-------- Original Message --------
Subject: New USGS Gila Cliff Dwellings National Monument Poster
Date: Tue, 19 Aug 2003 11:49:51 -0600
From: "Joseph J Kerski" <[log in to unmask]>


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Folks:

New USGS poster of the Gila Cliff Dwellings National Monument, New
Mexico,
see below.

Joseph Kerski
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Gila Cliff Dwellings
Stock #:    112312
Price:        $7.00 for the poster plus $5.00 handling

The first known inhabitants of the Gila Cliff Dwellings, the Mogollon
People, may not have been aware of how the caves they inhabited 1000
years
ago were formed, but scientists from the U.S. Geological Survey and the
National Park Service are well acquainted with the process.

Originally, the caves were probably excavated by a combination of stream
action and spring sapping.  As the stream in Cliff Dweller Canyon cut
down
through the layers of Gila conglomerate, it may have encountered a
relatively soft layer and cut laterally into it, initiating an alcove.
Lateral stream erosion is most effective where bends cause the stream to
impinge directly on the canyon walls.  Spring Sapping, or sapping, is a
natural erosion process that occurs, usually at the base of a cliff.
Softer layers are worn away, leaving upper layers unsupported, which can
then break off in large and small blocks.  It may work in conjunction
with
lateral stream erosion, or may be the main process in cave formation.

This poster describes in detail how these two natural erosion processes
carved through layers of the canyon walls to create the caves seen today
at
Gila Cliff Dwellings National Monument, located near Silver City, in
southwestern New Mexico.  The poster includes pictures of the seven
caves
that make up the monument.  There is also a section on the role of
exfoliation as it pertains to the development of the caves.

The poster measures 24"x 31.5"and is available from any USGS Earth
Science
Information Center (ESIC).  To locate the nearest ESIC, call 1-800-ASK
USGS, or visit:  http://www.usgs.gov.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Joseph J. Kerski, Ph.D.
Geographer:  Education/GIS
US Geological Survey
Building 810 - Entrance W-5 - Room 3000
Box 25046 - MS 507
Denver CO  80225-0046 USA
[log in to unmask]
Voice 303-202-4315
Fax    303-202-4137
http://rockyweb.cr.usgs.gov/public/outreach/
USGS:  Science for a Changing World
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