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Re: Sulfate 'n soot kills dinos!



Hi John,

> 
> According to Kevin Pope in _Impact dust not the cause of the
> Cretaceous-Tertiary mass extinction_, Geology, Feb 2002, pp99-102, impact
> dust is not the cause of the Cretaceous-Tertiary mass extinction.

Haven't read the paper althouhg I have the issue in question but you have piqued
my curiosity!
So before I get clobbered for what follows, I am speaking in only VERY general
terms. The K-T impact and impact-extinctions for that matter ar beleive it or 
no,
the other obsession in my research and one that I spent much time on before the
Arundel project went into high gear. Thus, all of my K-T refs are somewhere and
not readily available.

> Can anyone tell me how this works--
> 
> Is there lots of acid rain (frog-killing acid rain)?

I would assume so. There have been a couple papers in Both Geology and Science
but I do remember one that rebutted the Strangelove Ocean hypothesis. 
regardless,
I'd say some major acid rains followed for some time. Retallack had a paper in
Geotimes on this .

> 
> Do all forests start burning, even wet tropical forests?

Absolutely! There was a Nature paper called something like "Wildfires at the
K-T..." ca. 1991 with a bunhc of calculations that showed even wet forest litter
within a certain range could spontaneously ignite as a result of thermal
radiation. And speaking from a Nuclear bomb point of view (another interest I
have, there is hard data that shows that from say a 10 MT thermonuclear blast,
thermal radiation is capapble of causing spontaneous ignition in  dry material 
ot
to 30 mile from ground zero. Naturally a much closer ranges, moist material or
water containing objects like people also flame up spontaneously too. Ouch!

> 
> What is the length of time sulfate remains aloft compared to dust?

I _think_ the "half-life" of sulfate aerosols is only a few years. For example,
the aerosols lofted by Mt. Pinatubo hung around for a couple years but their 
most
profound effects were within the first year with a measured cooling of the 
global
climate.
> 
> Is this modeled anywhere?

Mostly based on volcanic models involving but I do seem to remember a much
publicezed and controversial experiment carried out in Canada a few years back
when Sagan was alive (and who pushed for it) to test the so called 'Nuclear
Winter' hypothesis. It seems some vast forrested part of the Great White North
was taken over by some "scrub" trees and they wanted to torch it to see if the
particulates released from this burning could be detected in the global scheme 
of
things and to see if (scaled up a few orders of mag) could influence the 
climate.
After some controversey with some environmentalists and others of the soundness
of this, it finally did occur but the results, IIRC were not that great. Oh, and
before I forget, the other imperative for torching this vast chunk of trees was
to remove the invading shrubs and allow for the recolinization of native 
species-
a tactic used widely. The difference was the considerably larger scale.

> 
> Does rain take it out of the atmosphere?

Over a few rears to deacdes yes.



> Would you expect a global signature--is there one?

See above.

> 
> Does this fit the extinction pattern as-well-as, or better-than, the dust?


I am sure is was a major contributing factor but there are some aspects of it
that I am not so sure about and likely have forgotten about since my attention
has long since turned elsewhere. I'll _try_ to look for them later this week or
so whilke I am doing my Spring cleaning!


Cheers,
Tom

Thomas R. Lipka
Geobiological Research
2733 Kildaire Drive
Baltimore, Md. 21234 USA