Earth sciences professor Christopher Scholz, far right, meets with tribal chiefs to receive their permission to put the R/V Kilindi on Lake Bosumtwi.
One of the team’s main problems was navigating the labyrinth of fishing nets that criss-cross the lake’s surface. To collect data, the boat had to travel in as straight a line as possible across the entire length of the lake. The sensitive equipment embedded in the 650-meter cable would be damaged if it got tangled in the nets, so the team worked with fishermen to clear the nets as the boat went across the lake. It was often a slow, tedious process. “After all was said and done, we were successful,” Brooks says. “We got the data.”
      For Brooks, a second-year master’s degree student, the experience was an unprecedented opportunity to do fieldwork on a major research project in a virtually unstudied area. “I have learned more in the past year than I did during my whole undergraduate career,” she says.
      Brooks will process much of the data in the team’s SU laboratory—under the guidance of Lezzar and Cattaneo—using a technique called seismic reflection analysis. She worked with Scholz during the spring semester to learn the technique and also took a courûe on the topic at Cornell University. After processing, the data will be used to create maps of the sedimentary layers of the lake’s subsurface. The data will also provide scientists with a three-dimensional perspective of the crater. “The data should tell us a lot about what happens to the Earth when a major meteorite hits,” Scholz says. “The information we collect will be of tremendous benefit to an international, interdisciplinary group of scientists, including planetary geologists, paleontologists, and scientists from NASA.”

Above, SU research team members Keely Brooks and Kiram Lezzar unwind cable, embedded with underwater microphones to record sound energy, into Lake Bosumtwi. At left, Brooks and Lezzar examine data being recorded from signals picked up by the underwater microphones.

      Preliminary analysis of the data, which was completed in May, uncovered the first documented central uplift of an impact crater, Scholz says. Scientists believe a crater’s shape depends on the size of the meteor. Smaller impacts are believed to create a simple bowl-shaped crater, while larger impacts may create a more complex crater featuring a central cone-like structure. Until now, such structures have not been documented in craters on Earth, Scholz says. Scientists believe the meteor that formed Lake Bosumtwi was about 500 meters in diameter, or about the size of 5 football fields, and that the impact was intense enough to create the central uplift seen in the data analysis. As more of the data is analyzed, additional details about the central uplift and the crater’s structure are expected to emerge, Scholz says.
      In late May, with preliminary maps in hand, Scholz returned to Lake Bosumtwi with a team of eight researchers to obtain core samples of the lake’s sediment. The other leaders of that expedition were John King, professor of oceanography at the University of Rhode Island Graduate School of Oceanography, and Jonathon Overpeck, director of the Institute for Studies of the Planet Earth at the University of Arizona. Some of the core material will be analyzed at SU. “Analyzing the sediment is like reading tree rings,” Scholz says. “It is one piece of the puzzle in determining climate conditions during the past million years. The sediment cores give us a one-dimensional perspective, while the seismic profiles give us two-dimensional perspectives across the entire basin.”
      After they obtained the cores, the team disassembled the R/V Kilindi and packed it back into the shipping crates. The boat and equipment were then shipped to Uganda for an upcoming project. Scholz also plans to use the equipment next year on Lake Malawi in East Central Africa, where he is a principal investigator on another major NSF climate study grant. “The boat can be used for a variety of scientific studies,” Scholz says. “We’re hoping to develop this modular vessel into a national facility for lake research.”

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