EAR-PF: Measuring the Effects of Large Volcanic Eruptions on a Shallow Magma Reservoir using Microanalytical Techniques

Dr. Madeline Lewis has been awarded an NSF EAR Postdoctoral Fellowship to investigate how large volcanic eruptions affect potentially hazardous magma stored beneath the surface of the Earth. Her research, professional development, and public outreach will take place at Stanford University alongside scientific mentor Dr.

Ayla Pamukçu. Volcanic centers are connected to magma storage reservoirs within Earth’s crust, yet not all magma is immediately eruptible. Magma storage conditions (pressure, temperature, and dissolved water content) strongly influence the potential for magma to erupt.

However, the extent to which eruptions influence magma storage conditions is poorly understood. Is magma stored after an eruption easily mobile and primed to erupt, or is it nearly solidified? Dr.

Lewis will address these questions using the extinct Stillwater Caldera Complex (SCC), Nevada, which exposes both volcanic rocks and portions of the now solidified magma storage system. She will collect geochemical data to calculate magma storage conditions during different stages of SCC magmatic activity. Dr.

Lewis’s earlier research established the sequence and duration of magmatic activity in the SCC, which she will use to evaluate changes to the magma storage conditions in response to major eruptions. Dr. Lewis will expand the broader impacts of her work by designing a virtual field trip, which will be a publicly available educational resource through Stanford Earth Field Education.

In addition, she will complete training in STEM education and volunteer as a mentor with the Palo Alto chapter of the Association for Women in Geoscience to improve retention and support for women pursing geoscience degrees and careers.

The uncertainty surrounding whether eruptible magmas remain in shallow storage after caldera forming eruptions will be improved by investigating both the intrusive and extrusive portions of a shallow silicic magma system. The Oligocene (~25 Ma) Stillwater Caldera Complex, Nevada, preserves a sequence of pre- and post-eruptive intrusions (magmatic history of ~106 yrs), as well as two very large (>350 km3) explosive deposits that record snapshots of definitively eruptible melts.

Dr. Lewis will collect and analyze the compositions of erupted (extrusive) and unerupted (intrusive) crystals and melt inclusions to establish magma storage conditions (e.g., temperatures, pressures, volatile contents) from mineral equilibria. She will apply these calculated parameters to thermodynamic and diffusion-based models to estimate magma crystallinity and the residence time of eruptible magma bodies.

Coupling these results with her existing high-precision geochronology data will enable tracking of reservoir conditions over the lifetime of the magma system. If eruptions are found to leave behind crystal-poor magmas in the shallow reservoir, this indicates the capacity of volcanic systems to produce “silent” eruptions with little seismic warning.

Conversely, if eruptible magma is not retained shallowly after eruption, this has significant implications for interpretation of magma injection signals as an indicator of impending eruptions.

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.