71°S 70°E / 71°S 70°E / -71; 70
84-697: Lambert Glacier is a major glacier in East Antarctica . At about 80 km (50 mi) wide, over 400 km (250 mi) long, and about 2,500 m (8,200 ft) deep, it is the world's largest glacier. It drains 8% of the Antarctic ice sheet to the east and south of the Prince Charles Mountains and flows northward to the Amery Ice Shelf . It flows in part of Lambert Graben and exits the continent at Prydz Bay . This glacier
168-574: A breeding ground for emperor penguins and Adélie penguins . In 1946, the Minister for External Affairs , H.V. Evatt indicated his support for a proposal by Douglas Mawson for the establishment of a permanent Australian base in Antarctica. It was another seven years before a suitable ship, the Kista Dan could be chartered to set up facilities on the southern continent. The station site
252-424: A cirque landform (alternatively known as a corrie or as a cwm ) – a typically armchair-shaped geological feature (such as a depression between mountains enclosed by arêtes ) – which collects and compresses through gravity the snow that falls into it. This snow accumulates and the weight of the snow falling above compacts it, forming névé (granular snow). Further crushing of the individual snowflakes and squeezing
336-420: A boulder strewn surface and conical peak near the center, standing between flow of Collins and Mellor Glaciers. Mapped by ANARE from air photos taken in 1956. Named by ANCA for Dr. Geoff Newton, medical officer at Mawson Station, 1960. 71°54′S 69°37′E / 71.900°S 69.617°E / -71.900; 69.617 . A small nunatak 20 nautical miles (37 km) northeast of Clemence Massif on
420-522: A glacier is usually assessed by determining the glacier mass balance or observing terminus behavior. Healthy glaciers have large accumulation zones, more than 60% of their area is snow-covered at the end of the melt season, and they have a terminus with a vigorous flow. Following the Little Ice Age 's end around 1850, glaciers around the Earth have retreated substantially . A slight cooling led to
504-601: A glacier may flow into a body of water, it forms only on land and is distinct from the much thinner sea ice and lake ice that form on the surface of bodies of water. On Earth, 99% of glacial ice is contained within vast ice sheets (also known as "continental glaciers") in the polar regions , but glaciers may be found in mountain ranges on every continent other than the Australian mainland, including Oceania's high-latitude oceanic island countries such as New Zealand . Between latitudes 35°N and 35°S, glaciers occur only in
588-411: A glacier via moulins . Streams within or beneath a glacier flow in englacial or sub-glacial tunnels. These tunnels sometimes reemerge at the glacier's surface. Most of the important processes controlling glacial motion occur in the ice-bed contact—even though it is only a few meters thick. The bed's temperature, roughness and softness define basal shear stress, which in turn defines whether movement of
672-408: A kilometer per year. Eventually, the ice will be surging fast enough that it begins to thin, as accumulation cannot keep up with the transport. This thinning will increase the conductive heat loss, slowing the glacier and causing freezing. This freezing will slow the glacier further, often until it is stationary, whence the cycle can begin again. The flow of water under the glacial surface can have
756-404: A large effect on the motion of the glacier itself. Subglacial lakes contain significant amounts of water, which can move fast: cubic kilometers can be transported between lakes over the course of a couple of years. This motion is thought to occur in two main modes: pipe flow involves liquid water moving through pipe-like conduits, like a sub-glacial river; sheet flow involves motion of water in
840-460: A lower heat conductance, meaning that the basal temperature is also likely to be higher. Bed temperature tends to vary in a cyclic fashion. A cool bed has a high strength, reducing the speed of the glacier. This increases the rate of accumulation, since newly fallen snow is not transported away. Consequently, the glacier thickens, with three consequences: firstly, the bed is better insulated, allowing greater retention of geothermal heat. Secondly,
924-574: A major rebuilding program that started in the late 1970s. By 1959, the facilities at Mawson Station had expanded significantly. Personnel at that time included 6 scientists, 4 technicians, 2 pilots, 2 weather observers, and 10 others. Scientific disciplines represented included cartography , geology and geomagnetism , glaciology , seismology , ionospheric and auroral physics, meteorology , and physiology . Vehicles included 2 de Havilland Canada DHC-2 Beaver aircraft, 3 Caterpillar D4 tractors, 1 TEA-20 Ferguson , and 1 Sno-Cat . Mawson Station
