A glacier (; ) is a persistent body of dense that is constantly moving under its own weight. A glacier forms where the accumulation of exceeds its over many years, often . Glaciers slowly deform and flow under stresses induced by their weight, creating s, s, and other distinguishing features. They also abrade rock and debris from their substrate to create landforms such as s, s, or s. Glaciers form only on land and are distinct from the much thinner and lake ice that forms on the surface of bodies of water. On Earth, 99% of glacial ice is contained within vast s (also known as "continental glaciers") in the s, but glaciers may be found in s on every continent other than the Australian mainland, including Oceania's high-latitude countries such as New Zealand. Between latitudes 35°N and 35°S, glaciers occur only in the , , and a few high mountains in , , and on in Iran. With more than 7,000 known glaciers, 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 or about 98% of Antarctica's , with an average thickness of . Greenland and also have huge expanses of continental glaciers. The volume of glaciers, not including the ice sheets of Antarctica and Greenland, has been estimated at 170,000 km3. Glacial ice is the largest reservoir of 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 as warmer summer temperatures cause the glacier to melt, creating a 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., , , and , are considered among the most sensitive indicators of and are a major source of variations in . A large piece of compressed ice, or a glacier, , as large quantities of . This is 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 the created ice's density.

Etymology and related terms

The word ''glacier'' is a from and goes back, via , to the ', derived from the ', and ultimately ', 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 . The corresponding area of study is called . Glaciers are important components of the global . Perito Moreno Glacier Patagonia Argentina Luca Galuzzi 2005.JPG, from the of the in western , Argentina. Grosser Aletschgletscher 3178.JPG, The , the largest glacier of the , in . Quelccaya Glacier.jpg, The is the second-largest glaciated area in the , in Peru.


Classification by size, shape and behavior

Glaciers are categorized by their morphology, thermal characteristics, and behavior. '' glaciers'' form on the crests and slopes of s. 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 is termed an ' or '. Ice caps have an area less than by definition. Glacial bodies larger than are called ''s'' or ''continental glaciers''. Several kilometers deep, they obscure the underlying topography. Only s 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 . Portions of an ice sheet or cap that extend into water are called ; they tend to be thin with limited slopes and reduced velocities. Narrow, fast-moving sections of an ice sheet are called '. In Antarctica, many ice streams drain into large . Some drain directly into the sea, often with an , like . ' are glaciers that terminate in the sea, including most glaciers flowing from Greenland, Antarctica, , , and s in Canada, , and the and s. As the ice reaches the sea, pieces break off or calve, forming s. Most tidewater glaciers calve above sea level, which often results in a tremendous impact as the iceberg strikes the water. Tidewater glaciers undergo centuries-long that are much less affected by climate change than other glaciers. Glacier mouth.jpg, Mouth of the Glacier near Innergschlöß, Austria. GrottaGelo.jpg, The ' is a cave of , the southernmost glacier in . Fjordsglacier.jpg, Sightseeing boat in front of a tidewater glacier, , Alaska.

Classification by thermal state

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 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'' 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 , as sliding ice promotes at rock from the surface below. Glaciers which are partly cold-based and partly warm-based are known as ''polythermal''.


Glaciers form where the of snow and ice exceeds . A glacier usually originates from a landform (alternatively known as a "corrie" or as a "cwm") – a typically armchair-shaped geological feature (such as a depression between mountains enclosed by s) – 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 (granular snow). Further crushing of the individual snowflakes and squeezing 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 (50  ft) of snow-ice. In temperate glaciers, snow repeatedly freezes and thaws, changing into granular ice called . Under 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 of the infrared mode of the water molecule. (Liquid appears blue for the same reason. The blue of glacier ice is sometimes misattributed to of bubbles in the ice.) GornerGlacier 002.jpg, in Switzerland. Aerial Photo of Monte Rosa Massif - Wallis - Switzerland (cropped).jpg, An of the Gorner Glacier (left side of image) together with the (r.) flowing into it, both framing the massif in the middle Packrafting at Spencer Glacier. Chugach National Forest, Alaska.jpg , A er passes a wall of freshly exposed blue ice on Spencer Glacier, in Alaska. Glacial ice acts like a filter on light, and the more time light spends traveling through the ice, the bluer it becomes. 153 - Glacier Perito Moreno - Grotte glaciaire - Janvier 2010.jpg , A located on the in Argentina.


