Moraine

Moraine at Mono Lake, California, United States

Moraines clearly seen on a side glacier of the Gorner Glacier, Zermatt, Switzerland. The lateral moraine is the high snow-free bank of debris in the top left hand quarter of the picture. The medial moraine is the double line of debris running down the centre-line of the glacier.

Ground moraine makes an irregular, rolling topography

Moraine is rock debris, fallen or plucked from a mountain and transported by glaciers or ice sheets. The moraine may be lying on the glacier's surface or have been deposited as piles or sheets of debris, where the glacier has melted. Till is another word used to describe the sediments left by melted glaciers but is not used to describe debris lying on a glacier's surface.

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 be 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 centre-line, called medial moraine.
Terminal moraine: When balance is maintained between the melting of the lower end of a glacier and its forward advance. The debris carried on (superglacial), within (englacial) and dragged along the bottom (sub-glacial) is deposited 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. These accumulations can hold back glacial lakes.
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, therefore such moraines are called interlobate moraine.
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.
Push moraine: when a glacier advances over a previously deposited moraine.
Recessional moraine: when a glacier remains in one position or slows down enough to deposit a mound of material.

Moraine

Types of moraine

See also