Active layer detachment morphology, sedimentology, and mechanisms, Fosheim Peninsula, Ellesmere Island

• Main Author: Favero, Pauline
• Format: Thesis
• Language: English
• Published: Université d'Ottawa / University of Ottawa 2009
• Subjects: Physical Geography.; Geomorphology.; Ellesmere Island; Fosheim Peninsula
• Online Access: https://dx.doi.org/10.20381/ruor-12426; http://www.ruor.uottawa.ca/handle/10393/28180

Active layer detachments on the Fosheim Peninsula have been assumed to develop over periods of minutes to a few hours. This assumption played an integral role in the understanding of relationships between active layer detachment deposit morphology, morphometry and sedimentology and active layer detachment dynamics. Field observations of two failures at 'Big Slide Creek' on the Fosheim Peninsula in August 2005 showed that while one failure conformed to the pre-existing assumption of near-instantaneous formation, movement and cessation of movement, the other failure did not and exhibited progressive expansion over several days. Several active layer detachments known to have initiated in 2005 were visited in 2006 to assess whether active layer detachments known to have failed via a prolonged mode display surficial and internal morphological characteristics that are unique from active layer detachments known to have failed via a near-instantaneous mode and to evaluate the ability of the infinite slope model to adequately predict slope stability. Results have indicated that active layer detachments known to have failed via a prolonged mode display a number of surficial and internal morphological characteristics that differ from those at active layer detachments known to have failed via a near-instantaneous mode. Based on Factor of Safety calculations, peak effective stress stability analysis indicates that Fosheim Peninsula slopes should be stable if pore-water pressures are not artesian, whereas residual effective stress stability analysis indicates that slopes greater than 6° on the Fosheim Peninsula are unstable even if pore water pressures are not artesian. Sensitivity analyses indicates that under peak conditions, Factors of Safety on Fosheim Peninsula slopes are most sensitive to changes in cohesion while under residual conditions, slope instability is related to increases in both slope angle and head of water above the slip plane.