glaciers Flashcards
(296 cards)
1
Q
pleistocene period
A
A geological period from about 2 million years ago to 11,500 years ago, the early part of the quaternary which included the most recent age
2
Q
greenhouse conditions
A
Much warmer interglacial condition
3
Q
interglacials
A
Warmer periods similar to present i.e. greenhouse periods
4
Q
glacials
A
Cold, ice-house periods within the Pleistocene
5
Q
ice house conditions
A
very cold glacial conditions
6
Q
what are the 4 main types of cold environment
A
polar
alpine
periglacial
glacial
7
Q
what is a polar environment
A
glacial environments are found in the high latitudes of the Antarctic and Arctic. They are characterised by extremely cold temperatures (average annually of -30 to -40°C and low levels of precipitation.
8
Q
what is a alpine environment
A
glacial environments are found at high altitudes in mountain ranges in the mid-low latitudes e.g. European Alps, the Himalayas and Andes. They are characterised by high levels of precipitation and a wide temperature range with frequent freeze-thaw cycles
9
Q
what is a glaciar environment
A
are slow-moving bodies of ice in valleys, which shape the landscape in both polar and alpine environments
10
Q
what is a periglacial environment
A
hese environments do not feature glaciers, but are usually found next to glacial areas. They are characterised by permafrost and occur in high latitude or high-altitude areas where seasonal temperatures vary above and below freezing point. E.g. Siberia, Alaska and northern Canada
11
Q
what are eons
A
the longest span of geological time; eras are the second longest
Eon often refers to a span of around one billion years.
12
Q
the pleistocene epoch
A
often known as the ice age as it contained 50 glacial-interglacial cycles and glacials reached their furthest extent in this time.
13
Q
what was the last glacial maximum
A
known as the Devensian which was 18,000 years ago
14
Q
what was the last UK glacial advance
A
the Lock Lomond Stadial which was 12,000 to 10,000 years ago and marked the end of the Pleistocene epoch
15
Q
what type of environment is the UK now
A
UK is now called a relict glacial environment (it no longer experiences glacial conditions but it does display evidence of the Pleistocene glaciation period.)
16
Q
when was the Start of the Pleistocene epoch/Quaternary period
A
2.6 million years ago
17
Q
when did the Devensian glacial end (lasr glacial maximum)
A
180,000 years ago
18
Q
when was the End of the Pleistocene/start of the Holocene epoch
A
11,500 years ago
19
Q
when was the Lock Lomond stadial (last UK glacial advance)
A
10,000-12,000 years ago
20
Q
stadial and interstadial
A
short-term fluctuations within ice-house and greenhouse conditions; stadials are colder periods that lead to ice re-advances, interstadials are shorter periods of warmth.
21
Q
why are there fluctuations of glacials and interglacials
A
long and short term causes of climate change
22
Q
long term causes of climate change (milankovitch cycles)
A
continental drift
eccentricity of the orbit
axial tilt
wobble
23
Q
short term causes of climate change
A
variations in solar output
volcanic causes
24
Q
continental drift
A
3 million years ago the North and South American tectonic plates collided. This re-routed ocean currents so that warm Caribbean waters were forced northwest, creating the Gulf Stream.
25
eccentricity of the orbit
The shape of the Earth’s orbit varies from circular to elliptical over 100,000 year cycles. The Earth receives less solar radiation in the elliptical orbit when the Earth is farthest from the Sun. (A position known as aphelion)
26
axial tilt
The tilt of the Earth’s axis varies between 21.5° and 24.5° over 41,000 year cycles. This changes the severity of the seasons.
27
wobble
the Earth wobbles as it spins on its axis, which means that the season during which the Earth is nearest to the Sun (a position known as perihelion) varies. At present, the northern hemisphere winter occurs in perihelion. i.e. milder conditions than previous winters in aphelion. This varies over approximately 21,000 year cycles resulting in changes in the intensity of the seasons.
28
variations in solar output
The dark areas of the Sun (sunspots) are caused by intense magnetic activity in the Sun’s interior. An increase in the number of sunspots means that the Sun is more active and giving off more energy. They appear to vary over an 11 year cycle.
29
volcanic causes
Large eruptions can eject huge volumes of ash, sulphur dioxide, water vapour and carbon dioxide into the atmosphere (volcanic aerosols) which are globally distributed by winds. This aerosol blocks the Sun’s radiation, cooling the Earth. The ash tends to settle back on Earth within a few months, however the sulphur dioxide gas can remain in the atmosphere for up to three years, which reflect the radiation back into space.
