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Encyclopedia > Glacier
Perito Moreno Glacier Patagonia Argentina
Perito Moreno Glacier Patagonia Argentina
Aletsch Glacier, Switzerland
Aletsch Glacier, Switzerland
Icebergs breaking off glaciers at Cape York, Greenland
Icebergs breaking off glaciers at Cape York, Greenland
"Glacial" and "Glaciation" redirect here. For the geological periods, see glacial period. For the story by Alastair Reynolds, see Glacial (short story).

A glacier is a large, slow moving river of ice, formed from compacted layers of snow, that slowly deforms and flows in response to gravity. The processes and landforms caused by glaciers and related to them are glacial (adjective); this term should not be confounded with glacial (noun), a cold period in ice ages (see glacial period). The process of glacier growth and establishment is called glaciation. Image File history File links Metadata Size of this preview: 800 × 533 pixelsFull resolution‎ (2,000 × 1,333 pixels, file size: 1. ... Image File history File links Metadata Size of this preview: 800 × 533 pixelsFull resolution‎ (2,000 × 1,333 pixels, file size: 1. ... Patagonia, Argentina - Perito Moreno Glacier The Perito Moreno Glacier () is a glacier located in the Los Glaciares National Park in the south west of Santa Cruz province, Argentina. ... Image File history File linksMetadata Download high resolution version (2048x1536, 2441 KB) Summary For camera information and shooting conditions see the EXIF info fields, contained in the file. ... Image File history File linksMetadata Download high resolution version (2048x1536, 2441 KB) Summary For camera information and shooting conditions see the EXIF info fields, contained in the file. ... Aletsch Glacier Aletsch Glacier Aletsch Glacier, the largest glacier in the Alps, covers more than 120 square kilometres (more than 45 square miles) in southern Switzerland. ... Image File history File linksMetadata Size of this preview: 800 × 533 pixelsFull resolution (3456 × 2304 pixel, file size: 4. ... Image File history File linksMetadata Size of this preview: 800 × 533 pixelsFull resolution (3456 × 2304 pixel, file size: 4. ... Glacier may refer to: Glacier, a geological formation of ice Glacier, Washington, a census-designated place in Whatcom County, Washington Ring name of professional wrestler Ray Lloyd Glacier Bay, located in southeastern Alaska Glacier County, Montana, in northwestern Montana, adjacent to the U.S.-Canada border Glacier View, Alaska, a... Variations in CO2, temperature and dust from the Vostok ice core over the last 400 000 years For the animated movie, see Ice Age (movie). ... Alastair Reynolds (born in 1966 in Barry, South Wales) is a Welsh science fiction author. ... Galactic North (ISBN 057507910X, published by Gollancz) is a collection of short stories by the science fiction author Alastair Reynolds. ... Image File history File links This is a lossless scalable vector image. ... For other uses, see Snow (disambiguation). ... Gravity is a force of attraction that acts between bodies that have mass. ... In grammar, an adjective is a word whose main syntactic role is to modify a noun or pronoun (called the adjectives subject), giving more information about what the noun or pronoun refers to. ... In linguistics, a noun or noun substantive is a lexical category which is defined in terms of how its members combine with other grammatical kinds of expressions. ... Variations in CO2, temperature and dust from the Vostok ice core over the last 400 000 years For the animated movie, see Ice Age (movie). ... Variations in CO2, temperature and dust from the Vostok ice core over the last 400 000 years For the animated movie, see Ice Age (movie). ...


The word glacier comes from French via the Vulgar Latin glacia, and ultimately from Latin glacies meaning ice.[1] Not to be confused with Latin profanity. ... For other uses, see Latins and Latin (disambiguation). ...

Contents

Overview

Glacier ice is the largest reservoir of fresh water on Earth, and second only to oceans as the largest reservoir of total water. Glaciers cover vast areas of polar regions but are restricted to the highest mountains in the tropics. For the village on the Isle of Wight, see Freshwater, Isle of Wight. ... This article is about Earth as a planet. ... Animated map exhibiting the worlds oceanic waters. ... Location of the polar regions Northern Hemisphere permafrost (permanently frozen ground) in purple. ...


Many geologic processes are interrupted or modified significantly by glaciers. Geologic features created by glaciers include end, lateral, ground and medial moraines that form from glacially transported rocks and debris; U-shaped valleys and cirques at their heads, and the glacier fringe, which is the area where the glacier has recently melted into water. Much precipitation becomes trapped in the glaciers instead of flowing immediately back to the oceans, causing sea level drops and greatly modifying the hydrology of streams. The Earth's crust is pushed down by the weight of the ice, and meltwater commonly collects and forms lakes along the ice margins. This article includes a list of works cited but its sources remain unclear because it lacks in-text citations. ... This article is about geological phenomena. ... Rock may refer to: Rock, a geologic substance composed of minerals Rock, short for Rock and Roll music Rock, a small offshore islet with minimal soil Rock, a confectionery made and sold in many of the UKs seaside holiday resorts Rock candy, a type of confectionery composed of large... Debris (French, pronounced (IPA) dibri) is a word used to describe the remains of something that has been otherwise destroyed. ... A glaciated valley in the Mount Hood Wilderness showing the characteristic U-shape. ... Iceberg Cirque in Glacier National Park, USA The Lower Curtis Glacier, North Cascades National Park, is a well developed cirque glacier. ... Water covers 70% of the Earths surface. ... Butchers Creek, Omeo, Victoria A stream, brook, beck, burn or creek, is a body of water with a detectable current, confined within a bed and banks. ... Geologic provinces of the world (USGS) In geology, a crust is the outermost solid shell of a planet or moon. ... For other uses, see Lake (disambiguation). ...


Glacial epochs have come and gone repeatedly over the last million years. Presently, Earth is in a relatively warm period, called an interglacial, exacerbated by global warming with the resulting retreat of the glaciers. The Earth has been cyclically plunged into cold episodes, however, called glacials, in which the extent of glaciers is expanded, colloquially referred to as ice ages. Glaciation, often called an ice age, is a geological phenomenon in which massive ice sheets form in the Arctic and Antarctic and advance toward the equator. ... Global warming refers to the increase in the average temperature of the Earths near-surface air and oceans in recent decades and its projected continuation. ... A view down the Whitechuck Glacier in North Cascades National Park in 1973 The same view as seen in 2006, where this branch of glacier retreated 1. ... Variations in CO2, temperature and dust from the Vostok ice core over the last 400 000 years For the animated movie, see Ice Age (movie). ...


Types of glaciers

Main article: Glacier morphology
Mouth of the Schlatenkees Glacier near Innergschlöß, Austria.
Mouth of the Schlatenkees Glacier near Innergschlöß, Austria.

There are two main types of glaciers: alpine glaciers, which are found in mountain terrains, and continental glaciers, which can cover larger areas. Most of the concepts in this article apply equally to alpine glaciers and continental glaciers. Glacier morphology, or the form a glacier takes, is influenced by temperature, precipitation, topography, and other factors. ... Image File history File links Download high resolution version (1600x1200, 611 KB) Mouth of the glacier de:Schlatenkees near de:Innergschlöß, Austria Source: taken by SehLax on 18/08/2005 File links The following pages link to this file: Glacier ... Image File history File links Download high resolution version (1600x1200, 611 KB) Mouth of the glacier de:Schlatenkees near de:Innergschlöß, Austria Source: taken by SehLax on 18/08/2005 File links The following pages link to this file: Glacier ...


A temperate glacier is at melting point throughout the year, from its surface to its base. The ice of polar glaciers is always below freezing point with most mass loss due to sublimation. Sub-polar glaciers have a seasonal zone of melting near the surface and have some internal drainage, but little to no basal melt. This article does not cite any references or sources. ...


Thermal classifications of surface conditions vary, so glacier zones are often used to identify melt conditions. The dry snow zone is a region where no melt occurs, even in the summer. The percolation zone is an area with some surface melt, and meltwater percolating into the snowpack, often this zone is marked by refrozen ice lenses, glands, and layers. 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 superimposed ice zone is a zone where meltwater refreezes as a cold layer in the glacier forming a continuous mass of ice. A glacier is a large, long-lasting river of ice that is formed on land and moves in response to gravity. ... For other uses, see Snow (disambiguation). ...


