Collaborative Research: A multidisciplinary reexamination of the precursory activity for an archetype M7 eruption, Mount Mazama, Oregon

University Of Oregon Eugene, Eugene OR

Investigators

Abstract

Large volcanic eruptions are rare but when they occur, they can devastate areas close to the volcano and have severe impacts on areas hundreds of miles away. But large eruptions do not occur without warning: they are typically preceded by earthquakes, gas emissions and smaller eruptions. Under these circumstances, it can be difficult to determine when, and how large, the main eruption will be. A good example of this behavior is the eruption that formed Crater Lake, Oregon, about 7700 years ago. Here explosive eruptions occurred over the decades before the big eruption, with several eruptions during the months leading up to the final event. The research team will study deposits from these eruptions to determine the changes in the system that produced the catastrophic event. This work will improve our ability to forecast volcanic activity. This project will not only train two PhD students but will also (1) engage students at a local community college in running a hazard assessment exercise simulating the buildup to the eruption, and (2) engage professionals in related fields to examine the long-term (decades to centuries) impact of the eruption on the vegetation, rivers and human occupants of the Pacific Northwest. This proposal to conduct a multidisciplinary re-examination of the precursory activity an archetype M7 eruption, Mount Mazama, Oregon will track, in P-T-X-t space, the products of explosive and effusive activity that both preceded (by ≤ ~200 years) and include the climactic Mazama eruption that formed Crater Lake, OR. The team's goal is to identify changes within the magma storage region that led to reservoir evacuation and caldera collapse, and, by doing so, to define key observables in eruptive products that could provide early warning of a major explosive eruption. Detailed studies of precursor eruptions are limited, because these smaller eruptions are over-shadowed by the climactic event and early deposits are often covered and/or destroyed by later activity. In this respect, deposits from precursor Mazama eruptions may be unique, both in their preservation and in the number and complexity of the precursor eruptive sequences that they record. The proposed approach is comprehensive in linking petrology to physical volcanology through detailed analysis of ash, pumice and lava samples. Ash samples, in particular, may be enriched in components that are not well-represented in larger clast sizes typically used for petrologic studies and that record conduit processes controlling eruptive transitions, including onset of a paroxysmal phase. The approach is innovative in using deposits from precursor eruptions to track changes in both the chemistry and physical properties of the larger magmatic system in space and time. The approach is unusual in combining textural analysis and diffusion chronometry to monitor P-T changes within eruptive sequences and link them to larger-scale processes operating within an evolving magmatic system. This project will not only train two PhD students but will also (1) engage students at a local community college in running a hazard assessment exercise simulating the buildup to the eruption, and (2) engage professionals in related fields to examine the long-term (decades to centuries) impact of the eruption on the vegetation, rivers and human occupants of the Pacific Northwest. 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.