Rock strength and stability modeling studies of Mount Shasta volcano, California

Mount Shasta, California, rises to 4,317 m making it the second highest volcano in the Cascade Range. Approximately 300,000 years before present a catastrophic landslide occurred on the ancestral edifice. The deposit from this failure has a volume of about 45 km3 and is the largest known Quaternary landslide. The deposit is viewed as a model for the type of failure that is possible from the current Mount Shasta. Mount Shasta is formed from four separate volcanic episodes, which post date the debris avalanche deposit. AVIRIS data shows that each eruptive episode has corresponding areas of argillic alteration, which significantly decreases the strength of the rock due to the presence of clay minerals. Numerical modeling of Mt. Shasta utilizing structural and strength data obtained from field and laboratory investigations show different edifice failure scenarios. The largest risks exist in the SE area of Mount Shasta in the Mud Creek region.