Vigil Network Site: Big View Slope Near Dickerson Park, Wyoming, U.S.A.
Submitted by: William W. Emmett
U.S. Geological Survey, Washington, D.C. 20242
Big View Slope is located in Fremount County, some 25 miles northwest of Lander, Wyoming. It is in the SE 1/4, Section 7, T. 2 S., R. 2 W., with coordinates lat. 42°53'51" N., long. 109°02'16" W. It is included on the topographic maps published by the U.S. Geological Survey entitled "Moccasin Lake, Wyo.," scale 1:62,500 and "Lander, Wyoming," scale 1:250,000 (parts of both appear in this folder, figures 1 and 2). To reach the site of Big View Slope, one drives northward from Lander on Highway 287 a distance of about 15 miles. At this point a secondary road leads westward to the small town of Wind River. Continuing on this road, which becomes only a gravelled surface and is called Moccasin Lake Road, a distance of about 10 miles and a number of switchbacks lead up the steep slopes toward Bald Mountain. At the third switchback from the top, one parks the vehicle and walks northward, diagonally up the slope a distance of about 200 yards to the site.
Big View Slope has developed over a bedrock of limestone a soil mantel of probably about three-foot depth. Bedrock is exposed at the top of the slope and there is about a two-foot drop from this horizontal bedrock surface down to the soil surface. In this two-foot cliff face, the bedded structure of the limestone is exposed. The ground surface is characterized by a range in size of particles from fines to large platy slabs of limestone. Apparently, sorting by freeze-thaw action brings the larger particles to the ground surface. A myriad of terracettes form a patterned ground characteristic of freeze-thaw action. Ski Basin Slope was chosen to measure rates of mass-movement and erosion on slopes subject to freeze-thaw.
Big View Slope is located at an elevation of about 9,000 feet above sea level. Average annual precipitation is about 16 inches per year.
At the time of preparation of this file, five field surveys had been made: July 21, 1963, July 31, 1965, June 19, 1966, September 8, 1967, and June 26, 1968. The 1963 survey consisted of establishing a downslope transect to measure rates of mass-movement and erosion. A ten-inch spike was driven horizontally into the bedded limestone at the top of the slope. On a line running downslope from this spike, referred to as the top bench mark, 10-inch long nails, slipped through a washer, were driven into the ground at 20-foot intervals. At each nail, erosion can be measured by the drop of the washer and deposition can be recorded as fill on top of the washer. The exact downslope position from the top bench mark to each nail was recorded using a taut steel tape. Subsequent positional remeasurements will indicate any downslope movement of the pins due to soil creep. A profile was surveyed for the 320-foot length of the nail washer line. The sketches in figure 3 help to visualize and locate the erosion line.
During the 1965 survey, a mass-movement line was established along a contour 129 feet downslope from the top bench mark. It consists of 8-inch long spikes driven into the ground and surveyed to determine their position from the line of sight between two end bench marks. Also a green painted line was sprayed onto all surface particles on a contour 40 feet downslope from the top bench mark. The line is 48 feet long, running between a post driven into the ground and the station 40 nail on the erosion line. Individual particles are checked for any downslope movement. During the 1968 survey, eight additional painted soil lines were sprayed onto the ground. Though no data have yet been collected the location of these lines are as follows:
Line 1 - between first and second pins on mass-movement line, red paint, five feet long.
Line 2 - between third and fourth pins on mass-movement line, red paint, five feet long.
Line 3 - fifty feet above mass-movement line, yellow paint, five feet long.
Line 4 - three feet below line installed in 1965, red paint, (x) feet long.
Line 5 - fifteen feet above line installed in 1965, yellow paint, five feet long.
Line 6 - ten feet below cliff face, red paint, five feet long.
Line 7 - fifty feet below mass-movement line, yellow paint, five feet long.
Line 8 - fifty feet below mass-movement line and on frost heave mound, yellow paint, five feet long.
All field visits include the resurvey of previously installed measurements as well as the installation of additional measurements. Table 1 lists the profile data and resurveys for the nail-washer erosion line, table 2 lists data observed from the mass-movement line, and table 3 lists data on movement of individual particles. Elevations in table 1 refers to an arbitrary elevation of 1000.00 feet for the top bench mark. The adding of 8000 feet will give the approximate elevation above sea level.
The file of original data includes color ground photography taken at the time of each survey. Original data are on file with William W. Emmett, U.S. Geological Survey, Washington, D.C. 20242, U.S.A.