North-Central Section (36th) and Southeastern Section (51st), GSA Joint Annual Meeting (April 3–5, 2002)

Digital Elevation Models (DEMs) and satellite imagery provide a range of detail about the surface of the landscape on which we live. In regions that were once glaciated, visualizations are particularly important. Satellite imagery instantly presents differences in vegetation and surface material that, by proxy, is indicative of a change in the substrate. DEMs show exceptional detail of shape, slope and pattern in a landscape that is usually masked by a myriad of cultural imprints. This paper demonstrates how the information extracted from DEMs and satellite imagery can aid in determining glacial processes that operated on the landscape in the past. Weaknesses in landscape interpretation are also pointed out. Examples are presented from three regions in North America. In southern Alberta, 25m resolution DEMs display spectacular fluted terrain. However, they do not show that the terrain is composed of preglacial gravels, and thus the sediment in the terrain predates the terrain surface. In Ohio, 30m DEMs display the boundaries between glaciated and non-glaciated terrain. Specifically, in NE Ohio and NW Pennsylvania, experiments with Landsat 7 imagery and DEMs reveal numerous large channels several kilometers across. Cross sections along channel bottoms extracted from the DEMs demonstrate that the channels have convex up-and-down profiles that have relief of up to 70m. Modern drainage patterns extracted from the DEMs also show divergent paths in these channels. As the channels end at the palaeo ice margin, it is inferred that their genesis is subglacial. In addition, the DEMs of the Allegheny plateau display information that is too subtle to be observed on satellite imagery, aerial photographs, and even topographic maps. For instance, large low-amplitude ridges that are transverse to other glacial features in the region are reasonably prominent on the DEMs. However, without detailed fieldwork it cannot be determined if the ridges are glaciotectonically thrust ridges, or large-scale glaciofluvial ripples. While absolute genesis cannot be determined, advanced computing techniques, as applied to DEMs and satellite imagery, can be used to make assumptions about general landscape origin. More importantly, these techniques can be used to identify key regions for further detailed study.