More about Lake Hitchcock

From here, look to the northwest, and see a great view of the main quad of Amherst College. At the end of the last glaciation, Amherst was inundated by glacial Lake Hitchcock. As shown in The Connecticut Valley 15,000 years ago exhibit at the Beneski Museum of Natural History, the Amherst College campus was an island in Lake Hitchcock.

Lake Hitchcock extended from a moraine dam in Rocky Hill, Connecticut to the ice front. As the ice retreated northwards, the length of the lake grew, extending all the way to central Vermont. With the ice gone, isostatic rebound uplifted the land north to south causing Lake Hitchcock to begin draining through a series of spillways with the eventual breach of the Rocky Hill dam, leaving behind ample evidence for curious geologists to ponder.

Varved Clay

Varved Clay

We infer Lake Hitchcock’s existence by studying sand and gravel deposits that formed along its shores and the varved clay that was deposited on the lake bottom. In winters, when the lake froze and there was very little mixing of the water, fine sediment could precipitate out, forming dark silty-clay layers at the lake bottom. During warm periods, when the water was more mobile, the only particles heavy enough to settle were larger, lighter silty-sands. Varved clay, like the one from Beneski Museum pictured below, displays these clear, alternating layers.