30
what is the cryosphere
The cryosphere consists of ice sheets and glaciers, together with sea ice, lake ice, permafrost and snow cover.
31
what are mass and energy constantly exchanged between
Mass and energy are constantly exchanged between the cryosphere and other major components of Earth systems; the hydrosphere. Lithosphere, atmosphere and biosphere
32
what are glaciers
large bodies of ice which flow downhill under the influence of gravity.
33
what are the two bases of glaciers
land based glacier
marine based
34
land based glaciers
their base is at or above sea level e.g Mer de Glace flows from Mont Blanc in the Alps, or glaciers flowing from the Rocky Mountains.
35
marine based glacier
where the base is below sea level. E.g. the West Antarctica Ice Sheet – which is 2000m below sea level actually frozen to the sea bed.
36
what are the two types of glaciers
warm based glaciers
cold based glaciers
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warm based gaciers
occur in high altitude areas outside the polar regions e.g. the Alps. The temperature of the ice is often close to zero and mild summer temperatures cause melting.
38
cold based glaciers
These occur in polar glacial environments such as Greenland and Antarctica. These glaciers are frozen onto the bedrock below and melting only occurs on the surface in the summer months.
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types of ice mass
ice sheet
ice cap
ice field
valley glacier
piedmont glacier
cirque glacier
ice shelf
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ice sheet
Complete submergence of regional topography; forms a gently sloping dome of ice several kilometres thick in the centre
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ice cap
Smaller version of ice sheet occupying upland areas; outlet glaciers and ice sheets drain both ice sheets and ice caps
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ice field
ice covering an upland area, but not thick enough to bury topography; many do not extend beyond highland source
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valley glacier
Glacier confined between valley walls and terminating in a narrow tongue; forms from ice caps/sheets or cirques; may terminate in sea as a tidewater glacier.
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piedmont glacier
Valley glacier which extends beyond the end of a mountain valley into a flatter area and spreads out like a fan
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cirque glacier
Smaller glacier occupying a hollow on the mountain side – carves out a corrie or cirque; smaller version is known as a niche glacier
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ice shelf
Large area of floating glacier ice extending from the coast where several glaciers have reached the sea and merge.
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ice sheet size
10-100,000 sq km
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ice cap size
3-10,000 sq km
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ice field size
10-10,000 sq km
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valley glacier size
3-1,500 sq km
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piedmont glacier
3-1,000 sq km
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cirque glacier
0.5-8 sq km
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ice shelf size
10-100,000 sq km
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the glacial system
Glaciers gain mass through the transformation of snow into ice and then flow downhill (in response to gravity) and eventually lose mass due to melting. Hence glaciers can be viewed as systems with inputs, stores, transfers and outputs.
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accumulation defintion
the input of snow and ice to a glacier
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ablation defintion
the output of snow and ice from a glacier
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sublimation
the process of a substance turning from a solid directly to a gas without the liquid stage in the middle.
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glacier mass balance
is calculated using the total accumulation and ablation within a year.
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equilibrium line
when losses from ablation are balanced by gains from the accumulation in a glacier
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accumulation (inputs)
avalanches from above slopes
rock debris
wind deposition
precipitation (mainly snow)
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ablation (outputs)
evaporation (sublimation)
break away of ice blocks and ice bergs (calving)
meltwater
melting (water)
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glacial budget
A glacier mass balance/annual budget is calculated using the total accumulation and ablation within a year.
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what does the glacial system involve
inputs, stores, transfers and outputs
Accumulation
Ablation
Sublimation
Equilibrium line
Mass balance
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how much greater was ice cover at the Pleistocene maximum than the present day
more than three times greater
65
general trends in ice cover
Major ice extensions were over North America and Europe.
Ice extensions over West and South of South America.
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ice cover of the Antarctica and Greenland ice sheets
The Antarctica and Greenland ice sheets only covered a slightly greater area than they do today. With the West Antarctica ice sheet expanding 10km either side of the peninsula
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ice cover of the Laurentide and Cordilleran ice sheets
The Laurentide and Cordilleran ice sheets covered East and West of North America stretching to around 3000km in width
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ice cover of the scandinavian ice sheet
The Scandinavian Ice Sheet across Europe, in particular covering the area of UK the UK widening to 500km
69
at present what % of Earths land area does ice cover
ice covers over 10% of the Earth’s land area which accounts for 75% of the world’s freshwater (about 1.8 % of all water on Earth.
