[meteorite-list] Re: Recent Flash Floods

From: Paul <lenticulina1_at_meteoritecentral.com>
Date: Thu Apr 22 10:16:35 2004
Message-ID: <20030822162555.39093.qmail_at_web21409.mail.yahoo.com>

On Thu, 21 Aug 2003 12:30:11 -0700 (PDT)
Robert Verish

>This most recent influx of moisture
>into the deserts has caused severe
>flash-flooding. Up until now, the
>"dry" lakes have been overly wet with
>standing water, but flash-flooding
>has the energy to bring large volumes
>of mud and rock with that water, out
>into the middle of these playas and
>bury any promising surface with a new
>layer of sediment.

First, the flooding is not going carry
any rock of any size into the playa.
Any rock, except for pumice, of any
size is going to drop out along the
edges of the playa lake. Just the finer-
grained sediments, i.e. mostly silt and
clay will get carried out into the playa.
Along the edges of any playa, there
might be a substantial accumulation of
sediments. However, the actual thickness
of accumulation will drastically decrease
towards the interior of any lake bed to
the point where it can be quite thin.

Finally, the deposition of sediment is
not altogether a bad thing. Any of the
clutter and garbage that has accumulated
on the playa lake surfaces because of
human activity should be buried, in a
some cases just awhile, giving the
meteorite hunter a clean surface on
which a person can more easily find
any meteorite falls after the lake
dries out.

I qualify my statements with "awhile"
because, in some lake beds, the
pedoturbation of the lake sediments
after the lake bed dries out might
cause larger pieces of rock, older
meteorites, and human debris to
resurface in the next decade or so
if they are not too deeply buried.
Also, after a lake dries out, wind
action can significantly erode and
move any silt, clay,or fine sand that
might accumulated during these floods
and also expose, in time, objects
buried outside of the lake margins.
Again, in time, some of stuff that
was buried by these floods within the
lake beds away from its margins will
start to resurface in the next few
years as wind erodes the new lake
sediments and deflates the lake surface.

Yours,

Paul
Baton Rouge, LA

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Received on Fri 22 Aug 2003 12:25:55 PM PDT