Collaborative Research: Integrating Petrochronology, Magma Dynamics, and Volcanic Unrest at the Three Sisters Volcanic Complex

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Volcanic eruptions have to potential to threaten agriculture, infrastructure, aviation, and human life at local to global scales. These events represent the intersection of geologic processes that proceed over thousands to millions of years and destabilization of the volcanic reservoir which may occur rapidly over only days to years. These processes may be interrogated through retrospective geologic studies of past eruptions and geophysical monitoring, respectively. This project is focused on integrating these approaches at the Three Sisters Volcanic Complex, a “very high threat potential” volcanic system located in the western United States. The goals are to elucidate hazards specific to the Three Sisters through the investigation of recent eruptions and volcanic unrest and produce new conceptual and quantitative models that can be applied to understand the hazards and improve eruption forecasting for active volcanoes globally. The results of this project will be disseminated to the general public through animation and videos published on-line and a self-guided geology hiking guide made available to the many recreational visitors to the Three Sister’s Wilderness Area.Linking the processes that catalyze the growth, evolution, destabilization, and eruption of magma reservoirs to their expression as observable unrest represents an important scientific frontier that requires inter-disciplinary collaborations across the geosciences. Parallel advances in geophysics, petrochronology, and numerical modeling have made substantial contributions to the understanding of magma reservoir processes. Yet, these methods remain poorly integrated. The unusual confluence of frequent late Pleistocene to late Holocene eruptions, which range in composition from basaltic andesite to rhyolite, with modern volcanic unrest make the Three Sisters a prime natural laboratory at which to pursue this integrated approach. This project will produce new crystal-scale petrochronologic data for lavas and associated explosive products erupted from the Three Sisters Volcanic Complex, central Oregon Cascades, during the last ca. 50,000 yr. These data will inform interpretations of: 1) the petrogenesis of the rhyolite and dacite lavas erupted at the Three Sisters and if there is a genetic relationship between these rock types; 2) the longevity and physical integration of the magma reservoir(s) that produced the late Pleistocene flare-up of intermediate and silicic volcanism; and 3) the nature and tempo of the processes that preceded, and potentially triggered, these eruptions. In parallel, a high-resolution Bouguer gravity survey will be conducted to constrain the physical structure of the modern magma reservoir. These new geochemical and geophysical data will be integrated with the existing geodetic observations of recent uplift in coupled models of magma dynamics and crustal deformation. Accordingly, these observations and models will quantitatively test if recent unrest at Three Sisters reflects similar processes to those associated with the late-Pleistocene volcanism.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.