glacier

from Wikipedia, the free encyclopedia
The Perito Moreno Glacier in Argentina

A glacier (in Tyrol and southern Germany also also Ferner , in Austria also Kees , in Switzerland rarely also firn ) is an ice mass that emerges from snow with a clearly defined catchment area, which is determined by the slope, structure of the ice, temperature and the mass The shear stress arising from the ice and the other factors moves independently.

When considering the geomorphological levels of the high mountains , the glacier region is referred to as the glacial level.

Glaciers store 70% of the world's fresh water and are the largest water reservoirs on earth after the oceans . They cover large parts of the land area in the polar regions. Glaciers are important suppliers of water for many river systems and have a decisive influence on the global climate.

Glaciers are also important landscape formers, in particular they were in the cold ages (Ice Age) of the Pleistocene , in which inland ice masses in the northern hemisphere reached into northern Central Europe. The glaciers of the Alps, which were even able to penetrate into the Alpine foothills during the cold ages, formed huge trough valleys and shape the landscape to this day.

Since the middle of the 19th century, a clear decline in glaciers has been observed almost worldwide (see glacier retreat since 1850 ).

There is no generally accepted criterion among scientists as to the dimension from which a glacier can be referred to. However, according to the standards of the United States Geological Survey, on the one hand the thickness must be at least 100  ft (30.48 m) (so that the mass is sufficient for its own movement), on the other hand, the surface must measure at least 0.1 km².

glacier

Etymology and synonyms

The originally Swiss-German word glacier developed from Romanesque dialect forms (see today's glačer in Valais), which derive from vulgar Latin * glaciārium , which is derived from late Latin glacia and Latin glaciēs ("ice").

In the Eastern Alps , from the Oberinntal to the Zillertal ( Zamser Grund ), the name Ferner (cf. Firn ) is common; so first of all the snow from afar (d) , i.e. H. from last year. East of the Zillertal ( Venediger Group , Hohe Tauern ) the name Kees is used , which probably comes from a pre- Indo-European language.

Formation of glaciers

Glaciers require a number of decisive factors for their formation. So a long-term sufficiently low temperature is necessary for snowfall to occur. The height line from which, on a long-term mean, more snow falls than can thaw there is the climatic snow line . This can deviate locally by several hundred meters from the actual mean value of the region due to shading or exposed sunshine (e.g. southern slope in a mountain range in the northern hemisphere). In this case one speaks of the orographic snow line. Only above these boundary lines can so much snow fall in the long term with a suitable relief that it can undergo a metamorphosis.

Accumulation and metamorphosis

The process of accumulation of snow masses is called accumulation and consequently the area in which a glacier is formed is called an accumulation area (nutrient area). If the thickness of the snow is sufficient for the lower layers to be pressed together by the load on the upper layers, the metamorphosis of the snow begins to form glacial ice. The air, which is still 90% of the volume in the fresh snow and trapped in cavities, is pressed out by the pressure, which increases in depth. The proportion of air in glacier ice can therefore drop to around 2%. Ice with such a small proportion of air usually has a bluish, rarely also a slightly greenish color.

Higher temperatures have a positive effect on metamorphosis in two ways. On the one hand, smaller ice crystals usually form in warmer ( tempered ) glaciers, which allows movement here and also in the preliminary stages of the ice such as firn and granular ice (also called firne ice in some literature), which allows air to be released more easily . In addition, superficial material can also melt and freeze again without leaving the glacier. In this way, at least in smaller quantities, snow can be transformed into ice even in the daily cycle without going through the intermediate stages customary in pressure metamorphosis.

It takes 10 m of fresh snow with a density of 0.1 g / cm 3 to produce 1.10 m of glacier ice with a density of 0.9 g / cm 3 . This in turn corresponds to a water column of 1 m.

Equilibrium line

The line of equilibrium is a height limit in glaciology . Below this line in the so-called depletion area (ablation area) of the glacier, the loss of mass due to ablation is greater than the increase in glacier ice. In the nutrient area above (accumulation area), more glacier ice is formed than is lost through ablation. In many areas the equilibrium line largely corresponds to the firn limit . The line of equilibrium is also referred to in technical jargon as the Equilibrium Line Altitude (ELA).

