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topic 1 Flashcards

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1
Q

what is mass balance

A

the gain and loss of ice from a glacier

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2
Q

what isa dynamic equilibrium

A

lack of change in a system as outputs and inputs remain in balance. If changes do occur, then feedbacks will allow its corrections.

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3
Q

what is feedbacks in a system/ the two kinds

A

In a system, an output which causes changes to that systems input. Negative and positive. Negative- one which reduces and possibly reverses the usual processes.
positive- one which exacerbates the usual processes

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4
Q

what are the inputs of an alpine glacier

A

snow fall- avalanches

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5
Q

what are the outputs dot an alpine glacier

A

melt water- higher in summer. Ice bergs too.

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6
Q

what are the two zones in a glacier system

A

Net accumulation zone-inputs>outputs

Net ablation zone- inputs<outputs

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7
Q

what are ice ages

A

times of extreme cooling of the Earths climate where ice sheets and other types of glaciers expand to cover large areas of land

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8
Q

what are the periods called in-between ice ages

A

interglacial periods

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9
Q

when was the most recent ice age

A

peaked 21,000 years ago

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10
Q

what causes ice ages

A

Not completely understood .The composition of our atmosphere changes in the position of our planet around the sun, and changes in ocean currents are some of the important factors that control the climate.

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11
Q

why is it possible that there is some advance during the year even though the net budget is negative and some retreat when it is positive

A

The ice in the glacier may more forward across the line of equilibrium due to gravity, even though it is retreating, appearing to advance.

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12
Q

what is glacial mass balance

A

The difference between the amount of snow and ice accumulation and the amount of ablation occurring in a glacier over a one year time period.

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13
Q

what is the accumulation zone

A

the upper reaches of a glacier and an area, where accumulation exceeds ablation.

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14
Q

where do most of the inputs of a glacier occur

A

at the lower levels where ablation exceeds accumulation

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15
Q

what Is the name of the line that divides the two zones of a glacier, where there is a balance between the two

A

equilibrium line

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16
Q

equation for annual budget

A

total ablation in 1 year- total accumulation

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17
Q

what are the factors that influence the development of glacial landscapes

A

latitude and altitude
geology (lithology and structure)
climate
relief and aspect

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18
Q

how does latitude and altitude influence the development of glacial landscapes

A

Locations at high altitudes- have cold dry climates which little seasonal variation in precipitation. Higher the latitude= more apparent this is.

Glaciated landscapes at such latitudes tend to develop under the influence of large, relatively stable ice sheets, such as those of Greenland and Antarctica. These landscapes are different to those which develop under the influence of dynamic valley glaciers in lower latitude but higher altitude locations.

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19
Q

What are some examples of glaciated landscapes that are in high latitude

A

Glacier in Iceland, Vatnajokull

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20
Q

examples of glaciated landscapes in high altitudes

A

Siachen hyglacier- India, Himalayas

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21
Q

what are erratics

A

an individual piece of rock, varying in size from a small pebble to a large boulder

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22
Q

how are erratics formed +example

A

eroded most likely by plucking, or added to supergalcial debris by weathering and rockfall of an area of one type of geology and then transported and deposited into an area of differing rock type.

Silution Shale erratic blocks deposited on carbonated limestone at Norbert in the Yorkshire Dales.

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23
Q

what is terminal moraine

A

A ridge of till extending across a glacial trough. They are usually steeper on up-valley side and tend to be crescent shaped, reaching further down-valley in the centre. These landforms mark the position of the maximum advance of the ice and were deposited at the glacial snout.

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24
Q

what is lateral moraine add an example

A

a ridge of till running along the edge of a glacial valley. The material accumulates on top of the glacier having been weathered from the exposed valley sides. As the glacier melts/retreats material sinks through the ice to the ground, deposited. e.g Arthabasca glacier Canada- 1.5 km long and 124m high.

