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Glacier morphology, or the form a
glacier 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#Glaciology, ablation over many years, often Century, centuries. It acquires dis ...
takes, is influenced by
temperature Temperature is a physical quantity that expresses quantitatively the perceptions of hotness and coldness. Temperature is measured with a thermometer. Thermometers are calibrated in various temperature scales that historically have relied o ...
,
precipitation In meteorology, precipitation is any product of the condensation of atmospheric water vapor that falls under gravitational pull from clouds. The main forms of precipitation include drizzle, rain, sleet, snow, ice pellets, graupel and hail. ...
,
topography Topography is the study of the forms and features of land surfaces. The topography of an area may refer to the land forms and features themselves, or a description or depiction in maps. Topography is a field of geoscience and planetary sci ...
, 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 sheet In glaciology, an ice sheet, also known as a continental glacier, is a mass of glacial ice that covers surrounding terrain and is greater than . The only current ice sheets are in Antarctica and Greenland; during the Last Glacial Period at Las ...
s, such as the Greenland ice sheet, to small
cirque glacier 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 eno ...
s found perched on mountain tops. Glaciers can be grouped into two main categories: * Ice flow is constrained by the underlying
bedrock In geology, bedrock is solid Rock (geology), rock that lies under loose material (regolith) within the crust (geology), crust of Earth or another terrestrial planet. Definition Bedrock is the solid rock that underlies looser surface mater ...
topography Topography is the study of the forms and features of land surfaces. The topography of an area may refer to the land forms and features themselves, or a description or depiction in maps. Topography is a field of geoscience and planetary sci ...
* Ice flow is unrestricted by surrounding topography


Unconstrained Glaciers


Ice sheets and ice caps

Ice sheet In glaciology, an ice sheet, also known as a continental glacier, is a mass of glacial ice that covers surrounding terrain and is greater than . The only current ice sheets are in Antarctica and Greenland; during the Last Glacial Period at Las ...
s and
ice cap In glaciology, an ice cap is a mass of ice that covers less than of land area (usually covering a highland area). Larger ice masses covering more than are termed ice sheets. Description Ice caps are not constrained by topographical features ...
s cover the largest areas of land in comparison to other glaciers, and their ice is unconstrained by the underlying topography. They are the largest glacial ice formations and hold the vast majority of the world's fresh water.


Ice sheets

Ice sheets are the largest form of glacial formation. They are continent sized ice masses that span areas over . They are dome shaped, and similarly to ice caps, exhibit radial flow. As ice sheets expand over the ocean, they become
ice shelves An ice shelf is a large floating platform of ice that forms where a glacier or ice sheet flows down to a coastline and onto the ocean surface. Ice shelves are only found in Antarctica, Greenland, Northern Canada, and the Russian Arctic. The b ...
. Ice sheets contain 99% of all the freshwater ice found on Earth, and form as layers of snow fall accumulate and slowly start to compact into ice. There are only two ice sheets present on Earth today, and they are the Antarctic ice sheet, and the Greenland ice sheet. Although only a tenth of modern Earth is covered by ice sheets, the
Pleistocene The Pleistocene ( , often referred to as the ''Ice age'') is the geological Epoch (geology), epoch that lasted from about 2,580,000 to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fina ...
epoch was characterized by ice sheets that covered a third of our land. This was also known as the
Last Glacial Maximum The Last Glacial Maximum (LGM), also referred to as the Late Glacial Maximum, was the most recent time during the Last Glacial Period that ice sheets were at their greatest extent. Ice sheets covered much of Northern North America, Northern Eur ...
.


