Moraine

A moraine is an accumulation of unconsolidated rock debris, sometimes called glacial till, that has been carried and then deposited by a glacier or ice sheet, found in regions that are or once were glaciated. The material in a moraine ranges from large boulders, in a form sometimes called boulder clay, down to gravel and sand set in a fine clayey matrix known as glacial flour, with individual fragments typically worn to sub-angular or rounded shapes rather than left sharp edged. A lateral moraine builds up along the side of a glacier, a terminal moraine marks the farthest point the ice reached, a ground moraine spreads a till sheet across the land the glacier has retreated from, and a medial moraine forms where two glaciers meet and their lateral moraines merge; because moraines record where a glacier's edge once stood, they are important evidence for reconstructing past glaciation.