25
Q

Recessional moraine

A

A series of ridges running traversal across glacial troughs and which are broadly parallel to each other and to the terminal moraine. Form during a temporary still-stand in retreat. Recessional moraines seldom exceed 100m in height.

26
Q

What is push moraine

A

Only formed by glaciers that have retreated and then advanced again. Existence of push moraine is evidence of a climate that is becoming relatively cooler after a warm period. Material that is already deposited is shoved pinto a pile as the ice advances, and because most of the moraine material was deposited by falling down not pushing up, there are characteristic differences in the orientation the rocks within a push moraine.

27
Q

what are drumlins

A

mounds of glacial debris that has been streamlined into an elongated hill, sometimes more than 1km in length ad 100 m high. Typically they are pair shaped and aligned in the direction of ice flow. Higher and wider stoss or blunt, while lee side is more gently faded.

28
Q

how are drumlins formed and examples

A

not fully understood could be-

-sub glacial mega flood
- reshaping of previously deposited material
-lodgment of subglacial debris as it melts out of the basal ice layers
- accumulation of material around bedrock structure

striations appear as till is mounded and sculpted under neath the glacier.

Central Iceland

29
Q

what are till sheets

A

A uniform bunker of glacial deposits in a lowland area

30
Q

how are till sheets formed and examples

A

when a large mass of unstratified drift is deposited at the end of a period of ice sheet advance, which smooths the underlying surface.
Structure is not very conspicuous in terms of relief, significant because of their shape
The till itself is variable in composition, depending greatly upon the rocks over which the ice has moved. If there is a high clay content, compaction by the weight of the overlying ice sheets may lead to relatively hard deposit

e.gEast anglia the till is chalky

e.g Minnisota, exte
nsive till sheets were formed by deposition during the retreat of the Laurentide ice sheet.

31
Q

Ellipsodal basins

A

Major landforms created by ice sheets
e.g Lurentide ice sheet created many ellipsoidal basins in North America - master basin holds Hudson Bay

32
Q

What are Aretes and pyramidal peaks and how are they formed

A

Arêtes are narrow steep sides ridges found between two corries. Pyramidal peaks are where three or more cores develop around a hill or mountain top and their back walls retreat, the remaining mass will be itself steepened to form a pyramidal peak. example Matterhorn in Swiss Alps is over 1200 m high.

An arete is formed by glacial erosion , with the steepening of slopes and the retreat of corries that are back to back or alongside each other e.g striding edge in Lake District- slopes that are 200-300 m high

33
Q

how are glacial troughs formed

A

glaciers flow down pre existing river valleys under gravity. As they move they erode the sides and floor of the valley, causing the shape to become deeper, wider and straighter. The mass of the ice has a large amount of erosive power. Erosion and weathering of the valley sides in glacial and subsequent periglacial period as the glacier retreats.

34
Q
A
34
Q

what are Roche mountains

A

projections or resistent rock that are found on the floor of glacial troughs

As advancing ice passes over them there is localised pressure melting on the up valley, the glacial ice compresses- larger pressure melting point, so there

35
Q

Why do glaciers form

A

System that transports water
Right combination of temperature and snowfall above 3000m- the snow line
Process of diagenesis the compression when water is squeezed out of snow.
Process:
-snow
-granular ice
-firn
-glacial ice

36
Q

What is a carcasse and how is it made

A

A deep wedge- shaped opening in a moving mass of ice called a glacier. Crevasses usually form in the top 50 meters (160 feet) of a glacier, where the ice is brittle. Below that, a glacier is less brittle and can slide over uneven surfaces without cracking. The inflexible upper portion may split as it moves over the changing landscape.

37
Q

What are the different glacier ice systems

A

Valley glacier
Niche glacier
Ice caps
Cirque/ Corrie
Piedmont
Ice shelves

38
Q

What is glacial isostatic adjustment

A

The ongoing movement of land once burdened by ice-age glaciers.

