Re: [pct-l] Erosion and Geologic Time Scales

[Greg Hummel <ghummel@hydrogenburner.com>]

Dear PCTL and Owen,

Previously I wrote:

>> The soil profiles that are there, under the meadows and low in the
valleys have taken millions (that's right millions) of years to form. Any
erosion caused by humans directly or indirectly is un-repairable and
non-reversible.

Owen wrote:

>Well written but I question the soils forming over millions of years.  The
>present environment that we see today has formed in the last 10,000
>years, the end of last major glaciers. Mother Nature is a lot more resilient
>than the sky-is-falling types would like to admit.  Does this give us the
>right to trash our environment. . . NO, but decisions must be made with the
>correct facts not with inflated numbers to justify the end.  You and I as
>scientists have a duty to public to provide correct information.
>
>Owen Kittredge
>California Registered Geologist #5853


Good point, Owen, the soils have formed only over several thousand years
since the last glacial event.  However, I was trying to point out that the
overall geologic setting that provided for the formation of the soils, ie.,
the valleys upon which the soils have formed, have filled with sediment
collected over the coarse of millions of years.  As I recall there is
evidence, including depositional evidence, of several glacial events in the
Sierras.  I didn't say it that way and admit I may have gotten carried away
with the numbers. I agree that inflating facts is unprofessional, uncalled
for and only detracts from the discussion.  I appreciate the check.

The point is that erosional damage is often non-reversible.  Once erosion
has begun, even in initially minor and almost undetectable ways, it
requires geologic time scales to repair.  Thousands of years? Millions of
years? To the human time scale it hardly matters.

Greg "Strider" Hummel
* From the Pacific Crest Trail Email List |  http://www.backcountry.net   *

==============================================================================