The smallest alpine glaciers form in mountain valleys and are referred to as valley glaciers. Larger glaciers can cover an entire mountain, mountain chain or even a volcano; this type is known as an ice cap. Ice caps feed outlet glaciers, tongues of ice that extend into valleys below, far from the margins of those larger ice masses. Outlet glaciers are formed by the movement of ice from a polar ice cap, or an ice cap from mountainous regions, to the sea. For other uses, see Mountain (disambiguation). ... Cleveland Volcano in the Aleutian Islands of Alaska photographed from the International Space Station For other uses, see Volcano (disambiguation). ... An ice cap is a dome-shaped ice mass that covers less than 50,000 km² of land area (usually covering a highland area). ... This article is about polar ice caps in general. ...


The largest glaciers are continental ice sheets, enormous masses of ice that are not visibly affected by the landscape and that cover the entire surface beneath them, except possibly on the margins where they are thinnest. Antarctica and Greenland are the only places where continental ice sheets currently exist. These regions contain vast quantities of fresh water. The volume of ice is so large that if the Greenland ice sheet melted, it would cause sea levels to rise some six meters (20 feet) all around the world. If the Antarctic ice sheet melted, sea levels would rise up to 65 meters (210 feet). An ice sheet is a mass of glacier ice that covers surrounding terrain and is greater than 50,000 km² (19,305 mile²).[1] The only current ice sheets are in Antarctica and Greenland; during the last ice age at Last Glacial Maximum (LGM) the Laurentide ice sheet covered much... Outline Map of Greenland with ice sheet depths. ... A satellite composite image of Antarctica The Antarctic ice sheet is the largest single mass of ice on Earth. ...


Plateau glaciers resemble ice sheets, but on a smaller scale. They cover some plateaus and high-altitude areas. This type of glacier appears in many places, especially in Iceland and some of the large islands in the Arctic Ocean, and throughout the northern Pacific Cordillera from southern British Columbia to western Alaska. The Pacific Coast Ranges are the series of mountain ranges that stretch along west coast of North America from Alaska to Mexico. ... Motto: Splendor sine occasu (Latin: Splendour without diminishment) Capital Victoria Largest city Vancouver Official languages English (de facto) Government Lieutenant-Governor Steven Point Premier Gordon Campbell (BC Liberal) Federal representation in Canadian Parliament House seats 36 Senate seats 6 Confederation July 20, 1871 (6th province) Area  Ranked 5th Total 944... For other uses, see Alaska (disambiguation). ...


Tidewater glaciers are glaciers that flow into the sea. As the ice reaches the sea pieces break off, or calve, forming icebergs. Most tidewater glaciers calve above sea level, which often results in a tremendous splash as the iceberg strikes the water. If the water is deep, glaciers can calve underwater, causing the iceberg to suddenly explode up out of the water. The Hubbard Glacier is the longest tidewater glacier in Alaska and has a calving face over ten kilometers long. Yakutat Bay and Glacier Bay are both popular with cruise ship passengers because of the huge glaciers descending hundreds of feet to the water. This glacier type undergoes centuries-long cycles of advance and retreat that are much less affected by the climate changes currently causing the retreat of most other glaciers. For other uses, see Iceberg (disambiguation). ... Map of Hubbard Glacier Hubbard Glacier is a tidewater glacier in the U.S. state of Alaska and the Yukon Territory of Canada. ... Map of Yakutat Bay Yakutat Bay is 29 km (18 mi) across, extending southwest from Disenchantment Bay to the Gulf of Alaska. ... The area around Glacier Bay in southeastern Alaska was first proclaimed a U.S. National Monument on February 25, 1925. ... The Taku Glacier The tidewater glacier cycle is the typically centuries-long behavior of tidewater glaciers that consists of recurring periods of advance alternating with rapid retreat and punctuated by periods of stability. ...


Formation

Low and high contrast images of the Byrd Glacier. The low-contrast version is similar to the level of detail the naked eye would see — smooth and almost featureless. The bottom image uses enhanced contrast to highlight flow lines on the ice sheet and bottom crevasses.
Low and high contrast images of the Byrd Glacier. The low-contrast version is similar to the level of detail the naked eye would see — smooth and almost featureless. The bottom image uses enhanced contrast to highlight flow lines on the ice sheet and bottom crevasses.
Formation of glacial ice
Formation of glacial ice

The snow which forms temperate glaciers is subject to repeated freezing and thawing, which changes it into a form of granular ice called névé. 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. In addition, a few hours after deposition, snow will begin to undergo metamorphism because of the presence of temperature gradients and/or convex and concave surfaces within individual crystals (causing differential vapour pressure). This causes the sublimation of ice from smaller crystals and the deposition of water vapour onto larger crystals, so many crystals become progressively more rounded over time. Depending on the type of metamorphism, the snowpack may become stronger or weaker as a result. Image File history File links Download high resolution version (540x710, 82 KB) Summary Licensing File links The following pages link to this file: Glacier ... Image File history File links Download high resolution version (540x710, 82 KB) Summary Licensing File links The following pages link to this file: Glacier ... The Byrd Glacier (80º20´S 159º00´E) is a major glacier, about 136 km long and 24 km wide, draining an extensive area of the polar plateau and flowing eastward between the Britannia Range and Churchill Mountains to discharge into the Ross Ice Shelf at Barne Inlet. ... Image File history File links Description: This graphic shows how the glacial ice is formed. ... Image File history File links Description: This graphic shows how the glacial ice is formed. ... Névé is a young, granular type of snow which has been partially melted, refrozen and compacted. ... Sampling the surface of a glacier. ...


The distinctive blue tint of glacial ice is often wrongly attributed to Rayleigh scattering which is supposedly due to bubbles in the ice. The blue color is actually created for the same reason that water is blue, that is, its slight absorption of red light due to an overtone of the infrared OH stretching mode of the water molecule [1]. Rayleigh scattering causing the blue hue of the sky and the reddening at sunset Rayleigh scattering (named after Lord Rayleigh) is the scattering of light, or other electromagnetic radiation, by particles much smaller than the wavelength of the light. ... Impact from a water drop causes an upward rebound jet surrounded by circular capillary waves. ... Approximate harmonic overtones on a string An overtone is a natural resonance or vibration frequency of a system. ... Infrared spectroscopy (IR spectroscopy) is the subset of spectroscopy that deals with the infrared region of the electromagnetic spectrum. ...


The lower layers of glacial ice flow and deform plastically under the pressure, allowing the glacier as a whole to move slowly like a viscous fluid. Glaciers usually flow downslope, although they do not need a surface slope to flow, as they can be driven by the continuing accumulation of new snow at their source, creating thicker ice and a surface slope. The upper layers of glaciers are more brittle, and often form deep cracks known as crevasses or bergschrunds as they move. Measuring snowpack in a crevasse on the Easton Glacier, North Cascades, USA A crevasse is a crack or fissure in a glacier or snow field. ... Bergschrund at the Schnapfenspitze, Austria A Bergschrund (also called rimaye) is a crevasse positioned at the rear of a corrie next to the steep back wall. ...


Crevasses form due to internal differences in glacier velocity between two quasi-rigid parts above the deeper more plastic substrate far below. As the parts move at different speeds and directions, shear forces cause the two sections to break apart opening the crack of a crevasse all along the disconnecting faces. Projected in effect over three dimensions, one may settle and tip, the other upthrust or twist, or all such combinations due to the effects of each floating on the plastic layers below and any contact with rock and such. Hence the distance between the two separated parts while touching and rubbing deep down, frequently widens significantly towards the surface layers, many times creating a wide chasm. In physics and mechanics, shear refers to a deformation that causes parallel surfaces to slide past one another (as opposed to compression and tension, which cause parallel surfaces to move towards or away from one another). ...


These crevasses make travel over glaciers hazardous. Subsequent heavy snow may form a fragile snow bridge, increasing the danger by hiding their presence at the surface. Glacial meltwaters flow throughout and underneath glaciers, carving channels in the ice (called moulins) similar to cave formation through rock and also helping to lubricate the glacier's movement. A crevasse with a snow bridge in the back For another meaning, see Avalanche snow bridge Snow bridge is an arc across a crevasse, a crack in rock, a creek, or some other opening in terrain. ... Schematic drawing of glacial features illustrating how moulins transport surface water to the base of the glacier. ... For other uses, see Cave (disambiguation). ...


