Stability and mechanism of failure of The Barrier, southwest British Columbia

The Barrier is a steep, 250 m-high escarpment of dacite in Garibaldi Provincial Park, British Columbia. The lava flow comprises four lobes, two of which (Lobes 3 and 4) came into contact with the late Pleistocene Cordilleran ice sheet. Lobe 3 was the source of a major landslide in 1855-1856 and a smaller event in 1977. This thesis investigates potential mechanisms responsible for landslides from The Barrier. Methods that I applied include magnetic surveys to determine the three-dimensional character of lava flows forming The Barrier, long-range photogrammetry to map the structure of the escarpment in digital terrain models, field mapping, distinct element modelling, and passive seismic landslide monitoring. Of particular importance to the stability of The Barrier are ice-contact structures in the volcanic rocks, which provide clues about emplacement environments. Results show that The Barrier should be considered potentially unstable and that past instability is intimately linked to structures produced by emplacement of the lavas against glacier ice. My work also provides new geophysical and geomechanical data for The Barrier