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#17327976338651008-517: A member of the ANARE field party in this area in 1961. 73°6′S 65°0′E / 73.100°S 65.000°E / -73.100; 65.000 . A mountain with two peaks separated by an ice-filled saddle, standing 20 nautical miles (37 km) west of Mount Stinear on the north side of Fisher Glacier. Discovered from ANARE aircraft in 1957. Named by ANCA for Norman R. Seddon, Managing Director of B.P. Australia Ltd. since 1957, in recognition of
1092-651: A result of this expedition, including Armstrong Peak , Bird Ridge , Mount Griffiths , Newman Nunataks , Wilkinson Peaks , and the Young Nunataks . In 2018, astronaut and academic Jay C. Buckey conducted research using virtual reality , at the Australian Antarctic Division ’s Mawson Station, wherein the expeditioners used VR headsets to view Australian beach scenes, European nature scenes, and North American nature scenes of forests and urban environments, which were different from
1176-429: A ski landing area (SLA) is constructed adjacent to Mawson. As sea ice conditions progressively worsen over summer, operations are moved to Rumdoodle SLA , a field camp on the inland ice plateau 10 km from Mawson. Rumdoodle SLA has been in use since the 1950s, and the glacier surface requires annual inspection and preparation prior to use. It is accessible from Mawson by Hägglunds ground vehicles. Mawson Station
1260-488: A thin layer. A switch between the two flow conditions may be associated with surging behavior. Indeed, the loss of sub-glacial water supply has been linked with the shut-down of ice movement in the Kamb ice stream. The subglacial motion of water is expressed in the surface topography of ice sheets, which slump down into vacated subglacial lakes. The speed of glacial displacement is partly determined by friction . Friction makes
1344-410: A tremendous impact as the iceberg strikes the water. Tidewater glaciers undergo centuries-long cycles of advance and retreat that are much less affected by climate change than other glaciers. Thermally, a temperate glacier is at a melting point throughout the year, from its surface to its base. The ice of a polar glacier is always below the freezing threshold from the surface to its base, although
1428-468: Is a persistent body of dense ice that is constantly moving downhill under its own weight. A glacier forms where the accumulation of snow exceeds its ablation over many years, often centuries . It acquires distinguishing features, such as crevasses and seracs , as it slowly flows and deforms under stresses induced by its weight. As it moves, it abrades rock and debris from its substrate to create landforms such as cirques , moraines , or fjords . Although
1512-456: Is above or at freezing at the interface and is able to slide at this contact. This contrast is thought to a large extent to govern the ability of a glacier to effectively erode its bed , as sliding ice promotes plucking at rock from the surface below. Glaciers which are partly cold-based and partly warm-based are known as polythermal . Glaciers form where the accumulation of snow and ice exceeds ablation . A glacier usually originates from
1596-584: Is accessible by sea for only a short period each austral summer, between February and March. It has a deep, sheltered natural harbour and is ice-free in February. A direct voyage from Hobart to Mawson takes about 10—12 days, due to variable weather and sea-ice conditions. The approach to Horseshoe Harbour is through the Mawson Corridor and the Entrance Shoal . Between 1953 and 1987, Mawson
1680-407: Is affected by factors such as slope, ice thickness, snowfall, longitudinal confinement, basal temperature, meltwater production, and bed hardness. A few glaciers have periods of very rapid advancement called surges . These glaciers exhibit normal movement until suddenly they accelerate, then return to their previous movement state. These surges may be caused by the failure of the underlying bedrock,
1764-411: Is because these peaks are located near or in the hyperarid Atacama Desert . Glaciers erode terrain through two principal processes: plucking and abrasion . As glaciers flow over bedrock, they soften and lift blocks of rock into the ice. This process, called plucking, is caused by subglacial water that penetrates fractures in the bedrock and subsequently freezes and expands. This expansion causes
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#17327976338651848-406: Is by basal sliding, where meltwater forms between the ice and the bed itself. Whether a bed is hard or soft depends on the porosity and pore pressure; higher porosity decreases the sediment strength (thus increases the shear stress τ B ). Porosity may vary through a range of methods. Bed softness may vary in space or time, and changes dramatically from glacier to glacier. An important factor
