[meteorite-list] Desert Varnish formation

From: Dave Freeman mjwy <dfreeman_at_meteoritecentral.com>
Date: Sat Mar 11 21:14:12 2006
Message-ID: <441383A1.8030809_at_fascination.com>

Dear Kevin;
YIKES! I found the Waynesword site just yesterday.
His information on early Earth and the connection with meteorites seems
really interesting. His other surf able information to "living
stromatolites" makes me think that there is some slim chance that recent
(maybe a few million years) meteorite hits MAY have seeded meteorites
again....as the So. California, Minnesota, and Oregon locations would
hold out. They would have been glaciated over but the stromatolites
came back to live again today. Then there's Yellowstone....mmm...no idea.

Any meteorite minds care to offer an opinion on recent seeding
possibilities?
Dave F.
With desert varnish.

Kevin Forbes wrote:

>
>
> ---------------------------------------------------------------------
>
> Desert Varnish formation
>
> http://waynesword.palomar.edu/ploct97.htm
>
> One of the most remarkable biogeochemical phenomena in arid desert
> regions of the world is desert varnish. Although it may be only a
> hundredth of a millimeter in thickness, desert varnish often colors
> entire desert mountain ranges black or reddish brown. Desert varnish
> is a thin coating (patina) of manganese, iron and clays on the surface
> of sun-baked boulders. Desert varnish is formed by colonies of
> microscopic bacteria living on the rock surface for thousands of
> years. The bacteria absorb trace amounts of manganese and iron from
> the atmosphere and precipitate it as a black layer of manganese oxide
> or reddish iron oxide on the rock surfaces. This thin layer also
> includes cemented clay particles which help to shield the bacteria
> against desiccation, extreme heat and intense solar radiation. It has
> been estimated that up to 10,000 years are required for a complete
> varnish coating to form on boulders in extreme arid desert regions.
>
> ---------------------------------------------------------------------
>
> Kevin, VK3UKF.
>
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Received on Sat 11 Mar 2006 09:12:49 PM PST