Glacial landform

Glacial landform
Antique postcard shows rocks scarred by glacial erosion.
Yosemite Valley from an airplane, showing the U-shape
Glacially-plucked granitic bedrock near Mariehamn, Åland Islands.

Glacial landforms are those created by the action of glaciers. Most of today's glacial landforms were created by the movement of large ice sheets during the Quaternary glaciations. Some areas, like Fennoscandia and the southern Andes, have extensive occurrences of glacial landforms; other areas, such as the Sahara, display very old fossil glacial landforms.

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Erosional landforms

Erosional landforms

As the glaciers expanded, due to their accumulating weight of snow and ice , they crushed and scoured surface rocks and bedrock. The resulting erosional landforms include striations, cirques, glacial horns, arêtes, trim lines, U-shaped valleys, roches moutonnées, overdeepenings and hanging valleys.

  • Cirque: Starting location for mountain glaciers
  • U-shaped valley: U-shaped valleys are created by mountain glaciers, called fjord when filled with ocean water, creating an inlet

Depositional landforms

Depositional landforms

Later, when the glaciers retreated leaving behind their freight of crushed rock and sand (glacial drift), they created characteristic depositional landforms. Examples include glacial moraines, eskers, and kames. Drumlins and ribbed moraines are also landforms left behind by retreating glaciers. The stone walls of New England contain many glacial erratics, rocks that were dragged by a glacier many miles from their bedrock origin.

  • Esker: Built up bed of a sub-glacial stream.
  • Kame: Irregularly shaped mound.
  • Moraine: Feature can be terminal (at the end of a glacier) or lateral (along the sides of a glacier).
  • Outwash fan: Braided stream flowing from the front end of a glacier.

Glacial lakes and ponds

Lakes and ponds may also be caused by glacial movement. Kettle lakes form when a retreating glacier leaves behind an underground or surface chunk of ice that later melts to form a depression containing water. Moraine-dammed lakes occur when a stream (or snow runoff) is dammed by glacial debris. Jackson Lake and Jenny Lake in Grand Teton National Park are examples of moraine-dammed lakes, although Jackson Lake is also enhanced by a man-made dam.

  • Kettle lake: Depression, formed by a block of ice separated from the main glacier, in which the lake forms.
  • Glacial Lake: A lake that formed between the front of a glacier and the last terminal moraine. Usually it is no longer in existence.

Ice Features

Apart from the landforms left behind by glaciers, glaciers themselves may be striking features of the terrain, particularly in the polar regions of the earth. Notable examples include valley glaciers where glacial flow is restricted by the valley walls, crevasses in the upper section of glacial ice, and icefalls, the ice equivalent of waterfalls.

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Look at other dictionaries:

  • glacial landform — ▪ geology Introduction  any product of flowing ice and meltwater. Such landforms are being produced today in glaciated areas, such as Greenland, Antarctica, and many of the world s higher mountain ranges. In addition, large expansions of present… …   Universalium

  • glacial landform —   a landform produced by glacial erosion or deposition …   Geography glossary

  • glacial lake —     a) A lake that derives much or all of its water from the melting of glacier ice, fed by meltwater, and lying outside the glacier margins (e.g., proglacial lake) or lying on a glacier (e.g., ice walled lake, ice floored lake) and due to… …   Glossary of landform and geologic terms

  • glacial —    (adjective)     a) Of or relating to the presence and activities of ice and glaciers, as in glacial erosion.     b) Pertaining to distinctive features and materials produced by or derived from glaciers and ice sheets, as in glacial lakes.… …   Glossary of landform and geologic terms

  • glacial groove —    A deep, wide, usually straight furrow cut in bedrock by the abrasive action of a rock fragment embedded in the bottom of a moving glacier; it is larger and deeper than a glacial striation, ranging in size from a deep scratch to a small glacial …   Glossary of landform and geologic terms

  • glacial till —    (not recommended: use till)    Till should only be used for describing glacial sediments, therefore glacial till is redundant.    GM …   Glossary of landform and geologic terms

  • glacial-valley floor —    The comparatively flat bottom of a mountain valley predominantly mantled by till but which can grade from glacial scour (scoured rock outcrop) near its head to a thick mantle of till, and ultimately merging with alluvium or colluvium further… …   Glossary of landform and geologic terms

  • glacial drainage channel —    A channel formed by an ice marginal, englacial, or subglacial stream during glaciation.    GG …   Glossary of landform and geologic terms

  • glacial drift —    (not recommended)    use drift …   Glossary of landform and geologic terms

  • glacial-marine sedimentation —    The accumulation of glacially eroded, terrestrially derived sediment in the marine environment. Sediment may be introduced by fluvial transport, by ice rafting, as an ice contact deposit, or by eolian transport.    Compare: glaciomarine… …   Glossary of landform and geologic terms

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