Wednesday, October 24, 2007

Still Grounded in McMurdo

In my blog post on Monday I told you that we weren't able to head out to field camp. Well, it's Wednesday afternoon and we're still here. The weather cleared up for a little while and we thought Helo Ops (the helicopter port) was going to call us down at some point in the afternoon. No such luck, and now another low pressure system is moving in and snow is blowing past the window again. I took this photo last night at about 10:30pm. The cloud ceiling lifted just enough to give us an incredible view of the Transantarctic Mountains glazed with sunlight.

Since I seem to have some time on my hands while we wait to hear about helicopter flights I thought I would give you an idea of who “we” are, where we’re heading, and what we’ll be doing once we get there. The “we” is a field party of ten people. Myself, two graduate students-Luke and Taylor, an undergraduate student-Jacob, a core driller-Kyle, a cook-Joan, an air gun technician-Andrew, a Geophysical Engineer-Marv, a Glacial Sedimentologist-Ross, and a mountaineer-Tim. We hope to have another core driller and another teacher joining us soon. We're know as Little ANDRILL. We will be setting up camp about 100 miles north and a little west of McMurdo Station in an area known as Granite Harbor. If you can find Cape Roberts on a map of Antarctica we’ll be just around the point from there. I’ve been told it’s really beautiful out there with granite cliffs on shore and blue sea ice under foot (I hope I don’t slip and fall). What we hope to accomplish while we’re there is to complete a seismic survey of the sea floor in the area of the Mackay Sea Valley, capturing Holocene sediment records. I’ll show you more of what this operation looks like once we get to our destination and start to work.

From Professor of Geophysical Engineering at Montana Tech Marv Speece, “We drill a 13 inch hole into 2-m-thick sea ice and then lower an air gun into the hole down into the water column. We then release 2000 pounds per square inch of pressure in the air gun as an air bubble into the water. The energy from the bubble travels through the water down to the rock layers. At rock layer boundaries some of the energy is returned as a reflection back through the water column and then back to the surface of the ice where we record the returning energy using geophones. Geophones measure the shaking of the ice caused by the returning reflections. We then use these reflections to build a picture of what the rocks look like under the sea floor.”

This is a sample of what seismic data looks like.
Geologists will study the seismic data we collect to determine the best location for a future core drilling operation to retrieve the sediment records that Ross Powell is seeking.

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