moraine

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moraine The term originally applied to the ridges of rock debris around the margins of Alpine glaciers. Subsequently its meaning has been widened to include till deposits. For example, ‘ground’ moraine may denote an irregularly undulating surface of till, glacial drift, or boulder clay, or it may describe the deposit itself. An ‘end’ or ‘terminal’ moraine is a ridge of glacially deposited material laid down at the leading edge of an active glacier. Its height is in the range 1–100 m, and it is accumulated by a combination of glacial dumping and pushing. A ‘recessional’ moraine is morphologically similar and is laid down at the terminus of a glacier during a period of stillstand that interrupts a sustained period of retreat of the ice margin. A ‘lateral’ moraine is a ridge of debris at the margin of a valley glacier and largely derived from rock fall. It is a prominent feature of many contemporary Alpine glaciers. A ‘medial’ moraine results from the merging of lateral moraines when two glaciers converge. A ‘washboard’ moraine is a single ridge in a closely spaced pattern (perhaps 9–12 per kilometre) and stands some 1–3 m above the adjacent depressions. It is found in the ‘end’ moraine belt. A ‘push’ moraine is a morainic ridge made of unconsolidated rock debris and pushed up by the snout of an advancing glacier. See also de Geer moraine; fluted moraine; and hummocky moraine.

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moraine Term originally applied to the ridges of rock debris around Alpine glaciers. Subsequently its meaning has been widened to include the rock debris deposit. For example, ‘ground’ moraine may denote an irregularly undulating surface of till, glacial drift, or boulder clay; or it may describe the deposit itself. An ‘end’ or ‘terminal’ moraine is a ridge of glacially deposited material laid down at the leading edge of an active glacier. Its height is in the range 1–100 m, and it is accumulated by a combination of glacial dumping and pushing. A ‘recessional’ moraine is morphologically similar and is laid down at the terminus of a glacier during a period of still-stand that interrupts a long period of retreat of the ice margin. A ‘lateral’ moraine is a ridge of debris at the margin of a valley glacier and largely derived from rock fall. It is a prominent feature of many contemporary Alpine glaciers. A ‘medial’ moraine results from the merging of lateral moraines when two glaciers converge. A ‘washboard’ moraine is a single ridge in a closely spaced pattern (perhaps 9–12 per kilometre) and stands some 1–3 m above the adjacent depressions. It is found in the ‘end’ moraine belt. A ‘push’ moraine is a morainic ridge made of unconsolidated rock debris and pushed up by the snout of an advancing glacier. See also DE GEER MORAINE; FLUTED MORAINE; and HUMMOCKY MORAINE.

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mo·raine / məˈrān/ • n. Geol. a mass of rocks and sediment carried down and deposited by a glacier, typically as ridges at its edges or extremity. DERIVATIVES: mo·rain·al / -ˈrānl/ adj. mo·rain·ic / -ˈrānik/ adj.

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moraine In geology, a mound, ridge, or other visible accumulation of unsorted glacial drift, predominantly till. End moraines form when a glacier is either advancing or retreating, and rock material accumulates at the glacier's edge. Ground moraines are sheets of debris left after a steady retreat of the glacier.

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moraine mountain debris carried down by a glacier. XVIII. — F.