70
what % of all glacier ice is contained in Antarctica
85%
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what factors affect distribution of ice mass distribution
latitude
altitude
aspect
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why is latitude a factor in ice mass distribution
particularly important for polar ice masses. In high latitudes the sun’s rays hits the ground at a lower angle, so the solar energy received has to heat a larger area.
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why is altitude a factor in ice mass distribution
particularly important for alpine glaciers. High altitudes are impacted by the environmental lapse rate (ELR) whereby temperature declines by 1° for every 100m above sea level
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why is aspect an important factor in ice mass distribution
This can determine the amount of snow falling and where it settles. In the northern hemisphere, north and east facing slopes are both more sheltered and shadier
75
periglacial meaning
The term ‘periglacial’ has previously been used to refer to cold environments on the margins of glaciers, today though the term is widely used to refer to non-glacial cold environments, which are characterised by periods of extreme cold, dry conditions.
76
what are periglacial environments also referred to as
the tundra – a term describing the treeless vegetation of dwarf shrubs, grasses, lichens and mosses.
77
what is permafrost
permanently frozen ground where subsoil temperatures remain below 0°C for at least two consecutive years.
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what % of the earth experiences periglacial conditions
20%
mainly in the northern hemisphere. During the Pleistocene glacial periods, this was higher at 33% and at much lower latitudes than today
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what are the 3 types of permafrost
continuous
sporadic
discontinous
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continuous permafrost
forms in the coldest areas of the world where mean annual temperatures are below -6°C. It is found at the highest latitudes. It can extend downwards for hundreds of metres.
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sporadic permafrost
occurs where the mean annual temperature is only just below freezing and permafrost cover amounts of less than 50% of the landscape
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discontinuous permafrost
is shallower and permanently frozen ground is fragmented by patches of unfrozen ground (talik). The surface layer of the ground melts during the summer months.
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what factors affect periglacial distribution
climate
proximity to water bodies
slope angle and aspect
ground surface
vegetation cover
84
climate
temperature and moisture determine the presence or absence, depth and extent of permafrost
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proximity to water bodies
lakes tend to be warmer so remain unfrozen
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slope angle and aspect
influencing solar radiation and therefore melting, freeze-thaw and wind
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ground surface
rock and soil types can determine degree and depth of permafrost
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vegetation cover
can insulate the ground
89
what processes shape periglacial landscapes and landforms
freeze thaw weathering
soliflvution
nivation
frost heave
groundwater freezing
ground contraction
aeolian action
meltwater erosion
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what is freeze thaw weathering
when water freezes in the cracks and joints of rock, it expands by 10%of its volume, weaknening the rock and causing disintergration through repeated freeze thaw cycles
process is also known as frost action or frost shattering
91
what landform does freeze thaw weathering create
an accumulation of frost shattered rock fragments known as a blockfield when on a flat surface and scree when on a slope
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solifluction
the downslope movement of the saturated active layer under the influence of gravity
known as gelifluction when it occurs over impermeable permafrost
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what periglacial landform does solifluction create
a tongue shaped feature at the foot of a slope knwon as a solifluction lobe
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nivation
a combination of processes weakens and erodes the ground beneath a snow patch
these processes include freeze thaw weathering solifluction and meltwater erosion
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what landform does nivation create
rounded nivation hollows formed in upland areas
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frost heave
the freezing and expansion of soil water causes the upward dislocation of soil and rocks
as the ground freezes, large stones become chilled more rapidly than the soil
water below such stones freezes and expands, pushing the stones upwards and forming small domes on the ground surface
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what landform does frost heave create
on flat ground stone polygons formed as the large stones settle around the edges of the domes
on slopes stone stripes formed as the stones moved downhill
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what is groundwater freezing
where water is able to filter down into the upper layers of the ground and then freeze
the expansion of the ice causes overlying sediments to heave upwards into a dome which may rise as high as 50m
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what landform is created by groundwater freezing
an ice cored dome called a pingo
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ground contraction
when dry areas of the active layer refreeze, the ground cracks and contracts
ice wedges will form when meltwater enters the crack during summer and freezes at the start of winter
repeated thawing and refreezing of the ice widens and deepens the crack, enlarging the ice wedges
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landform created by ground contraction
large scale polygonal patterns on the ground surface knwon as ice wedge polygons
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aeolian action
due to limited vegetation cover the wind is able to pick up and transport the fine dry sediment from the ground surface
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landform created by aeolian action
extensive accumulations of wind-blown deposits known as loess
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meltwater erosion
during the short summer, thawing creates meltwater which erodes stream or river channels
refreezing at the onset of winter causes a reduction in discharge and sediment deposition in the channel
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landforms created by meltwater erosion
braided streams with multiple channels separated by islands of deposited material
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periglacial landforms
blockfield
solifluction lobe
nivation hollows
stone polygons
pingo
ice wedge polygons
loess
braided stream
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ice wedges
When permafrost contracts under extremely low temperatures it cracks.
