New Estimates of Eruption Recurrence Rates, Volume, and Volume Flux Using the Volcanic Event Age Model - Medicine Lake Volcano, Northern California, USA

Medicine Lake Volcano (MLV) is the largest Cascade Volcano by volume (~600 km3) and has erupted 9 times during the Holocene. Detailed mapping by the USGS has shown that over the last 500 kyr MLV has erupted \u3e200 lava flows, one ash-flow tuff (VEI 5-6), and built at least 17 scoria cones. Rhyolite, dacite, andesite, basaltic-andesite, and basalt have all erupted throughout the geologic record, but mafic vents make up 78.2% of the total mapped vents. During the Holocene the proportion of felsic vents is significantly higher (54.5%) than mafic vents (39.9%). Using the Volcanic Event Age Model (VEAM), we calculate recurrence rates using 60 radiometric dates and 735 stratigraphic relationships. Results show Pleistocene mean recurrence rates to be relatively constant within a range of 0.5–2.0 events per kyr. A sharp uptick occurs between 12-13 ka reaching a peak rate of 7.8 events per kyr. A hiatus follows before elevated activity resumes at 6 ka and reaches 6.0 events per kyr at 1 ka. Using field measurements of lava flow thicknesses, we modify VEAM to account for variable flow thicknesses (largely controlled by geochemistry), as well as volumes of explosive eruptions. We then explore eruptive volumes, volume flux, and recurrence rates, over MLV’s 500 ka history. By investigating these parameters together, we gain a deeper understanding of MLV’s eruptive history, which is vital to anticipating the nature and hazards of future eruptions