Re: Oxygen level in Mesozoic - LONG

["James R. Cunningham" <jrccea@bellsouth.net>]

Allan Edels wrote:

> "    I guess that 35% would be the upper limit,............ since any
> references I've ever seen...... all use that as the highest level (I know
> - pure speculation).

I agree -- it seems to me the whole thing is pure speculation, not that it
isn't worth speculating about.

> Of course, the "spontaneous combustion of the biosphere" is
> also speculation (since there is no known occurrence of it).

I agree again.  Actually, it doesn't have to be spontaneous.  At high enough
oxygen levels, the first lightning strike can cause it.  Lightning as an
initating source of fires is not speculative.  I'm sure you are aware that
I'm not saying it ever occurred, just that it may provide a possible
practical upper limit for oxygen levels.  Consider the Apollo fire as an
example of what can happen at high oxygen pressures.

>  It reminds me of the fear that some of the Manhattan project scientists
> had,......  They still exploded it
> anyway......"

I remember the media making that case prior to the detonation of the first
hydrogen bomb too.  We all know how much faith to put in the media's take on
science.  Jeff Hecht, I admire your work and you are excluded from that
snide remark.  A few of the others who've talked to me about this stuff --
aren't.

> ROBERT DUDLEY,......"Concomitant with this reduction in carbon dioxide
>         concentration, the oxygen concentration of the late Paleozoic
>         atmosphere may have risen to as high as 35 % ...........
>         Atmospheric oxygen concentrations are unlikely to have
>         exceeded 35 %, as this value represents an approximate
>         threshold for spontaneous combustion of the biosphere (Watson
>         et al. 1978; Kump, 1989). "
>
> You [Jim] had referred to this article back in 1998.

I'm aware of that.  I've talked to Dudley about the 35%  value and have the
impression that he doesn't put a lot of faith in the accuracy of the
percentage.  However, I don't want to put numbers (or opinions) in his
mouth.

> Even though the data from amber is questionable, the speculations are
> still enticing.

Yes, they are.