glacial valley

glacial valley

▪ geological formation
also called  glacial trough 
 stream valley that has been glaciated, usually to a typical catenary, or U-shaped, cross section. U-shaped valleys occur in many parts of the world and are characteristic features of mountain glaciation. These glacial troughs may be several thousand feet deep and tens of miles long.

      When allowed to spread out, a glacier erodes the landscape uniformly, but when confined within valley walls it tends to deepen and widen the valley floor. The commonly V-shaped stream valley is converted to a U-shaped valley because the U-shape provides the least frictional resistance to the moving glacier. Because a glacier has a much greater viscosity and cross section than a river, its course has fewer and broader bends, and thus, the valley becomes straighter and smoother. The valley walls may be almost vertical and may be striated by boulders dragged by the glacier, and the valley floor may be covered with till or moraines.

      Because thickness of the ice is the dominant factor in the deepening process, smaller tributary glaciers erode their troughs less rapidly than the main glacier does. When the glaciers melt, the tributary troughs are left as hanging valleys high on the walls of the main glacial valley. Postglacial streams may form waterfalls from the mouths of the hanging valleys, a well-known example being Yosemite Falls, California.

* * *


Universalium. 2010.

Игры ⚽ Поможем написать реферат

Look at other dictionaries:

  • 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 valley —   (also glacial trough) a broad, flat bottomed (U shaped) valley created by glacial erosion and deposition. The erosion widened, deepened and straightened the original river valley. The deposition created the flat bottom …   Geography glossary

  • glacial valley — /gleɪʃəl ˈvæli/ (say glayshuhl valee) noun a U shaped valley formed by a moving glacier …  

  • glacial-valley wall —    The comparatively steep, glacially scoured, concave sides of a u shaped, mountain valley mantled by colluvium with little or no till; (not preferred: colloquial: western USA) sometimes called a trough wall.    SW …   Glossary of landform and geologic terms

  • 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

  • Valley — In geology, a valley (also called a vale, dale, glen or strath and near or in Appalachia, a draw) is a depression with predominant extent in one direction. A very deep river valley may be called a canyon or gorge. The terms U shaped and V shaped… …   Wikipedia

  • glacial — gla|cial [ˈgleıʃəl] adj [Date: 1600 1700; : Latin; Origin: glacialis, from glacies ice ] 1.) relating to ice and glaciers, or formed by glaciers ▪ a glacial valley ▪ glacial deposits 2.) a glacial look or expression is extremely unfriendly = ↑icy …   Dictionary of contemporary English

  • glacial — adjective 1 involving ice and glaciers, or formed by glaciers: a glacial valley 2 a glacial look or expression is extremely unfriendly 3 extremely cold: a glacial wind glacially adverb …   Longman dictionary of contemporary English

  • 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 trough —   see glacial valley …   Geography glossary

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”