During summer months, meltwater enters cracks in the ground.
During winter this meltwater freezes, forcing the crack to widen.
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patterned ground
The landforms are formed by a series of movements resulting from frost action.
Frost can push sediment upwards as well as outwards.
Larger sediments roll out to the outside of the pattern, leaving finer sediments in the middle
Mass movement can also cause stone nets and stripes – beyond a slope of 30°, these ground features no longer occur
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pingo
They are ice core mounds between 30-70m in height and 100 – 500m in diameter.
They can either be conical (cone shaped) or elongated
In the summer when the pingo ice core melts, it’s centre collapses to form a central dip or depression – this can sometimes be filled with water.
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where are open system pingos found
Found in discontinuous zone of permafrost or valley floors
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open system pingos
hydrolic pingos/east greenland type
Freely available groundwater is drawn towards the expanding ice core, so the pingo grows from below the ground.
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where are closed system pingos found
Associated with low-lying flat areas and only form in continuous zones of permafrost
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closed system pingos
They form from downward growth of permafrost
On the site of small lakes, groundwater can be trapped by freezing from above and by the permafrost below as it moves inwards from lakeside
Subsequent freezing and expansion of the trapped water pushes the overlying sediments upwards into a pingo form
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loess
Many periglacial areas are characterized by extreme aridity because most of the water is frozen and not available for plant growth.
The absence of vegetation provides abundant opportunities for wind action
Cold, strong winds pick up large amounts of material and redeposit it far from its source
In north-west China loess cover large areas and in some places are over 300 metres deep
Similar processes occur in the Gobi Desert today, forming loess in northern China – meaning this Aeolian process is not unique to periglacial environments
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how is glacier ice formed
Glacier ice is primarily formed from compacted snow, with smaller contributions from other precipitation such as hail and sleet, which freeze directly on top of or inside the glacier.
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how is neve or fern formed
Snow falls and collects on the glacier. Fresh layers of snow fall each day and build up.
As snow becomes compacted it starts freezing together becoming quite granular – this is called granular snow
As the granular snow becomes increasingly compressed it forms névé or firn
As the snow layers increase and the process continues and layers become deeper. The névé (or firn) transforms into glacier ice
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what affects rate of accumulation and ablation
Amount of precipitation
Average temperatures
Levels of solar insolation
Levels of wind speeds
Latitude
Continentality
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what is continentality
distance from the sea (seas/water are warmer influencing temperature around glaciers/permafrost)
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how does a positive regime affect glaciers
A positive regime is when the glacier is increasing in mass i.e. a usual situation would be accumulation exceeding ablation during the winter period.
