Collapsing mountains: the threat from giant, rapid landslides
by
Christopher Kilburn
Benfield Greig Hazard Research Centre, Department of Geological Sciences, University College London, Gower St, London WC1E 6BT, U.K.

Giant, catastrophic landslides are among the most powerful natural hazards on Earth. On land they may reach volumes and travel distances of 10-100 cubic km and 100 km; below the sea, they may reach 1000-10,000 cubic km and 200 km or more. Subaerial collapses are recorded about 3 or 4 times a decade; the frequency of submarine events is less-well constrained, but may be of the same order. In both environments, the travel distances are extraordinarily large and suggest that parts of a landslide must advance as a granular flow. However, the dynamic regimes of emplacement are poorly constrained, because giant landslides are rarely seen in operation and because, apart from surface layers, only limited data are available about the nature of their deposits. Current models favour a granular-flow mechanism to account for the long runout of giant collapses. Energy loss is attributed to fragments colliding, sliding and rolling past each other, as well as to any deformation of an interstitial medium. New studies indicate that essential features of their emplacement can be explained if kinetic energy is lost through effectively viscous deformation in one or more boundary layers. The boundary layers consist of rock fragments in a fine grained rock matrix. The matrix may behave as a fluid with a yield strength that brings sturzstroms to a rapid halt once driving stresses in the boundary layer become smaller than a critical value. The results well describe key relations between landslide runout, drop height and volume, and so offer the prospect of improving hazard assessment and mitigation strategies in mountain districts.

Date received: March 12, 2002

Copyright © 2002 by the author(s). The author(s) of this document and the organizers of the conference have granted their consent to include this abstract in Atlas Conferences Inc. Document # caiq-76.