Wellesley College’s Lake Waban Gives Clues About the Environment and Climate Thousands of Years Ago
Associate Professor of Geosciences Katrin Monecke has traveled the world, from Southeast Asia to New Orleans, investigating lake sedimentation and geology. This summer, a research project took her to Wellesley College’s own backyard: Lake Waban, where she and two of her students spent a day investigating the layers of sediment that lie beneath the lake floor.
For this geophysical survey, Monecke, Shannon Dennehy ’19, and Leafia Sheraden Cox ’20 used an inflatable boat traveling at two to three miles per hour that was equipped with a sub-bottom sonar system. The sonar emitted sound waves every 100 milliseconds, with some penetrating 12 meters below the lake floor. The sound reflected off of layers of sediment to a receiver aboard the boat, and the data was processed by specialized software that produced an image of the sediment below the lake floor.
The image shows various layers of sediment and the distribution of deposits. Each layer has different characteristics, offering clues about the climate and environmental history of Lake Waban. For instance, some reflection patterns indicated the presence of organic rich materials, like aquatic algae and pollen typical of today’s lake deposits. Deeper layers are more likely composed of sand and mud washed into the lake when the glaciers started to melt.
When Lake Waban was formed thousands of years ago, a glacier covered much of the New England region. As warmer climate conditions melted the ice sheet, the glacier receded, leaving behind a glacial lake that later became Lake Waban, with sediment deposits that accumulated in layers over the years.
“This allows us to begin to understand a little better the postglacial history of the area since 16,000 years ago, when the glacier that covered this area began to recede,” said Monecke. Dennehy and Cox will spend the next several weeks analyzing the data they collected in the survey.
Dennehy, a geosciences major, said she is interested in local geomorphology, which is the study of landforms and their processes, form, and sediments at the surface of the Earth. The Lake Waban survey taught her about the field work involved in collecting seismic data. “I learned how to set up the boat and steps necessary to collect seismic data in the field,” she said.
Monecke has used Lake Waban before for her research. In 2012, one of her students developed a depth survey system to assess the bathymetry of a body of water. Her class used the system to conduct a depth survey of Lake Waban. This new survey allows her to look below the lake floor.
The Lake Waban project is a part of the Science Center Summer Research Program. Monecke and her team collaborated with Brad Hubeny, a professor of geological sciences at Salem State University; Jack Daigle, manager of the Butler Boathouse, helped the team set up equipment and launch the boat.
“With further analysis, the sedimentary record of Lake Waban will complement paleoenvironmental studies from other lakes of northeastern Massachusetts, such as Sluice Pond, or Walden Pond in Concord,” Monecke said. “Together, this data will help to reconstruct the environmental history of this region since the glaciers receded.”
Leafia Sheraden Cox ’20 (left) and Shannon Dennehy’19 (center) collect data from Lake Waban with Salem State professor Brad Hubeny as part of their research project this summer with Wellesley professor Katrin Monecke.