MODELLING ROCK GLACIERS USING A MORPHO-DYNAMIC APPROACH: SAN JUAN MOUNTAINS, CO, USA

Alpine environments are dominated by high relief, steep slopes, tectonic activity and extreme micro-climates, all of which contribute to the energy and mass necessary for erosion and deposition. The transport of mass and energy are reflected in various landform assemblages, which serve as pathways to lower elevations. Understanding these transport pathways is fundamental to understanding the alpine environment. Although talus slopes are common in alpine regions, rock glaciers are the largest debris transport systems. Surface morphology and site conditions have often been used as surrogates to infer development and material properties of rock glaciers. Surrogates, however, promote speculation and may detract from the search for evidence of process/form. A conceptual movement away from speculation requires that the morpho- dynamics of rock glaciers be examined and modeled. To address this void we developed a simulation model that links morphological components of the alpine debris system to cascades of energy and mass. The San Juan Mountains of southwestern Colorado, a virtual warehouse of hundreds of rock glaciers, served as the field site. We collected various geometric measurements on basins and rock glaciers. The results from the simulation model suggest that the development of a rock glacier can be controlled by the shape of the basin, resistance to flow of energy, and supply of debris. The shape of the basin is more important than the role of supply of debris. We used a statistical analysis of the relationship between site conditions and surface morphology on thirty rock glaciers to validate the simulation model. Results suggest that transverse ridges and furrows on the rock glaciers vary in response to the geometry of the basin. Glacial and periglacial processes significantly impact how energy and mass move through the alpine system.