Ablation and sublimation

Melt water can leave the glacier superficially ( supraglacial ) or at its bottom ( subglacial ) and is thus withdrawn from the mass budget of the glacier. Subglacial meltwater usually emerges from an opening in the glacier tongue known as a glacier gate, which is located in the consumption area, the counterpart to the nutrient area above the equilibrium line. If such a drain is blocked or does not occur, a hidden glacial lake under the ice, the so-called water pocket, is created.

Polar glaciers, in particular, also lose mass through the process of sublimation , whereby water changes directly from a solid to a gaseous state.

Some glaciers are also forced to ablate by the relief. This is the case if, for example, ice falls over a steep rock edge on a mountain glacier or an inland ice mass grows up to a coast and no ice shelf can form there, but the glacier is forced to calve here . Parts of the ice break out and can then drift over the sea as icebergs . Tabular icebergs arise when parts of an ice shelf calve on the front. By displacing the water, calving glaciers can trigger dangerous tidal waves .

Movement of glaciers

Only moving ice masses are called glaciers. This excludes ice floating on water such as icebergs or pack ice. In general, there are two basic forms of movement in glaciers:

Ice flow; Deformation flow

If the higher-lying parts of a glacier exert sufficient thrust force on the deeper and therefore ahead of them, this pressure is reduced by a flowing movement of the ice . At the molecular level, ice consists of layers of molecules lying on top of one another with relatively weak bonding forces between the individual layers. When the tension on the overlying layer exceeds the bonding forces between the layers, the upper layer will move faster than the underlying layer. The entire ice mass does not shift evenly, but depends on the possibilities of the ice crystals to move within the overall structure. At the bottom of the glacier and on the flanks of a glacier, the ice can often freeze to the rock, which means that no movement is possible here. Therefore, the flow velocity of a glacier is higher on the surface than on the bottom and slower on the sides than in the middle.

Basal gliding

Basal gliding occurs especially in temperate glaciers with base temperatures just below 0 ° C, as there is a film of liquid water at the base on which the ice glides (see also Wandering rocks ). Since the melting point of ice drops by around 0.07 ° C per 100 m of ice that is loaded with pressure ( pressure melting ), a temperature-controlled glacier 500 m thick may have a temperature of at least −0.35 ° C at its base. At −1.9 ° C to −32 ° C, however, some glaciers are significantly colder than the pressure melting point, so that only the frictional heat is used here for the production of liquid water.

Crevasses, Séracs and Ogiven

Due to the relief, different surface shapes such as transverse and longitudinal crevices, séracs or ogives can arise in a glacier , which also serve as indicators for the shape of the subsoil and the flow behavior of a glacier.

Cross gaps arise in this case by a longitudinal elongation of the glacier surface. This happens when the front and therefore deeper part of a glacier can flow faster than the one behind and higher. This process is called extending flow . Cross gaps do not always arise with extending flow, but conversely the cross gaps are always a clear indication of extending flow. Longitudinal crevices, on the other hand, are created by a transverse expansion of the glacier surface. This can often be observed with foreland glaciers, which emerge from a narrow valley into a wide plain where the ice can expand widely.

Ogiven (Forbes tapes) on the Mer de Glace

Ogives areregular light and dark patterns across the direction of flow, named after the Gothic style element ofthe same name. These stripe patterns form below some ice breaks when the time the ice has passed through the break is roughly an uneven multiple of half a year.

  • Seasonal fluctuations in the mass balance in the ice break, possibly in connection with compressive flow at its lower end (higher parts of a glacier move faster than lower ones), lead to so-called wave ogives, which are subsequently formed as bulges by the flowing off Pulling glaciers.
  • Band ogives (stripe ogives), also known as Forbes bands , go back to the seasonally different intensity of dust and pollen input . As a result, they run through a relatively smooth glacier surface as a regular striped pattern. The ice of the dark bands broke through in summer, whereby melting processes favor the accumulation of the dark particles on the surface of the glacier. The light stripes come from ice that broke through mainly in winter.

Ogives get their characteristic arch shape from the fact that the flow velocity is higher in the middle of the glacier than at its edges.

Séracs are ice towers that are created by the interaction of longitudinal and transverse expansion and therefore usually occur together with or close to longitudinal and transverse crevices.

Ice fall with falling ice

An ice fall is the breaking off of larger pieces of ice from a glacier. The broken ice is also called fall ice.

