A geomorphic investigation of retrogressive thaw slumps and active layer slides on Herschel Island, Yukon Territory /

This thesis investigates the geomorphology of retrogressive thaw slumps and active layer slides on Herschel Island, northern Yukon Territory. In particular, it examines the formation and morphology of both landforms, and the ground ice characteristics of retrogressive thaw slumps. During 1988-1989 a number of retrogressive thaw slumps and active layer slides were surveyed and monitored. Field and laboratory investigations involved (1) documentation of landform distribution, setting and morphology, (2) examination of processes of landform formation, and (3) the examination of cryostratigraphy, ground ice characteristics and material properties.Retrogressive thaw slumps developed in areas of low to moderate slopes underlain by a variety of sediments with ice contents up to 4500% (on a dry weight basis). Slump headwall retreat rates of up to 19.5 m/yr were recorded. By comparison, active layer slides developed on steeper slopes underlain mainly by marine silts and clays. The sediments exposed in the slide floors and headwalls displayed no visible ground ice, but moisture contents were between 15-35%. Retrogressive thaw slumps and active layer slides form by entirely different processes. However, they do occur in close association and are influenced by many of the same parameters