Ice caps

An ice cap can be defined as a dome shaped mass of ice that exhibits a radial flow. They are often easily confused with ice sheets, but these ice structures are smaller in size. They are smaller than 50,000 km2, and obscure the entirety of the topography they span. They mainly form in polar and sub-polar regions that can be characterized by having particularly high elevation but flat ground. Ice caps come in a variety of shapes; they can be round, circular, or irregular in shape. Oftentimes, ice caps gradually merge into ice sheets making them difficult to track and document. Some examples of ice caps include: *
Jostedal Glacier Jostedal Glacier or is the largest glacier in continental Europe. It is in Vestland county in Western Norway. Jostedalsbreen lies in the municipalities of Luster, Sogndal, Sunnfjord, and Stryn. The highest peak in the area is Lodalskåpa at ...
, Norway *
Devon Ice Cap The Devon Ice Cap is an ice cap on eastern Devon Island, Nunavut, Canada, covering an area of over . The highest point on Devon Island is found at the summit of the ice cap, with an elevation of . The ice cap has a maximum thickness of , and h ...
, Canada *
Barnes Ice Cap The Barnes Ice Cap is an ice cap located in central Baffin Island, Nunavut, Canada. Geography It covers close to in the area of the Baffin Mountains. It has been thinning due to regional warming. Between 2004 and 2006, the ice cap was thinni ...
, Canada *
Vatnajökull Vatnajökull ( Icelandic pronunciation: , literally "Glacier of Lakes"; sometimes translated as Vatna Glacier in English) is the largest and most voluminous ice cap in Iceland, and the second largest in area in Europe after the Severny Island ice ...
, Iceland * Flade Isblink, Greenland


= Ice domes

= An ice dome is a part of an ice cap or ice sheet that is characterized by upstanding ice surface located in the
accumulation zone On a glacier, the accumulation zone is the area above the firn line, where snowfall accumulates and exceeds the losses from ablation, (melting, evaporation, and sublimation). The annual equilibrium line separates the accumulation and ablation z ...
. Ice domes are nearly symmetrical, with a convex or parabolic surface shape. They tend to develop evenly over a land mass that may be either a topographic height or a depression—often reflecting the sub-glacial topography. In ice sheets, domes may reach a thickness that may exceed . However, in ice caps, the thickness of the dome is much smaller; measuring roughly up to several hundred metres in comparison. In glaciated islands, ice domes are usually the highest point of the ice cap. An example of an ice dome is Kupol Vostok Pervyy in Alger Island,
Franz Josef Land , native_name = , image_name = Map of Franz Josef Land-en.svg , image_caption = Map of Franz Josef Land , image_size = , map_image = Franz Josef Land location-en.svg , map_caption = Location of Franz Josef ...
,
Russia Russia (, , ), or the Russian Federation, is a List of transcontinental countries, transcontinental country spanning Eastern Europe and North Asia, Northern Asia. It is the List of countries and dependencies by area, largest country in the ...
.


Ice streams

Ice stream An ice stream is a region of fast-moving ice within an ice sheet. It is a type of glacier, a body of ice that moves under its own weight. They can move upwards of a year, and can be up to in width, and hundreds of kilometers in length. They t ...
s rapidly channel ice flow out to the sea, ocean, or an ice shelf. For this reason, they are commonly referred to as the "arteries" of an ice sheet. Ice from continental sheets is drained into the ocean by a complex network of ice streams, and their activity is greatly affected by oceanic and atmospheric processes. They feature a higher velocity in the centre of the stream, and are bounded by slow moving ice on either side. Periods of greater ice stream flow result in more ice transfer from ice sheets to the ocean; subsequently impacting sea level by raising it. At the margin between glacial ice and water,
ice calving Ice calving, also known as glacier calving or iceberg calving, is the breaking of ice chunks from the edge of a glacier.Essentials of Geology, 3rd edition, Stephen Marshak It is a form of ice ablation or ice disruption. It is the sudden release ...
takes place as glaciers begin to fracture, and
iceberg An iceberg is a piece of freshwater ice more than 15 m long that has broken off a glacier or an ice shelf and is floating freely in open (salt) water. Smaller chunks of floating glacially-derived ice are called "growlers" or "bergy bits". The ...
s break off from the large masses of ice. Iceberg calving is a major contributor to
sea level rise Globally, sea levels are rising due to human-caused climate change. Between 1901 and 2018, the globally averaged sea level rose by , or 1–2 mm per year on average.IPCC, 2019Summary for Policymakers InIPCC Special Report on the Ocean and Cry ...
, but the ocean is not the only place that can experience ice calving. Calving can also take place in lakes,
fjord In physical geography, a fjord or fiord () is a long, narrow inlet with steep sides or cliffs, created by a glacier. Fjords exist on the coasts of Alaska, Antarctica, British Columbia, Chile, Denmark, Germany, Greenland, the Faroe Islands, Ice ...
s, and continental ice cliffs.