Glacier types

Falljökull, an outlet glacier of Öræfajökull , Iceland
Valley glacier, with clearly visible central moraines (Great Aletsch Glacier )
Grímsvötn in Vatnajökull , a plateau glacier in Iceland

Today, a distinction is made between the following types of glaciers, depending on how they were formed and how they were developed:

Outlet glacier
form on the edge of ice caps or ice sheets when the ice has to flow through relatively narrow outlets that are specified by the relief. Mostly they have the shape of valley glaciers, sometimes also of foreland glaciers .
Ice flow
Areas of ice sheets with a significantly higher flow velocity than the surrounding ice. Much of the runoff from the ice sheets is via the ice streams.
Ice stream network
If valley glaciers grow so strongly that the glacier ice can overflow the valley divisions, one speaks of an ice flow network - there is no direct connection to the above term ice flow . However, the movement of the ice is primarily controlled by the existing relief. The glaciers of the Alps created such a network at the height of the last glaciation. Today, such ice flow networks can still be found, for example, in Franz Josef Land (Arctic Ocean), Spitsbergen or Alaska .
Slope glacier
Usually comparatively small accumulations of ice on a mountain slope, which end without clear tongue formation or break off over a wall step ("ice balcony"). The hanging glacier is an extreme case .
Hanging glacier
are glaciers that “hang” on steep rock faces with an incline of over 40 °. Often they have no feeding area because the tongues break off under their own weight or end in a lower slope or valley glacier. Their nutrient area is usually formed by large firn channels, ice caps or slope glaciers .
Ice sheet or ice sheet
The largest glacier areas ever. Ice masses that are so thick that they almost completely cover the relief and also move largely independently of it (e.g. in Greenland or the Antarctic). However, some scientists distinguish the large inland ice masses from the smaller glaciers and therefore do not refer to them as glaciers.
Kar glacier
Eiskar , the only glacier in the Carnic Alps
Ice masses of small size, which are sheltered from the sun in a hollow, the so-called cirque . Kar glaciers do not have a clearly formed glacier tongue . Often they are hanging glaciers . Due to the protected hollow, they can occur deeper than valley glaciers.
Avalanche glacier or avalanche kettle glacier
Glaciers that lie below the snow line and therefore do not have their own nutrient area. They are mostly protected by large mountain walls facing away from the sun and are fed by deposited avalanche snow. Therefore, they can still occur very far below the snow line. Although they do not get very large, depending on the conditions, they show all typical glacier features such as ice movement and crevasses. Example: Höllentalferner .
Piedmont glacier or foreland glacier
Ice masses that advance from the valleys of the mountains spread out in a ring or fan shape in the upstream plains. The largest of its kind is the Malaspina Glacier in Alaska.
Plateau glacier or ice cap
Like the inland ice, a larger glaciation overlying the relief, but less powerful (examples: the Vatnajökull in Iceland, or the Jostedalsbreen in Scandinavia)
Valley glacier
Ice masses that have a clearly limited catchment area and move downwards in a valley under the influence of gravity . The big mountain glaciers are classic. Both the amount of melt water and the flow speed of the glacier vary over the course of the year, with a maximum in summer. Although valley glaciers only make up about one percent of the earth's glaciated areas, they are the best-known type of glacier due to their imposing appearance (example: Aletsch glacier ). They can take on enormous proportions even outside the polar regions: the largest glaciers of this type are the Fedchenko Glacier (78 km) in the Pamir, the Kahiltna Glacier (77 km) on Denali (Mount McKinley) (Alaska) and the Baltoro Glacier (57 km , with its tributaries Godwin-Austen- and Gasherbrum-Glacier about 78 km) in the Karakoram.

Block diagram of a slope glacier Block diagram of a Kar glacier Block diagram of a valley glacier Block diagram of a foreland glacier Block diagram of an ice shelf

From left to right: Slope glacier, Kargletscher, valley glacier, foreland glacier, ice shelf.

A rock glacier is, despite its name no glaciers, because it is not clear from snow but made iced mixed rubble and boulders. It crawls very slowly down the valley, which gives its completely stony surface a mostly wavy structure, and is a phenomenon of permafrost ( permafrost ).