39
Q

What was the impact of the laurentide ice sheet

A

Worn down the high mountains such that the highest peak are now only a modest 500-700 m high

40
Q

How large are ice sheets compared to valley glaciers and examples

A

More than 50,000 metres squared and an example of a ice sheet is in Minnesota, Laurentide ice sheet.
Valley glacier is in Lake District. Errofed landforms like Helvellyn which is a 11km long ridge over 600 m high.

41
Q

What are the different periglacial processes

A

Freeze thaw
Nivation
Solifluction
Fist heave
Groundwater freezing

42
Q

What is freeze thaw

A

Occurs in areas where temperatures rises in the day and drops in the night for a substantial part of winter. Water that enters cracks in the rocks freezes at night. Ice occupies more space than water and expands by 10% exerting pressure on the crack. This pressure continues widening the crack and eventually pieces of rock break off. On strap slopes this leads to collection of material at the base known as scree.

43
Q

What is nivation

A

Takes place beneath patches of snow in hollows, particularly on north and east facing slopes. Freeze thaw action and possibly chemical weathering, operating under the snow, cause the underlying rock to disintegrate. As some of the snow melts in spring, the weathered particles are moved downslope by the meltwater and by solifluction. Over a period of time, Thai leads to the formation of nivation hollows which when enlarged, can be the beginning of a Corrie.

44
Q

What is solifluction

A

When the active layer of a periglacial landscape thaws in summer, excessive lubrication reduces the friction between soil particles. Even on slopes as shallow as 2 degrees, parts of the active layer then begin to move downslope. This leads to solifluction sheets or lopes. Mounded tongue like featuresoften forming terraces on the sides of valleys, solifluction was widespread in southern Britain during quaternary period, such deposits are known as head.

45
Q

What is frost heave

A

As the active layer starts to redresse, ice crystals begin to develop. They increase the volume of the soil and cause an upward expansion of the surface soil. Most significant in fine braided material and, as it is uneven , it forms small domes on the surface. Within this material there are stones which because of their specific heat capacity, heat up and cool faster than the surrounding finer material. This means that the soil beneath the stones is likely to freeze and expand before the other material pushing the stone upwards until it reaches the surface on small domes, the larger stones more outwards effectively sorting itself out. When viewed above takes on a pattern. This patterned ground takes the form of stone polygons, where the ground is steeper, the stones move downhill to form stone stripes
Learn diagram

46
Q

Groundwater freezing

A

Where the permafrost is thin or discontinuous, water is able to seep into the upper layers of the ground and then freeze. The expansion of Thai ice causes the overlying sediment to heave upwards into a dome shaped feature known as pinhole which may rise as high as 50 im. Type is referred to as an open system pingo found commonly in East Greenland. In low lying areas with continuous permafrost , groundwater can be trapped by freezing from above and the permafrost beneath. As the water freezes it will expand , pushing up the overlying sediments into a closed-system pingo or Mackenzie type- Mackenzie delta- 1,000 pintos. Sometimes the surface of the pingo will collapse

Learn diagram

47
Q

what are the key aspects and influences of glacial landscapes

A

lithology
structure
latitude and altitude
relief and aspect

48
Q

how does relief and aspect influence glacial landscapes

A

the steeper the relief of the landscape, the greater of resultant force of gravity and as a glacier has more energy to move downslope.
Aspect is if the slope is in the direction of the sun receives more solar energy, therefore more melting occurs. These locations tend to be in retreat as the mass balance is negative.

an example is Greenland in which it has a gentle topography, with 9 glaciers predicted to thin more than 250km.