1932-434: Is called glaciology . Glaciers are important components of the global cryosphere . Glaciers are categorized by their morphology, thermal characteristics, and behavior. Alpine glaciers form on the crests and slopes of mountains. A glacier that fills a valley is called a valley glacier , or alternatively, an alpine glacier or mountain glacier . A large body of glacial ice astride a mountain, mountain range, or volcano
2016-416: Is called rock flour and is made up of rock grains between 0.002 and 0.00625 mm in size. Abrasion leads to steeper valley walls and mountain slopes in alpine settings, which can cause avalanches and rock slides, which add even more material to the glacier. Glacial abrasion is commonly characterized by glacial striations . Glaciers produce these when they contain large boulders that carve long scratches in
2100-588: Is higher, and the mountains above 5,000 m (16,400 ft) usually have permanent snow. Even at high latitudes, glacier formation is not inevitable. Areas of the Arctic , such as Banks Island , and the McMurdo Dry Valleys in Antarctica are considered polar deserts where glaciers cannot form because they receive little snowfall despite the bitter cold. Cold air, unlike warm air, is unable to transport much water vapor. Even during glacial periods of
2184-668: Is located at Holme Bay in Mac Robertson Land, East Antarctica, named in January 1930 by Sir Douglas Mawson during the first British Australian and New Zealand Antarctic Research Expedition (BANZARE) voyage, aboard Discovery . It is in a region which Mawson proclaimed as British territory on several occasions in 1930 and 1931 (including at Proclamation Island , Scullin Monolith and Cape Bruce), and later became Australian Antarctic Territory. Some notable geographic features in
2268-897: Is termed an ice cap or ice field . Ice caps have an area less than 50,000 km (19,000 sq mi) by definition. Glacial bodies larger than 50,000 km (19,000 sq mi) are called ice sheets or continental glaciers . Several kilometers deep, they obscure the underlying topography. Only nunataks protrude from their surfaces. The only extant ice sheets are the two that cover most of Antarctica and Greenland. They contain vast quantities of freshwater, enough that if both melted, global sea levels would rise by over 70 m (230 ft). Portions of an ice sheet or cap that extend into water are called ice shelves ; they tend to be thin with limited slopes and reduced velocities. Narrow, fast-moving sections of an ice sheet are called ice streams . In Antarctica, many ice streams drain into large ice shelves . Some drain directly into
2352-413: Is the region where there is a net loss in glacier mass. The upper part of a glacier, where accumulation exceeds ablation, is called the accumulation zone . The equilibrium line separates the ablation zone and the accumulation zone; it is the contour where the amount of new snow gained by accumulation is equal to the amount of ice lost through ablation. In general, the accumulation zone accounts for 60–70% of
2436-402: Is the underlying geology; glacial speeds tend to differ more when they change bedrock than when the gradient changes. Further, bed roughness can also act to slow glacial motion. The roughness of the bed is a measure of how many boulders and obstacles protrude into the overlying ice. Ice flows around these obstacles by melting under the high pressure on their stoss side ; the resultant meltwater
2520-552: Is then forced into the cavity arising in their lee side , where it re-freezes. As well as affecting the sediment stress, fluid pressure (p w ) can affect the friction between the glacier and the bed. High fluid pressure provides a buoyancy force upwards on the glacier, reducing the friction at its base. The fluid pressure is compared to the ice overburden pressure, p i , given by ρgh. Under fast-flowing ice streams, these two pressures will be approximately equal, with an effective pressure (p i – p w ) of 30 kPa; i.e. all of
2604-993: The Andes , the Himalayas , the Rocky Mountains , the Caucasus , Scandinavian Mountains , and the Alps . Snezhnika glacier in Pirin Mountain, Bulgaria with a latitude of 41°46′09″ N is the southernmost glacial mass in Europe. Mainland Australia currently contains no glaciers, although a small glacier on Mount Kosciuszko was present in the last glacial period . In New Guinea, small, rapidly diminishing, glaciers are located on Puncak Jaya . Africa has glaciers on Mount Kilimanjaro in Tanzania, on Mount Kenya , and in
Lambert Glacier - Misplaced Pages Continue
2688-690: The Australian Antarctic Division (AAD). Mawson lies in Holme Bay in Mac. Robertson Land , East Antarctica in the Australian Antarctic Territory , a territory claimed by Australia . Established in 1954, Mawson is Australia's oldest Antarctic station and the oldest continuously inhabited Antarctic station south of the Antarctic Circle . It houses approximately 20 personnel over winter and up to 53 in summer. Mawson
