Glacier

of the Mendenhall glaciers in Alaska

a glacier, in Austria also furthermore or Kees mentioned, is an ice mass come out from snow, which moves by its dead weight (and the pressure resulting from it).

Table of contents

glacier emergence and metamorphosis of the snow

glacier developing in areas, in which in the annual average more snow falls, as if to abtauen or evaporate can. In this way it comes to the accumulation (accumulation) of snow,therefore the metamorphosis goes through.

Freshly pleased new-fallen snow out hardly forms a layer for consolidated snow crystals and with air filled cavities. Again if snow falls, then it puts over this already existing layer and presses themselves the cavities filled with air in such a waytogether that they become smaller. Fusion processes support this procedure. Thus Firneis develops in the course of a yearly from the snow. The further compression of the Firneises lets Gletschereis develop finally. Starting from a power of approx. the ice begins 30 m,to move under the influence of the force of gravity and its own measures. A glacier developed.

In the course of the metamorphosis the air content sinks continuously. While it amounts to with powder snow still 90%, Gletschereis possesses on the average only 2% air. ThatAir content of Firn and/or. Firneis, the intermediate stages with the emergence of Gletschereis, amounts to 60% and/or. 30%. It comes thus in the process of the glacier ice formation to a strong compression of the material.

The duration of the metamorphosis of the snow hangs very strongly of thatdominant climate conditions off. With comparatively warm glaciers, like in the alps, the snow was converted in few years into Gletschereis. With cold and dry glaciers, for example in the Antarctic, no fusion processes support the ice formation. Thus there those lastsTransformation of snow in ice several decades.

appearance and characteristics of Gletschereis

of the Buarbreen, a glacier tongue of the Folgefonna, Norway, gleams bluish

pure Gletschereis is in thin layers (few cm) almost transparent, with larger thicknesses howeverstill shining through. If the crystals of a glacier do not change their situation to each other, Gletschereis retains its original layering during long periods also. Further the ice crystals have a granular structure; with lakes they are for example oblong. The density amounts to up tog/cm ³, can also be to 0,918 however with larger cavities under it. The density of powder snow amounts to to the comparison only 0.06 g/cm ³.

If the ice is strongly compressed by the self-pressure, the cavities in the ice become smaller. Thus all colors become except blue absorbed and only this reflects: the ice gleams bluish; with some glaciers also greenish.

possess feeding areas and

Grossglockner each glacier a feeding and a living area. In the feeding area at least a part remainsthe snow also during the summer receive, so that it transforms itself with pressure and Wärmeschwankungen in the course of several years to Gletschereis, which flows into deeper areas. Below a certain line, the equilibrium line, the Gletschereis regions reaches, in those thatMelt the ice in relation to the supply by snow outweighs. This region is called living area. With valley glaciers it often coincides with an impressive glacier tongue . At their lower end a constant meltwater stream , the so-called is into the glacier gate, from Glacier milk, herausplätschert. The size of the feeding and living area changes each year depending upon snow quantity in the winter and weather process in the summer. Thus over longer periods the total budget of the glacier is determined, speaks whether it become larger or made smaller. With onethe relationship from feeding area to living area corresponds to balanced mass household for instance to 2:1.

Other conditions prevail with glaciers, particularly in the polar areas, which flow into the sea or into a large lake. If at the face of the glacier tongue pieces of ice break off, callsone this calving the glacier. The broken off pieces become icebergs. Board icebergs against it develop only in the Antarctic, if up-swum parts of the inland ice (shelf ice) drive abrechen and as large ice sheets into the sea. In both caseshave these glaciers a comparatively small living area, which is clearly under the quotient indicated above.

kinds of glacier

valley glaciers, with clearly visible Mittelmoraenen (large Aletschglet)
Grímsvötn with respect to the Vatnajökull, a plateau glacier with respect to Iceland

depending upon developing way and development stage differentiatesone today the generally following kinds of glaciers:

