Lithologic, Structural, and Topographic Influences on Snow-Avalanche Path Location, Eastern Glacier National Park, Montana

Abstract

Abstract We examine the roles of lithology, structure, and topography as determinants of the location and morphology of snow-avalanche paths in east-central Glacier National Park, Montana. Most models of avalanche path location emphsize topographic interactions with prevailing winds and ignore the role of geologic influences. Landsat Thematic Mapper digital data, covering the study area, were enhanced through a combination of directional and nondirectional spatial filters, principal components analysis, and channel ratioing to delineate the relationships between lithology, structure, topography, and avalanche-path location. We used GIS technology to examine these spatial relationships. Fieldwork confirmed the remote sensing and GIS interpretations. More than 50 percent of the snow-avalanche paths are located directly beneath a widespread diorite sill, and roughly 25 percent and 20 percent of the additional paths were associated with topographic couloirs (probably structurally controlled) and structural lineaments respectively. Structural patterns also influenced slope aspect of the paths. Morphometric differences between these paths and those from a larger, previous study group are attributed to local climatic differences on opposite sides of the Continental Divide.