U-M geochemist and student on Antarctic expedition team
ANN ARBOR, Mich.—When temperatures turn bitter, many northerners scurry south to warmer weather. University of Michigan geology professor Samuel Mukasa heads south, too, but not to a more comfortable climate.
His research takes him to Antarctica, the southernmost continent, where he camps and collects data in temperatures as low as -40 ° F.
Usually, Mukasa's only companions on his Antarctic treks are a couple of students and a squad of mountaineers who help the scientists negotiate treacherous terrain. This year, however, he'll be part of an international research team converging on the frozen continent to try to understand what caused the supercontinent Gondwana to start breaking up about 185 million years ago, eventually forming Africa, Australia, India, South America and Antarctica.
"Antarctica was the nucleus from which all the other southern continents broke away," Mukasa said, “so it's a logical place to look for clues to what triggered the breakup.” The evidence is in a belt of rocks in a mountain chain, known as the Transantarctic Mountains, that runs like a curving spine across the continent. Those rocks formed from magma that erupted to the surface over a 1-million-year period when Gondwana was fracturing.
Studying the rocks will help the 27 scientists, led by Johns Hopkins University researcher Bruce Marsh, distinguish between two competing ideas of how the breakup occurred. In one view>the sand pile scenario—a hot plume from deep inside the Earth rose to the surface, pushing up a dome in the process. "Just like building a big sand pile at the beach, you can take it only so high before pieces will start sliding off in different directions," Mukasa said.
The alternate explanation could be called the bumper car hypothesis. "The idea is that different plates on the surface of the Earth simply reconfigure themselves, and when they do, they act like bumper cars. They move in all directions, and as they bump into each other, they're likely to change the direction of motion of any pieces they bump into." If that's how the breakup occurred, the rocks that the scientists plan to study would have formed by a process called decompression, the same process by which the oceanic crust is created today. In that process, Earth's crust splits, or rifts, which reduces the pressure on rocks deep inside the Earth and allows them to melt and ooze toward the surface.
Rocks formed from plumes that originate deep in the Earth have a different geochemical signature than those formed by decompression in rifts, and reading those signatures should help the scientists choose between the two possible explanations.
The geologists joining Marsh and Mukasa on the expedition come from universities throughout the United States, Canada and the United Kingdom, and each is an expert in one of four areas: magma dynamics, igneous layering, geochemistry and the mechanics of intrusions. They met as a group at Johns Hopkins in October to get acquainted and formulate research plans.
"This is probably the first time in the history of geology that experts in so many areas will come together to bring their disparate expertise and knowledge to bear collectively," Marsh said. The National Science Foundation, which is funding the expedition, "has never done anything quite like this—taking a group of world leaders in this area of science to conduct real-time research in the most remote part of the world.”.
Mukasa, a geochemist, is excited about the interdisciplinary approach to fieldwork. "When I go to Antarctica, I see things and I take pictures, and then I come back and talk to my colleagues and say, 'What do you think about this?' They will tell me what they think, but it's not the same thing as looking at it together at the same time."
Another expedition member with a Michigan connection is recent U-M graduate Jill VanTongeren of Grand Rapids, who accompanied Mukasa on a research trip to Antarctica last winter. On that trip the researchers were based on a ship in the Ross Sea, where they had access to e-mail, and when Mukasa received a message from Marsh about this year's team expedition, he encouraged VanTongeren to apply. She applied and was the only undergraduate accepted.
"This expedition will complement my previous education by integrating real-world field experience with the classroom knowledge that I received at the University of Michigan," said VanTongeren. "I am looking forward to seeing these spectacular 'textbook' exposures and learning the hands-on techniques that many of the participants use in the field."
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Contact: Nancy Ross-Flanigan