Publication Date

8-2016

Date of Final Oral Examination (Defense)

3-4-2016

Type of Culminating Activity

Thesis

Degree Title

Master of Science in Geophysics

Department

Geosciences

Supervisory Committee Chair

Jeffrey B. Johnson, Ph.D.

Supervisory Committee Member

Brittany Brand, Ph.D.

Supervisory Committee Member

Paul Michaels, Ph.D.

Abstract

A natural laboratory exists at Mount Erebus where strombolian activity from the lava lake is directly observed from the crater rim. Lava lake eruptions occur when pressurized bubble slugs distend the lake surface before bursting within a few tenths of a second. The unique setting presents an ideal site to quantify bubble growth through infrasound and video analysis. Two infrasound sensors and one video camera recorded eruptions ~330 m from the lava lake in 2006. Infrasound waveforms exhibit a high-amplitude bipolar pulse followed by a coda consisting of about five decaying oscillations. Video records are quantified by tracking the expanding bubble edge, which is approximated to a 3-D hemispherical volume. Video-inferred volumes scale closely with infrasound-inferred volumes during the bipolar pulse but deviate during the coda. Volcanic processes responsible for infrasound after the bipolar pulse are therefore unrelated to the inertially traveling lava lake fragments observed in the video during the coda. Two peak frequencies dominate coda spectra and reveal infrasound sources not observed in the video. Frequency peaks recorded at both stations suggest that echoes reflecting off the steep crater walls influence the infrasound codas. After removing echo contamination, both stations exhibit a single frequency peak at 1.48 Hz, which is attributed to a Helmholtz resonance within the evacuated magma conduit. Quantitatively relating infrasound to video thus gives a detailed chronology of a typical Mount Erebus eruption.

Download

Share

COinS