2772-644: The Faroe and Crozet Islands were completely glaciated. The permanent snow cover necessary for glacier formation is affected by factors such as the degree of slope on the land, amount of snowfall and the winds. Glaciers can be found in all latitudes except from 20° to 27° north and south of the equator where the presence of the descending limb of the Hadley circulation lowers precipitation so much that with high insolation snow lines reach above 6,500 m (21,330 ft). Between 19˚N and 19˚S, however, precipitation
2856-760: The Himalayas , Andes , and a few high mountains in East Africa, Mexico, New Guinea and on Zard-Kuh in Iran. With more than 7,000 known glaciers, Pakistan has more glacial ice than any other country outside the polar regions. Glaciers cover about 10% of Earth's land surface. Continental glaciers cover nearly 13 million km (5 million sq mi) or about 98% of Antarctica 's 13.2 million km (5.1 million sq mi), with an average thickness of ice 2,100 m (7,000 ft). Greenland and Patagonia also have huge expanses of continental glaciers. The volume of glaciers, not including
2940-562: The Quaternary , Manchuria , lowland Siberia , and central and northern Alaska , though extraordinarily cold, had such light snowfall that glaciers could not form. In addition to the dry, unglaciated polar regions, some mountains and volcanoes in Bolivia, Chile and Argentina are high (4,500 to 6,900 m or 14,800 to 22,600 ft) and cold, but the relative lack of precipitation prevents snow from accumulating into glaciers. This
3024-535: The Rwenzori Mountains . Oceanic islands with glaciers include Iceland, several of the islands off the coast of Norway including Svalbard and Jan Mayen to the far north, New Zealand and the subantarctic islands of Marion , Heard , Grande Terre (Kerguelen) and Bouvet . During glacial periods of the Quaternary, Taiwan , Hawaii on Mauna Kea and Tenerife also had large alpine glaciers, while
3108-448: The 1990s and 2000s. In a study using data from January 1993 through October 2005, more events were detected every year since 2002, and twice as many events were recorded in 2005 as there were in any other year. Ogives or Forbes bands are alternating wave crests and valleys that appear as dark and light bands of ice on glacier surfaces. They are linked to seasonal motion of glaciers; the width of one dark and one light band generally equals
3192-480: The Fisher Glacier, flowing northeast between Mount Bayliss and Mount Ruker. It was plotted from air photos taken by ANARE in 1956 and 1957, and was named by ANCA for Hendrik Geysen, officer in charge of Mawson Station, 1960. A tributary glacier, flowing north-northeast between Mount Newton and Mount Maguire and coalescing with Collins Glacier just prior to its junction with Lambert Glacier at Patrick Point. It
3276-567: The Lambert Glacier, about 100 nautical miles (190 km; 120 mi) long, flowing east past the north sides of Mount Menzies and Mount Rubin and joining the main stream of the Lambert Glacier just east of Mount Stinear. It was sighted from ANARE aircraft by K.B. Mather in 1957, and was named by ANCA for N.H. Fisher, chief geologist at the Bureau of Mineral Resources , Department of National Development, Australia . A large tributary to
3360-502: The Mellor Glacier, which it feeds from the southwest, located north of Mount Newton. It was mapped by ANARE from air photos taken in 1956 and 1960, and named by ANCA for Neville Joseph Collins, senior diesel mechanic at Mawson Station, 1960. 73°27′48″S 68°24′1″E / 73.46333°S 68.40028°E / -73.46333; 68.40028 . A small glacier, south of Casey Point flowing west to reach Lambert Glacier. It
3444-412: The advance of many alpine glaciers between 1950 and 1985, but since 1985 glacier retreat and mass loss has become larger and increasingly ubiquitous. Glaciers move downhill by the force of gravity and the internal deformation of ice. At the molecular level, ice consists of stacked layers of molecules with relatively weak bonds between layers. When the amount of strain (deformation) is proportional to
Lambert Glacier - Misplaced Pages Continue
3528-520: The air from the snow turns it into "glacial ice". This glacial ice will fill the cirque until it "overflows" through a geological weakness or vacancy, such as a gap between two mountains. When the mass of snow and ice reaches sufficient thickness, it begins to move by a combination of surface slope, gravity, and pressure. On steeper slopes, this can occur with as little as 15 m (49 ft) of snow-ice. In temperate glaciers, snow repeatedly freezes and thaws, changing into granular ice called firn . Under
3612-430: The amount of melting at surface of the glacier, the faster the ice will flow. Basal sliding is dominant in temperate or warm-based glaciers. The presence of basal meltwater depends on both bed temperature and other factors. For instance, the melting point of water decreases under pressure, meaning that water melts at a lower temperature under thicker glaciers. This acts as a "double whammy", because thicker glaciers have