Landscape formation by glaciers

Distribution of the vegetation zones during the cold maximum of the last glacial period , in the period 24,500 to 18,000 BC In Europe
white: glaciation; pink dashed line: southern limit of the tundra ; white dotted line: southern limit of the permafrost ground ; green line: steppe / tree line; yellow hatching: loess desert .

Glaciers are important landscape formers , which in their effectiveness clearly outperform the wind and flowing water. Particularly during the Ice Age , when large parts of the northern hemisphere were glaciated, very large areas were reshaped by them . This applies, for example, to the Alpine region and other high mountains as well as Northern Europe and northern Central Europe, large areas in North America and northern Asia. The effect of the glaciers is primarily based on the moraine material they carry with them. A distinction is made between forms of glacial erosion and forms and sediments in backfill areas.

Erosion and deposit forms

Schematic representation of the glacial deterion with rubble feed

Glacier cut and glacier scrapes

Rock material of various grain sizes carried along in the glacier ice - from fine clay to boulders measuring several meters - can leave clear traces in the rock bedrock. Fine-grained material usually results in a grinding comparable to the effect of sandpaper , while larger particles can leave clear scratches and grooves in the rock, supported by the strong pressure and the force of movement of the glacier. These grooves are called glacier ridges.

These shapes testify to the movement of the glacier ice over the subsurface and are therefore proof that the former glacier was able to move here by basal flow and was not frozen to the subsurface.

Detersion and Detraction

Hohbalm Glacier, above Saas-Fee, Valais, Switzerland

Glaciers can strongly shape their subsoil. If an obstacle protrudes from the rocky ground in the path of a glacier, a characteristic shape is created. On the side of the rock that faces the direction of flow of the ice (windward), the pressure in the ice increases, which makes it easier for a meltwater film to form here, on which the glacier can glide over the rock. The material carried by the glacier leads to erosion of the rock. The windward side is given a streamlined shape similar to that of a sand dune. This process is called deterion. On the opposite side (leeward) the pressure is again significantly lower, which means that no melt water film can form here. Instead, the ice freezes to the rock and as the glacier moves forward, the ice is carried along and parts of the rock are broken off. A so-called round hump is created from the detraction on the windward side and the detraction on the lee side . These can be found today as the remains of the Pleistocene glaciation in the Alps.

Valley formation

Rivers create deeply cut V-shaped valleys in the mountains . In contrast, glaciers are capable of much stronger side erosion, which means that glacial valleys have a distinctive U-shape and are known as trough valleys .

Often pre-glacial material was excavated from the glaciers in the primeval valleys and carried along. As a result, earlier layers of fluvial sediments were replaced by glacial till. The edge of the cut is often clearly visible on the valley slopes, which marks the thickness up to which a glacier once filled the valley.

Valley formation by glaciers

Nunatak

In ice stream networks, such as can still be found today in Alaska, for example, or as they were pronounced in the Pleistocene in the Alps, glaciers can also overflow valley divisions and therefore also form them erosively.

If a mountain protrudes out of an ice stream network or an inland glaciation, it is called a nunatak (plural: nunataker or nunatakker). The tip of a nunatak, which is not formed by glacier ice, is also known as a horn, which differs significantly from the more rounded lower area of ​​the mountain due to its sharp edges.

Fjell

As a landscape form in which mountain peaks were once covered by ice and are now only present as rounded peaks, the Scandinavian Fjell is very indicative of the formative power of the ice masses that once burdened Northern Europe.

Glacial deposits

Glacial series

Glacier tracks
Debris in front of Skaftafellsjökull, Iceland
  • Moraine: A moraine is the term used to describe all of the material transported by the glacier. Because glaciers are solid bodies, they can absorb, transport and deposit all grain size classes , from clay to sand to the coarsest blocks . Depending on their position in relation to the glacier, they are called upper, side, middle, inner, lower or terminal moraine. The term “moraine” now refers more to the corresponding landscape forms and no longer to the actual material, which is now referred to as boulder clay .
  • Forms of deposits: In the case of thawed mountain glaciers, the moraines are the most widespread deposits that can easily be associated with the glacier in question (if it is still present). In northern Central Europe and in the foothills of the Alps, the glaciers have left behind the glacial series with the elements ground moraine , terminal moraine , sand and (only in northern Germany) glacial valley as a typical society of forms . Here, too, there are numerous small forms such as boulders , drumlins , glacial channels , Oser (singular Os ) and Kames .

