moraine

Information about moraine

This article is about geological phenomena. For other uses, see Moraine (disambiguation).
Moraine refers to any glacially formed accumulation of unconsolidated debris which can occur in currently glaciated and formerly glaciated regions, such as those areas acted upon by a past ice age. This debris may have been plucked off the valley floor as a glacier advanced or fallen off the valley walls as a result of frost wedging. Moraines may be composed of silt like glacial flour to large boulders. The debris is typically angular. Moraines may be on the glacier’s surface or deposited as piles or sheets of debris where the glacier has melted. Moraines may also occur when glacier or iceberg transported rocks fall into the sea as the ice melts.

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Moraine at Mono Lake, California, United States

Types of moraines

Lateral moraines

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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.
Lateral moraines are parallel ridges of till deposited along the sides of an alpine glacier. The unconsolidated debris is deposited on top of the glacier by frost shattering of the valley walls and from tributary streams flowing into the valley. The till is carried along the glacial margin until the glacier melts. Because lateral moraines are deposited on top of the glacier, they do not experience the postglacial erosion of the valley floor and therefore, as the glacier melts, lateral moraines are usually preserved as high ridges. Lateral moraines stand high because they protect the ice under them from the elements, which causes it to melt or sublime less than the uncovered parts of the glacier. Multiple lateral moraines may develop as the glacier advances and retreats.

Ground moraines

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Ground moraine makes an irregular, rolling topography
Ground moraines are till covered areas with irregular topography and no ridges often forming gently rolling hills or plains. It is accumulated under the ice by lodgement, but may also be deposited as the glacier retreats. The ground moraine is located between the two lateral moraines.

End or terminal moraines

End moraines or terminal moraines are ridges of unconsolidated debris deposited at the snout or end of the glacier. They usually reflect the shape of the glacier's terminus. Glaciers act much like a conveyor belt carrying debris from the top of the glacier to the bottom where it deposits it in end moraines. End moraine size and shape is determined by whether the glacier is advancing, receding or at equilibrium. The longer the terminus of the glacier stays in one place the more accumulation there will be. There are two types of end moraines, terminal and recession moraines. Terminal moraines mark the maximum advance of the glacier. Recessional moraines are small ridges left as a glacier pauses during its retreat. After a glacier retreats the end moraine may be destroyed by postglacial erosion.

See also

References

  • Easterbrook, D. J. (1999) Surface processes and landforms. (Second Ed). Prentice Hall, Upper Saddle River, New Jersey.
  • Moraine, rock debris transported by glaciers
  • Moraine, a jazz quintet based in Seattle
  • Moraine Valley Community College, a community college in Palos Hills, Illinois
  • Moraine, Ohio, a city in Ohio, USA
  • Moraine State Park, in Pennsylvania

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ice age is a period of long-term reduction in the temperature of Earth's climate, resulting in an expansion of the continental ice sheets, polar ice sheets and mountain glaciers.
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Plucking, in the sense relating to glaciers, is when a glacier erodes away chunks of bedrock to be later deposited as glacial erratics. Glacial plucking exploits pre-existing fractures in the bedrock.
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glacier is a large, slow moving river of ice, formed from compacted layers of snow, that slowly deforms and flows in response to gravity. Glacier ice is the largest reservoir of fresh water on Earth, and second only to oceans as the largest reservoir of total water.
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Weathering is the decomposition of rocks, soils and their minerals through direct contact with the Earth's atmosphere. Weathering occurs in situ, or "with no movement", and thus should not to be confused with erosion, which involves the movement and disintegration of rocks
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Rock flour, or glacial flour, consists of clay-sized particles of rock, generated by glacial erosion or by artificial grinding to a similar size. Because the material is very small, it is suspended in river water making the water appear cloudy.
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iceberg is a large piece of freshwater ice that has broken off from a snow-formed glacier or ice shelf and is floating in open water[1]

Since the density of pure water ice is ca. 920 kg/m³, and that of sea water ca.
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Till is an unsorted glacial sediment. Glacial drift is a general term for the coarsely graded and extremely heterogeneous sediments of glacial origin. Glacial till is that part of glacial drift which was deposited directly by the glacier.
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Sublimation of an element or compound is a transition from the solid to gas phase with no intermediate liquid stage. Sublimation is a phase transition that occurs at temperatures and pressures below the triple point (see phase diagram).
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terminal moraine, also called end moraine, is a moraine that forms at the end of a glacier.

Terminal moraines mark the maximum advance of the glacier. An end moraine is at the present boundary of the glacier.
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glacier terminus, or snout, is the end of a glacier at any given point in time. Although glaciers seem motionless to the observer, in reality glaciers are in endless motion and the glacier terminus is always either advancing or retreating.
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Many now-familiar glacial landforms were created by the movement of huge sheets of ice called continental glaciers during the Pleistocene Epoch (more commonly called the Ice Age.
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A landform comprises a geomorphological unit, and is largely defined by its surface form and location in the landscape, as part of the terrain, and as such, is typically an element of topography.
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A drumlin (Irish droimnín, a little hill ridge) is an elongated whale-shaped hill formed by glacial action. Its long axis is parallel with the movement of the ice, with the blunter end facing into the glacial movement. Drumlins may be more than high and more than 0.
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Esker is a long, winding ridge of stratified sand and gravel, examples of which occur in glaciated and formerly glaciated regions of Europe and North America. Eskers are frequently several miles in length and, because of their peculiar uniform shape, somewhat resemble railroad
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Gettlinge is a village in the southwest portion of the island of Öland, Sweden. It is known for its impressive Viking stone ship burial ground.[1] Gettlinge is situated on the western fringe of the Stora Alvaret, a World Heritage Site designated by UNESCO.
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tarn (or corrie loch) is a mountain lake or pool, formed in a cirque excavated by a glacier. A moraine may form a natural dam below a tarn.[1] A corrie may be called a cirque.
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A moraine-dammed lake occurs when a terminal moraine has prevented some meltwater from leaving the valley. Its most common shape is that of a long ribbon (ribbon lake). Example of moraine dammed lakes include:
  • New Zealand

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Geomorphology (from Greek: γη, ge, "earth"; μορφή, morfé, "form"; and λόγος, logos
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cirque is an amphitheatre-like valley, or valley head, formed at the head of a glacier by erosion. A cirque is also known as a cwm in Wales, a coomb or coombe in England, and a corrie
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