[meteorite-list] Global Wildfires Did Not Kill The Dinosaurs

From: Sterling K. Webb <kelly_at_meteoritecentral.com>
Date: Thu Apr 22 10:17:43 2004
Message-ID: <3FD7D4AE.2D1F24EB_at_bhil.com>

Hi, All,

    In a wildfire more immense than our wildest dreams, there will be large amounts of
unburnt vegetation IF the fire consumes enough oxygen over a wide enough area that the
"local" oxygen level drops below the level required to sustain combustion at the
ambient temperature of the fire.

    Back in the 70's, several planetologists suggested that the Earth's oxygen levels,
which were then thought to have stayed relatively constant, were in a feedback cycle,
the upper bound of which was set by the calculation that at oxygen concentration of
over 24%, fires would break out spontanteously, burn off large areas of the planet and
lower the concentration.

    Those calculations are now suspect, and we now know that oxygen concentrations have
varied more widely than we thought. There is evidence that the Cretaceous levels were
30%. I wonder what oxygen level was assumed in this study? It could make a big
difference.

    You can still burn off a world without resorting to direct thermal radiation; just
blast hot materials all over an Earth with too much oxygen for its own good.


Sterling K. Webb
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Ron Baalke wrote:

>
>
> Global wildfires did not kill the dinosaurs

> The latest Cretaceous and earliest Tertiary rocks were found to contain an
> average of 16.3% charcoal, but neighbouring K-T rocks showed only 1.75%. More
> surprisingly, the K-T rocks also revealed considerable amounts of unaffected
> plant remains, with some sites containing as much as 60% non-charred plant
> fragments.
>
> "If we assume that extensive wildfires consumed the vegetation across the North
> American continent, it is hard to imagine a situation where so much plant
> material remained un-charred. This does not support the theory that North
> America was engulfed by wildfires at this time," said Claire Belcher, from Royal
> Holloway's Department of Geology.
>
Received on Wed 10 Dec 2003 09:21:35 PM PST