sentence-transformers/squad huggingface dataset:
Passage: 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.

Question: Under what circumstances do glaciers form?

Question: What is a cirque?

Question: What shape is a cirque, generally?

Question: How much ice and snow is minimally necessary to begin to slide on steep glaciers?
Passage: 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.

Question: What characteristics determine glacial zones?

Question: Which glacial zone area reports a net-loss in glacial mass?

Question: What is the name of the line seperating the ablation zone from the accumulation zone?

Question: How much glacial surface area is typically considered accumulation zone?
Passage: 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.

Question: Why are the tops of glaciers rigid?

Question: Which zone is the top of the glaciers?

Question: Why are glacial crevices formed?

Question: What are seracs?

Question: Most crevices are no deeper than what measure?
Passage: 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.

Question: Which crevasses form on the edge of the glacier?

Question: Why do marginal crevasses form on the edge of a glacier?

Question: What do bergschrunds resemble?

Question: How are bergschrunds different than crevasses?

Question: Where do transverse crevasses form?
Passage: 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.

Question: In what area of Greenland can glaciers move 20-30m per day?

Question: Increasing slope, thickness, snowfall, longitudinal confinement, basal temperature, and meltwater production result in increased what?

Question: How far do glaciers generally move per day?

Question: Why are some glaciers stagnant in Alaska?
Passage: 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.

Question: What is a glacial surge?

Question: What failure causes surges?

Question: At what rate have glaciers travelled during surges?
Passage: 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.

Question: How far does a glacier have to move to cause glacial earthquakes?

Question: How high can the seismic magnitude be of a glacial earthquake?

Question: Are Greenland's glacial earthquakes increasing or decreasing as time goes on?

Question: During which months do glacial earthquakes peak in Greenland?

Question: In what year were twice as many glacial earthquakes seen than in any other year in Greenland?
Passage: 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.

Question: What are ogives?

Question: What does the width of one dark and one light band measure?

Question: How are ogives formed?

Question: Under what conditions are ogives called wave or band ogives?
Passage: 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.

Question: How many countries contain glaciers?

Question: Which continent contains glaciers?

Question: Which mountain ranges contain glaciers?

Question: Where are glaciers in Africa located?

Question: Which sub-antarctic islands have glaciers?
Passage: 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.

Question: Do glaciers require permanent snow or only temporary coverage?

Question: Between which north latitudes are glaciers not found?

Question: Between which latitudes to mountains tend to have permanent snow?

Question: Why do mountains between 19N and 19S tend to have snow?
Passage: 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.

Question: Which areas in Antartica are considered polar deserts?

Question: Why can't glaciers form in polar deserts?

Question: Does cold or warm air facilitate the transport of water vapor?
Passage: 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.

Question: What cause glacial stiations?

Question: What can scientists deduct from the direction of the striations?

Question: What are chatter marks?

Question: How are chatter marks formed?
Passage: 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.

Question: When are glacial moraines visible?

Question: How are glacial moraines formed?

Question: Where are lateral moraines found?

Question: How are medial moraines formed?

Question: What are ground moraines also called?
Passage: 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.

Question: What shape do mountain valleys have pre-glacation?

Question: What gives mountain vallys their characteristic "V" shape before glacation?

Question: How is a fjord formed?

Question: What shape do glacial valleys have after being widened by glacation?
Passage: 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.

Question: On which side is a cirque opened?

Question: Where does ice start accululating in a glacier?

Question: What is a narrow ridge formed by two cirques eroding back to back called?

Question: What are extremely steep cirques called?

Question: How many sides are closed in a typical cirque?
Passage: 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.

Question: What is another name for roche moutonnee?

Question: What are roche moutonnee?

Question: How large are roche moutonnee?

Question: What shape do roche moutonnee have on their "up" side?

Question: What shape do roche moutonnee have on their "down" side?
Passage: 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.

Question: Where is post-glacial rebound occuring most?

Question: What has the ability to depress the crust of the Earth into the mantle?

Question: With what speed does post-glacial rebound occur?

Question: How much of a glacier's thickness is usually involved during crust depression into the mantle?
Passage: First recognized in 1900 by Max Planck, it was originally the proportionality constant between the minimal increment of energy, E, of a hypothetical electrically charged oscillator in a cavity that contained black body radiation, and the frequency, f, of its associated electromagnetic wave. In 1905 the value E, the minimal energy increment of a hypothetical oscillator, was theoretically associated by Einstein with a "quantum" or minimal element of the energy of the electromagnetic wave itself. The light quantum behaved in some respects as an electrically neutral particle, as opposed to an electromagnetic wave. It was eventually called the photon.

Question: What is considered the minimal energy increment of a hypothetical oscillator?

Question: In what year was the value E associated by Einstein with quantum theories of energy?

