Tracking ascent rates in an open-vent volcano: Testing textural and geochemical ascent speedometers

Board Of Regents, Nshe, Obo University Of Nevada, Reno, Reno NV

Investigators

Abstract

Volcanic eruptions are sourced from magma chambers in the crust. At what depth magmas are stored and how fast they move to the surface prior to an eruption is of great importance to assess the hazards associated with individual volcanoes. Open-vent volcanoes are particularly hazardous for their lack of unrest signals prior to an eruption. This project specifically focuses the 2018 eruption of the open-vent volcano Mt Veniaminof on the Alaska Peninsula, which poses substantial risk to local communities and aviation through ash emissions. Volatile elements that exsolved on ascent (especially H2O) are the drivers of explosive eruptions. Thus, constraining the volatile element budget in these magmas as well as how fast the volatiles are lost provide important constraints for eruption models and the eruptive behavior of this and similarly behaving volcanoes. A variety of techniques are used to estimate magma ascent and in this study, those techniques will be compared to improve their robustness and test their underlying assumptions. In addition to the scientific benefits, this project will foster collaboration between the USGS/AVO and the academic community, while this collaboration will ensure that existing data sets and samples will continue to be exploited. The Alaska Peninsula is a focus site of geologic research (GeoPRISMS) and our work will complement ongoing geophysical research activities (Amphibious Array). Volatile element data is of importance for geophysics and will inform crustal and upper mantle seismic and magnetotelluric studies. The project supports a collaboration with journalism colleagues to improve science communication and help build a new generation of science-literate journalists. The interplay between magma ascent and textural evolution of basaltic andesites of the 2018 Veniaminof eruption will be studied. Existing estimates for magma ascent rates during the 2018 eruption derived from microlites, will be compared against independently determined ascent rates from melt embayments hosted in olivine. To interpret the embayment and textural record, we will also collect melt inclusion volatile data to constrain the volatile element budget in the crustal storage region prior to ascent. The work includes a series of analytical techniques (Raman, x-ray computed tomography, SIMS, FTIR, EPMA, LA-ICPMS) to fully characterize and correct the volatile budget. Fundamental assumptions related to embayment studies will be tested: 1) the uniformity of ascent rates among embayments, 2) changes over the course of an eruptive episode, 3) the effect of embayment necking. The project will be complemented with the development of a thermodynamic model that captures the driving forces for crystallization and dissolution through the calculation of chemical affinities along any preferred P-T-X-time path. 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.