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Re: extinction



> "These findings indicate that the original K-T impact extinction
> hypothesis--the shutdown of photosynthesis by submicrometer-size
> dust--is not valid, because it requires more than two orders of
> magnitude more fine dust that is estimated here."
>
> "These results shed doubt on the importance of impact dust in the
> mass extinction that marks the K-T boundary. A global atmospheric
> loading of...submicrometer-sized dust would not cause the
> catastrophic impact winter often proposed...."
>
> Kevin did leave open other impact hazards such as global cooling
> caused by impact production of sulfate aerosols, and soot from global
> wildfires.

Well, it remains possible that these, together with ample nitric oxide -- a
dark red-brown gas -- could have produced cool temperatures and darkness for
a short time.

> With the seemingly virtual elimination of
> a K-T impact winter, and global wildfires,

This looks too rash to me. More patchy global wildfires are still wildfires
(perhaps it was just raining in the areas in question :-) ), and see above
for the impact winter.

> not many potential mass extinction killing mechanisms remain.

- Acid rain. Which leads to the leaching of poisonous metal ions (Al, Be,
Cu...) from continental soils/rocks.
- Nitric oxides.
- Pyrotoxins -- results of wildfires to which different groups of animals
are said to be very differently susceptible.
- The strong greenhouse: CO2 coming out of the dolomite, the fires and
rotting organic matter, CH4 bursting free from the failing continental
slopes, and the remaining NO2. The K-T sediments of New Zealand suggest more
complex climatic oscillations.
- This here http://www.dinosauria.com/jdp/impact/impact.htm, which may not
even leave charcoal, although it can't have been a global phenomenon.

And when I compare... what can effusive volcanism produce?

- An impressive but not so extreme greenhouse.
- Apparently not much else.