Glacier

qas: question: How long does it take glaciers to form?
answers: text: many years, often centuries

question: Do glaciers form on land, in the sea, or a combination of both?
answers: text: only on land

question: Which types of ice form on a body of water's surface?
answers: text: sea ice and lake ice

question: What causes glaciers to deform and flow?
answers: text: stresses induced by their weight

question: What are some distinguishing glacial features?
answers: text: crevasses, seracs

question: What is a semi-permanent body of ice that moves under its own weight?

question: What forms were ice accumulates?

question: What causes glaciers to remain smooth in uniform?

question: What other kinds of ice are thicker than glaciers?
context: A glacier (US /ˈɡleɪʃər/ or UK /ˈɡlæsiə/) is a persistent body of dense ice that is constantly moving under its own weight; it forms where the accumulation of snow exceeds its ablation (melting and sublimation) over many years, often centuries. Glaciers slowly deform and flow due to stresses induced by their weight, creating crevasses, seracs, and other distinguishing features. They also abrade rock and debris from their substrate to create landforms such as cirques and moraines. Glaciers form only on land and are distinct from the much thinner sea ice and lake ice that form on the surface of bodies of water.

qas: question: How much glacial ice is found surrounding the poles?
answers: text: 99%

question: Glaciers are found in mountain ranges on every continent except for which outlier?
answers: text: Australia

question: How much of Earth's land surface do glaciers cover?
answers: text: about 10 percent

question: What is the average thickness of an Antartican glacier?
answers: text: 2,100 m (7,000 ft)

question: What percent of Antartica's land is covered by glaciers?
answers: text: 98 percent

question: Where is 99% of the world snow contained?

question: What can be found on every continent of the world?

question: What percentage of the polar regions land surface is covered with glaciers?

question: What Connie Is Covered by 13,000,000 mi.² of glaciers?

question: Between what one want to latitudes or glaciers only found in valleys?
context: On Earth, 99% of glacial ice is contained within vast ice sheets in the polar regions, but glaciers may be found in mountain ranges on every continent except Australia, and on a few high-latitude oceanic islands. Between 35°N and 35°S, glaciers occur only in the Himalayas, Andes, Rocky Mountains, a few high mountains in East Africa, Mexico, New Guinea and on Zard Kuh in Iran. Glaciers cover about 10 percent of Earth's land surface. Continental glaciers cover nearly 13,000,000 km2 (5×10^6 sq mi) or about 98 percent of Antarctica's 13,200,000 km2 (5.1×10^6 sq mi), with an average thickness of 2,100 m (7,000 ft). Greenland and Patagonia also have huge expanses of continental glaciers.

qas: question: Do Earth's lakes or glaciers hold the most freshwater?
answers: text: glaciers

question: What causes glaciers to release meltwater?
answers: text: warmer summer temperatures

question: In which area are summer temperatures not high enough to release meltwater from glaciers?
answers: text: Antarctic environments

question: Under what circumstances would humans require water from a glacier?
answers: text: when other sources may be scant

question: Where is all the fresh water on earth contained?

question: What glaciers often release place during warm periods?

question: What creates in important water source for many plants and animals but not humans?

question: Who benefits from the Antarctic's meltwater?
context: Glacial ice is the largest reservoir of freshwater on Earth. Many glaciers from temperate, alpine and seasonal polar climates store water as ice during the colder seasons and release it later in the form of meltwater as warmer summer temperatures cause the glacier to melt, creating a water source that is especially important for plants, animals and human uses when other sources may be scant. Within high altitude and Antarctic environments, the seasonal temperature difference is often not sufficient to release meltwater.

qas: question: At what dimensions are glaciers called ice sheets or continental glaciers?
answers: text: 50,000 km2 (19,000 sq mi)

question: How many extant ice sheets exist?
answers: text: two

question: How much would global sea levels rise if Greenland and Antartica's glaciers were to melt?
answers: text: 70 m (230 ft)

question: What is the term for ice that protrude's from a glacier's surface?
answers: text: nunataks

question: Narrow, fast-moving pathways on an ice sheet are called what?
answers: text: ice streams

question: What are glaciers smaller it in 50,000 km² called?

question: What can often be seen beneath the sheets?

question: Where a sheets now extinct?

question: What are ice sheets that cover the sea called?

