Firn and ne’ve’ are repeated melting and refreezing forms of granules
Unconstrained these glaciers cover vast areas. Topography does not play a major role in the extent of these glaciers. Ice sheets and ice caps fall into the same category. The difference between them is one of scale. Ice sheets are larger. Typically the dividing line is around 50,000 km2. The glaciers that cover Antarctica and Greenland are ice sheets, and the glacier that covers Iceland is an ice cap. Two main components of ice sheets and ice caps are ice domes and outlet glacier. Ice shelves An ice shelf is a very thick sheet of ice that has been shoved out over the sea floor from a land-based glacier. It is still attached to land on one side but most of it is afloat. Massive icebergs (glossary) may calve off of ice shelves. Constrained These are the glaciers that are found in rugged topography and are typically bound within a valley or depression. Icefields An icefield is an extensive area of land ice covering a mountain region; its surface is approximately level and can be distinguished from an ice cap because it does not achieve the characteristic domelike shape, and because flow is strongly influenced by the underlying topography. Valley glaciers A valley glacier flows between the walls of a mountain valley in all or part of its length. It may originate in an icefield or a cirque. Cirque glaciers A cirque glacier is a small ice mass generally wide in relation to its length and characteristically occupying an armchair-shaped bedrock hollow. It is the most common type of glacier in the mountains of the western United States. Other small glaciers This category includes a wide variety of glaciers whose forms are closely controlled by the underlying topography. The permutations are almost limitless. Typically small glaciers are found in hollows or slight depressions in mountainous terrain or bordering coastlines. Cirque glacier-glacier confined by valley ,forms cirque(semicircular basin at head of valley formed by plucking of bedrock by glacier moving down hill Alpine glacier-form on mountain side and move downward through valleys. Create and deepen valleys by pushing dirt soil out of their way, Found in high mountains of every continent except Australia When two glaciers meet and merge at base of mountain, new glacier is called piedmont glacier- if it flows to the sea, called tidewater glacier Valley glacier-form in a valley Ice caps-cover mountain tops Icesheets- not limited to mountain areas, Form broad dome, spread out from center in all direction, Cover everything around them with ice Continental glaciers-largest ice sheets (antartica and island of Greenland) Dome shaped and flow away from central region and are largely unaffected by underlying topography Hanging glaciers-don’t flow down the entire length of mountain Avalanches and icefalls transfer glacial ice from hanging glaciers to a larger glacier beneath them, or directly to the valley below If a valley glacier extends down a valley and then covers a gentle slope beyond the mountain range, it is called a piedmont glacier. MOVEMENT
A View from Above Suppose stones are placed in a straight line across the surface of a valley glacier. In a year or two, the line would no longer be straight; it would be displaced and bent down-valley. This elementary study demonstrates that the center of a glacier, where the ice is the thickest, moves more rapidly than at the edges. A Sliced View Suppose a bendable pipe is inserted into a deep, narrow hole that was drilled vertically through a glacier from top to bottom. In a year or two, the inclination and position of the pipe would change. The pipe would be bent into a curve by greater movement at the top of the glacier. In addition to the pipe bending, it would also have moved down-valley, revealing that the glacier slipped over its bed. This experiment demonstrates the two dominant types of glacial movement: Mysterious...
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