We’ve been busy getting things set up and running over the past couple of weeks, since the weather has been great for work outdoors.
One of the science projects that is being carried out this field season is Paige Czoski’s infrasound and seismic work around the volcano.
Paige is a senior at New Mexico Tech. She is graduating in May 2012 with a BSc in Earth Sciences, focusing on volcanology. She has helped with infrasound and seismic deployments in Hawaii, Costa Rica, Colorado and off the coast of Oregon, but it’s her first Erebus field season. Paige let me accompany her on a couple of her trips to set up the instruments, and has spent a bit of time explaining her work.
Paige working on her infrasound array
Volcanofiles:What is infrasound?
Paige: Infrasound is normal sound but at a lower frequency that what we can normally hear. Humans can hear from 20 – 20 000 Hz, but infrasound is anything less than 20 Hz. Infrasound is good for studying volcanoes because, since it’s such a low frequency, it can travel long distances. It travels through the air so the energy doesn’t get scattered or lost between the source and the receiver. Infrasound is good for volcano monitoring because you can detect eruptions even if the volcano is obscured by clouds or ash, whereas seismic detectors only sense ground movement – you can’t necessarily tell if there’s anything coming out of the volcano. Infrasound is also used to study earthquakes, bomb testing, to track meteorites entering Earth’s atmosphere, and the weather (e.g. tornadoes and lightning).
Volcanofiles:What are you hoping to get from the infrasound on Erebus?
Paige: I’m putting out six infrasound detectors in a spoke shaped pattern about 60 m across, located a couple of kilometres from the summit. With this small array, I can pick up eruptions, rock falls and possibly ice quakes (caused by cracking of the ice). There are already infrasound sensors on Erebus that are monitoring year round (check out the MEVO website) but this experiment is different in that the sensors are so close together. The sensors measure the distance from the source, so I can use the time differences in when the signal arrives at each sensor to accurately pinpoint where the source is.
Volcanofiles:What is a seismometer?
Paige: A seismometer is a device that uses masses and springs to measure ground movement – volcanoes, from the magma moving beneath the surface, and from eruptions, create ground movement, so we can use seismometers to measure the inner workings of a volcano.
Changing a seismometer
Volcanofiles:How and why are you using seismometers at Erebus?
Paige: This is an experiment for Julien Chaput at New Mexico Tech., to study how energy is scattered off different rock layers and structures within the volcano.
I’m setting up an array of six seismometers in the shape of a 50 m wide square, with one in the middle and two on the same corner. The square shape is so that he can constrain the scattering in a certain area. Five of the seismometers are broadband seismometers, which means they can measure high and low frequency movement; and one of those on the same corner just measures high frequency movement.
Seismic array – the green and red boxes. The tents are where we sleep! Photo courtesy of Nels Iverson.
Julien recently published a paper in Nature on using seismic waves and scattering to locate magma.
Volcanofiles:Given that you’ve had experience of this sort of work in other places, what are some of the particular challenges and rewards of working out here in Antarctica?
Paige: The wires get really brittle and hard to work with, and my hands get cold! Otherwise, I love it here! I love the snow and it’s really cool being so isolated. Just being able to walk out and see the view from here is awesome – and the fact that we’re on an active volcano where you can see lava!
Seismic station on the Side Crater. From left: Nial Peters, Paige, Nels Iverson.
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