Constrained Glaciers


Icefields

An
icefield An ice field (also spelled icefield) is a mass of interconnected valley glaciers (also called mountain glaciers or alpine glaciers) on a mountain mass with protruding rock ridges or summits. They are often found in the colder climates and highe ...
is an example of glacier structure that covers a relatively large area, and is usually located in areas characterized by mountain terrain. Icefields are quite similar to ice caps; however, their morphology is much more influenced by the underlying mountainous topography. The rock formations found under the icefields are variable, and rocky mountain peaks known as
nunatak A nunatak (from Inuit ''nunataq'') is the summit or ridge of a mountain that protrudes from an ice field or glacier that otherwise covers most of the mountain or ridge. They are also called glacial islands. Examples are natural pyramidal peaks. ...
s tend to jut out from under the surface of icefields. Some examples of icefields include: *
Columbia Icefield The Columbia Icefield is the largest ice field in North America's Rocky Mountains. Located within the Canadian Rocky Mountains astride the Continental Divide along the border of British Columbia and Alberta, Canada, the ice field lies partly in ...
, Canada *
Juneau Icefield The Juneau Icefield is an ice field located just north of Juneau, Alaska, continuing north through the border with British Columbia, extending through an area of in the Coast Range ranging north to south and east to west. The icefield is the so ...
, Canada *
Southern Patagonian Ice Field The Southern Patagonian Ice Field ( es, Hielo Continental or '), located at the Southern Patagonic Andes between Chile and Argentina, is the world's second largest contiguous extrapolar ice field. It is the bigger of two remnant parts of the P ...
, Chile & Argentina *
Harding Icefield The Harding Icefield is an expansive icefield located in the Kenai Mountains of the Kenai Peninsula in Alaska. It is also partially located in Kenai Fjords National Park. It is named for U.S. President Warren G. Harding. Geography The Har ...
, USA


Outlet glaciers

Outlet glaciers are often found in valleys, and they originate from major ice sheets and ice caps. They move in a singular direction that is determined by the underlying landscape. Outlet glaciers drain inland glaciers through gaps found in the surrounding topography. A higher amount of inland glacial melt ultimately increases the amount of outlet glacier output. Studies predict that outlet glaciers found in Greenland can increase the global sea level considerably following an increase in global temperature, and a subsequently higher drainage output. Some examples of outlet glaciers include: * Helheim Glacier, Greenland * Kangerlussuaq Glacier, Greenland *
Jakobshavn Glacier Jakobshavn Glacier ( da, Jakobshavn Isbræ), also known as Ilulissat Glacier ( kl, Sermeq Kujalleq), is a large outlet glacier in West Greenland. It is located near the Greenlandic town of Ilulissat (colonial name in da, Jakobshavn) and ends a ...
, Greenland *
Petermann Glacier Petermann Glacier ( da, Petermann Gletsjer) is a large glacier located in North-West Greenland to the east of Nares Strait. It connects the Greenland ice sheet to the Arctic Ocean at 81°10' north latitude, near Hans Island. The glacier and its f ...
, Greenland


Valley glaciers

Valley glaciers are outlet glaciers that provide drainage for ice fields, icecaps or ice sheets. The flow of these glaciers is confined by the walls of the valley they are found in; but they may also form in mountain ranges as gathering snow turns to ice. The formation of valley glaciers is restricted by formations such as terminal
moraine A moraine is any accumulation of unconsolidated debris (regolith and rock), sometimes referred to as glacial till, that occurs in both currently and formerly glaciated regions, and that has been previously carried along by a glacier or ice shee ...
s, which are collections of unconsolidated rock material, or
till image:Geschiebemergel.JPG, Closeup of glacial till. Note that the larger grains (pebbles and gravel) in the till are completely surrounded by the matrix of finer material (silt and sand), and this characteristic, known as ''matrix support'', is d ...
deposited by the terminus of the glacier. Ice-free exposed bedrock and slopes often surround valley glaciers, providing a route for snow and ice to accumulate on the glacier via
avalanche An avalanche is a rapid flow of snow down a slope, such as a hill or mountain. Avalanches can be set off spontaneously, by such factors as increased precipitation or snowpack weakening, or by external means such as humans, animals, and earth ...
s. Some examples of valley glaciers include: * Sermilik Glacier, Canada * Fláajökull, Iceland


''Valley-head glaciers''

Valley head glaciers are types of valley glaciers that are only limited to the
valley head The head of the valley or, less commonly, the valley head, refers to the uppermost part of a valley.Leser (2005), p. 935. Description The head of a valley may take widely differing forms; for example, in highland regions the valley often ends i ...
. An example of this type of valley glacier is Bægisárjökull, found in Iceland.


