41°49′N72°38′W / 41.817°N 72.633°W /41.817; -72.633

Lake Hitchcock was aglacial lake that formed approximately 15,000 years ago in the latePleistocene epoch.^[2] After theLaurentide Ice Sheet retreated, glacial ice melt accumulated at the terminalmoraine and blocked up theConnecticut River, creating the long, narrow lake. The lake existed for approximately 3,000 years, after which a combination oferosion and continuing geological changes likely caused it to drain. At its longest, Lake Hitchcock stretched from the moraine dam, at present-dayRocky Hill, Connecticut, north toSt. Johnsbury, Vermont (about 320 kilometres (200 mi)). Although therift valley through which the river flows above Rocky Hill actually continues south toNew Haven, onLong Island Sound, the obstructing moraine at Rocky Hill diverted the river southeast to its present mouth atOld Saybrook.

Lake Hitchcock is an important part of thegeology of Connecticut. It experienced annual layering ofsediments, orvarves: silt and sand in the summertime (due to glacial meltwater) and clay in the wintertime (as the lake froze). Analysis of varves along Canoe Brook in Vermont was conducted by John Ridge and Frederick Larsen, including radiocarbon dating of organic materials. Their research indicates that the lake formed sometime prior to around 15,600 years ago. Later, abrupt changes in sediment composition around 12,400 years ago appear to mark the initial breaching of the lake's dam.^[1] These varved lake deposits were later used by European settlers forbrick-making. The lake was named afterEdward Hitchcock (1793–1864), a geology professor fromAmherst College who had studied it.

• Champlain Sea
• Lake Albany
• Lake Connecticut
• Lake Merrimack
• Lake Stowe

• Connecticut River
• Former lakes of the United States
• Glacial lakes of the United States
• Proglacial lakes

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