VLP-Discriminated Strombolian Event Families and Video Observations at Mount Erebus, Antarctica

Aster, R C, Mah, S Y, McNamara, S, Ruiz, M, Kyle, P, McIntosh, W, Dunbar, N

Department of Earth and Environmental Science, New Mexico Institute of Mining and Technology, 801 Leroy Place, Socorro, NM 87801 United States
New Mexico Bureau of Geology and Mineral Resources, New Mexico Institute of Mining and Technology, 801 Leroy Place, Socorro, NM 87801 United States

Strombolian eruptive activity from the phonolitic lava lake of Mt. Erebus generates VLP (Very Long Period) signals with spectral components as grave as 20 s. These signals have been observed on a seasonal basis with broadband seismometers during three Antarctic field seasons in targeted PASSCAL deployments and, more recently, with permanently installed broadband seismometers. Associated eruptive and other lava lake behavior has also been observed since 2000 with a time-stamped crater surveillance video camera. VLP signals persist for several minutes during lava lake refilling following eruptions and have highly similar waveform characteristics from event to event. The initial few seconds of signal associated with the pre-eruptive phase, however, exhibit significant variations and can be readily classified into 3 families, two simply based on initial polarity. A third event family, infrequently observed, shows a very different pulse-like shape and different frequency content. Video observation of eruptions suggest a correlation between the eruptive character and the initial polarity of the event. Positive polarity events have a vertical, jet-like eruptive style, while negative polarity events feature more radial ejecta. All lava lake eruptions are due to simple Strombolian gas slugs nucleating in the near-summit conduit system, becoming dislodged from buoyancy forces, and rising nearly intact to the lake surface. Distinct families of eruptive styles from a single vent and their correlation with VLP signals generated by ascent forces suggest distinct source zones and/or delivery paths of gas slugs to the lava lake surface.

URL: http://www.ees.nmt.edu/Geop/Erebus/erebus.html