3696-713: The annual movement of the glacier. Ogives are formed when ice from an icefall is severely broken up, increasing ablation surface area during summer. This creates a swale and space for snow accumulation in the winter, which in turn creates a ridge. Sometimes ogives consist only of undulations or color bands and are described as wave ogives or band ogives. Glaciers are present on every continent and in approximately fifty countries, excluding those (Australia, South Africa) that have glaciers only on distant subantarctic island territories. Extensive glaciers are found in Antarctica, Argentina, Chile, Canada, Pakistan, Alaska, Greenland and Iceland. Mountain glaciers are widespread, especially in
3780-487: The assistance given to ANARE by the company. 73°28′S 66°51′E / 73.467°S 66.850°E / -73.467; 66.850 . The northern point of Cumpston Massif, at the junction of Mellor and Lambert Glaciers. Mapped from air photos taken by ANARE in 1956. Named by ANCA for Patrick Albion, radio operator at Mawson Station, 1956. 74°1′S 65°30′E / 74.017°S 65.500°E / -74.017; 65.500 . A large humped mountain with
3864-432: The bedrock has frequent fractures on the surface, glacial erosion rates tend to increase as plucking is the main erosive force on the surface; when the bedrock has wide gaps between sporadic fractures, however, abrasion tends to be the dominant erosive form and glacial erosion rates become slow. Glaciers in lower latitudes tend to be much more erosive than glaciers in higher latitudes, because they have more meltwater reaching
3948-445: The bedrock. By mapping the direction of the striations, researchers can determine the direction of the glacier's movement. Similar to striations are chatter marks , lines of crescent-shape depressions in the rock underlying a glacier. They are formed by abrasion when boulders in the glacier are repeatedly caught and released as they are dragged along the bedrock. The rate of glacier erosion varies. Six factors control erosion rate: When
4032-459: The climate can have significant consequences for the flow of ice down the glacier. Most studies of the Lambert Glacier are done with remote sensing due to the harsh conditions in the area. The photo reproduced here (on the right) shows a small tributary right-flank glacier flowing down from the lofty, ice-covered East Antarctic Plateau , flanked by slower-moving ice flowing down over a steep escarpment. The ice-fall which so impressively illustrates
4116-571: The created ice's density. The word glacier is a loanword from French and goes back, via Franco-Provençal , to the Vulgar Latin glaciārium , derived from the Late Latin glacia , and ultimately Latin glaciēs , meaning "ice". The processes and features caused by or related to glaciers are referred to as glacial. The process of glacier establishment, growth and flow is called glaciation . The corresponding area of study
4200-467: The deep profile of fjords , which can reach a kilometer in depth as ice is topographically steered into them. The extension of fjords inland increases the rate of ice sheet thinning since they are the principal conduits for draining ice sheets. It also makes the ice sheets more sensitive to changes in climate and the ocean. Although evidence in favor of glacial flow was known by the early 19th century, other theories of glacial motion were advanced, such as
4284-483: The deformation to become a plastic flow rather than elastic. Then, the glacier will begin to deform under its own weight and flow across the landscape. According to the Glen–Nye flow law , the relationship between stress and strain, and thus the rate of internal flow, can be modeled as follows: where: The lowest velocities are near the base of the glacier and along valley sides where friction acts against flow, causing
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#17327976338654368-490: The east side of Lambert Glacier. It was photographed by ANARE in 1950, and was sighted and mapped by the ANARE Prince Charles Mountains surveys of 1969 and 1971. It was named by ANCA for M.J.M. Robertson, a geophysicist at Mawson Station in 1970, who took part in the ANARE Prince Charles Mountains survey in 1971. The glacier is important in the study of climate change because very small changes in
4452-418: The essentially correct explanation in the 1840s, although it was several decades before it was fully accepted. The top 50 m (160 ft) of a glacier are rigid because they are under low pressure . This upper section is known as the fracture zone and moves mostly as a single unit over the plastic-flowing lower section. When a glacier moves through irregular terrain, cracks called crevasses develop in