Anatomy

The Upper Grindelwald Glacier and the Schreckhorn, in Switzerland, showing accumulation and ablation zones
The Upper Grindelwald Glacier and the Schreckhorn, in Switzerland, showing accumulation and ablation zones

The upper part of a glacier that receives most of the snowfall is called the accumulation zone. In general, the accumulation zone accounts for 60-70% of the glacier's surface area. The depth of ice in the accumulation zone exerts a downward force sufficient to cause deep erosion of the rock in this area. After the glacier is gone, this often leaves a bowl or amphitheater-shaped isostatic depression called a cirque. Download high resolution version (500x790, 119 KB)The Upper Grindelwald Glacier and the Schreckhorn, in the Bernese Oberland, Switzerland. ... Download high resolution version (500x790, 119 KB)The Upper Grindelwald Glacier and the Schreckhorn, in the Bernese Oberland, Switzerland. ... This article is about the town in Switzerland. ... Schreckhorn is a peak (4,078 m) of Aarmassif in the Bernese Alps, at . The first ascent was made in 1861 by Peter Michel, Leslie Stephen, Ulrich Kaufmann and Chr. ... North-looking oblique aerial photograph showing a small, unnamed hanging glacier located in the Chugach Mountains, near Cordova Peak, Chugach National Forest, Alaska. ... For morphological image processing operations, see Erosion (morphology). ... Glacier Isostatic Depression is the term used by geologists for the sinking of large parts of the earths crust into the asthenosphere. ... Iceberg Cirque in Glacier National Park, USA The Lower Curtis Glacier, North Cascades National Park, is a well developed cirque glacier. ...


On the opposite end of the glacier, at its foot or terminal, is the deposition or ablation zone, where more ice is lost through melting than gained from snowfall and sediment is deposited. The place where the glacier thins to nothing is called the ice front. This article or section cites very few or no references or sources. ... An ice front is the place where the glacier thins and ends. ...


The altitude where the two zones meet is called the equilibrium line, also called the snow line. At this altitude, the amount of new snow gained by accumulation is equal to the amount of ice lost through ablation. Due to erosive forces at the edges of the moving ice, glaciers turn V-shaped river-carved valleys into U-shaped glacial valleys. The snow line is the point above which, or poleward of which, snow and ice cover the ground throughout the year. ...


The "health" of a glacier is defined by the area of the accumulation zone compared to the ablation zone. When directly measured this is glacier mass balance. Healthy glaciers have large accumulation zones. Several non-linear relationships define the relation between accumulation and ablation. Global glacial mass balance in the last fifty years, reported to the WGMS and NSIDC. The downward trend in the late 1980s is symptomatic of the increased rate and number of retreating glaciers. ...


In the aftermath of the Little Ice Age, around 1850, the glaciers of the Earth have retreated substantially. Glacier retreat has increased since the 1980s, the coldest decade since 1900. [2] The Little Ice Age (LIA) was a period of cooling occurring after a warmer era known as the Medieval climate optimum. ... A view down the Whitechuck Glacier in North Cascades National Park in 1973 The same view as seen in 2006, where this branch of glacier retreated 1. ...


Occurrence

Glaciers occur on every continent and in approximately 47 of the world's countries. Extensive glaciers are found in Antarctica, Patagonia, Canada, Greenland and Iceland. Mountain glaciers are widespread e.g. in the Andes, the Himalaya, the Rocky Mountains, the Caucasus, the Alps, in Norway, Japan, Turkey and the Iran. On mainland Australia no glaciers exist today, although a small glacier on Mount Kosciuszko was present in the last glacial period, and Tasmania was widely glaciated.[2] On New Zealand's South Island the West Coast bears the Fox and Franz Josef Glaciers. In New Guinea small glaciers are located on its highest summit massif of Puncak Jaya. Africa has glaciers on Mount Kilimanjaro in Tanzania, on Mount Kenya and in the Ruwenzori Range.[3] Patagonia, as most commonly defined (in orange). ... This article is about the mountain system in South America. ... Perspective view of the Himalaya and Mount Everest as seen from space looking south-south-east from over the Tibetan Plateau. ... For individual mountains named Rocky Mountain, see Rocky Mountain (disambiguation). ... It has been suggested that this article or section be merged with Caucasus Mountains. ... Alp redirects here. ... Mount Kosciuszko, located in the Snowy Mountains, in Kosciuszko National Park, is the highest mountain in Australia (not including its external territories), at 2,228 m above sea level. ... Slogan or Nickname: Island of Inspiration; The Apple Isle; Holiday Isle Motto(s): Ubertas et Fidelitas (Fertility and Faithfulness) Other Australian states and territories Capital Hobart Government Constitutional monarchy Governor William Cox Premier Paul Lennon (ALP) Federal representation  - House seats 5  - Senate seats 12 Gross State Product (2004-05)  - Product... The South Island The South Island is the larger of the two major islands of New Zealand, the other being the more populous North Island. ... The West Coast is one of the administrative regions of New Zealand, located on the west coast of the South Island, and is one of the more remote and most sparsely populated areas of the country. ... == == == == Ice cave in the terminal face of Fox glacier. ... Location of the Franz Josef glacier. ... Puncak Jaya (IPA: /pÊŠn. ... For other uses, see Kilimanjaro (disambiguation). ... Mount Kenya has a low profile typical of a shield volcano. ... The Ruwenzori Range, now officially called Rwenzori Mountains (the spelling having been changed in about 1980 to conform more closely with the local tribal name) is a small but spectacular mountain range of central Africa, often referred to as Mt. ...


Permanent snow cover is affected by factors such as the degree of slope on the land, amount of snowfall and the force and nature of the winds. As temperature decreases with altitude, high mountains — even those near the Equator — have permanent snow cover on their upper portions, above the snow line. Examples include Mount Kilimanjaro and the Tropical Andes in South America; however, the only snow to occur exactly on the Equator is at 4,690 m (15,387 ft) on the southern slope of Volcán Cayambe in Ecuador. This article is about the mathematical term. ... For other uses, see Wind (disambiguation). ... For other uses, see Temperature (disambiguation). ... Altitude is the elevation of an object from a known level or datum. ... For other uses, see Mountain (disambiguation). ... World map showing the equator in red For other uses, see Equator (disambiguation). ... The snow line is the point above which, or poleward of which, snow and ice cover the ground throughout the year. ... A noontime scene from the Philippines on a day when the Sun is almost directly overhead. ... South America South America is a continent crossed by the equator, with most of its area in the Southern Hemisphere. ... For other uses of Cayambe, see Cayambe (disambiguation page) Cayambe (or Volcán Cayambe) is the name of a volcano located in the Cordillera Oriental, a branch of the Ecuadorian Andes. ...


Conversely, many regions of the Arctic and Antarctic receive very little precipitation and therefore experience little snowfall despite the bitter cold (cold air, unlike warm air, cannot take away much water vapor from the sea). In Antarctica, the snow does not melt even at sea level. In addition to the dry, unglaciated regions of the Arctic, there are some mountains and volcanoes in Bolivia, Chile and Argentina that are high (4,500 metres (14,800 ft) - 6,900 m (22,600 ft)) 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 hyperarid Atacama desert. Further examples of these temperate unglaciated mountains is the Kunlun Mountains, Tibet and the Pamir Range to the north of the Himalayas in Central Asia. Here, just like the Andes, mountains in Central Asia can reach above 6,000 m (20,000 ft) and be barren of snow and ice due to the rain shadow effect caused by the taller Himalaya Range. For the ships, see USS Arctic, SS Arctic, MV Arctic The red line indicates the 10°C isotherm in July, sometimes used to define the Arctic region border Artificially coloured topographical map of the Arctic region The Arctic is the region around the Earths North Pole, opposite the Antarctic... For other uses, see Antarctica (disambiguation). ... An aridity index (AI) is a numerical indicator of the degree of dryness of the climate at a given location. ... Atacama Desert The Atacama Desert is a virtually rainless plateau in South America, extending 966 km (600 mi) between the Andes mountains and the Pacific Ocean. ... Region containing Kunlun Mountains Karakash River in the Western Kunlun Shan, seen from the Tibet-Xinjiang highway Peak in Kunlun range View of Western Kunlun Shan from the Tibet-Xinjiang highway The Kunlun mountain range (Simplified Chinese: ; Traditional Chinese: ; pinyin: ) is one of the longest mountain chains in Asia, extending... This article is about historical/cultural Tibet. ... Located in Central Asia, the Pamir Mountains are formed by the junction of the worlds greatest mountain ranges, a geologic structural knot from which the great Tian Shan, Karakoram, Kunlun, and Hindu Kush mountain systems radiate. ... For the movie Himalaya, see Himalaya (film). ... Map of Central Asia showing three sets of possible boundaries for the region Central Asia located as a region of the world Central Asia is a vast landlocked region of Asia. ... For the Australian television series see Rain Shadow (TV series). ...


