Ending a Powerful Explosive Eruption: The Case Study of Novarupta 1912, Alaska

University Of Hawaii, Honolulu

Investigators

Abstract

Short-lived but violent explosive episodes frequently occur during long-lived lava-forming eruptions at our larger volcanoes. Similar eruptions also occur during the build-up to or wind-down from powerful steady eruptions as seen at Mount Pinatubo in 1991. At least 24 such eruptions have occurred in the last 10 years in 12 different countries. These eruptions had few warning signs but yet impacted nearby regions with large, growing populations. The novelty of this study is its focus on an exceptionally well-studied event at Novarupta volcano, Alaska in 1912, which was the largest explosive eruption in the last 100 years. Three powerful eruption pulses, over approximately 60 hours, were followed by a series of violent, short explosions ejecting blocks showing a diverse range of magma textures. These textures form 'fingerprints' to the processes that caused the change in style of activity at the volcano. The project uses a variety of newly developed techniques to capture the rates of processes of gas release and escape in the shallow portions of the volcano's plumbing system. The techniques have in common that they are microanalysis of features of the erupted material on scales of millimeters to micrometers. They include 2D and 3D imaging of vesicles, i.e., the gas bubbles in the erupted material, and measurement of the residual gases in and the permeability of the blocks. The central aim of this study is to reconstruct the architecture of the shallow magma plumbing, and constrain the conditions that led to a transition from a powerful steady eruption style into a series of short unsteady pulsing explosions. The project will involve exchange of material, students and ideas between University of Hawaii at Manoa, University of California at Berkeley and Rice University with Université de Savoie, and Université d'Orléans, in France. Two new initiatives, Students to Schools and Teachers in the Field, are aimed at contact and dialog with school teachers and classes to motivate high school students to consider the earth sciences as a field of study in their undergraduate program.