question: What you shelves become is a melt?
context: Glacial bodies larger than 50,000 km2 (19,000 sq mi) are called ice sheets or continental glaciers. Several kilometers deep, they obscure the underlying topography. Only nunataks protrude from their surfaces. The only extant ice sheets are the two that cover most of Antarctica and Greenland. They contain vast quantities of fresh water, enough that if both melted, global sea levels would rise by over 70 m (230 ft). Portions of an ice sheet or cap that extend into water are called ice shelves; they tend to be thin with limited slopes and reduced velocities. Narrow, fast-moving sections of an ice sheet are called ice streams. In Antarctica, many ice streams drain into large ice shelves. Some drain directly into the sea, often with an ice tongue, like Mertz Glacier.

qas: question: What are glaciers called that end in the sea?
answers: text: Tidewater glaciers

question: Most glaciers from Greenland, Antarctica, and Southeast Alaska are of which type?
answers: text: Tidewater glaciers

question: Are tidewater glaciers more or less affected by climate change than other glaciers?
answers: text: much less

question: Do tidewater glaciers calve above or below sea level?
answers: text: above

question: How are icebergs formed?
answers: text: As the ice reaches the sea, pieces break off, or calve

question: What are tidal glaciers?

question: Hetero icebergs form glaciers?

question: What affects tidewater glaciers more than others?

question: What type of glaciers have been retreating for centuries?
context: Tidewater glaciers are glaciers that terminate in the sea, including most glaciers flowing from Greenland, Antarctica, Baffin and Ellesmere Islands in Canada, Southeast Alaska, and the Northern and Southern Patagonian Ice Fields. 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 impact as the iceberg strikes the water. Tidewater glaciers undergo centuries-long cycles of advance and retreat that are much less affected by the climate change than those of other glaciers.

qas: question: From where is the temperature of a glacier measured?
answers: text: base alone

question: Which type of glacier is above or at freezing at it's interface and is able to slide?
answers: text: warm-based glacier

question: What temperature makes a glacier polythermal?
answers: text: partly cold-based and partly warm-based

question: What temperature determines a polar glacier?
answers: text: always below freezing point from the surface to its base

question: What temperature characteristic determines a temperate glacier?
answers: text: melting point throughout the year, from its surface to its base

question: What temperature is a polar glacier always above?

question: What temperature is a temperate glacier always above?

question: What two types of ice are contained in a polar glacier?

question: Why are warm based glaciers not able to slide?

question: Why is it cold basically sure able to slide?
context: Thermally, a temperate glacier is at melting point throughout the year, from its surface to its base. The ice of a polar glacier is always below freezing point from the surface to its base, although the surface snowpack may experience seasonal melting. A sub-polar glacier includes both temperate and polar ice, depending on depth beneath the surface and position along the length of the glacier. In a similar way, the thermal regime of a glacier is often described by the temperature at its base alone. A cold-based glacier is below freezing at the ice-ground interface, and is thus frozen to the underlying substrate. A warm-based glacier is above or at freezing at the interface, and is able to slide at this contact. This contrast is thought to a large extent to govern the ability of a glacier to effectively erode its bed, as sliding ice promotes plucking at rock from the surface below. Glaciers which are partly cold-based and partly warm-based are known as polythermal.

qas: question: Under what circumstances do glaciers form?
answers: text: where the accumulation of snow and ice exceeds ablation

question: What is a cirque?
answers: text: The area in which a glacier forms

question: What shape is a cirque, generally?
answers: text: armchair-shaped

question: How much ice and snow is minimally necessary to begin to slide on steep glaciers?
answers: text: 15 m (50 ft)

question: What forms were snow and ice accumulation is equal to its melting

question: What geological features formed by glaciers?

question: What happens in a minimum of 15 feet of snow?

question: What causes a glaciers stop moving?
context: Glaciers form where the accumulation of snow and ice exceeds ablation. The area in which a glacier forms is called a cirque (corrie or cwm) - a typically armchair-shaped geological feature (such as a depression between mountains enclosed by arêtes) - which collects and compresses through gravity the snow which falls into it. This snow collects and is compacted by the weight of the snow falling above it forming névé. Further crushing of the individual snowflakes and squeezing the air from the snow turns it into 'glacial ice'. This glacial ice will fill the cirque until it 'overflows' through a geological weakness or vacancy, such as the gap between two mountains. When the mass of snow and ice is sufficiently thick, it begins to move due to a combination of surface slope, gravity and pressure. On steeper slopes, this can occur with as little as 15 m (50 ft) of snow-ice.

