Cirque glacier

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Lower Curtis Glacier is a corrie glacier in the North Cascades in the State of Washington Lowercurtis.jpg
Lower Curtis Glacier is a corrie glacier in the North Cascades in the State of Washington

A cirque glacier is formed in a cirque, a bowl-shaped depression on the side of or near mountains. Snow and ice accumulation in corries often occurs as the result of avalanching from higher surrounding slopes. If a cirque glacier advances far enough, it may become a valley glacier. Additionally, if a valley glacier retreats enough that it is within the cirque, it becomes a cirque glacier again.

Cirque An amphitheatre-like valley formed by glacial erosion

A cirque is an amphitheatre-like valley formed by glacial erosion. Alternative names for this landform are corrie and cwm. A cirque may also be a similarly shaped landform arising from fluvial erosion.

Avalanche sudden, drastic flow of snow down a slope

An avalanche is an event that occurs when a cohesive slab of snow lying upon a weaker layer of snow fractures and slides down a steep slope. Avalanches are typically triggered in a starting zone from a mechanical failure in the snowpack when the forces of the snow exceed its strength but sometimes only with gradual widening. After initiation, avalanches usually accelerate rapidly and grow in mass and volume as they entrain more snow. If the avalanche moves fast enough, some of the snow may mix with the air forming a powder snow avalanche, which is a type of gravity current.

In these depressions, snow persists through summer months, and becomes glacier ice. Snow may be situated on the leeward slope of a mountain, where it is sheltered from wind. Rock fall from above slopes also plays an important role in sheltering the snow and ice from sunlight. If enough rock falls onto the glacier, it may become a rock glacier.

Snow precipitation in the form of flakes of crystalline water ice

Snow comprises individual ice crystals that grow while suspended in the atmosphere—usually within clouds—and then fall, accumulating on the ground where they undergo further changes. It consists of frozen crystalline water throughout its life cycle, starting when, under suitable conditions, the ice crystals form in the atmosphere, increase to millimeter size, precipitate and accumulate on surfaces, then metamorphose in place, and ultimately melt, slide or sublimate away. Snowstorms organize and develop by feeding on sources of atmospheric moisture and cold air. Snowflakes nucleate around particles in the atmosphere by attracting supercooled water droplets, which freeze in hexagonal-shaped crystals. Snowflakes take on a variety of shapes, basic among these are platelets, needles, columns and rime. As snow accumulates into a snowpack, it may blow into drifts. Over time, accumulated snow metamorphoses, by sintering, sublimation and freeze-thaw. Where the climate is cold enough for year-to-year accumulation, a glacier may form. Otherwise, snow typically melts seasonally, causing runoff into streams and rivers and recharging groundwater.

Glacier Persistent body of ice that is moving under its own weight

A glacier is a persistent body of dense ice that is constantly moving under its own weight. A glacier forms where the accumulation of snow exceeds its ablation over many years, often centuries. Glaciers slowly deform and flow due to stresses induced by their weight, creating crevasses, seracs, and other distinguishing features. They also abrade rock and debris from their substrate to create landforms such as cirques and moraines. Glaciers form only on land and are distinct from the much thinner sea ice and lake ice that form on the surface of bodies of water.

Rock glacier Landform of angular rock debris frozen in interstitial ice, former "true" glaciers overlain by a layer of talus, or something in between

Rock glaciers are distinctive geomorphological landforms, consisting either of angular rock debris frozen in interstitial ice, former "true" glaciers overlain by a layer of talus, or something in-between. Rock glaciers may extend outward and downslope from talus cones, glaciers or terminal moraines of glaciers.

Randklufts may form beneath corrie glaciers as open space between the ice and the bedrock, where meltwater can play a role in deposition of the rock.

Randkluft

A randkluft or rimaye is the headwall gap between a glacier or snowfield and the adjacent rock face at the back of the cirque or, more loosely, between the rock face and the side of the glacier.

Deposition (geology) Geological process in which sediments, soil and rocks are added to a landform or land mass

Deposition is the geological process in which sediments, soil and rocks are added to a landform or land mass. Wind, ice, water, and gravity transport previously weathered surface material, which, at the loss of enough kinetic energy in the fluid, is deposited, building up layers of sediment.

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Mountaineering Sport of mountain climbing

Mountaineering or alpinism is the set of activities that involves traversing mountainous terrain. This terrain, constituting both natural and man-made landscapes, contains steep slopes that may be rocky or covered with ice and snow. The classic mountaineering activity is travelling to summits; this is often referred to as peak bagging. Today, the sport encompasses a wide variety of disciplines and endeavors, each requiring various degrees of experience, athletic ability, and technical knowledge. Recreational climbing, skiing, and snow travel are the disciplines most intricately linked to mountaineering. Hiking, camping, and navigation are also a major part of the sport. At its highest level, it is one of the extreme sports, among which it is sometimes cited as an archetypal example.

Valley Low area between hills, often with a river running through it.

A valley is a low area between hills or mountains typically with a river running through it. In geology, a valley or dale is a depression that is longer than it is wide. The terms U-shaped and V-shaped are descriptive terms of geography to characterize the form of valleys. Most valleys belong to one of these two main types or a mixture of them, at least with respect to the cross section of the slopes or hillsides.

Glaciology Scientific study of ice and natural phenomena involving ice

Glaciology is the scientific study of glaciers, or more generally ice and natural phenomena that involve ice.

