Pleistocene Glaciation and Climate of the Little Prickly Pear Watershed, Western Montana

Field mapping and aerial photo interpretation of the Little Prickly Pear Watershed in western Montana allowed us to identify glacial features from the last glacial maximum of the Pleistocene Epoch, nearly 20,000 years ago. We also documented glacial features in the field, such as cirques (where the glacier originated on the mountain) and moraines (a feature left behind by a glacier that is mainly composed of gravel, sand, and clay). Lateral and terminal moraines were identified in the field by their shape, position, and clast composition, then located using GPS. By interpreting our field data though Microsoft Excel and Geographic Information Systems (GIS) techniques, we were able to reconstruct the thickness of glacial ice, the extent to which it flowed, and the equilibrium line altitude (ELA) of these glaciers. An ELA is the line on a glacier above which it does not melt during the summer. We hypothesized that our reconstruction of ice elevation and extent would be lower than that suggested previous by workers. The results were that the average thicknesses of glacial ice for several of the nearby cirques and the extent of ice were larger than previously described. These results suggested a colder Pleistocene climate in the region than previous studies indicate