A geotechnical investigation into the Chaos Jumbles rockslide avalanches Lassen Volcanic National Park, California

The Chaos Jumbles are a series of rockfall-avalanches originating from one of the six domes at the Chaos Crags. The Chaos Jumbles extends northwest from the base of the Chaos Crags for 4.3 km, covers an area of 6.8km 2 and has an estimated volume of ∼0.15km3 . Field and laboratory investigations characterized the strength of the rock mass associated with the failure and were used to develop rock strength criteria and identify modes of failure. Failure scenarios were modeled using the limit equilibrium program SLIDE v.5.0 (2004). Stability analyses indicate that under low and moderate water table conditions some seismic loading is required for failure to occur. Under high water table conditions failure may occur with no seismic loading. Further research should be continued in identifying possible sources of the seismic loading that may have caused the failure.