The crevasse at the head of a glacier that separates the moving ice from the stationary ice is called a bergschrund . Movement of valley glaciers varies from a few mm to as much as 15m per day. Glaciers a powerful agents of erosion and leave characteristic land forms. Rock entrained in the ice will accumulate as moraines . Lateral moraines are those at the sides of the glacier, the terminal moraine marks the furthest advance of the ice.
Recessional moraines mark intermediate advances.
Medial moraines are rock entrained in ten middle of a glacier by the coalescing of lateral moraines where glaciers flow together. Glacial valleys have a characteristic U-shape with very little alluvial fill. They may have hanging tributaries. Where two cirques intersect the narrow ridge is called an arete . Aretes may intersect in a horn .