During glacial periods of the Quaternary, most of Siberia, central and northern Alaska and all of Manchuria, were similarly too dry to support glaciers, though temperatures were as low as or lower than in glaciated areas of Europe and North America. This was because dry westerly winds from ice sheets in Europe and the coastal ranges in North America reduced precipitation to such an extent that glaciers could never develop except on a few high mountains like the Verkhoyansk Range (which still supports glaciers today). The Quaternary Period is the geologic time period from the end of the Pliocene Epoch roughly 1. ... This article is about Siberia as a whole. ... Fall in Interior Alaska The Alaska Interior covers most of that U.S. states territory. ... ... For other uses, see Alaska (disambiguation). ... This article does not cite any references or sources. ... An ice sheet is a mass of glacier ice that covers surrounding terrain and is greater than 50,000 km² (19,305 mile²).[1] The only current ice sheets are in Antarctica and Greenland; during the last ice age at Last Glacial Maximum (LGM) the Laurentide ice sheet covered much... For other uses, see Europe (disambiguation). ... The Verkhoyansk Range (Russian: ) is a mountain chain of eastern Siberia, spanning ca. ...


Glaciers on Mars

Elsewhere in the solar system, the vast polar ice caps of Mars rival those of the Earth and show glacial features. Especially the south polar cap is compared to glaciers on earth.[4] Other glacial features on Mars are glacial debris aprons and the lineated valley fills of the fretted terrain in northern Arabia Terra.[5] Topographical features and computer models indicate the existence of more glaciers in Mars' past.[6] This article is about the Solar System. ... An ice cap is a dome-shaped ice mass that covers less than 50,000 km² of land area (usually covering a highland area). ... Adjectives: Martian Atmosphere Surface pressure: 0. ... Arabia Terra is large upland region in the north of Mars. ...


Motion

Main article: Ice sheet dynamics
The Perito-Moreno Glacier, showing cracks in brittle upper layer

Ice behaves like an easily breaking solid until its thickness exceeds about 50 meters (160 ft). The pressure on ice deeper than that depth causes plastic flow. The glacial ice is made up of layers of molecules stacked on top of each other, with relatively weak bonds between the layers. When the stress of the layer above exceeds the inter-layer binding strength, it moves faster than the layer below. Author: Chmouel Boudjnah. ... Author: Chmouel Boudjnah. ... For other uses, see Plasticity. ...


Another type of movement is basal sliding. In this process, the whole glacier moves over the terrain on which it sits, lubricated by meltwater. As the pressure increases toward the base of the glacier, the melting point of water decreases, and the ice melts. Friction between ice and rock and geothermal heat from the Earth's interior also contribute to thawing. This type of movement is dominant in temperate glaciers. The geothermal heat flux becomes more important the thicker a glacier becomes.[citation needed] There are very few or no other articles that link to this one. ... Earth cutaway from core to exosphere. ...


Fracture zone and cracks

Ice cracks in the Titlis Glacier
Ice cracks in the Titlis Glacier
Signs warning of the hazards of a glacier in New Zealand
Signs warning of the hazards of a glacier in New Zealand

The top 50 meters of the glacier are more rigid. In this section, known as the fracture zone, the ice mostly moves as a single unit. Ice in the fracture zone moves over the top of the lower section. When the glacier moves through irregular terrain, cracks form in the fracture zone. These cracks can be up to 50 meters deep, at which point they meet the plastic like flow underneath that seals them. Image File history File linksMetadata Download high resolution version (3264x2448, 837 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Glacier Metadata This file contains additional information, probably added from the digital camera or scanner used to create... Image File history File linksMetadata Download high resolution version (3264x2448, 837 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Glacier Metadata This file contains additional information, probably added from the digital camera or scanner used to create... Mount Titlis (3,238 m) is part of Swiss Alps located in the canton of Obwalden in Switzerland, overlooking Engelberg. ... Image File history File linksMetadata Size of this preview: 800 × 600 pixelsFull resolution (2272 × 1704 pixel, file size: 744 KB, MIME type: image/jpeg) Taken by user Swollib I, the creator of this work, hereby release it into the public domain. ... Image File history File linksMetadata Size of this preview: 800 × 600 pixelsFull resolution (2272 × 1704 pixel, file size: 744 KB, MIME type: image/jpeg) Taken by user Swollib I, the creator of this work, hereby release it into the public domain. ...


Speed

The speed of glacial displacement is partly determined by friction. Friction makes the ice at the bottom of the glacier move slower than the upper portion. In alpine glaciers, friction is also generated at the valley's side walls, which slows the edges relative to the center. This was confirmed by experiments in the 19th century, in which stakes were planted in a line across an alpine glacier, and as time passed, those in the center moved farther. For other uses, see Friction (disambiguation). ... Alternative meaning: Nineteenth Century (periodical) (18th century — 19th century — 20th century — more centuries) As a means of recording the passage of time, the 19th century was that century which lasted from 1801-1900 in the sense of the Gregorian calendar. ...


Mean speeds vary; some have speeds so slow that trees can establish themselves among the deposited scourings. In other cases they can move as fast as meters per day, as in the case of Antarctica's Byrd Glacier, which moves 750-800 meters per year. The Byrd Glacier (80º20´S 159º00´E) is a major glacier, about 136 km long and 24 km wide, draining an extensive area of the polar plateau and flowing eastward between the Britannia Range and Churchill Mountains to discharge into the Ross Ice Shelf at Barne Inlet. ...


Many glaciers have periods of very rapid advancement called surges. These glaciers exhibit normal movement until suddenly they accelerate, then return to their previous state. During these surges, the glacier may reach velocities far greater than normal speed.[7] These surges may be caused by failure of the underlying bedrock,[citation needed] the ponding of meltwater at the base of the glacier[8] - perhaps delivered from a supraglacial lake[citation needed] - or the simple accumulation of mass beyond a critical "tipping point".[9] Glacial surges are short-lived events where a glacier can move up to velocities 100 times faster than normal, and advance substantially. ...


Moraines

Glacial moraines are formed by the deposition of material from a glacier and are exposed after the glacier has retreated. These features usually appear as linear mounds of till, a non-sorted mixture of rock, gravel and boulders within a matrix of a 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, flowing in the same direction, coalesce and the lateral moraines of each combine to form a moraine in the middle of the merged glacier. Less apparent is the ground moraine, also called glacial drift, which often blankets the surface underneath much of the glacier downslope from the equilibrium line. Glacial meltwaters contain rock flour, an extremely fine powder ground from the underlying rock by the glacier's movement. Other features formed by glacial deposition include long snake-like ridges formed by streambeds under glaciers, known as eskers, and distinctive streamlined hills, known as drumlins. Moraine is the general term for debris of all sorts originally transported by glaciers or ice sheets that have since melted away. ... Glacial till with tufts of grass Till is an unsorted glacial sediment. ... Rock flour consists of clay sized particles of rock generated by glacial erosional actions. ... A part of the Mason Esker Esker in Sims Corner Eskers and Kames National Natural Landmark, Washington state. ... Drumlin in Cato, New York Drowned drumlin in Clew Bay Drumlin at Withrow Moraine and Jameson Lake Drumlin Field National Natural Landmark A drumlin (Irish droimnín, a little hill ridge) is an elongated whale-shaped hill formed by glacial action. ...


