Skip to content

Magmatic Structure and Melt Storage beneath the Katmai Volcanic Group, Alaska

Graham J Hill1, Paul A Bedrosian2, Bethany L Burton3, Cesar Castro1, Jade W Crosbie2, Alexander Grayver4, Bennett E Hoogenboom2, Michael A Mitchell2, Jared R Peacock2, Eric Roots1, Erin L Wallin5

  • Affiliations: 1Institute of Geophysics - Czech Academy of Sciences 2United States Geological Survey 3United States Bureau of Reclamation 4University of Cologne 5University of Hawaii

  • Presentation type: Poster

  • Presentation time: Friday 16:30 - 18:00, Room Poster Hall

  • Poster Board Number: 8

  • Programme No: 1.5.15

  • Theme 1 > Session 5

Abstract

The Katmai volcanic group (KVG) within the Alaskan Aleutian arc is an unusually dense group of active volcanic centres (Mounts Martin, Mageik, Trident, Katmai, Griggs, Snowy, and Novarupta). The KVG was the locus of the largest eruption of the 20th century. During the 1912 eruption, rhyolite was erupted from a new vent (Novarupta) contemporaneous with collapse of Mount Katmai (10 km away). A hydraulic connection has been hypothesized between the two vents based on the above observation and on a small volume of andesitic magma with the geochemical signature of Mount Katmai that erupted from Novarupta at the onset of the eruption. Unanswered questions about the structure and dynamics of the KVG include the origin and storage zone for the 1912 erupted rhyolite, its connection (if any) to the dense group of andesitic stratovolcanoes surrounding the Novarupta vent, the cause for off-arc centres such as Mount Griggs, and the reason for enhanced magmatic flux beneath the KVG relative to other segments of the arc. Our recent wideband (1 kHz -- 1 mHz) magnetotelluric survey of the region encompasses the Katmai group of volcanoes (110 sites) and is bisected by an arc-perpendicular profile crossing the Alaska Peninsula (18 sites) spanning subducting slab depths of 60-200 km. Coast effects are present in the magnetotelluric data; however, qualitative analysis of the data indicates the Jurassic sedimentary section upon which the arc is built, the highly resistive arc itself, and a swath of elevated conductivity beneath the arc axis that likely reflects melt storage.