qas: question: What characteristics determine glacial zones?
answers: text: surface snowpack and melt conditions

question: Which glacial zone area reports a net-loss in glacial mass?
answers: text: ablation zone

question: What is the name of the line seperating the ablation zone from the accumulation zone?
answers: text: equilibrium line

question: How much glacial surface area is typically considered accumulation zone?
answers: text: 60–70%

question: What is based on suface ice and melt conditions?

question: Wht line marks the center of the glacier?

question: What does the abilation zone cover 60-70% of?

question: What forces underlying rock upward?

question: What lakes where formed from a mountain depression
context: Glaciers are broken into zones based on surface snowpack and melt conditions. The ablation zone is the region where there is a net loss in glacier mass. The equilibrium line separates the ablation zone and the accumulation zone; it is the altitude where the amount of new snow gained by accumulation is equal to the amount of ice lost through ablation. The upper part of a glacier, where accumulation exceeds ablation, is called the accumulation zone. In general, the accumulation zone accounts for 60–70% of the glacier's surface area, more if the glacier calves icebergs. Ice in the accumulation zone is deep enough to exert a downward force that erodes underlying rock. After a glacier melts, it often leaves behind a bowl- or amphitheater-shaped depression that ranges in size from large basins like the Great Lakes to smaller mountain depressions known as cirques.

qas: question: Why are the tops of glaciers rigid?
answers: text: they are under low pressure

question: Which zone is the top of the glaciers?
answers: text: fracture zone

question: Why are glacial crevices formed?
answers: text: differences in glacier velocity

question: What are seracs?
answers: text: isolated peaks in the ice

question: Most crevices are no deeper than what measure?
answers: text: 46 m (150 ft)

question: Why is the lower 50m of a glacier rigid?

question: What is the free flowing upper section known as?

question: what forms where glaciers are unable to move?

question: What happens when two ridgid sections of a glacier collide?

question: What point do sercas form above?
context: The top 50 m (160 ft) of a glacier are rigid because they are under low pressure. This upper section is known as the fracture zone and moves mostly as a single unit over the plastically flowing lower section. When a glacier moves through irregular terrain, cracks called crevasses develop in the fracture zone. Crevasses form due to differences in glacier velocity. If two rigid sections of a glacier move at different speeds and directions, shear forces cause them to break apart, opening a crevasse. Crevasses are seldom more than 46 m (150 ft) deep but in some cases can be 300 m (1,000 ft) or even deeper. Beneath this point, the plasticity of the ice is too great for cracks to form. Intersecting crevasses can create isolated peaks in the ice, called seracs.

qas: question: Which crevasses form on the edge of the glacier?
answers: text: Marginal crevasses

question: Why do marginal crevasses form on the edge of a glacier?
answers: text: reduction in speed caused by friction of the valley walls

question: What do bergschrunds resemble?
answers: text: crevasses

question: How are bergschrunds different than crevasses?
answers: text: singular features at a glacier's margins

question: Where do transverse crevasses form?
answers: text: where steeper slopes cause a glacier to accelerate

question: What kind of crevasses form where steep slopes cause glaciers to deccelerate?

question: What kind of crevasses form where glaciers contract laterally?

question: What kind of crevasses form at the edge of a glacier due to an increase in speed?

question: What is formed when moving ice seperates from sragnant ice below?

question: What margins to crevasses form at?
context: Crevasses can form in several different ways. Transverse crevasses are transverse to flow and form where steeper slopes cause a glacier to accelerate. Longitudinal crevasses form semi-parallel to flow where a glacier expands laterally. Marginal crevasses form from the edge of the glacier, due to the reduction in speed caused by friction of the valley walls. Marginal crevasses are usually largely transverse to flow. Moving glacier ice can sometimes separate from stagnant ice above, forming a bergschrund. Bergschrunds resemble crevasses but are singular features at a glacier's margins.

qas: question: In what area of Greenland can glaciers move 20-30m per day?
answers: text: Jakobshavn Isbræ

question: Increasing slope, thickness, snowfall, longitudinal confinement, basal temperature, and meltwater production result in increased what?
answers: text: Velocity

question: How far do glaciers generally move per day?
answers: text: 1 m (3 ft)

question: Why are some glaciers stagnant in Alaska?
answers: text: trees can establish themselves on surface sediment deposits

question: What typically moves at around 3 meters a day?

question: What grows on moving glaciers in Alaska?

question: What makes some glaciers stagnant?