''Fjords''

True
fjords In physical geography, a fjord or fiord () is a long, narrow inlet with steep sides or cliffs, created by a glacier. Fjords exist on the coasts of Alaska, Antarctica, British Columbia, Chile, Denmark, Germany, Greenland, the Faroe Islands, Icela ...
are formed when valley glaciers retreat and seawater fills the now empty valley. They can be found in mountainous, glaciation affected terrain. Some examples of fjords include: *
Hvalfjörður Hvalfjörður (, "whale fjord") is situated in the west of Iceland between Mosfellsbær and Akranes. The fjord is approximately 30 km long and 5 km wide. The origin of the name Hvalfjörður is uncertain. Certainly today there is no pr ...
, Iceland *
Hornsund Hornsund is a fjord on the western side of the southernmost tip of Spitsbergen island. The fjord's mouth faces west to the Greenland Sea, and is wide. The length is , the mean depth is , and the maximal depth is . Hornsund cuts different geol ...
, Svalbard *
Sognefjord The Sognefjord or Sognefjorden (, en, Sogn Fjord), nicknamed the King of the Fjords ( no, Fjordenes konge), is the largest and deepest fjord in Norway. Located in Vestland county in Western Norway, it stretches inland from the ocean to the smal ...
, Norway * An existing valley glacier of this type is
Jakobshavn Glacier Jakobshavn Glacier ( da, Jakobshavn Isbræ), also known as Ilulissat Glacier ( kl, Sermeq Kujalleq), is a large outlet glacier in West Greenland. It is located near the Greenlandic town of Ilulissat (colonial name in da, Jakobshavn) and ends a ...
in Greenland


''Piedmont glaciers''

Piedmont glaciers are a sub-type of valley glaciers which have flowed out onto lowland plains, where they spread out into a fan-like shape. Some examples of Piedmont glaciers include: *
Malaspina Glacier __NOTOC__ The Malaspina Glacier (Lingít: ''Sít' Tlein'') in southeastern Alaska is the largest piedmont glacier in the world. Situated at the head of the Alaska Panhandle, it is about wide and long, with an area of some . Name The Lingít na ...
, USA * Endeavor Piedmont Glacier, Antarctica


''Cirque glaciers''

Cirque glacier 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 eno ...
s are glaciers that appear in bowl shaped valley hollows. Snow easily settles in the topographic structure; it is turned to ice as more snow falls and is subsequently compressed. When the glacier melts, a
cirque A (; from the Latin word ') is an amphitheatre-like valley formed by glacial erosion. Alternative names for this landform are corrie (from Scottish Gaelic , meaning a pot or cauldron) and (; ). A cirque may also be a similarly shaped landform ...
structure is left in its place. Some examples of cirque glaciers include: *
Lower Curtis Glacier Lower Curtis Glacier is in North Cascades National Park in the U.S. state of Washington. Named for photographer Asahel Curtis, the glacier is in a cirque on the western slopes of Mount Shuksan. Lower Curtis Glacier is rapidly retreating and ha ...
, USA *
Eel Glacier Eel Glacier is located to the north of Mount Anderson and east of West Peak, in Olympic National Park in the U.S. state of Washington. The northward-facing glacier starts at about in elevation, with an arm extending up to . As the glacier flows ...
, USA


''Hanging glacier''

A hanging glacier is a form of glacier that appears in a hanging valley, and has the potential to break off from the side of the mountain it is attached to. As bits and pieces of hanging glaciers break off and begin to fall, avalanches can be triggered. Examples of hanging glaciers include: *
Eiger Glacier The Eiger Glacier (german: Eigergletscher) is a glacier situated on the north-west side of the Eiger in the Bernese Alps of Switzerland. The glacier is within the Lauterbrunnen, municipality of Lauterbrunnen in the canton of Bern. In 1973 it had a ...
, Switzerland * Angel Glacier, Canada


References


Sources

*


External links

{{commons category-inline, Glacial geomorphology Glaciology Geomorphology