Glacial isostasis

Continental plates are usually in a state of equilibrium between the force of their mass and gravity and the buoyancy of the Earth's mantle. That balance is isostasis. However, it can be disturbed by the fact that large thicknesses of inland glaciation accumulate on a continental plate or parts of it. Due to the additional weight, the earth's crust is forced into a vertical compensatory movement in order to regain the state of isostasis.

The inland ice over Scandinavia caused this area to sink significantly during the cold ages. After these masses melted, most of Finland was even below sea level. Since then, Northern Europe has been rising again as a compensatory movement. The uplift rates here reach up to 9 mm per year.

Glacial eustasia

Due to the massive binding of water in the form of ice on land surfaces, the sea level fell during the cold periods and was up to 150 meters lower than today. This caused u. a. today's North Sea dry and formed a land bridge between Europe and Britain . Meuse and Thames were tributaries of the Rhine .

If the ice masses still existing today were to melt, the sea level would rise by another 60 to 70 meters. A rise in sea level caused by the melting of ice in the Antarctic in particular is expected in the context of global warming. The forecasts of climate experts still differ greatly from one another. Very low-lying countries such as Bangladesh or the depressed areas in the Netherlands would be particularly threatened .

Glaciers and climate

Glacial ice

Although glaciers only make up a small part of the earth's surface , it is largely undisputed that, depending on their size, they have a strong influence on the local and global climate . Two physical properties are important:

  • The albedo of the earth's surface increases significantly on a glacier as long as it has not bled : almost 90% of the incoming sunlight is reflected back, which means that it cannot develop its warming energy input into the biosphere . Once a glacier has expanded, it has a tendency to cool down further and to enlarge further. A high pressure area arises above it in connection with low temperatures .
  • Glaciers act as water reservoirs . It is stored as ice in the glaciers and is thus temporarily or permanently withdrawn from the water reservoir. With the melting of the glaciers as a result of the warming of the climate, the sea level can rise . This is especially true for the ice sheets in Greenland and Antarctica .

The effect of the increased influx of melt water on ocean currents , especially on the Gulf Stream system , is currently the subject of scientific research. One theory says that the melting of the Arctic pack ice or the Greenland ice sheet will reduce the salt content in the Arctic Ocean, thereby reducing the density of the seawater and preventing the seawater from sinking near Iceland. This can slow down the entire Gulf Stream and even lead to a cooling of the climate in Europe. Whether and to what extent this effect is stronger than global warming is not clear.

Conversely, glaciers are of course also influenced by the climate and are subject to major changes. These are not always predictable. The connection between glacier retreat or advances and climatic changes is seldom clear, as advances due to changed flow velocities can be caused by stronger melting (better sliding on the meltwater) or delayed by increased ice formation in earlier times and slow deeper flow. The mass balances are therefore more meaningful - i.e. H. the differences between newly formed and melted ice. Precipitation, for which an increase is forecast due to climate change, also plays an important role. For a glacier the question is then whether this increased amount of precipitation comes down as snow or as rain. Snow promotes ice formation, rain promotes melting.

Mountain glaciers are also subject to significant fluctuations. For plateau-shaped glaciers such as B. the Gepatschferner , the catchment areas are very flat. With only a slight increase in the average temperature and thus an increase in the snow line, large accumulation areas can fall completely below the snow line, which completely upsets the mass balance of the glacier. Due to the sinking of the glacier surface (in the summer of 2003 alone an average of 5 m on the Gepatschferner), subsequent cooling by the same amount is no longer sufficient to compensate for the loss of mass, as the now deeper ice surface remains below the snow line.

Glaciers are an indicator of long-term climate change. As a result of global warming , massive glaciers have melted worldwide since the beginning of industrialization .

Glaciers as fresh water reserves

A glacier in Antarctica

In many regions, glaciers provide a reliable water supply for rivers in the summer with little precipitation, as they melt mainly during this time. They also have a balancing effect on the water level, for example on the Rhine . In the desert mountain regions of the Pamir and Karakoram, the valley floors and mountain slopes are almost exclusively irrigated and made arable with the help of glacier water. There are also extensive networks of canals in the dry valleys of the Alps ( Vinschgau , Wallis ), some of which are still in use today. The environmental toxins trapped in the ice from earlier times can be a danger.