4536-617: The feature did not immediately appear on published maps. As a result the name Lambert Glacier, as applied by the Antarctic Names Committee of Australia (ANCA) in 1957 following mapping of the area by Australian National Antarctic Research Expeditions (ANARE) in 1956, has become established for this feature. It was named for Bruce P. Lambert, Director of National Mapping in the Australian Department of National Development. A prominent western tributary to
4620-810: The flow characteristics of glacier ice is only about 6 km wide, and the Lambert Glacier proper is off the bottom right corner of the photo. The ice here is flowing at about 500 m per year, but velocities of over 1200 m per year are known at the edge of the Amery Ice Shelf, which is fed by this gigantic stream of ice. On the lower photo north is at the bottom, and the ice velocities are approximate as follow: [REDACTED] This article incorporates public domain material from "Lambert Glacier" . Geographic Names Information System . United States Geological Survey . Glacier A glacier ( US : / ˈ ɡ l eɪ ʃ ər / ; UK : / ˈ ɡ l æ s i ər , ˈ ɡ l eɪ s i ər / )
4704-475: The fracture zone. Crevasses form because of differences in glacier velocity. If two rigid sections of a glacier move at different speeds or directions, shear forces cause them to break apart, opening a crevasse. Crevasses are seldom more than 46 m (150 ft) deep but, in some cases, can be at least 300 m (1,000 ft) deep. Beneath this point, the plasticity of the ice prevents the formation of cracks. Intersecting crevasses can create isolated peaks in
4788-495: The glacial base and facilitate sediment production and transport under the same moving speed and amount of ice. Material that becomes incorporated in a glacier is typically carried as far as the zone of ablation before being deposited. Glacial deposits are of two distinct types: Mawson Station Mawson Station , commonly called Mawson , is one of three permanent bases and research outposts in Antarctica managed by
4872-453: The glacier to melt, creating a water source that is especially important for plants, animals and human uses when other sources may be scant. However, within high-altitude and Antarctic environments, the seasonal temperature difference is often not sufficient to release meltwater. Since glacial mass is affected by long-term climatic changes, e.g., precipitation , mean temperature , and cloud cover , glacial mass changes are considered among
4956-428: The glacier will be accommodated by motion in the sediments, or if it'll be able to slide. A soft bed, with high porosity and low pore fluid pressure, allows the glacier to move by sediment sliding: the base of the glacier may even remain frozen to the bed, where the underlying sediment slips underneath it like a tube of toothpaste. A hard bed cannot deform in this way; therefore the only way for hard-based glaciers to move
5040-510: The glacier's surface area, more if the glacier calves icebergs. Ice in the accumulation zone is deep enough to exert a downward force that erodes underlying rock. After a glacier melts, it often leaves behind a bowl- or amphitheater-shaped depression that ranges in size from large basins like the Great Lakes to smaller mountain depressions known as cirques . The accumulation zone can be subdivided based on its melt conditions. The health of
5124-619: The ice at the bottom of the glacier move more slowly than ice at the top. In alpine glaciers, friction is also generated at the valley's sidewalls, which slows the edges relative to the center. Mean glacial speed varies greatly but is typically around 1 m (3 ft) per day. There may be no motion in stagnant areas; for example, in parts of Alaska, trees can establish themselves on surface sediment deposits. In other cases, glaciers can move as fast as 20–30 m (70–100 ft) per day, such as in Greenland's Jakobshavn Isbræ . Glacial speed
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#17327976338655208-420: The ice sheets of Antarctica and Greenland, has been estimated at 170,000 km . Glacial ice is the largest reservoir of fresh water on Earth, holding with ice sheets about 69 percent of the world's freshwater. Many glaciers from temperate , alpine and seasonal polar climates store water as ice during the colder seasons and release it later in the form of meltwater as warmer summer temperatures cause
5292-556: The ice to act as a lever that loosens the rock by lifting it. Thus, sediments of all sizes become part of the glacier's load. If a retreating glacier gains enough debris, it may become a rock glacier , like the Timpanogos Glacier in Utah. Abrasion occurs when the ice and its load of rock fragments slide over bedrock and function as sandpaper, smoothing and polishing the bedrock below. The pulverized rock this process produces
