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Cirque (landform)
A (; from the Latin word ) is an amphitheatre-like valley formed by glacial erosion. Alternative names for this landform are corrie (from , meaning a pot or cauldron) and ; ). A cirque may also be a similarly shaped landform arising from fluvial erosion. The concave shape of a glacial cirque is open on the downhill side, while the cupped section is generally steep. Cliff-like slopes, down which ice and glaciated debris combine and converge, form the three or more higher sides. The floor of the cirque ends up bowl-shaped, as it is the complex convergence zone of combining ice flows from multiple directions and their accompanying rock burdens. Hence, it experiences somewhat greater erosion forces and is most often overdeepened below the level of the cirque's low-side outlet (stage) and its down-slope (backstage) valley. If the cirque is subject to seasonal melting, the floor of the cirque most often forms a tarn (small lake) behind a dam, which marks the downstream limit of the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Firn Line
__NOTOC__ Firn (; from Swiss German "last year's", cognate with ''before'') is partially compacted névé, a type of snow that has been left over from past seasons and has been recrystallized into a substance denser than névé. It is ice that is at an intermediate stage between snow and glacial ice. Firn has the appearance of wet sugar, but has a hardness that makes it extremely resistant to shovelling. Its density generally ranges from 0.35 g/cm3 to 0.9 g/cm3, and it can often be found underneath the snow that accumulates at the head of a glacier. Snowflakes are compressed under the weight of the overlying snowpack. Individual crystals near the melting point are semiliquid and slick, allowing them to glide along other crystal planes and to fill in the spaces between them, increasing the ice's density. Where the crystals touch, they bond together, squeezing the air between them to the surface or into bubbles. In the summer months, the crystal metamorphosis can ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pyramidal 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. Formation Glaciers, typically forming in drainages on the sides of a mountain, develop bowl-shaped depression (geology), basins called cirques (sometimes called 'corries' – from Scottish Gaelic [kʰəɾə] (a bowl) – or s). Cirque glaciers have rotational sliding that abrades the floor of the basin more than walls and that causes the bowl shape to form. As cirques are formed by glaciation in an alpine environment, the headwall and ridges between parallel glaciers called arêtes become more steep and defined. This occurs due to Frost wedging, freeze/thaw and mass wasting beneath the ice surface. It is widely held that a common cause for headwall steepening and extension headward is the crevasses known as bergschrund that ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Arête
An arête ( ; ) is a narrow ridge of rock that 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 arête steepened through mass wasting events and the erosion of exposed, unstable rock. The word ''arête'' is French for "edge" or "ridge"; similar features in the Alps are often described with the German equivalent term ''Grat''. Where three or more cirques meet, a pyramidal peak is created. Cleaver A cleaver is a type of arête that separates a unified flow of glacial ice from its uphill side into two glaciers flanking, and flowing parallel to, the ridge, analogous to an exposed mid-channel bar in a braided river. Cleaver gets its name from the way it resembles a meat cleaver slicin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lake Seal Mt Field NP Edit
A lake is often a naturally occurring, relatively large and fixed body of water on or near the Earth's surface. It is localized in a basin or interconnected basins surrounded by dry land. Lakes lie completely on land and are separate from the ocean, although they may be connected with the ocean by rivers. Lakes, as with other bodies of water, are part of the water cycle, the processes by which water moves around the Earth. Most lakes are fresh water and account for almost all the world's surface freshwater, but some are salt lakes with salinities even higher than that of seawater. Lakes vary significantly in surface area and volume of water. Lakes are typically larger and deeper than ponds, which are also water-filled basins on land, although there are no official definitions or scientific criteria distinguishing the two. Lakes are also distinct from lagoons, which are generally shallow tidal pools dammed by sandbars or other material at coastal regions of oceans or lar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Frost Weathering
Frost weathering is a collective term for several mechanical weathering processes induced by stresses created by the freezing of water into ice. The term serves as an umbrella term for a variety of processes, such as frost shattering, frost wedging, and cryofracturing. The process may act on a wide range of spatial and temporal scales, from minutes to years and from dislodging mineral grains to fracturing boulders. It is most pronounced in high-altitude and high-latitude areas and is especially associated with alpine, periglacial, subpolar maritime, and polar climates, but may occur anywhere at sub- freezing temperatures (between ) if water is present. Ice segregation Certain frost-susceptible soils expand or heave upon freezing as a result of water migrating via capillary action to grow ice lenses near the freezing front. This same phenomenon occurs within pore spaces of rocks. The ice accumulations grow larger as they attract liquid water from the surrounding pores. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bergschrund
