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An intrusion (the forcible entry of molten rock or magma into or between other rock formations) in Antarctica. Unlike Minnesota, geologists get a perfectly clear view of intrusions in Antarctica.
UMD scientist studies Minnesota's rock in Antarctica
By June Kallestad
July 20, 2007
Geologists learn by looking at rocks. Of course, it's not that simple. Here in Minnesota, the tapestry of mineral-laden geology lies buried under forests, soils and parking lots. This makes Dean Peterson's job difficult. As one of the economic geologists at the University of Minnesota, Duluth's Natural Resources Research Institute (NRRI), his job is to understand the state's geology--where and what types of ore minerals were deposited some 1.1 to 2.7 billion years ago. In Minnesota, geologists figure it out by reading scattered outcroppings and drilling holes. It's doable, but it's difficult.
So when Peterson was offered an opportunity to spend a month in Antarctica's Dry Valleys, he jumped at the chance. Yes, that's a long way from Minnesota, but surprisingly, the geology is the same. Both areas were focal points of dynamic magmatic systems associated with continental rifting-molten rock flowed up from the earth's mantle, forming intrusions in the upper crust. The geologic setting was the same.
But the beauty of Antarctica for geologists is the 100 percent exposure of rock. They can look at layer upon ancient layer of deposits, up to 10,000 feet high. In Minnesota, the Duluth Complex, a large, composite of mafic rocks (rich in dark-colored minerals like magnesium and ireon) in northeastern Minnesota, was the hot spot for dynamic magmatic molten movement. It's where NRRI's economic geologists go to identify valuable mineral deposits.
Understanding local deposits"In the Duluth Complex, I study the 'plumbing' of the intrusions. That's the key to finding the higher grade ore deposits," says Peterson. "So in the Dry Valleys I can actually see how the magma moves up from the earth's crust, how it crosses certain rock bodies, and where it picks up sulfur to form sulfide minerals. In Antarctica I could see the 'plumbing' that I can't see in Minnesota."
Did you know?
Antarctica is the coldest, windiest, and harshest continent. The continent is covered in continuous darkness during the austral winter and continuous sunlight in the summer. (The average annual temperature is -56?F at the Amundsen-Scott South Pole Station, the southernmost continually inhabited place on the planet).
Source U.S. Antarctic Program
If that wasn't exciting enough for Peterson (and it was) he also spent a month with one of the most renowned geologists in the country, Bruce Marsh of Johns Hopkins University.
"Spending time seeing this fabulous geology and learning from Dr. Marsh is really something special," says Peterson.
Paul Morin, a visualization expert in the geology and geophysics department on the U's Twin Cities campus, and researchers from Poland and Slippery Rock University in Pennsylvania joined Peterson on the expedition. The trip was funded by a grant from the National Science Foundation.
From Peterson's travel notebook:
- Antarctica is not as cold as people might think. Temperatures were, on average, in the 20s to 30s Fahrenheit and sometimes down to 10 at night, but we got used to it right away. After a day we were in shirtsleeves and a windbreaker. The sun is always out and intense.
- When the wind stops blowing there is utter silence. There is nothing to make a noise. It's eerie at first, but then I got used to it. The silence really gives you time to think. When we went back to McMurdo (U.S. Field Station) the noise created by 1,100 people living in close quarters was unbelievable.
- Humans have evolved in humid environments where water vapor in the atmosphere selectively absorbs light--as you look into the distance things get bluer and bluer. We unconsciously perceive distance using the air's absorption of light. Antarctica is the driest place on earth. The humidity in the Dry Valleys averages about 1 or 2 percent. The air's dryness adds an additional dimension to an Antarctic experience--light doesn't change color with distance. Mount Erebus, 120 miles away, will look exactly like it would if you were right next to it. It's hard to visually calculate any distance.