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how does a negative regime affect glaciers
A negative regime is when the glacier is decreasing in mass i.e. when ablation exceeds accumulation during the summer. Glacier begins to think/shrink
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how do long term trends affect glacier health
Trends can be summarised over a decade from annual net balance
These long term trends determine the ‘health’ of a glacier and whether it will significantly advance or retreat and if thinning/retreating contributes to increased concerns over global sea level rises
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what % of the worlds ice masses are experiencing 'rising trends' in their net negative balances
75%
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what happens if their are changes in the level of inputs (accumulation) of a glacier
may cause instability within the glacial system
The system naturally responds to this instability in the form of feedback cycle
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what happens if the glacier system is balanced
inputs are the same as outputs, this is an equilibrium
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how does a negative feedback system act
acts to minimise the effect of new inputs in order to regain stability and equilibrium
E.g. if there is more snowfall, the glacier would advance (grow) meaning more ice would enter the ablation zone so more snowmelt would occur
This would mean that a balance would be gained whereby the input of snowfall would equal the output of snowmelt
The system remains balanced
126
how does a positive feedback system
A positive feedback cycle amplifies the effects of an input which would cause a shift in the system
E.g. if a glacier has a positive mass balance and the glacier surface area is increasing, there will be an increase in ice albedo. This will cause a further reduction in air temperature, thus increasing accumulation and initiating a positive feedback cycle in which the glacier will continue to advance (this works the other way round too
The system will not be balanced
127
whats a warm based glacier
occur in high altitude areas outside the polar regions e.g. the Alps. The temperature of the ice is often close to zero and mild summer temperatures cause melting
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whats a cold based glacier
These occur in polar glacial environments such as Greenland and Antarctica. These glaciers are frozen onto the bedrock below and melting only occurs on the surface in the summer months
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pressure melting point
This is the temperature at which the ice is on the verge of melting
On the surface of the glacier the PMP is normally 0°
However this can be lower within a glacier due to the pressure (weight of the glacier)
This means that at the base of a glacier, ice can melt at below 0°C, allowing the ice to move with the help of melt water even if the air temperature is below freezing point
130
movement of cold based glaciers
Not affected by pressure melting point (too cold)
Polar (cold based) glaciers are frozen onto bedrock and only move under the influence of one process called Internal Deformation
n a polar glacier the ice crystals cause movement in two ways
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in a polar glacier what are the two ways ice chrystals move
inter granular movement
intra granular movement
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inter granular movement
individual ice crystals slip and slide over each other
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intra granular movement
ice crystals deform due to stress within the ice and eventually moves downhill under the influence of gravity.
134
movement of warm based glaciers
Temperate (warm-based) glaciers reach the pressure melting point and therefore produce a great deal of meltwater, which lubricates and increases the rate of movement by a number of processes called basal slip
Basal slip can be subdivided into three processes: creep and regelation; extending and compressing flow; and surges
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how do temperate (warm based) glaciers move
move by basal slip and internal deformation
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how do polar (cold based) glaciers move
move by internal deformation
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basal slip
occurs when the base of a glacier is at the pressure melting point, which means meltwater is present and acts as a lubricant, enabling the glacier to slide more rapidly over the bedrock
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what further porcesses can basal slip be divided into
creep and regelation
extending and compressing flow
surges
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creep and regelation
basal slip is enhanced by obstacles on the valley floor
a large bedrock obstacle causes an increase in pressure which makes the ice plastically deform around the feature (creep)
smaller obstacles will cause pressure melting, increasing ice movement by basal slip
the ice refreezes on the downglacier (lee) side of the obstacle
the process of melting under pressure and refreezing is known as regelation
140
extending and compressing flow
over steep slopes the rate of basal slip will increase and the ice will accelerate and thin
this is known as extending flow
over shallower slopes basal slip slows and and the ice decelerates and thickens, knwon as compressing flow
141
surges
in these short lived events a glacier can advance substantially moving up to 100 times faster than normal
they have various causes (eg earthquakes) but most common is enhanced basal sliding triggered by the build up of meltwater at the ice-rock interface
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internal deformation
when the weight of the glacier ice and gravity causes ice chrystals to deform so the glacier moves downslope very slowly
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what factors affect movement of glaciers
altitude
gravity and gradient slope
ice mass/thickness
rock type
ice temperature
meltwater
144
altitude
affects precipitation and temperature. Greater precipitation and lower temperatures increase the supply of snow and ice, and so its mass balance
145
gravity and gradient slope
Gravity causes ice to move; the steeper the gradient, the faster it flows.
146
ice mass/thicnkess
the heavier/greater the mass the greater the pressure in the ice which causes faster movement
147
rock type
if rock is permeable then meltwater may percolate through, slowing the movement of the glacier. If rocks are impermeable there will be more meltwater, causing the glacier to more quicker
148
ice temperature
Colder ice moves slowly as it does not deform as easily and it stays stuck to the bedrock
149
meltwater
the more meltwater there is the faster the movement as basal slippage increases.
