The Living Laboratory

The Bottom of the Lake

The muck, goop, and crud that lie there represent a treasure trove of historical data.

You don’t have to watch much PBS to learn that the distinct layers of rock visible wherever the crust of the earth has cracked tell a rich story to any scientist who understands them. But the layers of sediment that lie beneath a very deep lake may be even better.

Sediment samples — or "cores" — are a very big part of limnology (the study of lakes). Of the three geoscience faculty members who work with the lake, Assistant Professor John Halfman has the tightest specialty in sediment studies. His research on Seneca is augmented by work he does on a family of lakes in Africa. Although different in some respects, all of them, here and there are deep — really deep.

Beneath the lake is sediment perhaps 200 meters deep. The top two meters represents the past 2,000 years. Another eight meters is post-glacial. Everything else was left by the glacier some 12,000 years ago. Halfman and his colleagues employ a variety of data-collection and analysis techniques — for example, a bottom-skimming probe that utilizes a sonar-like technology, known as the "fish" — to draw conclusions about climate and species in these eras. For example: "We think we have some evidence that the lake might have been 60 feet lower than it is," he says. That bears further question, as there is no other relevant findings in paleontology to support this. "It’s a dilemma."

Halfman’s work returns to the classroom, of course. The department’s courses on limnology, hydrogeology, and environmental geology connect, as does undergraduate research. Damien Herrick ‘97 did an independent study focused on the sedimentation history of the lake as the last glacier left the basin.

"You can learn a lot by looking through the lake at the sediments and variations as you move up and down." How things happened, when they happened, and even why certain events happened; part of Seneca’s beauty is relatively easy access to millions of years of data.

When Herrick was considering undergraduate schools, Seneca was a powerful magnet. "I knew about the Lake and geoscience at the Colleges — that’s definitely what attracted me — but I had never seen it," says Herrick, now a graduate student at Duke University. "In my mind, the Colleges and the Lake were intertwined."

According to Halfman, Herrick is an example of what happens when an excellent liberal arts school creates a geoscience department and buys a boat: "What we’re getting out of it is a bunch of topnotch students who are getting into topnotch programs." — P.R./D.C.

The Seneca Lake series was researched and written by Dana Cooke and Peter Rolph '85 — writer/editors in the Office of College Relations. Portions of the series also appear in the Fall '97 issue of The Pulteney St. Survey. To request a copy, e-mail Susan Murad at murad@hws.edu.