Question: Who discovered an association between the value E and quantum energy?

Question: What did the light quantum behave the same as in laboratory experiments?

Question: What type of charge did a particle have that behaved similarly to light quantum energy?

Question: What is energy abbreviated to in science?

Question: What is frequency also known as in science?

Question: What term describes a small amount of element?

Question: What did the light quantum, in some ways, behave as?

Question: What was later termed the photon?

Question: When did Max Planck first recognize the value of the Planck constant?

Question: Which scientist associated the Planck constant with a quantum five years after Planck's recognition?

Question: Instead of an electromagnetic wave, what did the light quantum behave as in some regards?

Question: What is the simple name given to the light quantum today?
Passage: Classical statistical mechanics requires the existence of h (but does not define its value). Eventually, following upon Planck's discovery, it was recognized that physical action cannot take on an arbitrary value. Instead, it must be some multiple of a very small quantity, the "quantum of action", now called the Planck constant. Classical physics cannot explain this fact. In many cases, such as for monochromatic light or for atoms, this quantum of action also implies that only certain energy levels are allowed, and values in between are forbidden.

Question: What does classical statistics mechanics not define the value of?

Question: What is required to exist in classical statistics mechanics?

Question: After Planck's findings, what was determined could not take on an arbitrary value?

Question: What is the "quantum of action" called?

Question: What does the Planck Constant refer to?

Question: Classical statistical mechanics requires the existence of what?

Question: What was realized after Planck's discovery?

Question: What is the Planck constant formerly known as?

Question: Regarding atoms, what does the Planck constant imply?

Question: Regarding atoms, what are values in between certain energy levels considered by the Planck constant?

Question: Following Planck's discovery, what was realized about values of physical action?

Question: The Planck constant initially was given what name?

Question: How is the proportional nature of the Planck constant explained?

Question: For certain cases of light or atoms, what does the quantum of action yield?
Passage: Equivalently, the smallness of the Planck constant reflects the fact that everyday objects and systems are made of a large number of particles. For example, green light with a wavelength of 555 nanometres (the approximate wavelength to which human eyes are most sensitive) has a frequency of 7014540000000000000♠540 THz (7014540000000000000♠540×1012 Hz). Each photon has an energy E = hf = 6981358000000000000♠3.58×10−19 J. That is a very small amount of energy in terms of everyday experience, but everyday experience is not concerned with individual photons any more than with individual atoms or molecules. An amount of light compatible with everyday experience is the energy of one mole of photons; its energy can be computed by multiplying the photon energy by the Avogadro constant, NA ≈ 7023602200000000000♠6.022×1023 mol−1. The result is that green light of wavelength 555 nm has an energy of 7005216000000000000♠216 kJ/mol, a typical energy of everyday life.

Question: What are common things like furniture and stationary objects actually made of?

Question: Which light wavelength is the human eye most sensitive to?

Question: What color of light is the human eye most sensitive to?

Question: What does the smallness of the Planck constant show?

Question: At about what wavelength of light are human eyes most sensitive?

Question: What frequency does green light with a wavelength of 555 nanmetres have?

Question: How is the energy from one mole of photos computed?

Question: How much energy does a green light of wavelength 555 nm contain?

Question: What is the wavelength of light to which human eyes are most sensitive?

Question: What is the frequency of the light to which the human eye is most sensitive?

Question: What is the energy of a photon?

Question: How much energy is contained in the light to which human eyes are most sensitive?
Passage: In the last years of the nineteenth century, Planck was investigating the problem of black-body radiation first posed by Kirchhoff some forty years earlier. It is well known that hot objects glow, and that hotter objects glow brighter than cooler ones. The electromagnetic field obeys laws of motion similarly to a mass on a spring, and can come to thermal equilibrium with hot atoms. The hot object in equilibrium with light absorbs just as much light as it emits. If the object is black, meaning it absorbs all the light that hits it, then its thermal light emission is maximized.

Question: What type of radiation was Planck studying in the late 19th century?

Question: How many years prior to Planck's study had the scientific community first discussed black body radiation?

Question: What scientist first studied black body radiation?

Question: What is required for the electromagnetic field to come to thermal equilibrium?

Question: What does a hot object in equilibrium absorb as much as it emits?

Question: What was Planck studying in the last part of the nineteenth century?

Question: Who posed the problem of black-body radiation?

Question: Cooler objects glow less than objects that are what?

Question: What does a black object do to any of the light that hits it?

Question: What is maximized as a result of a black object absorbing all the light that hits it?

Question: Planck studied what problem posed originally by Kirchhoff?

Question: If an object is black, what is known about its thermal light emission?

Question: What is known about the light absorption of a hot object in equilibrium with light?

Question: Electromagnetic fields obey what laws?