150
what are the four glacial processes
erosion
entrainment
transport
sedimentation
151
more glacial processes
plucking/quarrying
abrasion
crushing
basal melting
152
plucking/quarrying
freeze thaw weathering with basal melt water
153
abrasion
rocks being transported scratch bedrock
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crushing
direct fracturing of weak bedrock by the weight of the glacier, producing large angular rocks
155
basal melting
meltwater causes fluvial erosion processes such as abrasion, hydraulic action, attrition and corrosion
156
glacial landforms created
cirque
arete and pyrimidial peak
hanging valley
roche Mountonee
knock and lochan
crag and tail
glacial trough (U-shaped valley)
157
cirque
A large rounded hollow high on the mountain side, eroded and deepened by plucking and abrasion
158
eg of a cirque
Cwm Idwal, Snowdonia
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arete
An arête is a sharp ridge between two cirques.
160
pyrimidial peak
A pyramidal peak is a pointed mountain peak between three or more cirques
161
eg of an arete
Striding Edge, Lake District
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pyramidial peak
A pyramidal peak is a pointed mountain peak between three or more cirques
163
eg of a pyramdial peak
The Matterhorn, Alps
164
hanging valley
Formed from small tributary ‘V-shaped’ or ‘U shaped’ valleys high above the main glacier floor
165
eg of a hanging valley
Pistyll Rhaeadr, Berwyn Mountains, Wales
166
roche mountonee
Bare rock on the valley floor with a smooth ‘stoss’ (up-side valley) and a jagged ‘lee’ (down-side valley.
167
eg of a roche mountennee
Lembert Dome, Yosemite National Park, California
168
knock and lochan
A lowland area with alternating small rock hills (knock) and hollows, often containing small lakes (lochan)
169
eg of a knock and lochan
Shetland Islands, Scotland
170
crag and tail
A large mass of hard rock forms a steep ‘stoss’ with a gently sloping tail of deposited material
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eg of a crag and tail
Castle Rock, Edinburgh
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glacial trough (U-shaped valley)
A steep-sided, flat-floored, straight valley
173
eg of a glacial trough
Nant Ffrancon Valley, Snowdonia.
ribbon lake-: Llyn Ogwen
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what are the different scales of glacial landforms
macro scale
meso scale
micro scale
175
macro scale
Large scale landforms, Around 1km or greater in size and form the major elements in a glaciated highland landscape
176
meso scale
Medium-scale landforms largely found within macro features e.g. found on a valley floor.
177
micro scale
Small-scale landforms less than 1 m long e.g. striations
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what are the 4 distinct types of glaciated landscapes
upland
lowland
active
relict
179
upland
those at higher altitudes in hills and mountains
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lowland
Those at lower altitudes on valley floors and coastal plains
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active
Currently experiencing glaciation, active glacial processes and landform development.
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relict
Are not currently characterised by glaciers but feature fossilised glacial landforms due to past glaciation
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what are the 4 glacial environments
sub glacial
ice marginal
proglacial
periglacial
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subglacial
the environment beneath the glacier ice
subject to immense pressure from the overlying weight of the ice; beneath temperate glaciers there may be large volumes of meltwater
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ice marginal
environments at the edge of the glacial ice where a combination of glacial and fluvioglacial processes occur
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proglacial
environments located at the front of a glacier, ice cap or ice sheet and dominated by fluvioglacial processes
187
periglacial
environments near glaciers are dominated by freeze-thaw processes, but not charachterized by moving ice
188
supraglacial
Mainly weathered material carried on top of the ice.
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englacial
Formally supraglacial material, but now buried by fresh snow and carried within the ice.
190
subglacial
Material carried below the ice
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what is till
Material deposited underneath ice
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what are erratics
Till could have been transported a long distance and deposited in areas with different geology. These contrasting rock fragments are known as erratics
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what is a moriane
generic term for landforms associated with the deposition of till from within, on top of, and below a glacier.