A glacier originates at a location called its glacier head and terminates at its glacier foot, snout, or . Glaciers are broken into zones based on surface snowpack and melt conditions. The ablation zone 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 . 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 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 s. The accumulation zone can be subdivided based on its melt conditions. # The dry snow zone is a region where no melt occurs, even in the summer, and the snowpack remains dry. # The percolation zone is an area with some surface melt, causing meltwater to percolate into the snowpack. This zone is often marked by refrozen , glands, and layers. The snowpack also never reaches the melting point. # Near the equilibrium line on some glaciers, a superimposed ice zone develops. This zone is where meltwater refreezes as a cold layer in the glacier, forming a continuous mass of ice. # The wet snow zone is the region where all of the snow deposited since the end of the previous summer has been raised to 0 °C. The health of a glacier is usually assessed by determining the 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 's end around 1850, . A slight cooling led to 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, or flow, downhill by the force of and the internal deformation of ice. Ice behaves like a brittle solid until its thickness exceeds about 50 m (160 ft). The pressure on ice deeper than 50 m causes . At the molecular level, ice consists of stacked layers of molecules with relatively weak bonds between layers. When the stress on the layer above exceeds the inter-layer binding strength, it moves faster than the layer below. Glaciers also move through . In this process, a glacier slides over the terrain on which it sits, by the presence of liquid water. The water is created from ice that melts under high pressure from frictional heating. Basal sliding is dominant in temperate or warm-based glaciers. Although evidence in favor of glacial flow was known by the early 19th century, other theories of glacial motion were advanced, such as 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. came up with the essentially correct explanation in the 1840s, although it was several decades before it was fully accepted.

Fracture zone and cracks

The top of a glacier are rigid because they are under low . 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 s develop in the fracture zone. Crevasses form because of differences in glacier velocity. If two rigid sections of a glacier move at different speeds or directions, forces cause them to break apart, opening a crevasse. Crevasses are seldom more than deep but, in some cases, can be at least deep. Beneath this point, the plasticity of the ice prevents the formation of cracks. Intersecting crevasses can create isolated peaks in the ice, called s. 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 the stagnant ice above, forming a . 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 s. 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 a glacier via . Streams within or beneath a glacier flow in englacial or sub-glacial tunnels. These tunnels sometimes reemerge at the glacier's surface. TitlisIceCracks.jpg, Ice cracks in the Glacier. Glaciereaston.jpg, Crossing a on the , , in the , United States. 20171012-FS-Tongass-AD-001 (44831586714).jpg, An exposed glacier tube that once transported water down the interior of the glacier.


The speed of glacial displacement is partly determined by . Friction makes 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 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 per day, such as in Greenland's . Glacial speed 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 . 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, the pooling of meltwater at the base of the glacier — perhaps delivered from a  — or the simple accumulation of mass beyond a critical "tipping point". Temporary rates up to 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, s occur. These are large scale earthquakes that have seismic magnitudes as high as 6.1."Seasonality and Increasing Frequency of Greenland Glacial Earthquakes"
, Ekström, G., M. Nettles, and V.C. Tsai (2006) ''Science'', 311, 5768, 1756–1758,
"Analysis of Glacial Earthquakes"
Tsai, V. C. and G. Ekström (2007). J. Geophys. Res., 112, F03S22,
The number of glacial earthquakes in Greenland peaks every year in July, August, and September and increased rapidly in 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 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 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 island territories. Extensive glaciers are found in Antarctica, Argentina, Chile, Canada, Alaska, Greenland and Iceland. Mountain glaciers are widespread, especially in the , the , the , the , , and the . glacier in Mountain, with a of 41°46′09″ N is the southernmost glacial mass in Europe.Grunewald, p. 129. Mainland Australia currently contains no glaciers, although a small glacier on was present in the . In New Guinea, small, rapidly diminishing, glaciers are located on . Africa has glaciers on in Tanzania, on , and in the . Oceanic islands with glaciers include Iceland, several of the islands off the coast of Norway including and to the far north, New Zealand and the subantarctic islands of , , and . During glacial periods of the Quaternary, , on and also had large alpine glaciers, while the and 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 s except from 20° to 27° north and south of the equator where the presence of the descending limb of the lowers precipitation so much that with high s reach above . Between 19˚N and 19˚S, however, precipitation is higher, and the mountains above usually have permanent snow. Even at high latitudes, glacier formation is not inevitable. Areas of the , such as , and the in Antarctica are considered s 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 the , , lowland , and and , 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 () and cold, but the relative lack of precipitation prevents snow from accumulating into glaciers. This is because these peaks are located near or in the .

Glacial geology

Glaciers erode terrain through two principal processes: and . 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 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 , like the 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 is called 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 s. Glaciers produce these when they contain large boulders that carve long scratches in the bedrock. By mapping the direction of the striations, researchers can determine the direction of the glacier's movement. Similar to striations are s, 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: *Velocity of glacial movement * Thickness of the ice * Shape, abundance and hardness of rock fragments contained in the ice at the bottom of the glacier * Relative ease of erosion of the surface under the glacier * Thermal conditions at the glacier base * Permeability and water pressure at the glacier base When 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 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: * ''Glacial till'': material directly deposited from glacial ice. Till includes a mixture of undifferentiated material ranging from clay size to boulders, the usual composition of a moraine. * ''Fluvial and outwash sediments'': sediments deposited by water. These deposits are stratified by size. Larger pieces of rock that are encrusted in till or deposited on the surface are called "s". They range in size from pebbles to boulders, but as they are often moved great distances, they may be drastically different from the material upon which they are found. Patterns of glacial erratics hint at past glacial motions.


