Limit equilibrium stability analysis utilizing geotechnical data at Mount Baker, Washington

Hydrothermal argillically altered rocks are much weaker than their un-altered counterparts and progressive alteration within a volcano can lead to the catastrophic collapse of the edifice. The need for stability modeling at Mt. Baker is made evident by a geologic history of flank collapses, a high degree of hydrothermal alteration of the edifice, and the presence of residences and infrastructure, including two reservoir dams within the lahar inundation zone map produced by the USGS (2000). This research uses published geologic spatial distribution of materials, geologic history, and historical accounts, combined with fieldwork, laboratory testing and limit equilibrium modeling to gain insight into past and possible future edifice or flank collapses originating from Mt. Baker, Washington.;Historical data indicate small, localized slope failures are a common occurrence on Mt. Baker. Large failures from the edifice have been associated with volcanic unrest, which would have likely increased pore pressures at depth and involved seismic activity. Limit equilibrium stability analysis results also indicate small, localized failures to occur in saturated areas heavily altered by geothermal activity. Based on geologic history and modeling results, a large, deep-seated edifice collapse is not considered likely without associated volcanic activity to include elevated pore pressures and seismic activity. In the event of a volcanic eruption, the most likely location of a sector or edifice collapse would be the hydrothermally altered southeast sector including the Sherman Crater.