194
what are glacial depositional features
erratics
moraines
drumlins
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what are the 4 types of moraines
medial
lateral
recessional
terminal
196
medial moraine
This is formed when lateral moraines from two merging glaciers join up – leaving a line of debris in the centre of the combine glacier’s flow. As the combined glaciers melt, the medial moraine is deposited to form a low ridge
197
lateral moraine
A high and almost symmetrical ridge, formed along the outer edge of a glacier. It can be several metres high. Formed from freeze-thaw on the valley sides that causes the material to fall onto the edge of the glacier below
198
recessional moraine
Retreating glaciers may experience periods of stability, when a secondary ridge of sediment forms at the snout. This has the same characteristics as terminal moraine, but doesn’t mark the furthest extent of the ice
199
terminal moraine
A ridge of sediment piled up at the furthest extent of an advancing glacier. It commonly appears as a line of hills (rather than a solid ridge) due to the erosive action of meltwater streams from the retreating glacier
200
what is a drumlin
A typical drumlin is an oval or ‘egg-shaped’ hill made up of glacial till and aligned in the direction of ice flow
201
how big are drumlins
They can vary in size but are commonly between 30-50 metres high and 500-1000 metres long
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where are drumlins found
They usually occur in clusters or ‘swarms’ on flat valley floors or lowland plains and forming ‘basket of eggs’ topography
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how are drumlins thought to be formed
controversy over their formation. Although some have a rocky core (with sediment moulded around it), most do not. Some partly consist of fluvial sediments as well as glacial till, suggesting that meltwater played a part in their formation
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how big are erratics
Erratics are so called because they are of a different rock type to the bedrock in they sit on
Huge erratic boulders weighing up to 16,000 tonnes were carried over 300km from the Canadian Rockies to the plains of Alberta by the Cordilleran Ice Sheet
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lowland depositional features
till plain
lodgement till
ablation till
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till plains
Formed when a large section of ice detaches from the main body of the glacier and melts. The suspended debris will be deposited and form a large plain of unsorted till
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lodgement till
Lodgement is a process that occurs beneath the ice mass when subglacial debris that was being transported becomes ‘lodged’ or stuck on the glacier bed
Lodgement occurs when the friction between the subglacial debris and the bed becomes greater than the drag of the ice moving over it
commonly associated with glaciers carrying huge loads of debris and where the glacier is very slow moving, if not static
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ablation till
Ablation till is material that has been dumped as the glacier melts and thaws. It can include material that has travelled within the glacier at any point i.e. supraglacial; englacial; and subglacial
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what is a till fabric analysis
used to indicate the direction of a former glacial advance
Material tends to lie parallel to the direction of ice movement
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how does glacial meltwater behave
in the same way as a river
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whats a glacial outburst
Occasionally, a huge amount of meltwater becomes trapped, either beneath the ice or as surface lakes. When these eventually burst (called a glacial outburst), the surging meltwater has the power to carve deep channels or gorges
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fluvio glacial processes
Meltwater travels in the same places material travels in a glacier system: supraglacial; englacial and sub-glacial channels
Meltwater discharged from supraglacial and sub-glacial streams is higher during the summer months
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what are the two types of fluvio glacial landforms
ice contact features
pro-glacial features
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fluvio glacial landforms
kame
sandur
esker
kettle hole
kame terrace
meltwater channel
proglacial lake
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compared to glacial deposits (till) what are fluvioglacial deposits like
Generally smaller due to energy of meltwater
Generally smoother and rounder
Are sorted horizontally
Stratified vertically with distinctive layers which reflect either seasonal or annual sediment accumulation
glacial till is more angular, poorly sorted and non-stratified
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fluvial deposit charachteristics
stratification
sorting
imbrication
grading
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cultural value
relates to the ideas and behaviour of society.
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environmental value
biotic (living) and abiotic (non-living) things around us
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environmental values of glaciated landscapes
water cycling
climate control
carbon cycle
weather system control
fragile ecosystems
carbon sequestration
genetic diversity
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cultural value of glaciated landscapes
spiritual and religous inspiration
leisure and recreation opportunities eg skiing
native people with distinct cultures
scientific research ie core analysis
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econmic value of glaciated landscapes
The majority of active and periglacial landscapes can be classified as ‘true wilderness’ as they are remote, possess a harsh physical environment and carry little or no population
Relict landscapes on the other hand e.g. the Lake District, are often more densely populated as they provide many more opportunities for economic development and employment
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factors of economic importance of glaciated landscapes
farming
forestry
mining and quarrying
tourism
hydroelectricity
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farming
In developing country’s, mountainous regions suffer from limitations in transport links, access to essential supplies and markets and employment opportunities In countries such as Nepal, Bolivia (Altiplano) and Ethiopia (Bale Mountains), the highlands are largely inhabited by indigenous communities who gain their living from subsistence farming (growing crops to feed themselves).