Glacial s are formed by the deposition of material from a glacier and are exposed after the glacier has retreated. They usually appear as linear mounds of , a non-sorted mixture of rock, gravel, and boulders within a matrix of fine powdery material. Terminal or end moraines are formed at the foot or terminal end of a glacier. Lateral moraines are formed on the sides of the glacier. Medial moraines are formed when two different glaciers merge and the lateral moraines of each coalesce to form a moraine in the middle of the combined glacier. Less apparent are s, also called ''glacial drift'', which often blankets the surface underneath the glacier downslope from the equilibrium line. The term ''moraine'' is of French origin. It was coined by peasants to describe alluvial embankments and rims found near the margins of glaciers in the French . In modern geology, the term is used more broadly and is applied to a series of formations, all of which are composed of till. Moraines can also create moraine-dammed lakes.


s are asymmetrical, canoe-shaped hills made mainly of till. Their heights vary from 15 to 50 meters, and they can reach a kilometer in length. The steepest side of the hill faces the direction from which the ice advanced (''stoss''), while a longer slope is left in the ice's direction of movement (''lee''). Drumlins are found in groups called ''s'' or ''drumlin camps''. One of these fields is found east of ; it is estimated to contain about 10,000 drumlins. Although the process that forms drumlins is not fully understood, their shape implies that they are products of the plastic deformation zone of ancient glaciers. It is believed that many drumlins were formed when glaciers advanced over and altered the deposits of earlier glaciers.

Glacial valleys, cirques, arêtes, and pyramidal peaks

Before glaciation, mountain valleys have a characteristic , produced by eroding water. During glaciation, these valleys are often widened, deepened and smoothed to form a glacial valley or glacial trough, as it is sometimes called. The erosion that creates glacial valleys truncates any spurs of rock or earth that may have earlier extended across the valley, creating broadly triangular-shaped cliffs called . Within glacial valleys, depressions created by plucking and abrasion can be filled by lakes, called s. If a glacial valley runs into a large body of water, it forms a . Typically glaciers deepen their valleys more than their smaller . Therefore, when glaciers recede, the valleys of the tributary glaciers remain above the main glacier's depression and are called s. At the start of a classic valley glacier is a bowl-shaped cirque, which has escarped walls on three sides but is open on the side that descends into the valley. Cirques are where ice begins to accumulate in a glacier. Two glacial cirques may form back to back and erode their backwalls until only a narrow ridge, called an is left. This structure may result in a . If multiple cirques encircle a single mountain, they create pointed s; particularly steep examples are called .

Roches moutonnées

Passage of glacial ice over an area of bedrock may cause the rock to be sculpted into a knoll called a '','' or "sheepback" rock. Roches moutonnées may be elongated, rounded and asymmetrical in shape. They range in length from less than a meter to several hundred meters long. Roches moutonnées have a gentle slope on their up-glacier sides and a steep to vertical face on their down-glacier sides. The glacier abrades the smooth slope on the upstream side as it flows along, but tears rock fragments loose and carries them away from the downstream side via plucking.

Alluvial stratification

As the water that rises from the ablation zone moves away from the glacier, it carries fine eroded sediments with it. As the speed of the water decreases, so does its capacity to carry objects in suspension. The water thus gradually deposits the sediment as it runs, creating an . When this phenomenon occurs in a valley, it is called a ''valley train''. When the deposition is in an , the sediments are known as . Outwash plains and valley trains are usually accompanied by basins known as "". These are small lakes formed when large ice blocks that are trapped in alluvium melt and produce water-filled depressions. Kettle diameters range from 5 m to 13 km, with depths of up to 45 meters. Most are circular in shape because the blocks of ice that formed them were rounded as they melted.

Glacial deposits

When a glacier's size shrinks below a critical point, its flow stops and it becomes stationary. Meanwhile, meltwater within and beneath the ice leaves alluvial deposits. These deposits, in the forms of columns, and clusters, remain after the glacier melts and are known as "glacial deposits". Glacial deposits that take the shape of hills or mounds are called ''s''. Some kames form when meltwater deposits sediments through openings in the interior of the ice. Others are produced by fans or created by meltwater. When the glacial ice occupies a valley, it can form terraces or kames along the sides of the valley. Long, sinuous glacial deposits are called ''s''. Eskers are composed of sand and gravel that was deposited by meltwater streams that flowed through ice tunnels within or beneath a glacier. They remain after the ice melts, with heights exceeding 100 meters and lengths of as long as 100 km.

