Glacial moraine
Moraine is the general term for debris of all sorts originally transported by glaciers or ice sheets that have since melted away. The following are commonly recognized types of moraine:
- Lateral moraine: The talus and other material from the sides of a glacial valley accumulated on the glacier and carried along with it. The mass of debris distributed along the lateral edges of the glacier are thus called lateral moraine. In the case of valley glaciers which have disappeared, their former existence may often by proved by the traces of lateral moraines left along the sides of the valley.
- Medial moraine: If one or more tributary glaciers coalesce with the main glacier the lateral moraines unite to form trains of debris on the surface of the glacier at or near its center, called medial moraines.
- Terminal moraine: When balance is maintained between the melting of a glacier and its forward advance, the debris carried on (superglacial), within (englacial), and dragged along the bottom (subglacial) is dumped at that point and builds up a heterogeneous mass of the transported material called the terminal moraine. If a glacier is slowly retreating and makes successive halts farther and farther up the valley, a series of terminal moraines are formed which are spoken of as recessional moraines.
- Interlobate moraine: If large glaciers and continental ice sheets advance irregularly so that their margins are lobate, when the margins retreat by melting the resulting terminal moraines of boulders, clay, and sand simulate the original interlobate shape of the glacier or glaciers, and therefore such moraines are called interlobate.
- Ground moraine: When a valley glacier melts completely away the debris carried on or within it are dropped on the valley floor, forming a deposit called ground moraine. The ground moraine from the melting of the great Pleistocene ice sheets is usually spoken of as till.
See also: List of landforms, drumlin, esker, tarn (lake)
