Colorado Front Range Rock Glaciers: Distribution and topographic Characteristics

Janke, Jason

In the Colorado Front Range, rock glacier distribution has been noted on U.S. Geological Survey maps and in several publications; however, a comprehensive account of distribution is not available. When analyzed in a Geographic Information System (GIS), Digital Elevation Model variables (elevation, slope, or aspect) could reveal unique topographic characteristics of rock glaciers. The objectives of this study are to provide an accurate, complete account of rock glacier locations in a digital format, to compare topographic variables of rock glacier form and activity classes, and to evaluate glacier and rock glacier topographic information. Rock glacier locations were obtained from previous studies and were re-digitized on high resolution digital orthophotos. Glacier distribution was determined through classification of a satellite image. Topographic information for rock glacier form and activity classes as well as for glaciers was obtained through zonal overlay in a GIS. Results indicate that tongue-shaped rock glaciers occur at higher elevations, have more northerly aspects, and have gentler slopes compared to lobate rock glaciers. Active, inactive, and fossil forms showed typical elevation and aspect gradients. Active rock glaciers are found at the highest elevations and most northern aspects. Inactive rock glaciers are found at lower elevations on all aspects with a tendency to face northeast, and fossil rock glaciers occur at the lowest elevations on all aspects. Topographic variables for all rock glaciers were statistically different compared to glacier locations; however, active tongue-shaped rock glaciers had similar topographic variables compared to glaciers, but lobate forms showed a significant difference. In the Front Range, active tongue-shaped rock glaciers are developed by glacial processes and active lobate forms are the product of periglacial processes.

Colorado Front Range Rock Glaciers: Distribution and topographic Characteristics

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