question: What causes increased thickness?
context: Mean speeds vary greatly, but is typically around 1 m (3 ft) per day. There may be no motion in stagnant areas; for example, in parts of Alaska, trees can establish themselves on surface sediment deposits. In other cases, glaciers can move as fast as 20–30 m (70–100 ft) per day, such as in Greenland's Jakobshavn Isbræ (Greenlandic: Sermeq Kujalleq). Velocity increases with increasing slope, increasing thickness, increasing snowfall, increasing longitudinal confinement, increasing basal temperature, increasing meltwater production and reduced bed hardness.

qas: question: What is a glacial surge?
answers: text: periods of very rapid advancement

question: What failure causes surges?
answers: text: failure of the underlying bedrock

question: At what rate have glaciers travelled during surges?
answers: text: 90 m (300 ft) per day

question: What is the term for a gradual increase in a glaciers speed?

question: What is caused by underground water?

question: What does accumulaion of rock under the glacier cause?
context: A few 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. These surges may be caused by failure of the underlying bedrock, the pooling of meltwater at the base of the glacier — perhaps delivered from a supraglacial lake — or the simple accumulation of mass beyond a critical "tipping point". Temporary rates up to 90 m (300 ft) per day have occurred when increased temperature or overlying pressure caused bottom ice to melt and water to accumulate beneath a glacier.

qas: question: How far does a glacier have to move to cause glacial earthquakes?
answers: text: one km per year

question: How high can the seismic magnitude be of a glacial earthquake?
answers: text: 6.1

question: Are Greenland's glacial earthquakes increasing or decreasing as time goes on?
answers: text: increasing

question: During which months do glacial earthquakes peak in Greenland?
answers: text: July, August and September

question: In what year were twice as many glacial earthquakes seen than in any other year in Greenland?
answers: text: 2005

question: What occurs where glaciers are moving slower than 1 km per day?

question: What peaks Every July in Iceland?

question: What is causing a decrease in Greenlands glacial earthquakes?

question: What has been decreasing over time?
context: In glaciated areas where the glacier moves faster than one km per year, glacial earthquakes occur. These are large scale temblors that have seismic magnitudes as high as 6.1. The number of glacial earthquakes in Greenland peaks every year in July, August and September and is increasing over time. In a study using data from January 1993 through October 2005, more events were detected every year since 2002, and twice as many events were recorded in 2005 as there were in any other year. This increase in the numbers of glacial earthquakes in Greenland may be a response to global warming.

qas: question: What are ogives?
answers: text: alternating wave crests and valleys that appear as dark and light bands of ice on glacier surfaces

question: What does the width of one dark and one light band measure?
answers: text: annual movement of the glacier

question: How are ogives formed?
answers: text: when ice from an icefall is severely broken up, increasing ablation surface area during summer

question: Under what conditions are ogives called wave or band ogives?
answers: text: consist only of undulations or color bands

question: what is the term for crests of ice on the glaciers surface?

question: What is formed when an icefall is covered up?

question: What do ogives prevent from accumulating?

question: What is made of both undulations and color bands?
context: Ogives are alternating wave crests and valleys that appear as dark and light bands of ice on glacier surfaces. They are linked to seasonal motion of glaciers; the width of one dark and one light band generally equals the annual movement of the glacier. Ogives are formed when ice from an icefall is severely broken up, increasing ablation surface area during summer. This creates a swale and space for snow accumulation in the winter, which in turn creates a ridge. Sometimes ogives consist only of undulations or color bands and are described as wave ogives or band ogives.

qas: question: How many countries contain glaciers?
answers: text: fifty

question: Which continent contains glaciers?
answers: text: every continent

question: Which mountain ranges contain glaciers?
answers: text: Andes, the Himalayas, the Rocky Mountains, the Caucasus, and the Alps

question: Where are glaciers in Africa located?
answers: text: Mount Kilimanjaro in Tanzania, on Mount Kenya and in the Rwenzori Mountains

question: Which sub-antarctic islands have glaciers?
answers: text: Marion, Heard, Grande Terre (Kerguelen) and Bouvet

question: What are found on every coninant including Australia?

question: What sub-arctic islands do not have glaciers?

question: What Australian mountain has a glacier?

