6800 ft (2072 m)--upland portion
General Topographic Description
The site occupies a promontory of gently rolling upland at the confluence of two canyons, and extends into the canyons onto the talus slopes to the east, south, and west. The soil on the site is Quaternary aeolian loess. Bedrock (Dakota formation) is exposed around the great tower complex and along the canyon rim at the northwest edge of the site.
Perennial Water Source(s)
Springs in the two canyons that border the site on the east and west
Runoff in drainages on the site
A north-south trending earth-berm and rubble dam (Nonstructure 2001, Feature 1) is located at the west edge of a large natural depression in the southwest portion of the site. Four masonry dams cross a natural drainage that bisects the great tower complex (see great tower complex map); three of these dams would also have slowed the flow of water from a spring surrounded by this complex.