the Deccan 
> Traps 
> and K-T iridium distribution problem, and ones that I have long 
> meditated on. David Marjanovic also addressed the topic.
> 
> Before responding, I've contacted one of NASA's foremost experts on 
> 
> experimental biomass burns to get the latest information on how 
> widely particulates from single events are globally distributed. He 
> 
> provided some information, and will send me more details.



But is the burning of biomass a good analog for pumping flood basalt
iridium into the stratosphere?

This is a critical issue for the Deccan Traps supporters, because, as I
understand it,  iridium does not aerosolize out of basalt flows.  In
fact, iridium doesn't aerosolize at all.  The chlorides, fluorides, and
oxides of iridium (which have to be produced under laboratory conditions)
are all dense solids.
  
Another issue:  Can carbon soot produced from a point source cross the
equator and deposit itself in the opposite hemisphere?  From what I have
read, soot tends to stay within the hemisphere that produced the soot. 
Would volcanically-produced iridium dust behave the same way?  My
understanding is that the K-T iridium spike is found in both the northern
and southern hemispheres.

If soot produced from a forest-fire point source cannot be deposited
globally, then heavier iridium-laden dust produced from a quiet lava flow
probably has a poorer chance of being deposited globally.


> After I 
> receive the information, I'll discuss your first two questions at 
> the 
> same time.
> 
> Re the Columbia River flood basalts, I've studied the literature, 
> but 
> have never  done anything with it. I'm far more interested in 
> linkages between older episodes of flood basalt volcanism and mass 
> extinctions such as the K-T and P-Tr, etc.


Its probably all for the best, considering that there are no documented
extinctions (neither local or global) associated with the CRB floods. 
Perhaps this should be a data point in your analysis.  ;-)

cheers,
<pb>
--








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