Multidisciplinary perspectives on Shishaldin Volcano: an open-system, deforming volcano

Mario Angarita, Ronni Grapenthin , Darren Tan, Pablo Saunders-Shultz, Társilo Girona, Revathy M. Parameswaran, Taryn M. Lopez, Pavel E. Izbekov, David Fee , Vanesa Burgos, Jamshid A. Moshrefzadeh, Tara Shreve, Jessica F. Larsen

The integration of multidisciplinary data across multiple eruptions is essential to improve our understanding of a volcanic system. Shishaldin Volcano is one of the most active volcanoes in Alaska, with several reported eruptions over the last 300 years. We synthesize multidisciplinary datasets going back to 1997 and focus our analyses on the 2014–2015, 2019–2020, and 2023 eruptive periods. We find pronounced periods of volcanic tremor, long-period and volcano-tectonic seismicity; thermal anomalies with a radiative power ranging from 10 to 1000MW; 1–2°C increase in the median, low-pass filtered thermal anomaly; SO₂ emission rates ranging from 30 to 287 kt/year; and previously unrecognized surface deformation that includes two episodes of ∼1 cm/year inflation preceding the 2014–2015 and the 2019–2020 eruptions, and deflation prior to, during, and after the 2023 eruption in the GNSS records. The new ground-based geodetic observations allow us to refine previous interpretations of the magmatic plumbing system. Borehole tilt records are best explained by a shallow, 1–1.5 km long conduit centered at sea level with a radius of 150 m. From the GNSS records, we find a pressurized sphere between 2 and 4 km below sea level (bsl) depth, and a 10 km long conduit centered at ∼6 km bsl depth as the most probable inflation and deflation sources, respectively. We propose that the observed seismicity at a nearby fault system can be explained by magma/fluid flow among our resolved magma sources, that modulate the local stress field. We integrate these models and observations into a conceptual magma system model, building upon previous findings for Shishaldin Volcano.