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