48
Q

how does latitude and altitude influence glacial landscapes

A

altitude is a measurement for height of an object above sea level.
Latitude is a measurement for the location of a point on the Earths surface north or south of the equator
high altitude- Rocky Mountains, high precipitation, more changing temperatures
.high latitudes- large, stable ice sheets- Greenland, less variation in temperature
decreases in temperature with altitude +less energy in air

49
Q

how does geology influence glacial landscapes

A

lithology describes the physical and chemcal composition of rocks. Some types of rocks e.g clay have a weak lithology, allowing them to be easily eroded as the bonds between the particles in the rocks are weak. some rocks are made of more dense interlocking crystals and so are more resistant to weathering and erosion, therefore can form glaciated landforms such as arêtes and pyramidal peaks

50
Q

how does structure influence glaciated landscapes

A

about the properties of rock types such as jointing, bending and faulting. In porous rocks e.g chalk there are tiny air spaces. These pores can absorb and store water. With processes such as freeze thaw ports rocks can easily be eroded. structure also includes the angle of dip rocks and can have a strong influence on valley side profiles.

51
Q

how does climate influence glaciated landscapes

A

wind- a moving force , able to carry out erosion, transportation and deposition, also can contribute to the shaping of glaciated landscapes, especially on fine material.
precipitation- affects mass balance of a glacier provides the main input of snow sleet and rain high latitude- low precipitation.
temperature-If temperatures rise above 0 accumulated snow and ice will start to met becoming an output of a system.e.g Kilimanjaro-

52
Q

what are kames

A

a hill or hummock composed of stratified sand and gravel laid down by glacial meltwater.
two types, Delta kames and terrace names.
Delta kames form in different ways, some are formed by en-glacial streams emerging at the snout of the glacier. They lose energy at the base of the glacier and deposit their load. Others are the result of supra glacial streams depositing material on entering ice-marginal lakes, losing energy as they enter the static body of water. Widespread in East Lothain, Scotland.
Kame terraces are ridges of material running along the edge of the valley floor. Supraglacial streams on the edge of the glacier pick up and carry lateral moraine which is later deposited on the valley floor as the glacier retreats. The streams form due to the melting of the ice in contact with the valley sides as a result of friction. Unlike lateral moraines they are composed of glacis-fluvio deposits that are more rounded and sorted. In. Yorkshire dales a name terrace extends for about 2km along the north side of the valley.

53
Q

What is an Esker

A

is a long sinuous ridge composed of stratified sand and grave laid down by glacial meltwater. Material is deposited in sub-glacial tunnels as the supply as the supply of meltwater decreases at the end of the glacial period. Sub-glacial tunnels may carry huge amounts of debris under pressure in confined tunnels at the base of the glacier. Scientists argue that deposition occurs when pressure is released and meltwater emerges at the glacier snout. As it retreats, the point of deposition will move backwards. Explains why some eskers have a beaded pattern- significant variation in height and width, greater size representing periods when the rate of retreat slowed or halted. Other scientists argue that beading is caused as the result of the greater load carried by summer meltwater. Trim Esker near Dublin is 14.5 km long

54
Q

what are outwash plains

A

also known as sandur is a flat expense of sediment in the pro-glacier area. Asmeltwater streams gradually lose energy as they enter lowland areas beyond the ice front, they deposit their load. The largest material is deposited nearest the ice front and the finest further away. Typically drained by braided streams. River channels subdivided by islets and channels. Debris-laden braided streams lose water at the end of the melting period and so carry less material. The material is deposited in the channel, causing it to divide. Discharge decreases after a flood or snow melt, causing the coarsest particles in the load not be deposited first. As discharge continues to decrease, finer material is then added to the bar, increasing its size. At high times of low discharge, channel bars are stabalisedby vegetation and become more permanent features. South coast of Iceland.

55
Q

climate change and the effects on geomorphic processes

A

Freeze-thaw weathering is a dominant process in periglacial environments. Due to seasonal fluctuations in temperature around freezing.

56
Q

modification of glacis- flucio landforms

A

as temps rise, further melting continues to rise, further melting and retreat of glaciers results in the production of meltwater more and thus creates a greater expanse and accumulation of outwash material in the pro-glacial zone. James and esker will be exposed in greater number and greater length during this continued retreat

physical geography (3 decks)

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