Stoss-and-lee erosional features are formed by glaciers and show the direction of their movement. Long linear rock scratches (that follow the glacier's direction of movement) are called glacial striations, and divots in the rock are called chatter marks. Both of these features are left on the surfaces of stationary rock that were once under a glacier and were formed when loose rocks and boulders in the ice were transported over the rock surface. Transport of fine-grained material within a glacier can smooth or polish the surface of rocks, leading to glacial polish. Glacial erratics are rounded boulders that were left by a melting glacier and are often seen perched precariously on exposed rock faces after glacial retreat. Glacial grooves caused by the Wisconsin glaciation at Kelleys Island, Ohio Glacial striations or glacial grooves are scratches or gouges cut into the bedrock by process of glacial abrasion during one of the Earths Ice Ages or by mountain glaciers. ... A Chatter mark is one or, more commonly, a series of marks left on basal rocks which have been glaciated where a stone or boulder has ben dragged by the ice over the basal rocks leaving a more or less crescent shaped gouge as it contacted and then released as... Glacial polish is a characteristic of rock surfaces where glaciers have passed over bedrock, typically granite or other hard igneous or metamorphic rock. ... A Glacial erratic is a piece of rock carried by glacial ice some distance from the rock outcrop from which it came. ... This article is about the large rocks. ...


The term moraine is of French origin, and it was coined by peasants to describe alluvial embankments and rims found near the margins of glaciers in the French Alps. In modern geology, the term is used more broadly, and is applied to a series of formations, all of which are composed of till. Alp redirects here. ...


Drumlins

A drumlin field forms after a glacier has modified the landscape. The teardrop-shaped formations denote the direction of the ice flow.
A drumlin field forms after a glacier has modified the landscape. The teardrop-shaped formations denote the direction of the ice flow.

Drumlins are asymmetrical, canoe shaped hills with aerodynamic profiles made mainly of till. Their heights vary from 15 to 50 meters and they can reach a kilometer in length. The tilted side of the hill looks toward the direction from which the ice advanced (stoss), while the longer slope follows the ice's direction of movement (lee). Image File history File links This is a lossless scalable vector image. ... Drumlin in Cato, New York Drowned drumlin in Clew Bay Drumlin at Withrow Moraine and Jameson Lake Drumlin Field National Natural Landmark A drumlin (Irish droimnín, a little hill ridge) is an elongated whale-shaped hill formed by glacial action. ...


Drumlins are found in groups called drumlin fields or drumlin camps. An example of these fields is found east of Rochester, New York, and it is estimated that it contains about 10,000 drumlins. Drumlin Field in Eastern Wayne County, New York A drumlin field is a cluster of dozens to hundreds of similarly shaped, sized and oriented drumlins. ... This article is about the city of Rochester in Monroe County. ...


Although the process that forms drumlins is not fully understood, it can be inferred from their shape 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.


Ogives

Ogives are alternating dark and light bands of ice occurring as ridges and valleys on glacier surfaces. They only occur below icefalls but not all icefalls have ogives below them. Once formed, they bend progressively downglacier due to the increased velocity toward the glacier's centerline. Ogives are likely linked to seasonal motion of the glacier as the width of one dark and one light band generally equals the annual movement of the glacier. The ridges and valleys are formed because ice from an icefall is severely broken up thereby increasing ablation surface area during the summertime creating a swale and creating space for snow accumulation in the winter creating a ridge.[10] Sometimes ogives are described as either wave ogives or band ogives in which they are solely undulations or varying color bands respectively.[11]


Erosion

Rocks and sediments are added to glaciers through various processes. Glaciers erode the terrain principally through two methods: abrasion and plucking. Glacially abraded rocks in western Norway near Jostedalsbreen glacier. ... Plucking, in the sense relating to glaciers, is when a glacier erodes away chunks of bedrock to be later deposited as erratics. ...

Diagram of glacial plucking and abrasion
Diagram of glacial plucking and abrasion

As the glacier flows over the bedrock's fractured surface, it softens and lifts blocks of rock that are brought into the ice. This process is known as plucking, and it is produced when subglacial water penetrates the fractures and the subsequent freezing expansion separates them from the bedrock. When the water expands, it acts as a lever that loosens the rock by lifting it. This way, sediments of all sizes become part of the glacier's load. Image File history File links No higher resolution available. ...


Abrasion occurs when the ice and the load of rock fragments slide over the bedrock and function as sandpaper that smooths and polishes the surface situated below. This pulverized rock is called rock flour. This flour is formed by rock grains of a size between 0.002 and 0.00625 mm. Sometimes the amount of rock flour produced is so high that currents of meltwaters acquire a grayish color. Rock flour consists of clay sized particles of rock generated by glacial erosional actions. ... A millimetre (American spelling: millimeter), symbol mm is an SI unit of length that is equal to one thousandth of a metre. ...


Another of the visible characteristics of glacial erosion are glacial striations. These are produced when the bottom's ice contains large chunks of rock that mark trenches in the bedrock. By mapping the direction of the flutes the direction of the glacier's movement can be determined. Chatter marks are seen as lines of roughly crescent shape depressions in the rock underlying a glacier caused by the abrasion where a boulder in the ice catches and is then released repetitively as the glacier drags it over the underlying basal rock. Glacial grooves caused by the Wisconsin glaciation at Kelleys Island, Ohio Glacial striations or glacial grooves are gouges or grooves cut into the bedrock by glacial ice and meltwater as it slowly ground its way along during one of the Earths Ice Ages or by mountain glaciers. ... Cartography or mapmaking (in Greek chartis = map and graphein = write) is the study and practice of making maps or globes. ... A Chatter mark is one or, more commonly, a series of marks left on basal rocks which have been glaciated where a stone or boulder has ben dragged by the ice over the basal rocks leaving a more or less crescent shaped gouge as it contacted and then released as...


A glacier may also erode its environment through katabatic winds. A katabatic wind, from the Greek word katabatikos meaning going downhill, is a wind that blows down a topographic incline such as a hill, mountain, or glacier. ...


The rate of glacier erosion is variable. The differential erosion undertaken by the ice is controlled by six important factors:

  • 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.

Material that becomes incorporated in a glacier are 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 deposited by water. These deposits are stratified through various processes, such as boulders being separated from finer particles.

The larger pieces of rock which are encrusted in till or deposited on the surface are called glacial erratics. They may range in size from pebbles to boulders, but as they may be moved great distances they may be of drastically different type than the material upon which they are found. Patterns of glacial erratics provide clues of past glacial motions. A Glacial erratic is a piece of rock carried by glacial ice some distance from the rock outcrop from which it came. ...


Glacial valleys

A glaciated valley in the Mount Hood Wilderness showing the characteristic U-shape and flat bottom.
A glaciated valley in the Mount Hood Wilderness showing the characteristic U-shape and flat bottom.
This image shows the termini of the glaciers in the Bhutan Himalaya. Glacial lakes have been rapidly forming on the surface of the debris-covered glaciers in this region during the last few decades.
This image shows the termini of the glaciers in the Bhutan Himalaya. Glacial lakes have been rapidly forming on the surface of the debris-covered glaciers in this region during the last few decades.

Before glaciation, mountain valleys have a characteristic "V" shape, produced by downward erosion by water. However, during glaciation, these valleys widen and deepen, forming a "U"-shaped glacial valley. Besides the deepening and widening of the valley, the glacier also smooths the valley due to erosion. In this way, it eliminates the spurs of earth that extend across the valley. Because of this interaction, triangular cliffs called truncated spurs are formed. Image File history File links Download high resolution version (1382x1509, 392 KB) Glacial valley, Mount hood wilderness source:me File links The following pages link to this file: Glacier Glaciated valley Mount Hood Wilderness ... Image File history File links Download high resolution version (1382x1509, 392 KB) Glacial valley, Mount hood wilderness source:me File links The following pages link to this file: Glacier Glaciated valley Mount Hood Wilderness ... The Mount Hood Wilderness is a protected wilderness area inside the Mount Hood National Forest. ... Image File history File linksMetadata Download high resolution version (3000x1665, 2030 KB) This image shows the termini of the glaciers in the Bhutan-Himalaya. ... Image File history File linksMetadata Download high resolution version (3000x1665, 2030 KB) This image shows the termini of the glaciers in the Bhutan-Himalaya. ... Perspective view of the Himalaya and Mount Everest as seen from space looking south-south-east from over the Tibetan Plateau. ... The term V-shaped is used in Geography to characterize the form of steep eroded valleys. ... A glaciated valley in the Mount Hood Wilderness showing the characteristic U-shape. ... Truncated spurs occur when the action of a glacier does not follow the original course of the river that wound round interlocking spurs, but, as the force of a glacier is much more powerful and cannot flow as freely around corners, it can carve its way though the rock cutting...


