Saturday, December 1, 2007

Field Trips, Field Trips and More Field Trips...

Sorry to have been away from my computer for so long. I've been busy seeing more of Antarctica, specifically the ANDRILL drill site, Robert Scott's hut at Cape Evans, and the Wright Valley. In this blog I'll start with the most recent trip and work backwards because I really want to share this photograph with you.

On Wednesday (11/28) a group of us from ANDRILL went on a field excursion to one of the valleys. We flew in aboard a helicopter that dropped us on the flat area near where I'm standing. Here is a quote from the introduction section of the Wright Valley Field Excursion guide given out to us:
"The Dry Valleys have long been a feature of great interest on the Antarctic continent. Not only because of their unique absence of ice and snow but as a result of this, their accessibility to geologic features that are ice covered in a majority of the continent. Little was known of the region until 1955 when the New Zealand party of the Commonwealth Trans-Antarctic Expedition, 1955-1958, resulted in the first thorough geologic assessment of Victoria Land." (Peter Webb, whom I photographed at our Open House, was one of the students on that expedition.) "...On this trip a variety of erosional and depositional features will be observed that reflect the complex Cenozoic history of the region."

In the photograph above, the distant peaks behind where I'm standing you can see the deposited layers that are lighter in color. Those layers are part of the Beacon Supergroup composed of sedimentary rocks like siltstones, limestones and sandstones and also have fossils of fresh water fish and plants from the Mesozioc Triassic time. The valley that is directly behind me clearly shows erosion from giant glaciers during the Cenozoic era. The other thing you should note is the glacier way off in the distance. That is the Wright Upper Glacier. Beyond that is the East Antarctic ice sheet that covers the largest portion of the continent.

One of the other cool things about this are is that the ground responds to the temperature fluctuations, freezing and thawing causing cracks that form the land into pattern ground- connected polygons. If you look closely at this photograph you will see some rocks laying flat and some sitting on edge. If you look at the lines created by the rocks sitting on their edges you will see lines that meet where the snow is. This is where three polygons of the pattern ground join together. As the helicopter took us to the bottom of the valley I took this next photograph of the valley floor where you can see some of these polygons, pattern ground.

The helicopter dropped us off at a New Zealand hut next to Vanda Lake. We left our gear and hiked around until lunch, came back to the hut and feasted. (I'm glad there was a port-o-potty next to the hut!) We picked up our gear and hiked a few more miles through what will be a very broad, shallow stream bed later in the season. For now, it was dry sand and pebbles.

We dropped our stuff off again at a US hut where some guys were working on the upkeep of a seismic array. They had a very cozy hut and had coffee waiting for us! That's one thing I really, really like about being here- everyone is a friendly neighbor. Too bad we can't all live that way off ice. After coffee and more hiking, the helicopter picked us up right on time and delivered us back to McMurdo just in time for dinner.

This photo shows the lower portion of the Wright Valley. Imagine where I was standing in the first photo as the top of the valley, this would be near the middle and the Ross Sea is still beyond.

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