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Geologic Map
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Generalized Geologic Map of the Conterminous United States
North America Shaded Relief


  The North American Tapestry of Time and Terrain

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Terminal Moraines

  Close-up of
 Southern New England terminal moraines

Terminal moraines marking the southern limit of Pleistocene glaciation were deposited on a submarine ridge of Tertiary rocks off the coasts of Massachusetts and Connecticut 15,000 to 20,000 years ago. These hummocky piles of clay-rich, poorly-sorted glacial material, and the smoother plains of sandy outwash deposits immediately south of them, form much of Long Island, Cape Cod, Martha's Vineyard, and Nantucket Island. They also controlled the post-glacial development of beaches, offshore islands, and other Holocene coastal landforms.