Last Glacial Period River, which in turn was formed during an earlier glacial period. In its retreat, the Wisconsin Episode glaciation left terminal moraines that form Long Island, Block Island, Cape Cod, Nomans Land, Martha's Vineyard, Nantucket, Sable Island, and the Oak Ridges Moraine in south central Ontario, Canada. In Wisconsin itself, it left the Kettle Moraine. The drumlins and eskers formed at its melting edge are landmarks of the Lower Connecticut River Valley. In the Sierra Nevada, there are three named stages of glacial maxima (sometimes incorrectly called ice ages) separated by warmer periods. These glacial maxima are called, from oldest to
Glacial striation provide the abrasive power to cut trough-like "glacial grooves". Finer sediments also in the base of the moving glacier further scour and polish the bedrock surface, forming a "glacial pavement". Ice itself is not a hard enough material to change the shape of rock but because the ice has rock embedded in the basal surface it can effectively abrade the bedrock. Most glacial striations were exposed by the retreat of glaciers since the Last Glacial Maximum or the more recent Little Ice Age. As well as indicating the direction of flow of the glacial ice, the depth and extent of