Detection of a meteorite Lake- đề thi IELTS 10.6.
2023
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As the sun rose over picturesque Lake Bosumtwi, a team of Syracuse University prepared for
another day of using state-of-the-art equipment to help unlock the mysteries hidden below the
lake bottom. Nestled in the heart of Ghana, the lake holds an untapped reservoir of information
that could help scientists predict future climate changes by looking at evidence from the past.
This information will also improve the scientist’s understanding of the changes that occur in a
region stuck by a massive meteorite.
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The project, led by earth sciences professor Christopher Scholz of the College of Arts and
Sciences and funded by the National Science Foundation (NSF), is the first large-scale effort to
study Lake Bosumtwi, Earth’s surface. The resulting crater is one of the largest an most well-
preserved geologically young craters in the world, says Scholz, who is collaborating on the
project with researchers from the University of South Carolina, the University of Rhode Island,
and several Ghanaian institutions. “Our data should provide information about what happens
when an impact hits hard, pre-Cambrian, crystalline rocks that are a billion years old”, he says.
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Equally important is the fact that the lake, which is about 8 kilometers in diameter, has no natural
outlet. The rim of the crater rises about 240 meters above the water’s surface. Streams flow into
the lake, Scholz says, but the water leaves only by evaporation, or by seeping through the lake
sediments. For the past million years, the lake has acted as a tropical rain gauge, filling and
drying with changes in precipitation and the tropical climate. The record of those changes is
hidden in sediment below the lake bottom. “The lake is one of the best sites in the world for the
study of tropical climate change,”Scholz says. “The tropics are the heart engine for the Earth’s
climate. To understand global climate, we need to have records of climate changes from many
sites around the world, including the tropics.”
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Before the researchers could explore the lake’s surface, they need a boat with a large, working
deck area that could carry eight tons of scientific equipment. The boat-dubbed R/V Kilindi-was
built in Florida last year. It was constructed in modules that were dismantled, packed inside a
shipping container, and reassembled over a 10-day period in late November and early December
Group: ORIGINAL EXAMS- DỰ ĐOÁN ĐỀ THI IELTS 20231999 in the rural village of Abono,
Ghana. The research team then spent the next two weeks
testing the boat and equipment before returning to the United States for the holidays.
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In mid-January, five members of the team-Keely Brooks, an earth sciences graduate student;
Peter Cattaneo, a research analyst; and Kiram Lezzar, a postdoctoral scholar, all from SU; James
McGill, a geophysical filed engineer; and Nick Peters, a Ph.D. Student in geophysics from the
University of Miami-returned to Abono to begin collecting data about the lake’s subsurface
using a technique called seismic reflection profiling. In this process, a high-pressure air gun is
used to create small, pneumatic explosions in the water. The sound energy penetrates about
1,000 to 2,000 meters into the lake’s subsurface before bouncing back to the surface of the water.
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The reflected sound energy is detected by underwater microphones-called hydrophones-
embedded in a 50-meter long cable that is towed behind the boat as it crosses the lake in a
carefully designed grid pattern. On-board computers record the signals, and the resulting data are
then processed and analyzed in the laboratory.” The results will give us a good idea of the shape
of the basin, how thick the layer of sediment are, and when and where there were major changes
in sediment accumulation,” Scholz says, “we are now developing three-dimensional perspective
of the lake’s subsurface and the layers of sediment that have been laid down.”
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Team members spent about four weeks in Ghana collecting the data. They worked seven days a
week, arriving at the lake just after sunrise. On a good day, when everything went as planned, the
team could collect data and be back at the dock by early afternoon. Except for a new relatively
minor adjustments, the equipment and the boat worked well. Problems that arose were primarily
non-scientific-tree stumps, fishing nets, cultural barriers, and occasional misunderstandings with
local villagers.
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Lake Bosumtwi, the largest natural freshwater lake in the country, is scared to the Ashanti
people, who believe their souls come to the lake to bid farewell to their god. The lake is also the
primary source of fish for the 26 surrounding villages. Conventional canoes and boats are
forbidden. Fishermen travel on the lake by floating on traditional planks they propel with small
paddles. Before the research project could begin, Scholz and his Ghanaian counterparts had to
secure special permission form tribal chiefs to put the R/V Kilindi on the lake.