5376-488: The ice, called seracs . Crevasses can form in several different ways. Transverse crevasses are transverse to flow and form where steeper slopes cause a glacier to accelerate. Longitudinal crevasses form semi-parallel to flow where a glacier expands laterally. Marginal crevasses form near the edge of the glacier, caused by the reduction in speed caused by friction of the valley walls. Marginal crevasses are largely transverse to flow. Moving glacier ice can sometimes separate from
5460-411: The idea that meltwater, refreezing inside glaciers, caused the glacier to dilate and extend its length. As it became clear that glaciers behaved to some degree as if the ice were a viscous fluid, it was argued that "regelation", or the melting and refreezing of ice at a temperature lowered by the pressure on the ice inside the glacier, was what allowed the ice to deform and flow. James Forbes came up with
5544-418: The increased pressure can facilitate melting. Most importantly, τ D is increased. These factors will combine to accelerate the glacier. As friction increases with the square of velocity, faster motion will greatly increase frictional heating, with ensuing melting – which causes a positive feedback, increasing ice speed to a faster flow rate still: west Antarctic glaciers are known to reach velocities of up to
5628-423: The infrared OH stretching mode of the water molecule. (Liquid water appears blue for the same reason. The blue of glacier ice is sometimes misattributed to Rayleigh scattering of bubbles in the ice.) A glacier originates at a location called its glacier head and terminates at its glacier foot, snout, or terminus . Glaciers are broken into zones based on surface snowpack and melt conditions. The ablation zone
5712-560: The isolation of the whiteness and silence of Antarctica. The research will inform psychological techniques to support long-duration spaceflight such as for astronauts going to Mars. Mawson is 5,475 km (3,402 mi) from Hobart , the AAD's main supply hub for Antarctic operations, and 5,201 km (3,232 mi) from Fremantle . Mawson's infrastructure includes an ANARESAT satellite antenna Earth station for communication. In early summer when sea ice conditions are most favourable,
5796-679: The most deformation. Velocity increases inward toward the center line and upward, as the amount of deformation decreases. The highest flow velocities are found at the surface, representing the sum of the velocities of all the layers below. Because ice can flow faster where it is thicker, the rate of glacier-induced erosion is directly proportional to the thickness of overlying ice. Consequently, pre-glacial low hollows will be deepened and pre-existing topography will be amplified by glacial action, while nunataks , which protrude above ice sheets, barely erode at all – erosion has been estimated as 5 m per 1.2 million years. This explains, for example,
5880-445: The most sensitive indicators of climate change and are a major source of variations in sea level . A large piece of compressed ice, or a glacier, appears blue , as large quantities of water appear blue , because water molecules absorb other colors more efficiently than blue. The other reason for the blue color of glaciers is the lack of air bubbles. Air bubbles, which give a white color to ice, are squeezed out by pressure increasing
5964-725: The pooling of meltwater at the base of the glacier — perhaps delivered from a supraglacial lake — or the simple accumulation of mass beyond a critical "tipping point". Temporary rates up to 90 m (300 ft) per day have occurred when increased temperature or overlying pressure caused bottom ice to melt and water to accumulate beneath a glacier. In glaciated areas where the glacier moves faster than one km per year, glacial earthquakes occur. These are large scale earthquakes that have seismic magnitudes as high as 6.1. The number of glacial earthquakes in Greenland peaks every year in July, August, and September and increased rapidly in
6048-410: The pressure of the layers of ice and snow above it, this granular ice fuses into denser firn. Over a period of years, layers of firn undergo further compaction and become glacial ice. Glacier ice is slightly more dense than ice formed from frozen water because glacier ice contains fewer trapped air bubbles. Glacial ice has a distinctive blue tint because it absorbs some red light due to an overtone of
6132-478: The region include the Framnes Mountains , which form the dramatic backdrop to Mawson Station. The Framnes Mountains were named in the 1930s by Norwegian explorers financed by the shipowner and whaling magnate Lars Christensen . Mawson Station experiences a Polar climate : During March and April 1960, an ANARE survey party from Mawson Station carried out a barometric mapping control traverse along