Many glaciers deepen their valleys more than their smaller tributaries. Therefore, when the glaciers recede from the region, the valleys of the tributary glaciers remain above the main glacier's depression, and these are called hanging valleys. Look up tributary in Wiktionary, the free dictionary. ... Bridal Veil Falls in Yosemite National Park flowing from a hanging valley. ...


In parts of the soil that were affected by abrasion and plucking, the depressions left can be filled by lakes, called paternoster lakes. A Paternoster Lake is one of a series of glacial cirques, connected by esker streams. ...


At the 'start' of a classic valley glacier is the cirque, which has a bowl shape with escarped walls on three sides, but open on the side that descends into the valley. In the cirque, an accumulation of ice is formed. These begin as irregularities on the side of the mountain, which are later augmented in size by the coining of the ice. Once the glacier melts, these corries are usually occupied by small mountain lakes called tarns. Iceberg Cirque in Glacier National Park, USA The Lower Curtis Glacier, North Cascades National Park, is a well developed cirque glacier. ... Triad Lake in Glacier Peak Wilderness View of Tarn Hows, Cumbria A tarn (or corrie loch) is a mountain lake or pool, formed in a corrie excavated by a glacier. ...


There may be two glacial cirques 'back to back' which erode deep into their backwalls until only a narrow ridge, called an arête is left. This structure may result in a mountain pass. The Garden Wall, an arête in Glacier National Park (U.S.) An arête is a thin, almost knife-like, ridge of rock which is typically formed when two glaciers erode parallel U-shaped valleys. ... In a range of hills, or especially of mountains, a pass (also gap, notch, col, saddle, bwlch or bealach) is a lower point that allows easier access through the range. ...


Glaciers are also responsible for the creation of fjords (deep coves or inlets) and escarpments that are found at high latitudes. Fjord in Sunnmøre, Norway Geirangerfjord, Norway A fjord (or fiord) is a long, narrow estuary with steep sides, made when a glacial valley is filled by rising sea water levels. ... In geology, an escarpment is a transition zone between different physiogeographic provinces that involves an elevation differential, often involving high cliffs. ...

Features of a glacial landscape
Features of a glacial landscape

Image File history File links Glacial_landscape. ...

Arêtes and horns (pyramid peak)

An arête is a narrow crest with a sharp edge. The meeting of three or more arêtes creates pointed pyramidal peaks and in extremely steep-sided forms these are called horns. This article is about a glacial landform. ... The Matterhorn, a classic peak A pyramidal peak, or sometimes in its most extreme form called a glacial horn, is a mountaintop that has been modified by the action of ice during glaciation and frost weathering. ... A glacial horn (or, if unambiguous from context, simply a horn) is a mountain formed by glacial erosion. ...


Both features may have the same process behind their formation: the enlargement of cirques from glacial plucking and the action of the ice. Horns are formed by cirques that encircle a single mountain.


Arêtes emerge in a similar manner; the only difference is that the cirques are not located in a circle, but rather on opposite sides along a divide. Arêtes can also be produced by the collision of two parallel glaciers. In this case, the glacial tongues cut the divides down to size through erosion, and polish the adjacent valleys.


Sheepback rock

Some rock formations in the path of a glacier are sculpted into small hills with a shape known as roche moutonnée or sheepback. An elongated, rounded, asymmetrical, bedrock knob can be produced by glacier erosion. It has a gentle slope on its up-glacier side and a steep to vertical face on the down-glacier side. The glacier abrades the smooth slope that it flows along, while rock is torn loose from the downstream side and carried away in ice, a process known as 'plucking'. Rock on this side is fractured by combinations of forces due to water, ice in rock cracks, and structural stresses. In glaciology, a roche moutonnée (or sheepback) is a rock formation created by the passing of a glacier. ...


Alluvial stratification

The water that rises from the ablation zone moves away from the glacier and carries with it fine eroded sediments. As the speed of the water decreases, so does its capacity to carry objects in suspension. The water then gradually deposits the sediment as it runs, creating an alluvial plain. When this phenomenon occurs in a valley, it is called a valley train. When the deposition is to an estuary, the sediments are known as "bay mud". On a glacier, the zone of ablation or zone of wastage is the area in which annual loss of snow through melting, evaporation, iceberg calving and sublimation exceeds annual gain of snow and ice on the surface. ... An alluvial plain is a relatively flat and gently sloping landform found at the base of a range of hills. ... For other meanings, see Estuary (disambiguation) Río de la Plata estuary An estuary is a semi-enclosed coastal body of water with one or more rivers or streams flowing into it, and with a free connection to the open sea. ... Richardson Bay mudflats of are exposed layers of bay mud Bay mud consists of thick deposits of soft, unconsolidated silty clay, which is saturated with water; these soil layers are situated at the bottom of certain estuaries, which are normally in temperate regions that have experienced cyclical glacial cycles. ...

Landscape produced by a receding glacier
Landscape produced by a receding glacier

Alluvial plains and valley trains are usually accompanied by basins known as kettles. Glacial depressions are also produced in till deposits. These depressions are formed when large ice blocks are stuck in the glacial alluvium and after melting, they leave holes in the sediment. Image File history File links Receding_glacier-en. ... Image File history File links Receding_glacier-en. ... A kettle is a landform feature in glaciated terrain. ...


Generally, the diameter of these depressions does not exceed 2 km, except in Minnesota, where some depressions reach up to 50 km in diameter, with depths varying between 10 and 50 meters.[citation needed] Capital Saint Paul Largest city Minneapolis Largest metro area Minneapolis-St. ...


Deposits in contact with ice

When a glacier reduces in size to a critical point, its flow stops, and the ice becomes stationary. Meanwhile, meltwater flows over, within, and beneath the ice leave stratified alluvial deposits. Because of this, as the ice melts, it leaves stratified deposits in the form of columns, terraces and clusters. These types of deposits are known as deposits in contact with ice. Stratification gooberini went to lousville to dance on a praire and then he went down the hill to hang out with jarry. ... For other uses, see Column (disambiguation). ... This page is a candidate for speedy deletion. ... Look up cluster in Wiktionary, the free dictionary. ...


When those deposits take the form of columns of tipped sides or mounds, which are called kames. Some kames form when meltwater deposits sediments through openings in the interior of the ice. In other cases, they are just the result of fans or deltas towards the exterior of the ice produced by meltwater. A kame among the glacial drift on the terminal morraine of the Okanagon Lobe of the Cordilerion Glacier on the Waterville Plateau of the Columbia Plateau in Washington, United States. ... Nile River delta, as seen from Earth orbit. ...


When the glacial ice occupies a valley it can form terraces or kame along the sides of the valley.


A third type of deposit formed in contact with the ice is characterized by long, narrow sinuous crests composed fundamentally of sand and gravel deposited by streams of meltwater flowing within, beneath or on the glacier ice. After the ice has melted these linear ridges or eskers remain as landscape features. Some of these crests have heights exceeding 100 meters and their lengths surpass 100 km. For other uses, see Sand (disambiguation). ... Gravel (largest fragment in this photo is about 4 cm) Gravel is rock that is of a certain particle size range. ... A part of the Mason Esker Esker in Sims Corner Eskers and Kames National Natural Landmark, Washington state. ... A crest is the section of a wave that rises above an undisturbed position. ...


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 eolian loess deposits may be very deep, even hundreds of meters, as in areas of China and the Midwestern United States. Rock flour consists of clay sized particles of rock generated by glacial erosional actions. ... Eolian (or aeolian or æolian) processes pertain to the activity of the winds and more specifically, to the winds ability to shape the surface of the Earth and other planets. ... This article or section does not cite any references or sources. ...


Transportation

  • Entrainment is the picking up of loose material by the glacier from along the bed and valley sides. Entrainment can happen by regelation or by the ice simply picking up the debris.
  • Basal Ice Freezing is thought to be to be made by glaciohydraulic supercooling, though some studies show that even where physical conditions allow it to occur, the process may not be responsible for observed sequences of basal ice.
  • Plucking is the process involves the glacier freezing onto the valley sides and subsequent ice movement pulling away masses of rock. As the bedrock is greater in strength than the glacier, only previously loosened material can be removed. It can be loosened by local pressure and temperature, water and pressure release of the rock itself.
  • Supraglacial debris is carried on the surface of the glacier as lateral and medial moraines. In summer ablation, surface melt water carries a small load and this often disappears down crevasses.
  • Englacial debris is moraine carried within the body of the glacier.
  • Subglacial debris is moved along the floor of the valley either by the ice as ground moraine or by meltwater streams formed by pressure melting.