  • Karglet: Ice masses of small size, which itself in a hollow, which so-called Kar finds. Karglet possess no clearly trained glacier tongue. They are often remnants of valley glaciers, which lost their tonguehave.
  • Valley glacier: Ice masses, which possess a clearly limited catchment area and under the influence of the force of gravity in a valley downward move. Both the quantity of the meltwater and the velocity of flow of the glacier vary in the yearly process with a maximum inSummer. Although valley glaciers constitute only about 1% of the vergletscherten areas of the earth, they are because of their impressive appearance the most well-known type of glacier (e.g.Aletschglet).
  • Ice electricity mains: Waxes valley glaciers so strongly on that the Gletschereis can run off the valley sheaths, one speaksof ice electricity mains. The movement of the ice is steered however nevertheless particularly by the existing relief. The glaciers of the alps produced such a net on the high point of the last freezing up.
  • Inland ice or ice sheet: The largest glaciers at all. Ice masses, thoseit becomes so powerful that they cover the relief nearly completely and also to a large extent independently of it move. Some scientists separate however the large inland ice masses from the smaller glaciers and do not designate them therefore not than glaciers.
  • Plateau glacier or ice cap:A small inland ice, limits on high plateaus.
  • Discharge opening glaciers form at the edge of ice caps or ice sheets, if the ice must flow by relatively narrow discharge openings, which are given by the relief.
  • A block glacier is not despite its name no glacier, there itfrom snow follows, but out with ice mixed debris and Felsblöcken. He creeps very slowly talwärts, which lends a usually wavy structure to its completely stony surface, and is a feature of the Permafrostes (permafrost soil).

glaciers and climate

Gletschereis

Although glaciers constitute only a small part of the earth's surface, it is to a large extent undisputed that they affect the local like world-wide climate strongly. Are two physical characteristics of importance:

  • The albedo of the earth's surface increases on a glacier importantly: arriving sunlightto almost 90% it is back-reflected whereby it cannot unfold its warming energy entry into the biosphere. A once expanded glacier has the tendency to cool down and further become larger further. Over it develops in connection with low temperatures Hochdruckgebiet.
  • Glaciers work as water reservoirs. It is stored as ice in the glaciers and extracted so from the water reservoir passing or longer continuously. With the melting of the glaciers in consequence of the heating up of the climate it can to a risethe sea level come. This applies particularly to the ice sheets of Greenland and the Antarctic.
  • The effect of the increased entry of meltwater on the Meeresströmungen, in particular on the gulf current system, is at present the subject of scientific investigations.
  • Glaciers are an indicatorfor long-term climatic changes. Today many of them melt in the mountains due to the global heating up .

glaciers as landscape molder

glacier are important landscape molders, which exceed the wind and the flowing water clearly in their effectiveness. In particularduring the ice age age, when large parts of the north hemisphere were vergletschert, very large areas were transformed by it. The effect of the glaciers been based particularly on the Moränen transported by them. Depending upon the situation to the glacier one designatesit as upper, side, central, interior, under or Stirnmoräne. The terms Grundmoräne and Endmoräne refer meanwhile rather to the appropriate landscape forms and no more to the actual material.

  • Moränen:Moräne one calls the whole from the glacier transportedMaterial. Since glaciers are firm body, they can take up all grain size classes, from the clay/tone over sand up to roughest blocks, transport and again to deposit.
  • Demolition forms: Impressive witnesses of the demolition procedures by glaciers are in mountains the trough valleys, their U-formdue to the glacier erosion developed. In the areas vergletscherten by the inland ice one finds very frequently round peak landscapes . In both landscape types often deeply out-dug basins occur, which are today usually filled out by lakes. Small forms of the demolition are above all glacial actionson the rock surfaces. These are caused by the carried Moränenmaterial.Glacier mills result from the clearing away effect of the meltwaters of the ice.
  • Deposit forms:With back-thawed mountain glaciers the Moränen the furthest common deposits, those is easy with the glacier concerned (if itis still present) in connection to bring are. In northern Central Europe and in the Alpine foreland the glaciers left the Glaziale series with the elements Grundmoräne, Endmoräne, Sander and ( only in Northern Germany) Urstromtal as a typical form company. Gives also hereit numerous small forms like for example Drumlins, Glaziale gutters, OS and Kames.

current meaning and use of glaciers

  • water regime: Glaciers represent a safe water supply of the rivers in the summer time of light precipitation in many regions,since it particularly in this time melt. They affect so compensatorily the water level (e.g. with the Rhine).
  • Tourism:Due to their impressive feature glaciers have today an enormous meaning for the tourism in mountains and in the highWidths. They are always one point of attraction. In addition glaciers are suitable all year round for winter sports.
  • Science:Glaciers and their effects play a large role in the sciences already for quite some time. The science, itself directly with glaciers, their water regime,Flow behavior etc. busily, is the glaciology. With the deposits (sediments) and surface forms, which the ice leaves, geology is occupied and/or. the Glazialmorphologie. Gletschereis is further very valuable geoscientific archives, there with the emergence of theIce the dominant climatic and environmental condition to be stored. By ice drillings one can win and evaluate this archives.

research history

the conception that glaciers along-formed the landscapes of this earth crucially, is not old yet. Until far in 19. Most scholars recorded century inside to the fact that the Sintflut had coined/shaped the shape of the earth.