question: What are spreading rapidly in New Guinea?
context: Glaciers are present on every continent and approximately fifty countries, excluding those (Australia, South Africa) that have glaciers only on distant subantarctic island territories. Extensive glaciers are found in Antarctica, Chile, Canada, Alaska, Greenland and Iceland. Mountain glaciers are widespread, especially in the Andes, the Himalayas, the Rocky Mountains, the Caucasus, and the Alps. Mainland Australia currently contains no glaciers, although a small glacier on Mount Kosciuszko was present in the last glacial period. In New Guinea, small, rapidly diminishing, 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 Rwenzori Mountains. Oceanic islands with glaciers occur on Iceland, Svalbard, New Zealand, Jan Mayen and the subantarctic islands of Marion, Heard, Grande Terre (Kerguelen) and Bouvet. During glacial periods of the Quaternary, Taiwan, Hawaii on Mauna Kea and Tenerife also had large alpine glaciers, while the Faroe and Crozet Islands were completely glaciated.

qas: question: Do glaciers require permanent snow or only temporary coverage?
answers: text: permanent snow cover

question: Between which north latitudes are glaciers not found?
answers: text: 20° to 27° north

question: Between which latitudes to mountains tend to have permanent snow?
answers: text: 19˚N and 19˚S

question: Why do mountains between 19N and 19S tend to have snow?
answers: text: precipitation is higher

question: What affects the perminant ice layer needed for glaciers to form?

question: What can be found in every country from 20 degrees to 27 degess north and south of the equator?

question: At what lattitudes does the Hadley circulation rais percipitation?

question: At what latitudes does low percipitation lead to permanent snow?
context: The permanent snow cover necessary for glacier formation is affected by factors such as the degree of slope on the land, amount of snowfall and the winds. Glaciers can be found in all latitudes except from 20° to 27° north and south of the equator where the presence of the descending limb of the Hadley circulation lowers precipitation so much that with high insolation snow lines reach above 6,500 m (21,330 ft). Between 19˚N and 19˚S, however, precipitation is higher and the mountains above 5,000 m (16,400 ft) usually have permanent snow.

qas: question: Which areas in Antartica are considered polar deserts?
answers: text: Banks Island, and the McMurdo Dry Valleys

question: Why can't glaciers form in polar deserts?
answers: text: they receive little snowfall

question: Does cold or warm air facilitate the transport of water vapor?
answers: text: warm air

question: What is inevitable at hight latitudes?

question: What kind of deserts do glaciers form in?

question: What does cold air transport?

question: What formed in central and north Alaska during the last ice age due to the extreme cold?
context: Even at high latitudes, glacier formation is not inevitable. Areas of the Arctic, such as Banks Island, and the McMurdo Dry Valleys in Antarctica are considered polar deserts where glaciers cannot form because they receive little snowfall despite the bitter cold. Cold air, unlike warm air, is unable to transport much water vapor. Even during glacial periods of the Quaternary, Manchuria, lowland Siberia, and central and northern Alaska, though extraordinarily cold, had such light snowfall that glaciers could not form.

qas: question: What cause glacial stiations?
answers: text: large boulders that carve long scratches in the bedrock

question: What can scientists deduct from the direction of the striations?
answers: text: direction of the glacier's movement

question: What are chatter marks?
answers: text: lines of crescent-shape depressions in the rock underlying a glacier

question: How are chatter marks formed?
answers: text: abrasion when boulders in the glacier are repeatedly caught and released

question: What charactrerizes glacial striations?

question: What is formed when glaciers lack boulders?

question: What helps scientists determine the speed of a glacier?

question: What is formed when glaciers crush boulders?
context: Glacial abrasion is commonly characterized by glacial striations. Glaciers produce these when they contain large boulders that carve long scratches in the bedrock. By mapping the direction of the striations, researchers can determine the direction of the glacier's movement. Similar to striations are chatter marks, lines of crescent-shape depressions in the rock underlying a glacier. They are formed by abrasion when boulders in the glacier are repeatedly caught and released as they are dragged along the bedrock.

qas: question: When are glacial moraines visible?
answers: text: after the glacier has retreated

question: How are glacial moraines formed?
answers: text: deposition of material from a glacier

question: Where are lateral moraines found?
answers: text: sides of the glacier

question: How are medial moraines formed?
answers: text: when two different glaciers merge and the lateral moraines of each coalesce to form a moraine in the middle of the combined glacier

question: What are ground moraines also called?
answers: text: glacial drift

question: What are no longer visable after a glacier retreats?

question: What type of moraines are formed at the begining of the glacier?

question: What mraines are formed when two ice sheets meet?

question: What blankets the surface of a glacier?

