Laurentide subgiacial outburst floods: landform evidence from digital elevation models

Abstract

Various lines of landform evidence in many parts of Canada are comprehensively explicable as products of subglacial sheetfloods–outburst floods. In the Northwest Territories, northern Saskatchewan, and Alberta, landform associations such as scoured bedrock tracts, cavity-fill drumlins, erosional drumlins, erosional giant flutes–remnant ridges, tunnel channels, channeled scabland, and hummocky terrain with upstanding moraine plateaus reflect primary glaciofluvial erosional processes and secondary depositional activities. The Livingstone Lake event major sheetfloods path arcs obliquely upslope from the Keewatin District, Northwest Territories, through northern Saskatchewan and much of Alberta into Montana, U.S.A. Hill-shaded maps generated from digital elevation models, at widely varying scales, are used to illustrate regional to local examples of megaflood landform suites. Complementary maps and diagrams are derived from more conventional data sources. Speculations regarding extraglacial implications of the outburst floods in the Missouri–Mississippi basins, Mississippi Delta, and Gulf of Mexico are offered for testing by others.