DIGITAL ELEVATION MODELS IN GEOMORPHIC RECONNAISSANCE: MAPPING THE EXTENT OF PROGLACIAL LAKE SWAN, NORTH-CENTRAL MONTANA
DEM data (30-m grid) was obtained from the National Elevation Dataset and re-projected to match existing state plane data. This data set was then resampled to 1-m resolution. Neighborhood statistics were used to look for trends in the surficial fabric of the landscape. A contour file representing an elevation of 1290 m, the hypothesized sill/spillway elevation, was extracted and used to create a representation of proglacial Lake Swan at its highstand.
Our DEM-based mapping helps to identify and visualize key geomorphic features related to the proglacial-lake hypothesis. The controlling sill/spillway at the southern end of the valley is readily observed, as are the giant glacial grooves at the northern end of the valley. The important morphologic differences between the knob-and-kettle topography of the valley floor and the wave-washed glacio-lacustrine deposits (once inferred to be ice-margin deposits) of the valley margins are clearly elucidated.
In summary, it is possible to produce a DEM-based map of Lake Swan supportive of Lockes (1995) hypothesis and consistent with previous geologic mapping. Our work serves to demonstrate the value of DEMs in reconnaissance-level mapping and the initial testing of geomorphic hypotheses.