Loess deposits

Very fine glacial sediments or rock flour is often picked up by wind blowing over the bare surface and may be deposited great distances from the original fluvial deposition site. These deposits may be very deep, even hundreds of meters, as in areas of China and the . s can be important in this process.

Climate change

Glaciers are a valuable resource for tracking climate change over long periods of time because they can be hundreds of thousands of years old. To study the patterns over time through glaciers, s are taken, providing continuous information including evidence for climate change, trapped in the ice for scientists to break down and study. Glaciers are studied to give information about the history of climate change due to natural or human causes. Human activity has caused an increase in es creating a global warming trend, causing these valuable glaciers to melt. Glaciers have an effect and the melting of glaciers means less albedo. In the Alps the summer of 2003 was compared to the summer of 1988. Between 1998 and 2003 the albedo value is 0.2 lower in 2003. When glaciers begin to melt, they also cause a rise in sea level, "which in turn increases and elevates storm surge as warming air and ocean temperatures create more frequent and intense coastal storms like hurricanes and typhoons." Thus, human causes to climate change creates a positive with the glaciers: The rise in temperature causes more glacier melt, leading to less albedo, higher sea levels and many other climate issues to follow. From 1972 all the way up to 2019 NASA has used a satellite that has been used to record glaciers in , and . This Landsat project has found that since around 2000, glacier retreat has increased substantially.

Isostatic rebound

Large masses, such as ice sheets or glaciers, can depress the crust of the Earth into the mantle. The depression usually totals a third of the ice sheet or glacier's thickness. After the ice sheet or glacier melts, the mantle begins to flow back to its original position, pushing the crust back up. This , which proceeds very slowly after the melting of the ice sheet or glacier, is currently occurring in measurable amounts in and the region of North America. A geomorphological feature created by the same process on a smaller scale is known as ''dilation-faulting''. It occurs where previously compressed rock is allowed to return to its original shape more rapidly than can be maintained without faulting. This leads to an effect similar to what would be seen if the rock were hit by a large hammer. Dilation faulting can be observed in recently de-glaciated parts of Iceland and Cumbria.

On Mars

The polar ice caps of show geologic evidence of glacial deposits. The south polar cap is especially comparable to glaciers on Earth. Topographical features and computer models indicate the existence of more glaciers in Mars' past. At mid-latitudes, between 35° and 65° north or south, Martian glaciers are affected by the thin Martian atmosphere. Because of the low atmospheric pressure, ablation near the surface is solely caused by , not . As on Earth, many glaciers are covered with a layer of rocks which insulates the ice. A radar instrument on board the found ice under a thin layer of rocks in formations called s (LDAs).Holt, J. et al. 2008. Radar Sounding Evidence for Ice within Lobate Debris Aprons near Hellas Basin, Mid-Southern Latitudes of Mars. Lunar and Planetary Science XXXIX. 2441.pdf The pictures below illustrate how landscape features on Mars closely resemble those on the Earth. Wikielephantglacier.jpg, 's Elephant Foot Glacier in the Earth's Arctic, as seen by Landsat 8. This picture shows several glaciers that have the same shape as many features on Mars that are believed to also be glaciers. The next three images from Mars show shapes similar to the Elephant Foot Glacier. File:Glacier as seen by ctx.JPG, Mesa in , as seen by CTX. Mesa has several glaciers eroding it. One of the glaciers is seen in greater detail in the next two images from HiRISE. Image from . File:Wide view of glacier showing image field.JPG, Glacier as seen by HiRISE under the . Area in the rectangle is enlarged in the next photo. Zone of accumulation of snow at the top. Glacier is moving down valley, then spreading out on plain. Evidence for flow comes from the many lines on surface. Location is in in . File:Glacier close up with hirise.JPG, Enlargement of area in rectangle of the previous image. On Earth, the ridge would be called the terminal moraine of an alpine glacier. Picture taken with HiRISE under the HiWish program. Image from .

See also

* * * * *



* An excellent less-technical treatment of all aspects, with superb photographs and firsthand accounts of glaciologists' experiences. All images of this book can be found online (see Weblinks: Glaciers-online) * * * An undergraduate-level textbook. * A textbook for undergraduates avoiding mathematical complexities * A textbook devoted to explaining the geography of our planet. * A comprehensive reference on the physical principles underlying formation and behavior.

Further reading

* Moon, Twila
Saying goodbye to glaciers
''Science,'' 12 May 2017, Vol. 356, Issue 6338, pp. 580–581,

External links

* , a report in the (GEO) series.
Glacial structures – photo atlas

Photo project tracks changes in Himalayan glaciers since 1921
* Short radio episode

' from ''The Mountains of California'' by John Muir, 1894.
– Before/After Images by Simon Oberli {{Authority control Montane ecology