Regelation is the phenomenon of melting under pressure and freezing again when the pressure is reduced. ... Bedrock is the native consolidated rock underlying the Earths surface. ... This article is about geological phenomena. ...

Deposition

  • Lodgement till is identical to ground moraine. It is material that is smeared on to the valley floor when its weight becomes too great to be moved by the glacier.
  • Ablation till is a combination of englacial and supraglacial moraine It is released as a stationary glacier begins to melt and material is dropped in situ.
  • Dumping is when a glacier moves material to its outermost or lowermost end and dumps it.
  • Deformation flow is the change of shape of the rock and land due to the glacier.

Glacial deposition takes place in two forms: glaciofluvial deposition and till deposits. In situ is a Latin phrase meaning in the place. ...

  • Glaciofluvial deposition comes from glacial meltwater. The water that is a result from melting glaciers carry material much like a river would and sorts it is it moves along. Examples of these landforms would include outwash plains and kettle holes.
  • Till deposits are unsorted mounds of sand, gravel and rock that form around a glacier. Examples of these are moraines, kame terraces etc.

It has been suggested that this article or section be merged into sandur. ... A kettle hole is a geological feature formed by receding glaciers. ... This article is about geological phenomena. ...

Isostatic rebound

Main article: Isostatic rebound
Isostatic pressure by a glacier on the Earth's crust
Isostatic pressure by a glacier on the Earth's crust

This rise of a part of the crust is due to an isostatic adjustment. A large mass, such as an ice sheet/glacier, depresses the crust of the Earth and displaces the mantle below. The depression is about a third the thickness of the ice sheet. After the glacier melts the mantle begins to flow back to its original position pushing the crust back to its original position. This post-glacial rebound, which lags melting of the ice sheet/glacier, is currently occurring in measurable amounts in Scandinavia and the Great Lakes region of North America. Post-glacial rebound (sometimes called continental rebound, isostatic rebound or isostatic adjustment) is the rise of land masses that were depressed by the huge weight of ice sheets during the last ice age, through a process known as isostatic depression. ... Image File history File links Description: This illustration depicts the stress under which the curst layer undergoes when compressed by the load of a glacier and what happens when the load is released. ... Geologic provinces of the world (USGS) In geology, a crust is the outermost solid shell of a planet or moon. ... This article needs to be wikified. ... Earth cutaway from core to exosphere. ... Changes in the elevation of Lake Superior due to glaciation and post-glacial rebound Post-glacial rebound (sometimes called continental rebound, isostatic rebound or isostatic adjustment) is the rise of land masses that were depressed by the huge weight of ice sheets during the last ice age, through a process... For other uses, see Scandinavia (disambiguation). ... The Great Lakes from space The Laurentian Great Lakes are a group of five large lakes in North America on or near the Canada-United States border. ...


An interesting geomorphological feature created by the same process, but on a smaller scale, is known as dilation-faulting. It occurs within rock where previously compressed rock is allowed to return to its original shape, but more rapidly than can be maintained without faulting, leading to an effect similar to that which would be seen if the rock were hit by a large hammer. This can be observed in recently de-glaciated parts of Iceland.


Ice ages

Main article: Ice age

Variations in CO2, temperature and dust from the Vostok ice core over the last 400 000 years For the animated movie, see Ice Age (movie). ...

Divisions

A quadruple division of the Quaternary glacial period has been established for North America and Europe. These divisions are based principally on the study of glacial deposits. In North America, each of these four stages was named for the state in which the deposits of these stages were well exposed. In order of appearance, they are the following: Nebraskan, Kansan, Illinoisan, and Wisconsinan. This classification was refined thanks to the detailed study of the sediments of the ocean floor. Because the sediments of the ocean floor are less affected by stratigraphic discontinuities than those on land, they are useful to determine the climatic cycles of the planet. The Quaternary Period is the geologic time period from the end of the Pliocene Epoch roughly 1. ... North American redirects here. ... For other uses, see Europe (disambiguation). ... The seabed (also sea floor, seafloor, or ocean floor) is the bottom of the ocean. ... Stratigraphy, a branch of geology, is basically the study of rock layers and layering. ...


In this matter, geologists have come to identify over twenty divisions, each of them lasting approximately 100,000 years. All these cycles fall within the Quaternary glacial period.


During its peak, the ice left its mark over almost 30% of Earth's surface, covering approximately 10 million km² in North America, 5 million km² in Europe and 4 million km² in Asia. The glacial ice in the Northern hemisphere was double that found in the Southern hemisphere. This is because southern polar ice cannot advance beyond the Antarctic landmass. It is now believed that the most recent glacial period began between two and three million years ago, in the Pleistocene era.


The last major glacial period began about 2,000,000 years B.P. and is commonly known as the Pleistocene or Ice Age. During this glacial period, large glacial ice sheets covered much of North America, Europe, and Asia for long periods of time. The extent of the glacier ice during the Pleistocene, however, was not static. The Pleistocene had periods when the glaciers retreated (interglacial) because of mild temperatures, and advanced because of colder temperatures (glacial). Average global temperatures were probably 4 to 5° Celsius colder than they are today at the peak of the Pleistocene. The most recent glacial retreat began about 14,000 years B.P. and is still going on. We call this period the Holocene epoch. The Pleistocene epoch (IPA: ) on the geologic timescale is the period from 1,808,000 to 11,550 years BP. The Pleistocene epoch had been intended to cover the worlds recent period of repeated glaciations. ... Variations in CO2, temperature and dust from the Vostok ice core over the last 400 000 years For the animated movie, see Ice Age (movie). ... North American redirects here. ... For other uses, see Europe (disambiguation). ... For other uses, see Asia (disambiguation). ... For other uses, see Celsius (disambiguation). ... Before Present (BP) years are the units of time (counted backwards to the past) used to report raw radiocarbon ages and dates referenced to the BP scale origin in the year AD 1950 (identical to 1950 CE). ... The Holocene Epoch is a geologic period that extends from the present back about 10,000 radiocarbon years. ...


Causes

Generalized glaciations have been rare in the history of Earth. However, the Ice Age of the Pleistocene was not the only glacial event, since tillite deposits have been identified. Tillite is a sedimentary rock formed when glacial till is lithified. Geological time put in a diagram called a geological clock, showing the relative lengths of the eons of the Earths history. ... Variations in CO2, temperature and dust from the Vostok ice core over the last 400 000 years For the animated movie, see Ice Age (movie). ... The Pleistocene epoch (IPA: ) on the geologic timescale is the period from 1,808,000 to 11,550 years BP. The Pleistocene epoch had been intended to cover the worlds recent period of repeated glaciations. ... Tillite is lithified till. ...


These deposits found in strata of differing age present similar characteristics as fragments of fluted rock, and some are superposed over bedrock surfaces of channeled and polished rock or associated with sandstone and conglomerates that have features of alluvial plain deposits. This article is about the geological formation. ... A conglomerate with iron oxide cementing material Conglomerate, Submarine Landslide located at Point Reyes, Marin County California. ...


Two Precambrian glacial episodes have been identified, the first approximately 2 billion years ago, and the second (Snowball Earth) about 650 million years ago. Also, a well documented record of glaciation exists in rocks of the late Paleozoic (the Carboniferous and Permian). The Precambrian (Pre-Cambrian) is an informal name for the supereon comprising the eons of the geologic timescale that came before the current Phanerozoic eon. ... One computer simulation of conditions during the Snowball Earth period. ... The Paleozoic Era (from the Greek palaio, old and zoion, animals, meaning ancient life) is the earliest of three geologic eras of the Phanerozoic eon. ... The Carboniferous is a geologic period and system that extends from the end of the Devonian period, about 359. ... The Permian is a geologic period that extends from about 299. ...


Although there are several scientific hypotheses about the determining factors of glaciations, the two most important ideas are plate tectonics and variations in Earth's orbit (Milankovitch cycles). The tectonic plates of the world were mapped in the second half of the 20th century. ... Milankovitch cycles are the collective effect of changes in the Earths movements upon its climate, named after Serbian civil engineer and mathematician Milutin Milanković. The eccentricity, axial tilt, and precession of the Earths orbit vary in several patterns, resulting in 100,000 year ice age cycles of the...


