Landslides and landscape evolution in the Rocky Mountains and adjacent Foothills area, southwestern Alberta, Canada
Published:January 01, 2002
Lionel E. Jackson, Jr., 2002. "Landslides and landscape evolution in the Rocky Mountains and adjacent Foothills area, southwestern Alberta, Canada", Catastrophic Landslides, Stephen G. Evans, Jerome V. Degraff
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Distinctive suites of landslides occur in five stratigraphic-structural provinces in the Foothills area of southwestern Alberta. The Porcupine Hills are characterized by slumps and earthflows on slopes steepened by fluvial activity. The ridges of the Rocky Mountain Foothills have a low frequency of landsliding due to slope angles that are generally lower than bedding-plane dip angles. Extensive landsliding around the Mokowan Butte upland is likely due to shearing of bedrock beneath the Lewis thrust and glacial oversteepening. Glaciolacustrine valley fills form the floors of interridge valleys within the Foothills. These glaciolacustrine sediments fail as rotational slumps and flows. Rockslides and rock avalanches cluster along major thrust faults in the eastern Rocky Mountains. Glacial steepening and the exposure of cliff-forming Proterozoic and Paleozoic carbonates and clastics overlying recessive clastics, particularly along thrust faults, are identified as significant destabilizing factors. A mass-wasting feedback loop is suggested, cliff-forming massifs driving failure in underlying recessive rocks, which in turn triggers failures in the massif. Creep is suspected as a factor in footwall slope instability. Landsliding has likely been a prime agent in the retreat of the mountain front for at least the past 2.6 m.y. Recession rates of 0.2 cm/yr can be computed for this period.
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>This volume documents further advances in our knowledge of catastrophic landslides since the pioneering compilations of the late 1970s by Barry Voight. It provides a worldwide survey of catastrophic landslide events written by leading authorities. Catastrophic Landslides begins by drawing upon South America to dramatically illustrate the impact of these phenomena on human populations. The occurrence of catastrophic landslides, including site-specific insights, is shown through six events of the past 20 years. Several other chapters focus on the mechanisms involved with catastrophic landsides both in relation to geologic factors in a particular geographic area as well as to specific geologic processes.