Alps

the Swiss nature-searching society wrote however 1817 a price for a paper to the topic out “is true it thatour higher alps since a set of years verwildern?“and further, searched is Gle” a unpartheyische compilation of observations of several years over the partial advance and withdrawing that in the transverse valleys, over setting and disappearing limited the same upthe heights; Visiting and determination of the former tiefern borders of different glaciers here and there recognizable by the advanced rock rubble “.

Were distinguished 1822 a work of Ignaz Venetz, which closed because of the distribution of Moränen and Findlingen that oncefar parts of Europe were vergletschert. He found however only hearing with Jean de Charpentier, who spoke again 1834 Venetz `thesis in Luzern and created it to convince Louis Agassiz of it. The rednerisch talented Agassiz, that in the following yearsit operated, finally succeeded intensive studies to the Gletscherkunde to intersperse the former Vergletscherung of far areas as general Lehrmeinung.

Northern Germany

in Northern Germany first vouchers for a Vergletscherung from Scandinavia were already collected from 1820 to 1840. They knew the old Lehrmeinung howeverdo not bring to the collapse. Only starting from 1875, under the realizations of the Swedish geologist Otto Torell, which proved clear glacial actions in rudder village with Berlin, sat down the freezing up theory also in Northern Germany through.

dangers by glaciers

ofAre divided for glaciers outgoing dangers according to their causes into the following categories:

  • Driven by lengthening and changes of geometry:By changes of geometry buildings, which are directly at the edge of glacier, can be endangered. After glacier decrease opened Moränen and cliffs can become unstable, so that itto slips and slope crashes comes.
  • Driven by glacier flood (see also ice artificial lake):Glacier floods are precipitation-conditioned usually, but develop, if lakes, which the glacier accumulated, suddenly empty themselves. These outbreaks cause often devastating tsunami, those to large damage inValley lead. In Iceland one calls these outbreaks glacier run.
  • Driven by glacier and ice falls: With hanging glaciers it comes regularly to large ice aborts. Thus released ice avalanches can be a danger for settlements and traffic routes.
  • Glacier columns place particularly for touristsa danger, which should be underestimated in no case. Above all often too few persons rope themselves together on and in to small distances with glacier crossings. Glacier columns can be very deep and are partially covered with Schneebrücken,so that they are not to be seen.

at present are covered

worth knowing over glacier Engabreen,

Svartisen, Norway 15 million km ² the firm earth's surface of Gletschereis. That corresponds to about 10% of all land surfaces. During the last ice age was therenevertheless 32% of the land surface.

Size:

Valley height:

  • The glacier handing in the alps into a valley is deepest with to approximately1,400 m and.NN of the Glacier of the Bossons at the Mont blank.

Near-equator one:

Velocity of flow:

  • The fastest flowing glacier of the earth is the Kutiah glacier (Pakistan); 1953 became a velocity of flowfrom 12 km in three months measured, on the average 112 m per day correspond.
  • Alps - glaciers move with 30 to 150 m per year.
  • Himalaya - glaciers flow with 500 to 1,500 m in the year, thus 2 to 4m on the day.
  • The discharge opening glaciers of Greenland move 3 to 10 km per year and/or. zirka 10 to 30 m on the day.

Glacier in Germany: In Germany there are five glaciers, all in Bavaria:

  1. Northern snow-far
  2. of southern snow-far
  3. Hell-valley-far
  4. Watzmannglet
  5. blue ice glacier (at the high-cold)

the total area of these five glaciers decreased from 1850 to 2005 from 329 to 98 hectares, since the temperature in the alps rose in the last 100 years over up to two degrees.If it should remain with this development, the two snow far glaciers will have disappeared in 20 to 30 years and within further ten years also the remaining German glaciers.

literature

  • Erich fruit, Josef Schmithüsen, Friedrich William: Text book thatGeneral geography, Bd.3/3, snow customer and Gletscherkunde; Gruyter publishing house; 1974; ISBN 3110049058

see also

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