Moraine, << muh RAYN, >> is an accumulation of rocks, dirt, and other earth material that a glacier deposits when the ice melts. Moraine also means a band of such material in a glacier or on its surface, or an uneven ridge of material deposited at the edge of the melting ice. On each side of a glacier in a mountain valley are rock fragments that have rolled onto the ice from nearby slopes. These rock fragments form a lateral moraine.
When two mountain glaciers unite, they form a compound glacier. The lateral moraines between them merge into a medial moraine along the middle of the compound glacier. When the ice front of a mountain glacier or continental ice sheet remains stationary, the melting ice deposits rocks carried by the glacier. These rocks form an end moraine or terminal moraine–that is, an irregular ridge with hills and depressions. Some end moraines formed by the great ice sheets and mountain glaciers of the Pleistocene Epoch, which ended about 11,500 years ago, are long ranges of hills. A ground moraine is a thin, uneven layer of material deposited beneath the ice or at its edge as the ice margin retreats. A recessional moraine forms when a retreating glacier pauses for a long time.