A bergschrund (from the German for ''mountain cleft''; sometimes abbreviated in English to "schrund") is a crevasse that forms where moving glacier ice separates from the stagnant ice or firn above. It is often a serious obstacle for mountaineering, mountaineers. Bergschrunds extend to the bedrock, and can have a depth of well over . A bergschrund is distinct from a randkluft, which is a crevasse with one side formed by rock. The randkluft arises in part from the melting of the ice due to the presence of the warmer rock face. However, a randkluft is sometimes called a bergschrund. The French word ''rimaye'' encompasses both randklufts and bergschrunds. In a corrie or cirque, the bergschrund is positioned at the rear, parallel to the back wall of the corrie. It is caused by the rotational movement of the glacier. In a longitudinal glacier, the bergschrund is at the top end of the glacier at a right angle to the flow of the glacier. It is caused by the downwards flow of the glacier ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Plucking (glaciation)
Plucking, also referred to as ''quarrying'', is a Glacier, glacial phenomenon that is responsible for the weathering and erosion of 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 sliding, 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 (a form of hydraulic wedging), gradually loosening the rock between the joints. This produces large chunks of rock called joint blocks. Eventually these joint blocks come loose and become trapped in the glacier. In this way, plucking has been linked to regelation. Rocks of all sizes can become trapped in the bottom of the glacier. Joint blocks up to three meters have been "plucked" and transported. These entrained rock fragments can also ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bowl (vessel)
A bowl is a typically round dish or container generally used for preparing, serving, storing, or consuming food. The interior of a bowl is characteristically shaped like a spherical cap, with the edges and the bottom, forming a seamless curve. This makes bowls especially suited for holding liquids and loose food, as the contents of the bowl are naturally concentrated in its center by the force of gravity. The exterior of a bowl is most often round, but can be of any shape, including rectangular. The size of bowls varies from small bowls used to hold a single serving of food to large bowls, such as punch bowls or salad bowls, that are often used to hold or store more than one portion of food. There is some overlap between bowls, cups, and plates. Very small bowls, such as the tea bowl, are often called cups, while plates with especially deep wells are often called bowls. In many cultures, bowls are the most common kind of vessel used for serving and eating food. Historica ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Abrasion (geology)
Abrasion is a process of weathering that occurs when material being transported wears away at a surface over time, commonly occurring with ice and glaciers. The primary process of abrasion is physical weathering. Its the process of friction caused by scuffing, scratching, wearing down, marring, and rubbing away of materials. The intensity of abrasion depends on the hardness, concentration, velocity and mass of the moving particles. Abrasion generally occurs in four ways: glaciation slowly grinds rocks picked up by ice against rock surfaces; solid objects transported in river channels make abrasive surface contact with the bed with ppl in it and walls; objects transported in waves breaking on coastlines; and by wind transporting sand or small stones against surface rocks. Abrasion is the natural scratching of bedrock by a continuous movement of snow or glacier downhill. This is caused by a force, friction, vibration, or internal deformation of the ice, and by sliding over the rocks ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ice Segregation
Ice segregation is the geological phenomenon produced by the formation of ice lenses, which induce erosion when moisture, diffused within soil or rock, accumulates in a localized zone. The ice initially accumulates within small collocated pores or pre-existing cracks, and, as long as the conditions remain favorable, continues to collect in the ice layer or ice lens, wedging the soil or rock apart. Ice lenses grow parallel to the surface and several centimeters to several decimeters (inches to feet) deep in the soil or rock. Studies between 1990 and present have demonstrated that rock fracture by ice segregation (i.e., the fracture of intact rock by ice lenses that grow by drawing water from their surroundings during periods of sustained subfreezing temperatures) is a more effective weathering process than the freeze-thaw process which older texts proposed."Periglacial weathering and headwall erosion in cirque glacier bergschrunds"; Johnny W. Sanders, Kurt M. Cuffey, Jeffrey R. M ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
