New England harbors the greatest concentration of glacial terrain in the eastern U.S. and one of its most striking features is the terminal moraine of the Wisconsin Glacier. As the last of the Pleistocene Ice Sheets formed across northern Canada and Europe, water was locked in the glaciers and sea level dropped; at the peak of the Wisconsin Glaciation, the coast of the New England mainland was at least forty miles east of its present-day location.
As the Glacier plowed its way to the south and east, it sculpted the peaks and valleys of the Northern Appalachians and hauled the remnant debris toward the coast. Reaching its maximum extent some 23,000 years ago, the lobulated Ice Sheet produced a ridge of till, rocks and boulders along its outer edge; some of this debris had been plowed along in front of the glacier while the rest was dumped by meltwater flow atop and within the ice. As the Glacier retreated to the north, it left behind this "terminal moraine," which rose above the surrounding coastal plain.
With continued melting of the Continental Glaciers, sea level rose once again, flooding the plain and surrounding the higher ridge of the terminal moraine; the latter has since been eroded by the frequent storms of the North Atlantic. Today, Cape Cod, Nantucket Island, Martha's Vineyard, Block Island and Long Island persist as remnants of this glacial edge.
