Glacial Lake Connecticut formed over what is now

Long Island Sound Long Island Sound is a marine sound and tidal estuary of the Atlantic Ocean. It lies predominantly between the U.S. state of Connecticut to the north and Long Island in New York to the south. From west to east, the sound stretches from the Eas ...

and coastal

Connecticut Connecticut () is the southernmost state in the New England region of the Northeastern United States. It is bordered by Rhode Island to the east, Massachusetts to the north, New York to the west, and Long Island Sound to the south. Its cap ...

at the fore edge of the ice sheet of the

Wisconsin glaciation The Wisconsin Glacial Episode, also called the Wisconsin glaciation, was the most recent glacial period of the North American ice sheet complex. This advance included the Cordilleran Ice Sheet, which nucleated in the northern North American Cor ...

, as the lobe of the

Laurentide Ice Sheet The Laurentide Ice Sheet was a massive sheet of ice that covered millions of square miles, including most of Canada and a large portion of the Northern United States, multiple times during the Quaternary glacial epochs, from 2.58 million years a ...

began to retreat, some 18 to 20,000 years before present. It was dammed by the

terminal moraine A terminal moraine, also called end moraine, is a type of moraine that forms at the terminal (edge) of a glacier, marking its maximum advance. At this point, debris that has accumulated by plucking and abrasion, has been pushed by the front edge ...

that now forms the spine of

Long Island Long Island is a densely populated island in the southeastern region of the U.S. state of New York (state), New York, part of the New York metropolitan area. With over 8 million people, Long Island is the most populous island in the United Sta ...

and

Fishers Island Fishers Island (Pequot: ''Munnawtawkit'') is an island that is part of Southold, New York, United States at the eastern end of Long Island Sound, off the southeastern coast of Connecticut across Fishers Island Sound. About long and wide, it i ...

. About 15,000 BP, the moraine dam that impounded Lake Connecticut failed; the outlet, known as The Race for its tidal

rip current A rip current, often simply called a rip (or misleadingly a ''rip tide''), is a specific kind of water current that can occur near beaches with breaking waves. A rip is a strong, localized, and narrow current of water which moves directly away ...

s, 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 An unconformity is a buried erosional or non-depositional surface separating two rock masses or strata of different ages, indicating that sediment deposition was not continuous. In general, the older layer was exposed to erosion for an interval o ...

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 Block Island Sound is a strait in the open Atlantic Ocean, approximately wide, separating Block Island from the coast of mainland Rhode Island. On the west, it extends to Montauk Point on the eastern tip of Long Island, as well as Plum Isl ...

and

Buzzards Bay Buzzards Bay is a bay of the Atlantic Ocean adjacent to the U.S. state of Massachusetts. It is approximately 28 miles (45 kilometers) long by 8 miles (12 kilometers) wide. It is a popular destination for fishing, boating, and tourism. Since ...

, 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 Rock flour, or glacial flour, consists of fine-grained, silt-sized particles of rock, generated by mechanical grinding of bedrock by glacial erosion or by artificial grinding to a similar size. Because the material is very small, it becomes suspe ...

, 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 Rising may refer to: * Rising, a stage in baking - see Proofing (baking technique) *Elevation * Short for Uprising, a rebellion Film and TV * "Rising" (''Stargate Atlantis''), the series premiere of the science fiction television program ''Starga ...

and

isostatic rebound Post-glacial rebound (also called isostatic rebound or crustal rebound) is the rise of land masses after the removal of the huge weight of ice sheets during the last glacial period, which had caused isostatic depression. Post-glacial rebound a ...

of land depressed by the former weight of ice sheets adjusted to one another.

References

* Former lakes of the United States Glacial lakes of the United States Lakes of Connecticut Long Island Sound Natural history of Connecticut Natural history of New York (state) {{palaeo-geo-stub

See also

References