THE EFFECTS OF TOPOGRAPHY, LATITUDE, AND LITHOLOGY ON THE DISTRIBUTION OF ROCK GLACIERS IN THE LEMHI RANGE, CENTRAL IDAHO

To investigate the development and preservation of rock glaciers in the Northern Rocky Mountains, we inspected more than 120 cirques in the Lemhi Range of central Idaho using optical remote sensing techniques, digital topographic analysis, and ground truthing. Over 40 rock glaciers were found and examined for lichen cover, evidence of ice presence, and specific signs of movement. These data were used to divide the cirques into four groups: cirques with active rock glaciers, cirques with stagnant rock glaciers, cirques with fossil rock glaciers, and cirques that contain no evidence of rock glaciers.

The distribution of rock glaciers in semi-arid areas is generally thought to be dependent on numerous factors including shading, lithology, relief, aspect, and elevation. Comparing the results of the rock glacier classification with factors such as topographic shading, lithology, relief, aspect, and elevation allows us to determine which factors play the most important role in rock glacier creation and preservation. Preliminary results have shown that elevation above 2600 meters, a north facing aspect (300 – 60 degrees), and less than 2300 hours of direct sunlight per year are necessary conditions for the existence of rock glaciers in any form. Statistical analysis evaluates these and other factors affecting the activity level of rock glaciers.