Lake Connecticut
Encyclopedia
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 18,000 to 20,000 years ago. It was dammed by the terminal moraine
that now forms the spine of Long Island
and Fishers Island
. About 15,000 years ago the moraine dam that impounded Lake Connecticut failed; and the outlet known as "The Race" for its tidal rip current
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
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 years ago and subsequent refreshening, as rising sea levels and isostatic rebound of land depressed by the former weight of ice sheets adjusted to one another.
Long Island Sound
Long Island Sound is an estuary of the Atlantic Ocean, located in the United States between Connecticut to the north and Long Island, New York to the south. The mouth of the Connecticut River at Old Saybrook, Connecticut, empties into the sound. On its western end the sound is bounded by the Bronx...
and coastal Connecticut
Connecticut
Connecticut is a state in the New England region of the northeastern United States. It is bordered by Rhode Island to the east, Massachusetts to the north, and the state of New York to the west and the south .Connecticut is named for the Connecticut River, the major U.S. river that approximately...
at the fore edge of the ice sheet of the Wisconsin glaciation
Wisconsin glaciation
The last glacial period was the most recent glacial period within the current ice age occurring during the last years of the Pleistocene, from approximately 110,000 to 10,000 years ago....
, as the lobe of the Laurentide ice sheet
Laurentide ice sheet
The Laurentide Ice Sheet was a massive sheet of ice that covered hundreds of thousands of square miles, including most of Canada and a large portion of the northern United States, multiple times during Quaternary glacial epochs. It last covered most of northern North America between c. 95,000 and...
began to retreat, some 18,000 to 20,000 years ago. It was dammed by the terminal moraine
Terminal moraine
A terminal moraine, also called end moraine, is a moraine that forms at the end of the glacier called the snout.Terminal moraines mark the maximum advance of the glacier. An end moraine is at the present boundary of the glacier....
that now forms the spine of Long Island
Long Island
Long Island is an island located in the southeast part of the U.S. state of New York, just east of Manhattan. Stretching northeast into the Atlantic Ocean, Long Island contains four counties, two of which are boroughs of New York City , and two of which are mainly suburban...
and Fishers Island
Fishers Island
Fishers Island, approximately 9 miles long and 1 mile wide, is located at the eastern end of Long Island Sound, 2 miles off the southeastern coast of Connecticut across Fishers Island Sound...
. About 15,000 years ago the moraine dam that impounded Lake Connecticut failed; and the outlet known as "The Race" for its tidal rip current
Rip current
A rip current, commonly referred to by the misnomer rip tide, is a strong channel of water flowing seaward from near the shore, typically through the surf line. Typical flow is at 0.5 metres per second , and can be as fast as 2.5 metres per second...
s, lies between the North Fork
North Fork, Suffolk County, New York
The North Fork is a 30-mile-long peninsula in the northeast part of Suffolk County, New York, roughly parallel with an even longer peninsula known as the South 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
Unconformity
An unconformity is a buried erosion 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 of time before deposition of the younger, but the term is used to describe...
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
Block Island Sound is a strait in the open Atlantic Ocean, approximately wide, separating Block Island from the coast of Rhode Island in the United States...
and Buzzards Bay
Buzzards Bay
Buzzards Bay is a bay along the southern edge of Massachusetts in the United States. The name may also refer to:*Buzzards Bay, Massachusetts, a village in Bourne, Massachusetts*Buzzards Bay , the name of the horse that won the 2005 Santa Anita Derby...
, 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
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...
, 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 years ago and subsequent refreshening, as rising sea levels and isostatic rebound of land depressed by the former weight of ice sheets adjusted to one another.