Use of glaciers by humans

Glacier ice workers on the Lower Grindelwald Glacier around 1912.

Due to their imposing appearance, glaciers are of enormous importance for tourism in mountains and at high latitudes. They are always a point of attraction when they are accessible by traffic. Then they are also suitable for winter sports as a snow-sure glacier ski area .

Until the general spread of cooling systems, glacier ice was mined and exported on some glaciers.

Glaciers as a habitat

Glaciers form a habitat called Kryal , in which, for example, biofilms , snow algae and glacier fleas live.

The Taylor Glacier in Antarctica covers a very rare microbial ecosystem. The Blood Falls are a red colored discharge from the glacier tongue.

Glacier research

Research history

The idea that glaciers have decisively shaped the landscape of this earth is not yet old. Until well into the 19th century, most scholars held that the Flood had shaped the shape of the earth and was responsible for legacies such as boulders .

Alps

In 1817 the Swiss Society for Natural Research wrote a prize for a thesis paper on the topic “ Is it true that our higher Alps have been overgrown for a number of years? "And further narrowed it , looking for" an impartial compilation of several years of observations on the partial advancement and retreat of the glaciers in the transverse valleys, on the attachment and disappearance of these on the heights; Exploration and determination of the former deep boundaries of various glaciers, which are recognizable here and there by the rock debris pushed forward ”..

In 1822, the award was given to a work by Ignaz Venetz , who, because of the distribution of moraines and boulders , concluded that large parts of Europe were once glaciated. However, he was only heard from Jean de Charpentier , who in turn presented Venetz's thesis in Lucerne in 1834 and managed to convince Louis Agassiz of it. The oratorically gifted Agassiz, who carried out intensive studies on glacier science in the following years, finally succeeded in enforcing the former glaciation of wide areas as a general doctrine.

Northern Germany

In northern Germany, the first evidence of glaciation from Scandinavia was already collected between 1820 and 1840. However, they could not overthrow the old doctrine. It was only from 1875 onwards, due to the findings of the Swedish geologist Otto Torell , who demonstrated clear glacier cuts in Rüdersdorf near Berlin , that the theory of glaciation also prevailed in northern Germany.

archeology

In the nutrient zone of a glacier, snow is transformed into glacier ice, organic and inorganic objects are included. Over time, the ice flows down into the valley and the objects move into the depletion area, where the glacier ice thaws. During the course of the year, ice melts in the northern hemisphere is highest in September, so that archaeological finds are most likely to be made at this time . In addition to this moving ice, there are isolated depressions where ice remains stationary for a long time, which is now thawing due to global warming. The advantage of these stationary ice surfaces is that the forces generated when a glacier flows are eliminated from the enclosed objects. On the Schneidejoch , a mountain pass in the Bernese Alps, finds from various time periods were found by former passers-by. The famous glacier mummy Ötzi, on the other hand, was in a 40 m long, 2.5–3 m deep and 5–8 m wide rock hollow, over which a glacier moved for over 5300 years without changing the ice in the hollow.

Climate archive

The ice of the glaciers can be used to research the climate history of the earth. To do this, ice cores are removed and analyzed. For the Greenland Ice Core Project , they drilled to a depth of 3,029 meters, where the ice is more than 200,000 years old, and in the European Project for Ice Coring in Antarctica , even 900,000-year-old ice was drilled.

Another climate archive related to glaciers is glacier wood. These are the remains of trees that were trapped in the ice centuries ago and where the annual rings can be evaluated.

Dangers from glaciers

Roped party on the ascent to the Klockerin

The dangers posed by glaciers are divided into the following categories according to their causes:

  • Risks from changes in length and geometry: Structures that are located directly on the edge of the glacier can be endangered by changes in geometry. Moraines and rock walls exposed after the glacier retreat can become unstable, leading to landslides and slopes falling .
  • Dangers from glacier floods : Glacier floods are usually not caused by precipitation, but arise when lakes dammed up by the glacier or hidden water pockets stored in the ice masses suddenly empty. These eruptions often cause devastating tidal waves that cause great damage in the valley. In Iceland these eruptions are called glacier runs .
  • Danger from glaciers and ice falls: Large ice breaks regularly occur on hanging glaciers. The resulting ice avalanches or ice falls can pose a threat to settlements and traffic routes, and when they hit water surfaces can trigger dangerous tidal waves due to the displacement pressure of the water masses.
  • Crevasses are cracks in the ice that are up to dozen meters deep and pose the risk of falling and, in addition, getting stuck in the surface of the glacier. It is insidious that they can be difficult to see due to the overlay of snow and that these snow bridges sometimes collapse under stress. A not aperer glacier should therefore not beenteredalone, but only in a rope team , whereby the distances between the rope team members should be chosen large enough to be able to react to someone else's sudden fall.
  • The thawing of glacier dams that form ice reservoirs can cause flood disasters . The largest known flood disasters in Europe, Asia and America can be traced back to it.
  • Subglacial eruptions caused by volcanism , in addition to the dangers of a volcanic eruption, can trigger glacial run and flood disasters.

Data on glaciers

Engabreen, Svartisen, Norway
Quelccaya, Peru

Size, location and behavior

At present, 15 million square kilometers of the earth's solid surface are covered by glacial ice. This corresponds to about 10% of all land areas. During the last glacial period it was 32% of the land surface.

size
  • The largest glacier on earth (excluding the inland ice ) is the Lambert Glacier (Antarctica).
  • The largest extra-polar mountain glacier on earth is the Malaspina (Alaska) with an area of ​​4275 km² .
  • The longest extra-polar valley glacier on earth is the Fedtschenko Glacier in the Pamirs in Tajikistan with a length of 77 km
  • The largest European glacier in terms of area is the Austfonna ( Svalbard / Norway) with an area of 8,200 km² .
  • It is followed by the largest plateau glacier in Iceland, the Vatnajökull , with an area of ​​8100 km² . With a thickness of up to 900 m, it is the largest European glacier in terms of volume.
  • The largest European mainland glacier is the Jostedalsbreen (Norway) with an area of ​​around 500 km² .
  • The largest and longest Alpine glacier is the Aletsch Glacier (117.6 km² / 23.6 km long; Switzerland).
  • The largest of the five glaciers in Germany is the Northern Schneeferner on the Zugspitze .
  • The largest glacier in Austria is the Pasterze on the Großglockner .
  • The largest and longest glacier in the Caucasus is the Besengi near the Besengi Wall in the Besengi region.
  • The largest glacier in the tropical climate zone is the Coropuna ice cap in Peru . Until the 2010s, the Quelccaya ice cap was considered the largest tropical glacier, but its melting rate was even higher than that on the Coropuna, so that it is only the second largest.
  • The largest glacier in South America is the Campo de Hielo Sur in Argentina and Chile.
Minimum height of the glacier tongue in the Alps
Flow rate
  • Alpine glaciers move at up to 150 m per year.
  • Himalayan glaciers flow at up to 1500 m a year, i.e. up to 4 m a day.
  • The outlet glaciers of Greenland move up to 10 km per year or up to around 30 m per day. The Jakobshavn Isbræ on the west coast of Greenland is considered to be the glacier with the highest permanent speed, but surge glaciers can flow considerably faster during the active phase and cover more than 100 m per day.
Near the equator

See also

Web links

Wiktionary: Glacier  - explanations of meanings, word origins, synonyms, translations
Commons : Glacier  album with pictures, videos and audio files

