When people hear “Walden Pond” they usually first think of the writer, transcendentalist, and philosopher Henry David Thoreau, who spent two years living in solitude on the shore of the pond, culminating in his classic 1854 book Walden; or, Life in the Woods. But Walden is not just appealing to members of Wellesley’s English faculty—Katrin Monecke, associate professor of geosciences, was drawn to studying the pond to better understand the history of earthquakes in New England.

“You need to have a deep lake if you want to have a good sedimentary record,” says Monecke. Since Walden is the deepest natural body of water in Massachusetts, with one of its basins measuring 103 feet deep, it is an ideal place to study the geological history of the area. Looking at layers of sediment underneath the water, Monecke can understand the history of Walden itself and also the area surrounding the pond.

“You can, for example, see when there was logging happening in the area, which triggered quite a bit of erosion,” says Monecke. “There was also much more erosion when heavy recreational use of the pond started in the 1930s.” Thoreau’s time at Walden was also at the peak of the industrial revolution: “The railroad had just been built, so we can see that fires become more frequent, so there are charcoal particles in the sediment core.”

Monecke’s goal is to reconstruct earthquake history in the area. “Lake sediments can get disturbed when you have ground shaking,” says Monecke, who looks for intervals where the sediments have been moved around. “Originally, this was our main focus, but right now we are at a stage where we still just need to understand the background sedimentation. What is normal for the lake? We have to figure that out, before we can say, OK, this is an unusual layer, potentially linked to an earthquake.”

Monecke studies sediments from an eight-meter-long core extracted from the bottom of Walden in 2017. This sediment core goes back 13,000 years. This past summer, Monecke and the students working in her lab—Nivale Baxendell ’27, Grace Knuth ’27, and Alice Ma ’26—processed the samples.

Baxendell says that she didn’t know exactly what “lake sediment research” would involve before she started working in the lab. “But Professor Monecke was just so passionate about it, and that drew me in,” says Baxendell. “She would get so excited talking about the project.”

The processing itself took patience. “We would add hydrogen peroxide in small increments over time to get rid of the organic matter—algae, shells, stuff like that,” says Knuth. It’s important to remove this material because it can mask the minerals and distort the particle size of the mineral grains. Grain size is important because, generally, the grains are coarser at the lake shore and get finer deeper into the water, so finding larger grains in a deep section can indicate they were jostled by an underwater landslide triggered by an earthquake. “It was a lot of adding chemicals to the samples and waiting,” says Baxendell. But the things that Monecke and her students learned from the samples both illuminated the past and have implications for modeling the future. “When people hear we were looking at grain-size data, it is not very meaningful to them,” says Knuth, “but it has implications for the climate and human history and colonization.” By looking at the history of Walden, Monecke and her students can project models to try to predict the future of the pond and others like it.

“You can never ignore these lake studies, since they record environmental changes over time so sensitively,” says Monecke. “You can never ignore the environmental history.”

In June, Monecke and associate professor of environmental studies Alden Griffith took a group of geosciences and environmental studies students to Walden to collect more samples and enjoy an afternoon swim. Baxendell, who is from Virginia, had never been to the pond before. “When we look at the cores in the lab it doesn’t have a lot of context to it, it’s just a bunch of small amounts of dirt in tubes,” she says. “It was so gratifying to see Walden Pond in person and understand this is the context, the history behind it.”