Plate tectonics

Because glaciers can form only on dry land, plate tectonics suggest that the evidence of previous glaciations seen in tropical latitudes is due to the drift of tectonic plates from tropical latitudes to circumpolar regions. Evidence of glacial structures in South America, Africa, Australia, and India support this idea, because it is known that they experienced a glacial period near the end of the Paleozoic Era, some 250 million years ago. The tectonic plates of the world were mapped in the second half of the 20th century. ... This article is about the geographical term. ... Plates in the crust of the earth, according to the plate tectonics theory Continental drift refers to the movement of the Earths continents relative to each other. ... The tectonic plates of the world were mapped in the second half of the 20th century. ... South America South America is a continent crossed by the equator, with most of its area in the Southern Hemisphere. ... A world map showing the continent of Africa Africa is the worlds second-largest and second most-populous continent, after Asia. ... The Paleozoic Era (from the Greek palaio, old and zoion, animals, meaning ancient life) is the earliest of three geologic eras of the Phanerozoic eon. ...


The idea that the evidence of middle-latitude glaciations is closely related to the displacement of tectonic plates was confirmed by the absence of glacial traces in the same period for the higher latitudes of North America and Eurasia, which indicates that their locations were very different from today. For other uses, see Eurasia (disambiguation). ...


Climatic changes are also related to the positions of the continents, which has made them vary in conjunction with the displacement of plates. That also affected ocean current patterns, which caused changes in heat transmission and humidity. Since continents drift very slowly (about 2 cm per year), similar changes occur in periods of millions of years.


A study of marine sediment that contained climatically sensitive microorganisms until about half a million years ago were compared with studies of the geometry of Earth's orbit, and the result was clear: climatic changes are closely related to periods of obliquity, precession, and eccentricity of the Earth's orbit. A cluster of Escherichia coli bacteria magnified 10,000 times. ... For other uses, see Geometry (disambiguation). ... Axial tilt is an astronomical term regarding the inclination angle of a planets rotational axis in relation to its orbital plane. ... Precession redirects here. ... In astrodynamics, under standard assumptions any orbit must be of conic section shape. ...


In general it can be affirmed that plate tectonics applies to long time periods, while Milankovitch's proposal, backed up by the work of others, adjusts to the periodic alterations of glacial periods of the Pleistocene. In both mechanisms the radiation imbalance of the earth is thought to play a large role in the build-up and melt of glaciers.


See also

There are very few or no other articles that link to this one. ... A cryoseism, also known as a frost quake[1][2] or ice quake, is a non-tectonic seismic event caused by a sudden freezing action in soil or rock materials saturated with water or ice. ... Graphical description of risks and impacts from global warming from the Third Assessment Report of the Intergovernmental Panel on Climate Change. ... The Erebus Ice Tongue extends into McMurdo Sound from Ross Island between Cape Royds and McMurdo Station. ... This image shows the termini of the glaciers in the Bhutan-Himalaya. ... The area around Glacier Bay in southeastern Alaska was first proclaimed a U.S. National Monument on February 25, 1925. ... Global warming refers to the increase in the average temperature of the Earths near-surface air and oceans in recent decades and its projected continuation. ... An icefall is a phenomenon found in some glaciers. ... An ice cap is a dome-shaped ice mass that covers less than 50,000 km² of land area (usually covering a highland area). ... An ice field (also called an icefield) is a flat land area (or a basin surrounded by mountains) covered by ice, usually formed by long periods of snow. ... An ice sheet is a mass of glacier ice that covers surrounding terrain and is greater than 50,000 km² (19,305 mile²).[1] The only current ice sheets are in Antarctica and Greenland; during the last ice age at Last Glacial Maximum (LGM) the Laurentide ice sheet covered much... Established in 1980 by the Alaska National Interest Lands Conservation Act, Kenai Fjords National Park is a United States National Park on the Kenai Peninsula in southcentral Alaska near the town of Seward. ... This is a list of glaciers: Adams Glacier Vatnajokull Iceland Agassiz Icecap - Ellesmere Island, Nunavut, Canada Aletsch Glacier - Swiss Alps, largest in Alps Angel Glacier - Cavell Meadows, Jasper National Park, Canada Antarctica -Continental glacier Athabasca Glacier - Canadian Rockies Aurora Glacier - Glacier Bay, Alaska Austfonna - Nordaustlandet, Svalbard Barnard Glacier - Alaska Beardmore... This article is about the geologic period. ... A view down the Whitechuck Glacier in North Cascades National Park in 1973 The same view as seen in 2006, where this branch of glacier retreated 1. ... It is known that during the Ice Age, probably on more than one occasion, a huge glacier referred to as The Irish Sea Glacier flowed southwards from its source areas in Scotland and Northern Ireland and across the Isle of Man, Anglesey and Pembrokeshire. ...

Cited references

  1. ^ Simpson, D.P. (1979). Cassell's Latin Dictionary, 5, London: Cassell Ltd., 883. ISBN 0-304-52257-0. 
  2. ^ C.D. Ollier: Australian Landforms and their History, National Mapping Fab, Geoscience Australia
  3. ^ http://www.piste-off.com/world-snow-and-glacier-index.asp List of Countries with glaciers
  4. ^ Kargel, J.S. et al.:Martian Polar Ice Sheets and Mid-Latitude Debris-Rich Glaciers, and Terrestrial Analogs, Third International Conference on Mars Polar Science and Exploration, Alberta, Canada, October 13-17, 2003 (pdf 970 Kb)
  5. ^ Fretted Terrain: Lineated Valley Fill, Mars Global Surveyor Mars Orbiter Camera, Malin Space Science Systems/NASA
  6. ^ Martian glaciers: did they originate from the atmosphere?, ESA Mars Express, 20 January 2006
  7. ^ T. Strozzi et al.: The Evolution of a Glacier Surge Observed with the ERS Satellites (pdf, 1.3 Mb)
  8. ^ The Brúarjökull Project: Sedimentary environments of a surging glacier. The Brúarjökull Project research idea.
  9. ^ Meier & Post (1969)
  10. ^ Easterbrook, D.J. (1999). Surface Processes and Landforms, 2, New Jersey: Prentice-Hall, Inc., 546. ISBN 0-13-860958-6. 
  11. ^ http://pubs.usgs.gov/of/2004/1216/no/no.html Glossary of Glacier Terminology

Uncited references

  • This article draws heavily on the corresponding article in the Spanish-language Wikipedia, which was accessed in the version of 24 July 2005. It was translated by the Spanish Translation of the Week collaboration.
  • Hambrey, Michael; Alean, Jürg (2004). Glaciers, 2nd ed., Cambridge University Press. ISBN 0-521-82808-2.  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)
  • Benn, Douglas I. (1999). Glaciers and Glaciation. Arnold. 
  • Bennett, M. R.; Glasser, N. F. (1996). Glacial Geology: Ice Sheets and Landforms. John Wiley & Sons. 
  • Hambrey, Michael (1994). Glacial Environments. University of British Columbia Press, UCL Press.  An undergraduate-level textbook.
  • Knight, Peter G (1999). Glaciers. Cheltenham: Nelson Thornes. ISBN 0-7487-4000-7.  A textbook for undergraduates avoiding mathematical complexities
  • Walley, Robert (1992). Introduction to Physical Geography. Wm. C. Brown Publishers.  A textbook devoted to explaining the geography of our planet.
  • W. S. B. Paterson (1994). Physics of Glaciers, 3rd ed., Pergamon Press.  A comprehensive reference on the physical principles underlying formation and behavior.

External References

Glaciers shrinking at record rate Retrieved Mar 17 2008


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Global dimming is the gradual reduction in the amount of global direct irradiance at the Earths surface that was observed for several decades after the start of systematic measurements in 1950s. ... Global warming potential (GWP) is a measure of how much a given mass of greenhouse gas is estimated to contribute to global warming. ... A schematic representation of the exchanges of energy between outer space, the Earths atmosphere, and the Earth surface. ... Top: Increasing atmospheric levels as measured in the atmosphere and ice cores. ... The Keeling Curve is a graph measuring the increase in the levels of carbon dioxide in the atmosphere since 1958. ... Land Use, Land-Use Change and Forestry (LULUCF) is a term often used in climate change topics. ... Tokyo, a case of Urban Heat Island. ... For other uses, see Albedo (disambiguation). ... 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