6216-710: The route of a 242 kilometres (150 mi) dog sledge journey from Cape Batterbee through the Napier Mountains to Martin Island in Edward VIII Bay . The members of this survey party — led by Syd Kirkby — were the first people to set foot in the Napier Mountains. The highest peak of this small range — Mount Elkins — was identified and named at this time for Terence James Elkins . Many other terrain features were mapped, visited or named as
6300-567: The sea, often with an ice tongue , like Mertz Glacier . Tidewater glaciers are glaciers that terminate in the sea, including most glaciers flowing from Greenland, Antarctica, Baffin , Devon , and Ellesmere Islands in Canada, Southeast Alaska , and the Northern and Southern Patagonian Ice Fields . As the ice reaches the sea, pieces break off or calve, forming icebergs . Most tidewater glaciers calve above sea level, which often results in
6384-409: The stagnant ice above, forming a bergschrund . Bergschrunds resemble crevasses but are singular features at a glacier's margins. Crevasses make travel over glaciers hazardous, especially when they are hidden by fragile snow bridges . Below the equilibrium line, glacial meltwater is concentrated in stream channels. Meltwater can pool in proglacial lakes on top of a glacier or descend into the depths of
6468-423: The stress being applied, ice will act as an elastic solid. Ice needs to be at least 30 m (98 ft) thick to even start flowing, but once its thickness exceeds about 50 m (160 ft) (160 ft), stress on the layer above will exceeds the inter-layer binding strength, and then it'll move faster than the layer below. This means that small amounts of stress can result in a large amount of strain, causing
6552-438: The surface snowpack may experience seasonal melting. A subpolar glacier includes both temperate and polar ice, depending on the depth beneath the surface and position along the length of the glacier. In a similar way, the thermal regime of a glacier is often described by its basal temperature. A cold-based glacier is below freezing at the ice-ground interface and is thus frozen to the underlying substrate. A warm-based glacier
6636-417: The weight of the ice is supported by the underlying water, and the glacier is afloat. Glaciers may also move by basal sliding , where the base of the glacier is lubricated by the presence of liquid water, reducing basal shear stress and allowing the glacier to slide over the terrain on which it sits. Meltwater may be produced by pressure-induced melting, friction or geothermal heat . The more variable
6720-473: Was chosen in 1953 by Phillip Law , the first director of the AAD, who drew aerial photographs taken during the U.S. Operation Highjump (OpHjp) of 1946-1947 to select the site for its large natural harbour ( Horseshoe Harbour ) and permanently exposed rock for building. The station was built during 1954. Some of the small pre-fabricated huts used in the first years remain on the station, but these are overshadowed by large steel-framed modular buildings dating from
6804-664: Was delineated and named in 1952 by American geographer John H. Roscoe who made a detailed study of this area from aerial photographs taken by Operation Highjump , 1946–47. He gave the name "Baker Three Glacier", using the code name of the Navy photographic aircraft and crew that made three flights in this coastal area in March 1947 resulting in geographic discoveries. The glacier was described in Gazetteer No. 14, Geographic Names of Antarctica ( U.S. Board on Geographic Names , 1956), but
6888-458: Was mapped from air photos taken by ANARE in 1956, and was named by ANCA after English-born glaciologist Malcolm Mellor (1933–91), who worked at Mawson Station in 1957, and as an engineer with the U.S. Army 's Cold Regions Research and Engineering Laboratory from 1961 to 1991. 73°41′S 65°55′E / 73.683°S 65.917°E / -73.683; 65.917 . A glacier about 11 nautical miles (20 km) wide at its confluence with
6972-887: Was named in honour of the Australian Antarctic explorer Sir Douglas Mawson . Mawson was listed on the Register of the National Estate in 2001 and listed on the Commonwealth Heritage List on 22 June 2004, reflecting the post-World War Two revival of Australia's scientific research and territorial interests in Antarctica. Mawson Station is an active base for scientific research programs including an underground cosmic ray detector, various long-term meteorological aeronomy and geomagnetic studies, as well as ongoing conservation biology studies, in particular of nearby Auster rookery ,
7056-529: Was plotted from ANARE aerial photographs taken in 1956, 1960 and 1973, and named by ANCA after P. Arriens, geochronologist with the ANARE Prince Charles Mountains survey party in 1973. 73°10′S 61°58′E / 73.167°S 61.967°E / -73.167; 61.967 . Two nunataks 16 nautical miles (30 km) west of Mount Scherger, near the head of Fisher Glacier. Mapped from ANARE air photos and surveys, 1958 and 1960–61. Named by ANCA) for J.A. Seavers , assistant cook at Mawson Station ,
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