Rock glaciers in the Front Range: An analysis of distribution, topoclimatic variables, permafrost, and flow.

摘要

This dissertation examines several important characteristics of rock glaciers in the Front Range of Colorado using a combination of geospatial techniques. In the first paper, I present a regional account of rock glacier locations as well as associated topoclimatic variables. Topoclimatic variables for all rock glaciers were distinguishable from glacier and icefield locations. Active tongue-shaped rock glaciers had similar topoclimatic variables, but lobate forms showed a significant difference compared to glaciers and icefields. This suggests that active tongue-shaped rock glaciers are influenced by glacial processes and active lobate forms are the product of periglacial processes.; Since rock glaciers are related to permafrost occurrence, a predictive permafrost model was created from the topoclimatic variables and land cover criteria, the topic of a second paper. The model, which showed a good correlation with BTS and MAAT measurements, revealed that permafrost covers some 243.0 km2. In the third paper, I compared rock glacier sensitivity to warmer and cooler climates. After comparing model scores with rock glacier activity, it was determined that temperatures were once 3.0° to 4.0°C cooler during the Pleistocene. In a warmer climate, a 2.0 to 2.5°C increase in temperature could dramatically reduce permafrost extent.; In the fourth paper, I updated a displacement detection network established in the 1960s on three tongue-shaped rock glaciers. Mean velocities of 7.3, 6.3, and 9.7 cm/yr were obtained for Arapaho, Taylor, and Fair rock glaciers, respectively. Displacements were within 10% of short-term estimates, indicating that rock glacier flow rates have not significantly changed over 40-plus years, thus climate and talus input have remained stable. This was expected since the global warming trend remains unclear for the Front Range.; The final paper investigates long-term flow patterns, while assessing spatial uncertainty on five rock glaciers using a combination of GIS and photogrammetry techniques. Mean velocity over approximately a 20-year period averaged about 10 to 20 cm/yr. An attempt was made to detect a climatic signal over 10 year periods, but mean velocity increased only 2 cm/yr, a negligible amount that is likely the product of uncertainty rather than a slight temperature and precipitation increase.