Upper Thornton Lake Cirque in North Cascades National Park

A cirque (French for "circus") is an amphitheatre-like valley, or valley head, formed at the head of a glacier by erosion. North Cascades National Park is a US National Park located in the state of Washington. French ( français,) is a Romance language spoken around the world by 118 million people as a native language and by about 180 to 260 million people A circus is most commonly a traveling company of performers that may include acrobats, Clowns trained animals trapeze acts Hoopers, tightrope walkers An amphitheatre (alternatively amphitheater) is an open-air venue for spectator sports concerts rallies or theatrical performances In Geology, a valley (also called a vale, dale, glen or strath and near or in Appalachia, a draw) is "Glacial" and "Glaciation" redirect here For the geological periods see Glacial period. Erosion is the carrying away or displacement of solids ( Sediment, Soil, rock and other particles usually by the agents of currents such as wind A cirque is also known as a coombe or coomb in England, a combe or comb in America, a corrie in Scotland and Ireland, and a cwm in Wales, although these terms apply to a specific feature of which several may be found in a cirque. England is a Country which is part of the United Kingdom. Its inhabitants account for more than 83% of the total UK population whilst its mainland The United States of America —commonly referred to as the Scotland ( Gaelic: Alba) is a Country in northwest Europethat occupies the northern third of the island of Great Britain. Ireland (pronounced /ˈaɾlənd/ Éire) is the third largest island in Europe, and the twentieth-largest island in the world The term "comb" is often found at the end of placenames such as Newcomb and Maycomb, where it is pronounced /kəm/. Toponymy refers to the scientific study of place-names ( toponyms) their origins meanings use and Typology. To Kill a Mockingbird is a Pulitzer Prize -winning Novel by Harper Lee published in 1960.

Formation

Formation of cirque and resulting tarn. A tarn (or corrie loch) is a mountain Lake or pool formed in a Cirque excavated by a Glacier.

A Cirque is a landform found in the mountains as a result of alpine glaciers. They can be up to a square kilometre in size, situated high on a mountain side near the firn line, and are typically partially surrounded on three sides by steep cliffs. In Geography and Geology, a cliff is a significant vertical or near vertical rock exposure The highest cliff is often called a headwall. In Physical geography, the headwall of a glacial cirque is its highest cliff The fourth side is the "lip" which is the side that the glacier flowed away from the cirque. Many glacial cirques contain tarns dammed by either till or a bedrock threshold. A tarn (or corrie loch) is a mountain Lake or pool formed in a Cirque excavated by a Glacier. When enough snow accumulates it can flow out the opening of the bowl and form valley glaciers which can be several kilometers long.

Cirques form in conditions which are favorable; which in the northern hemisphere includes the north-east slope where they are protected from the majority of the sun’s energy and from the prevailing winds. If the accumulation of snow increases, the snow transforms into glacial ice. These areas are sheltered from heat, and so, they encourage the accumulation of snow. If the accumulation of snow increases, the snow transforms into glacial ice. The process of nivation follows (where a hollow in a slope may be enlarged by freeze-thaw weathering and glacial erosion). Nivation is the process of alternative freeze and thaw by which fallen snow gets converted into mass of ice or Névé, hence the term nivation Weathering is the decomposition of earth rocks, Soils and their Minerals through direct contact with the planet's Atmosphere. The freeze-thaw erodes at the lower rocks and causes it to disintegrate, which can result in an avalanche bringing down more snow and rock to add to the growing glacier. Eventually, this hollow can become big enough so that glacial erosion intensifies. Debris (or till) in the ice may also abrade (glacial abrasion) the bed surface; should ice move down a slope it would have a ‘sandpaper effect’ on the bedrock beneath on which it scrapes. Abrasion is mechanical scraping of a rock surface by Friction between rocks and moving particles during their transport in Wind, Glacier, Waves Bedrock is the native consolidated rock underlying the surface of a terrestrial planet usually the Earth.

The Lower Curtis Glacier in North Cascades National Park is a well developed cirque glacier. North Cascades National Park is a US National Park located in the state of Washington. A corrie glacier is formed in a corrie, bowl-shaped depressions on the side of mountains If the glacier continues to retreat and melt away, a lake may form in the basin

Eventually, the hollow can become a large bowl shape in the side of the mountain, with the headwall being weathered by constant freezing and thawing, and eroded by plucking. A bowl is a common open-top container used in many cultures to serve Food, and is also used for Drinking and storing other items 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 The basin will become deeper if it continues to become eroded by abrasion. Should plucking and abrasion continue, the dimensions of the cirque will increase, but the proportion of the landform would remain roughly the same. A bergschrund forms when the movement of the glacier separates the moving ice from the stationary ice forming a crevasse. A bergschrund is a Crevasse that forms where the moving glacier ice separates from the stagnant ice above The method of erosion of the headwall lying between the surface of the glacier and the cirque’s floor has been attributed to freeze-thaw mechanisms. The temperature within the bergschrund changes very little, however studies have shown that frost shattering can happen with only small changes in temperature. Water that flows into the bergschrund can be cooled to freezing temperatures by the surrounding ice allowing freeze-thaw mechanisms to occur.

Peñalara cirque, Sierra de Guadarrama, Spain

If two adjacent cirques erode toward one another, an arête, or steep sided ridge, forms. Peñalara is the highest mountain peak in the Mountain range of Guadarrama, a subsection of Spain's larger Sistema Central mountain chain which lies at the center The Sierra de Guadarrama (for Spanish: Guadarrama mountain range) is a mountain chain spanning half of the Sistema Central (a Mountain range Spain () or the Kingdom of Spain (Reino de España is a country located mostly in southwestern Europe on the Iberian Peninsula. This article is about a glacial landform See Arete for other meanings When three or more cirques erode toward one another, a pyramidal peak is created. A pyramidal peak, or sometimes in its most extreme form called a glacial horn, is a Mountaintop that has been modified by the action of Ice during In some cases, this peak will be made accessible by one or more arêtes. The Matterhorn in the European Alps is an example of such a peak. "Cervino" redirects here For the Italian town see Cervino (CE.

Glaciers can only originate above the snowline, studying the location of present day cirques provides information on past glaciations patterns and climate change.

Notable cirques

• Blue Lake Cirque, NSW, Australia
• Mount Ashland, Oregon, United States
• Chandra Taal, Himachal Pradesh, India
• Circo de Gredos, Sierra de Gredos, Spain
• Cirque de Gavarnie, Pyrenees, France
• Cirque de Navacelles, Massif Central, France
• Cirque of the Towers, Wyoming, United States
• Cirque Valley, Hindu Kush, Pakistan
• Gerlachovský štít, High Tatras, Slovakia
• Great Basin, Maine, United States
• Iceberg Cirque, Montana, United States
• Ramon Crater, Israel
• Śnieżne Kotły, Giant Mountains, Poland
• Tuckerman Ravine, New Hampshire, United States
• Western Cwm, Khumbu Himal, Nepal

See also

• Glacial landforms

External links

• Photographs and case study of corrie glacier