UNDERSTANDING THE HISTORY OF MONO LAKE DEFORMATION USING SHALLOW LAKE SEDIMENTS

Volcanic eruptions are often preceded by ground deformation. We examine the processes driving ground deformation at Mono Lake, California, and its connection to the hydrothermal and volcanic system in the Mono basin. Previous studies have mapped subsurface landslides, but have not studied their post-emplacement deformation which provides insights into the most recent volcanic and hydrothermal activity on the lake floor. We address this gap by analyzing seismic reflection data of deformed landslide deposits and conducting core analysis to understand sediment properties. Using a model for sediment compaction, we differentiate between recent deformation and the effects of sedimentation on the structure of the landslide deposits. Areas of peak subsidence on the northeast and southwest side Paoha Island may have cumulative vertical displacements of -18 meters. The landslide deposits were emplaced during the uplift of Paoha Island 300-350 years BP; if this vertical displacement occurred exclusively since the time of island formation this would imply a time averaged subsidence rate of up to 5 cm/yr. Rapid subsidence may have occurred immediately following the intrusion of magma and volcanic eruptions that formed Paoha Island, or more slowly through cooling of a distributed hydrothermal system. We identified localized areas of significant subsidence, which could aid in hazard management by helping to distinguish between deformation connected to magmatic processes and deformation from shallow processes unrelated to volcanic hazards.