On a cold winter day with temperatures around 10 degrees, students from a Colby earth climate course walked with microspikes across Parker Pond in Vienna while towing a large coring machine behind a snowmobile. They came to extract an 11.9-foot core of sediment from the bottom of the lake.
The expedition was a first step in reconstructing the lake’s climate history, or the paleoclimate. It also was a huge step for undergraduates aspiring to become geoclimate researchers.
Studies of core sediment of this kind are most often conducted for master’s or doctorate work, or at large research universities. So for the Colby students who intend to pursue advanced geology degrees, and even for those who don’t, it was a transformative experience.
“It’s pretty mind blowing to hold the core and know it goes back 13,000 years,” said Dru Gahl ’22, who graduated with a degree in environmental policy.
The study of ancient sediment had been done only a few times before at Colby since the College purchased the equipment used to drill into the lake bottom—the Livingston coring system—four years ago.
In the end, the study’s findings were not remarkable; geologists already knew that the Laurentide Ice Sheet began retreating across Maine about 20,000 years ago during the last ice age, leaving deposits and forming lakes across the land as the ice melted. But the hands-on study using raw samples that were converted into data, graphics, and a presentation for the local lake community amounted to something far beyond the expectations of the students in Visiting Assistant Professor of Geology Alena Giesche’s course Earth Climate: Past, Present, and Future.
“It was really eye-opening. I took geology to get a requirement out of the way, to be totally honest. Now I am strongly considering majoring in it because of this hands-on level of fieldwork,” said Teddy DeClue ’25. “Clearly, it was the work of upper-level students and researchers.”
Extracting the core and having it analyzed in professional laboratories is both time consuming and expensive. Colby partnered with researchers from the University of Maine’s Climate Change Institute for this project. The UMaine team assisted with the field work to identify a location using radar and broke down 20 pollen samples into liquid form in its lab. Colby also sent samples for radiocarbon dating to a lab in Florida.
The experiment using these methods has only been conducted at Colby a handful of times, Giesche said. Already, Colby geology students are building “a great tradition. … Having the equipment is a big service. With it, we’re able to get that research experience for the students with them doing a real study—and not just pretending to have a data set. They have a lot more invested if it’s a real place and they touch the sediment.”
The first day in the field the students worked with UMaine Assistant Professor Seth Campbell and graduate student Ian Nesbitt with ground-penetrating radar to identify a location to extract the core, one free of boulders. Then the class spent an entire Saturday on the pond transporting the coring equipment and drilling into the sediment of a basin that was about 30 feet deep to pull up several small sections. They encased each in plastic piping to transport to Colby.
Back at Colby’s lab, they prepared the samples to send to the two labs for analysis. And later, after the pollen was converted to a liquid form, the students viewed it under microscopes, where they found evidence of pine, birch, maple, and oak trees and other flora.
“This is a little bit unique in that not a lot of research facilities do pollen work,” said Andrea Nurse with the UMaine Climate Change Institute, who did the chemical processing of the pollen samples. “It is a bit unusual for a small private liberal arts college.”
But by far, the “holy grail” of the study—as DeClue called it—was a birch twig found deep in the core, since terrestrial organic matter is the most reliable sample for carbon dating.
The Florida lab dated the twig to 13,000 years ago.
“We didn’t expect to find such a large birch twig so deep in the sediment. It was almost in the clay. It dated to a time that was at the very end of the last ice age, right when the ice sheets were melting completely. That’s not what we expected to see,” said Tate Senden ’23.
In the spring, students presented their findings on Zoom to an audience that included members of the lake community, a local earth science high school class, and Nurse, who called it “the actual work of scientists.”
“In graduate school, you learn all of these techniques for doing analysis. In undergraduate, you learn what you might learn after getting the core. It’s really nice to put the two together,” said Senden, who plans to pursue a master’s degree in geophysics and work on glaciers. “I thought it was really cool to see how it culminated into a big lesson at the end. It’s what you do if you’re defending a thesis.”
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