question: What are upslope from the equilibrium line?
context: Glacial moraines are formed by the deposition of material from a glacier and are exposed after the glacier has retreated. They usually appear as linear mounds of 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 merge and the lateral moraines of each coalesce to form a moraine in the middle of the combined glacier. Less apparent are ground moraines, also called glacial drift, which often blankets the surface underneath the glacier downslope from the equilibrium line.

qas: question: What shape do mountain valleys have pre-glacation?
answers: text: characteristic "V" shape

question: What gives mountain vallys their characteristic "V" shape before glacation?
answers: text: eroding water

question: How is a fjord formed?
answers: text: a glacial valley runs into a large body of water

question: What shape do glacial valleys have after being widened by glacation?
answers: text: "U"-shaped

question: What has a V shape after a glacier recedes?

question: What are U shaped before glaciation?

question: What fills depressions to form fjord?

question: What do glacial valleys run into to form paternoster lakes?
context: Before glaciation, mountain valleys have a characteristic "V" shape, produced by eroding water. During glaciation, these valleys are widened, deepened, and smoothed, forming a "U"-shaped glacial valley. The erosion that creates glacial valleys eliminates the spurs of earth that extend across mountain valleys, creating triangular cliffs called truncated spurs. Within glacial valleys, depressions created by plucking and abrasion can be filled by lakes, called paternoster lakes. If a glacial valley runs into a large body of water, it forms a fjord.

qas: question: On which side is a cirque opened?
answers: text: the side that descends into the valley

question: Where does ice start accululating in a glacier?
answers: text: Cirques

question: What is a narrow ridge formed by two cirques eroding back to back called?
answers: text: arête

question: What are extremely steep cirques called?
answers: text: horns

question: How many sides are closed in a typical cirque?
answers: text: three sides

question: What is on the side that ascends out of a valley?

question: What do cirques gorm in mountains?

question: What are shallow cirques called?
context: At the start of a classic valley glacier is a bowl-shaped cirque, which has escarped walls on three sides but is open on the side that descends into the valley. Cirques are where ice begins to accumulate in a glacier. Two glacial cirques may form back to back and erode their backwalls until only a narrow ridge, called an arête is left. This structure may result in a mountain pass. If multiple cirques encircle a single mountain, they create pointed pyramidal peaks; particularly steep examples are called horns.

qas: question: What is another name for roche moutonnee?
answers: text: "sheepback" rock

question: What are roche moutonnee?
answers: text: elongated, rounded, and asymmetrical bedrock knobs that can be produced by glacier erosion

question: How large are roche moutonnee?
answers: text: less than a meter to several hundred meters long

question: What shape do roche moutonnee have on their "up" side?
answers: text: gentle slope

question: What shape do roche moutonnee have on their "down" side?
answers: text: steep to vertical face

question: what are ice formations made by glaciers called?

question: What are short round bedrock knobs?

question: What are steep on their upside and and gentle on their down side?

question: What is smooth on the downstream side?
context: Some rock formations in the path of a glacier are sculpted into small hills called roche moutonnée, or "sheepback" rock. Roche moutonnée are elongated, rounded, and asymmetrical bedrock knobs that can be produced by glacier erosion. They range in length from less than a meter to several hundred meters long. Roche moutonnée have a gentle slope on their up-glacier sides and a steep to vertical face on their down-glacier sides. The glacier abrades the smooth slope on the upstream side as it flows along, but tears loose and carries away rock from the downstream side via plucking.

qas: question: Where is post-glacial rebound occuring most?
answers: text: Scandinavia and the Great Lakes region of North America.

question: What has the ability to depress the crust of the Earth into the mantle?
answers: text: Large masses, such as ice sheets or glaciers

question: With what speed does post-glacial rebound occur?
answers: text: very slowly

question: How much of a glacier's thickness is usually involved during crust depression into the mantle?
answers: text: a third of the ice sheet or glacier's thickness

question: Where has post-glacial rebound stopped occuring?

question: What totals a thirs of the glaciers length?

question: What happens quickly after the ice sheet melts?

question: What pushes up the mantle of the Earth?
context: Large masses, such as ice sheets or glaciers, can depress the crust of the Earth into the mantle. The depression usually totals a third of the ice sheet or glacier's thickness. After the ice sheet or glacier melts, the mantle begins to flow back to its original position, pushing the crust back up. This post-glacial rebound, which proceeds very slowly after the melting of the ice sheet or glacier, is currently occurring in measurable amounts in Scandinavia and the Great Lakes region of North America.