ArĂȘte A narrow ridge of rock which separates two valleys

An arête is a narrow ridge of rock which separates two valleys. It is typically formed when two glaciers erode parallel U-shaped valleys. Arêtes can also form when two glacial cirques erode headwards towards one another, although frequently this results in a saddle-shaped pass, called a col. The edge is then sharpened by freeze-thaw weathering, and the slope on either side of the arete steepened through mass wasting events and the erosion of exposed, unstable rock. The word ‘arête’ is actually French for edge or ridge; similar features in the Alps are described with the German equivalent term Grat.

Pyramidal peak Angular, sharply pointed mountain peak

A pyramidal peak, sometimes called a glacial horn in extreme cases, is an angular, sharply pointed mountain peak which results from the cirque erosion due to multiple glaciers diverging from a central point. Pyramidal peaks are often examples of nunataks.

Scree Broken rock fragments at the base of steep rock faces, that has accumulated through periodic rockfall

Scree is a collection of broken rock fragments at the base of crags, mountain cliffs, volcanoes or valley shoulders that has accumulated through periodic rockfall from adjacent cliff faces. Landforms associated with these materials are often called talus deposits. Talus deposits typically have a concave upwards form, while the maximum inclination corresponds to the angle of repose of the mean debris size.

Mount Timpanogos mountain in Utah County, Utah, United States

Mount Timpanogos, often referred to as Timp, is the second highest mountain in Utah's Wasatch Range. Timpanogos rises to an elevation of 11,752 ft (3,582 m) above sea level in the Uinta-Wasatch-Cache National Forest. With 5,270 ft (1,610 m) of topographic prominence, Timpanogos is the 47th-most prominent mountain in the contiguous United States.

Cadair Idris Mountain in Wales

Cadair Idris or Cader Idris is a mountain in Gwynedd, Wales, which lies at the southern end of the Snowdonia National Park near the town of Dolgellau. The peak, which is one of the most popular in Wales for walkers and hikers, is composed largely of Ordovician igneous rocks, with classic glacial erosion features such as cwms, moraines, striated rocks, and roches moutonnées.

Glacial landform Landform created by the action of glaciers

Glacial landforms are landforms 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 rare and very old fossil glacial landforms.

Bergschrund A crevasse between moving glacier ice and the stagnant ice or firn above

A bergschrund or rimaye is a crevasse that forms where moving glacier ice separates from the stagnant ice or firn above. It is often a serious obstacle for mountaineers, who sometimes abbreviate "bergschrund" to "schrund".

Plucking (glaciation) glacial quarrying

Plucking, also referred to as quarrying, is a glacial phenomenon that is responsible for the erosion and transportation of individual pieces of bedrock, especially large "joint blocks". This occurs in a type of glacier called a "valley glacier". As a glacier moves down a valley, friction causes the basal ice of the glacier to melt and infiltrate joints (cracks) in the bedrock. The freezing and thawing action of the ice enlarges, widens, or causes further cracks in the bedrock as it changes volume across the ice/water phase transition, gradually loosening the rock between the joints. This produces large pieces of rock called joint blocks. Eventually these joint blocks come loose and become trapped in the glacier.

Glacier morphology

Glacier morphology, or the form a glacier takes, is influenced by temperature, precipitation, topography, and other factors. The goal of glacial morphology is to gain a better understanding of glaciated landscapes, and the way they are shaped. Types of glaciers can range from massive ice sheets, such as the Greenland ice sheet, to small cirque glaciers found perched on mountain tops. Glaciers can be grouped into two main categories:

  1. Ice flow is constrained by the underlying bedrock topography
  2. Ice flow is unrestricted by surrounding topography
Coire an t-Sneachda mountain in United Kingdom

Coire an t-Sneachda is a glacial cirque or corrie landform in the Cairngorm or Am Monadh Ruadh mountain range in the Grampian Mountains of the Scottish Highlands.

Overdeepening Characteristic of basins and valleys eroded by glaciers

Overdeepening is a characteristic of basins and valleys eroded by glaciers. An overdeepened valley profile is often eroded to depths which are hundreds of metres below the deepest continuous line along a valley or watercourse. This phenomenon is observed under modern day glaciers, in salt-water fjords and fresh-water lakes remaining after glaciers melt, as well as in tunnel valleys which are partially or totally filled with sediment. When the channel produced by a glacier is filled with debris, the subsurface geomorphic structure is found to be erosionally cut into bedrock and subsequently filled by sediments. These overdeepened cuts into bedrock structures can reach a depth of several hundred metres below the valley floor.

Discrete debris accumulation (DDA) is a non-genetic term in mountain glacial geology to aid identification of non-lithified sediments on a valley or mountain slope or floor. It is intended that the debris accumulation is discrete such that it can be mapped, in the field and/or from aerial or satellite imagery. The origin or formative process may well not be known clearly or be changed by subsequent investigators it is advisable to have a non-genetic field reference so that discussion can then be used to ascertain, if possible, the origin. Mountain areas may currently have glaciers (glacierized) or have had glaciers (glaciated) or be subject to forms of periglacial activity. A moraine would be an easily identified DDA as would an esker. Although scree (talus) is generally easily identified and mapped, these deposits may be modified by ice, avalanches or downlope movement to create essentially new landforms. Many small slope failures and landslides can give the appearance of moraines or protalus ramparts on slopes. After mapping as a DDA, further investigation might draw light on the origin of the feature.

Valley step

A valley step is a prominent change in the longitudinal slope of a valley, mainly in trough valleys formed by glaciers.