literature

Individual evidence

  1. ↑ Duden online
  2. ↑ Furthermore, the; -s, - (Tyrol, Bavarian for glacier) and Kees, that; -es, -e (Austrian landsch. for glaciers) . - In: Duden - The German spelling . CD-ROM edition. 25th, completely revised and expanded edition. Bibliographisches Institut AG, Mannheim 2009, ISBN 978-3-411-06828-9 .
  3. ↑ Werner Bätzing : Small Alpine Lexicon. Environment - economy - culture. CH Beck, Munich 1997, ISBN 3-406-42005-2 , pp. 104-108.
  4. ↑ a b Is there a size criterion for a glacier? In: USGS . Retrieved on August 19, 2019 .
  5. ↑ a b What makes it a glacier? In: USGS . Retrieved on August 19, 2019 .
  6. ↑ Duden.de: Glacier
  7. ↑ Pfeifer, Etymological Dictionary
  8. ↑ August von Böhm : That or the Kees? In: Mitteilungen des Deutschen und Österreichischen Alpenverein , year 1911 (Volume XXXVII), p. 254. (Online at ALO ).
  9. ↑ Stefan Winkler: Glaciers and their landscapes. An illustrated introduction . Primus-Verlag, Darmstadt 2009, ISBN 978-3-89678-649-4 .
  10. ^ Dictionary of General Geography , Diercke, ISBN 978-3-423-03422-7
  11. ↑ Andreas Aschwanden: Mechanics and Thermodynamics of Polythermal Glaciers - Abstract German / English , dissertation at ETH Zurich , 2008, accessed on December 28, 2018
  12. ↑ Marc Müller: Ice flows and ice shelves on the coast of the Amundsen Sea (West Antarctica), observed with ERS-SAR. (PDF; 3.2 MB) Diploma thesis at Johannes Gutenberg University Mainz. (No longer available online.) June 29, 2001, p. 34 , archived from the original on March 4, 2012 ; Retrieved July 21, 2012 .
  13. ↑ Zinal Glacier ( memento from October 29, 2013 in the Internet Archive ) globezoom.info
  14. ↑ Roland Weisse: Glacial small sinks in the Potsdam area ( PDF ; 1.2 MB), p. 54.
  15. ↑ Peter U. Clark, Arthur S. Dyke, Jeremy D. Shakun, Anders E. Carlson, Jorie Clark, Barbara Wohlfarth, Jerry X. Mitrovica, Steven W. Hostetler, A. Marshall McCabe: The Last Glacial Maximum . In: Science . tape 325 , no. 5941 , 2009, p. 710-714 , doi : 10.1126 / science.1172873 .
  16. ↑ Hans Oerlemans (2005): Extracting a Climate Signal from 169 Glacier Records , in: Science, March 3, online
  17. ↑ Intergovernmental Panel on Climate Change (2007): Fourth Assessment Report - Working Group I, Chapter 4: Observations: Changes in Snow, Ice and Frozen Ground , pp. 356-360 (PDF; 4.9 MB)
  18. ↑ klimafakten.de (2012): Even if there are some growing glaciers, an overall view shows that glaciers are shrinking significantly worldwide
  19. ↑ https://www.br.de/klimawandel/alpen-gletscher-schmelzen-klimawandel-100.html
  20. ↑ Cinthia Briseño: Melting glaciers release old toxins. In: Spiegel.de.
  21. ↑ M. Grosjean, PJ Suter, M. Trachsel and H. Wanner: Ice-borne prehistoric finds in the Swiss Alps reflect Holocene glacier fluctuations. ( Memento from January 30, 2012 in the Internet Archive ) In: giub.unibe.ch. (PDF; 284 kB).
  22. ↑ South Tyrol Museum of Archeology: The site. In: archaeologiemuseum.it.
  23. ↑ dw-world.de: Project Future: Gletscherholz - Climate archive under ice  ( page can no longer be accessed , search in web archives )  Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice.@1@ 2Template: Dead Link / www.dw-world.de  
  24. ↑ Axel Bojanowski : Geologists discover ditches from the Baltic Sea deluge
  25. ↑ [1]
  26. ↑ Andrey Tchepalyga: Late glacial great flood in the Black Sea and Caspian Sea. The Geological Society of America 2003 Seattle Annual Meeting. 2003 [2]
  27. ↑ Timothy G. Fisher: River Warren boulders, Minnesota, USA: catastrophic paleflow indicators in the southern spillway of glacial Lace Agassiz. In: Boreas, Volume 33, pp. 349–358, 2004 Archive link ( Memento from October 29, 2013 in the Internet Archive ) (PDF; 2.8 MB)
  28. ^ MN Hanshaw, B. Bookhagen: Glacial areas, lake areas, and snow lines from 1975 to 2012: status of the Cordillera Vilcanota, including the Quelccaya Ice Cap, northern central Andes, Peru . In: The Cryosphere . March 2014, doi : 10.5194 / tc-8-359-2014 .
  29. ^ Glacier des Bossons and Glacier de Taconnaz. In: Glaciers online. Retrieved November 1, 2019 .
  30. ↑ See When Glaciers Flow Rapidly , NZZ of October 2, 2002.