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.