Figure 2. Location map of end moraines (black polygons) and submerged ridges (dashed lines) in southern New York and New England (modified from Gustavson and Boothroyd, 1987). The Ronkonkoma-Block Island-Nantucket end moraine represents the maximum advance of the Laurentide Ice Sheet about 20,000 years ago, and the Harbor Hill-Roanoke Point-Charlestown-Buzzards Bay end moraine represents a retreated ice-sheet position from about 18,000 years ago (Uchupi and others, 2001).