Glacial Lake Connecticut formed over what is now Long Island Sound and coastal Connecticut at the fore edge of the ice sheet of the Wisconsin glaciation, as the lobe of the Laurentide Ice Sheet began to retreat, some 18 to 20,000 years before present. It was dammed by the terminal moraine that now forms the spine of Long Island and Fishers Island. About 15,000 BP, the moraine dam that impounded Lake Connecticut failed; the outlet, known as The Race for its tidal rip currents, lies between the North Fork of Long Island and Fishers Island. For a time, much of the lake bed was exposed to wind-driven erosion: the cue is found in soundings that reveal regional unconformities in the sediment bed of Long Island Sound.

The fore-edge lake formed by glacial meltwater expanded to be about the same size as present-day Long Island Sound; it may have been connected at times with similar freshwater lakes in Block Island Sound and Buzzards Bay, while sea level was low. The fairly shallow average depth of 78 feet (24 m) of today's Long Island Sound is the result of fine lake-bottom sediments deposited as glacial outwash slowed in Lake Connecticut. Suspended as rock flour, the fine sediments would have rendered Lake Connecticut a turquoise blue-green.

The end of Lake Connecticut was marked by a series of intervals of salt water incursion after about 15,000 BP and subsequent refreshening, as rising sea levels and isostatic rebound of land depressed by the former weight of ice sheets adjusted to one another.

• Glacial Lake Cape Cod
• Glacial Lake Nantucket Sound

• Geologic History of Long Island Sound at the Wayback Machine (archived May 29, 2010)

v t e Pleistocene proglacial lakes and related seas
Africa	Lake Makgadikgadi Lake Ptolemy
Antarctica	Lake Washburn
Asia	Mundafan West Siberian Glacial Lake Lake Bandung Lake Tengger
Europe	Baltic Sea Ancylus Lake Baltic Ice Lake Littorina Sea Mastogloia Sea Yoldia Sea Russia Lake Komi Great Britain Lake Harrison Lake Lapworth Lake Pickering
North America	Nelson River drainage Proglacial lakes of Minnesota Lake Agassiz Lake Bassano Lake Souris James Bay drainage Lake Ojibway Tyrrell Sea Great Lakes Lake Admiralty Lake Algonquin (Multiple basins) Lake Arkona Lake Chicago Lake Chippewa Lake Duluth Early Lake Erie Lake Frontenac Lake Houghton (glacial) Glacial Lake Iroquois Lake Lundy Lake Dana Lake Maumee Lake Minong Nipissing Great Lakes (Multiple basins) Early Lake Ontario Lake Saginaw Lake Stanley Lake Tonawanda Lake Warren Lake Wayne Lake Whittlesey Champlain Sea Columbia River system Lake Allison Glacial Lake Columbia Lake Lewis Glacial Lake Missoula Great Basin system Lake Bonneville Lake Lahontan Puget Sound system Glacial Lake Russell Glacial Lake Hood Lake Nisqually Lake Puyallup Glacial Lake Sammamish Lake Skokomish Upper Missouri River Lake Cut Bank Lake Chouteau Lake Great Falls Lake Circle Lake Jordan (Montana) Lake Musselshell Lake Glendive Lake McKenzie Upper Mississippi drainage Lake Kankakee Kankakee Outwash Plain Lake Wisconsin Ohio drainage Lake Monongahela Lake Tight Teays River Hudson valley Lake Albany Lake Passaic New England Lake Cape Cod Lake Connecticut Lake Hitchcock Lake Merrimack Lake Nantucket Sound Lake Stowe California Lake Cahuilla Lake Corcoran Lake Harper Lake Manix Lake Manly Lake Modoc Lake Mojave Lake Panamint Lake Russell Lake Tecopa Lake Thompson Rio Grande Rift Lake Alamosa Lake Estancia Lake Palomas Lake San Agustín Alaska Lake Atna
South America	Lake Ballivián Cabana Lake Escara Inca Huasi Mataro Lake Minchin Ouki Sajsi Salinas Lake Tauca Great Tehuelche Paleolake
Summary	List of prehistoric lakes
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