Collaborative Research: Probing transcrustal magmatism at a transform fault: The Mt. Edgecumbe (Lux Shaa) Volcanic Field in the Context of Regional Tectonics

University Of Alaska Fairbanks Campus, Fairbanks AK

Investigators

Abstract

Volcanoes are dangerous for people living and working nearby because they create ash fall and ash clouds. Mt. Edgecumbe volcano is located in Southeast Alaska, about 15 miles northwest of the City of Sitka. Sitka has 8500 people living there year round, and each summer a few hundred thousand visitors from cruise ships. An eruption from Mt. Edgecumbe will cause problems from ash fall for Alaskans living in the Sitka and Southeast Alaska region, and boats and airplanes traveling downwind from the volcano. In the past, Mt. Edgecumbe had eruptions that created ash fall that covered the Sitka area with more than a foot of ash. Recently, there have been earthquakes and ground movement around the volcano from new magma. Researchers will use rock samples to recreate Mt. Edgecumbe magma and observations of ground movement measured using satellites to estimate the depths within the volcano where magma resides. This project will also examine how the tectonic plates move around the Mt. Edgecumbe region to better understand why the volcano has formed near a transform fault. This type of plate tectonic boundary is not commonly associated with volcanoes. This work will help answer questions about how magma is created in the Earth’s mantle in this unusual location. Together, these results will result in new knowledge such as why Mt. Edgecumbe exists, where magma resides inside the volcano, and what the earthquakes and ground movement might indicate about future eruptions. This work will help volcano scientists decide what future signs of unrest mean and improve eruption forecasts. Researchers will also work with the Sitka Sound Science Center and Sitka Tribe of Alaska to share the results about seismic and volcanic hazards. Researchers will also work with schools to provide hands-on activities in the area and offer training opportunities for community members in volcano science methods. The Mt. Edgecumbe Volcanic Field (MEVF) exists in an unusual tectonic location, in proximity to the Queen Charlotte – Fairweather transform fault, which forms part of the plate boundary between the Pacific and North American plates. The MEVF can produce large, silicic explosive eruptions that have in the past covered the region around Sitka, Alaska, with thick ash deposits. In response to recent seismic and geodetic unrest, this study will use an interdisciplinary approach combining experimental petrology and melt inclusion analyses with geodetic data and models to refine the magma plumbing system model for the MEVF. The outcomes of this work will include a new regional tectonic model that will resolve the cause of magma generation in the region, testing how local extension may play a role in decompression melting feeding the MEVF. Petrology-based magma storage constraints will be combined with recent volcano deformation results that are based on long multi-platform InSAR time series, including tests of how rheological heterogeneities impact the deformation models. Research will also synthesize the tectonic geodesy, volcano deformation, and petrology-based magma plumbing system constraints into a comprehensive unified magma-tectonic model that gives insights into the current state of the MEVF and potential future activity. Ultimately, this project will help inform volcanic unrest in the region and help volcanologists assess the likelihood of future eruptions based on monitoring data. Researchers will also work with the Sitka Sound Science Center and Sitka Tribe of Alaska to share the results about seismic and volcanic hazards. This project is jointly funded by NSF EAR/Chemical Evolution of the Solid Earth and Volcanology and the Established Program to Stimulate Competitive Research (EPSCoR). 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.