In Bolivia 70% of people live in the High Andes, growing crops such as potatoes, quinoa and beans to feed themselves, as well as rearing llamas and alpacas, yet they only earn 30% of the country’s GDP. Almost all of the 60% of Bolivia’s population living below the poverty line are indigenous Indians living in the Altiplano of the High Andes.
n Alpine areas in developed countries, the agriculture in upland glaciated regions is primarily pastoral (livestock) because of the above-average precipitation, rugged terrain with steep slopes and stony, shallow soils, which together make growing crops very difficult. In the truly Alpine areas a traditional farming system is used to take advantage of the seasonal climate cycle – in summer animals are grazed at high altitudes on Alpine meadows, which become free from snow and provide high quality grass – at the same time, the grass in the valley bottom can be made into hay for winter feed which is used when the animals are brought down in the winter.
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tourism
tourist industry has seen a large increase in recent decades, which has brought many economic benefits to mountainous regions, with visitors attracted to the spectacular scenery of both present-day and relict glaciated landscapes. A huge range of year-round, outdoor activities are possible in Alpine landscapes such as hill walking, climbing, mountaineering and skiing. Thanks to long haul travel and modern communications, mass tourism is not only affecting traditional areas such as the Swiss Alps but also affecting more remote polar regions in the Arctic (Alaska, Greenland and Iceland) and Antarctic (South Georgia and the Antarctic Peninsula). Other developing areas are: Everest base camp and ascent, Nepal; Franz Josef and Fox Glaciers, New Zealand for guided walks, heli-rides and heli-skiing on the glaciers; and Mer de Glace, Chamonix French Alps to get the cable car to Aiguille du Midi for glacier viewing and hiking as well as visiting the ice cave beneath the glacier
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forestry
Upland areas are being used increasingly for forestry due to the difficulty to use the land for hill farming. In the UK this is carried out by the Forestry Commission and private investors , with the main type of tree being non-native, quick growing conifers such as Sitka spruce, grown for softwood timber, wood pulp and even paper. Conifers tolerate harsh climates and acidic soils that would not be suitable for other land uses
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mining and quarrying
Glacial erosion plays an important role in removing regolith (loose overlying soil)and vegetation to expose economically valuable rocks. In many active or relict areas there are mines ad quarries of mineral deposits and ores, as well as rocks such as slates as many of the glaciated mountains are made from igneous and metamorphic rocks
n lowland areas, outwash deposits from the Pleistocene Ice Sheets provide a very important source of sand and gravel for the building industry, pre-sorted by meltwater into sands and gravels to be sold as aggregates, making them very useful for making concrete
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hydroelectricity
Hydroelectric power (HEP)is a major use of water derived from glaciers. Both Norway and New Zealand derive over 90% of their electricity from this source. In most cases either a natural ribbon lake or a dam and reservoir in a glaciated valley provide HEP
Switzerland has over 500 HEP stations producing some 70% of its electricity. Clearly HEP is a renewable ‘green’ source, although there are issues with both the reliability of water supply and environmental concerns over damming rivers. In mountain settlements in developing nations, such as Nepal and Bolivia , micro-hydros can revolutionise the quality of life in many villages
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arctic tundra (periglacial environment) conditions
Tundra plants have to adapt to low temperatures, drying winds and snow blasts in winter blizzards
The Arctic is a harsh environment, with long, dark winters and short summers. The growing season only lasts for 3 months – when average temperatures rise to 12˚C
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arctic tundra ecosystem
Vegetation occurs in periglacial areas that aren’t covered in ice, both in high latitudes (Arctic) and high altitude (Alpine), covering around 8 million km2 of the Earth’s surface
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vegertation in lower arctic latitudes (70-75N)
Continuous cover of ground vegetation including sedges and mosses in the wetter hollows and scattered dwarf trees (elder and birches) on the lower ridges.
Elsewhere heaths, grasses and rapidly flowering plants flourish
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vegetation cover in higher arctic latitudes (75-80N) and higher altitudes
Polar desert conditions prevail
However, a small range of plants survive in favourable sheltered locations such as the purple saxifrage and the arctic poppy
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acrtic tundra ecosystem in summer
The surface layer of permafrost melts to form bogs and shallow lakes
These attract insects, which in turn attract migrating birds
The tundra also supports a variety of larger animals such as the Arctic Fox, grey wolves, snow geese and musk oxen
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arctic tundra ecosystem in winter
Temperatures fall well below freezing
Plants – which many animals rely on for food – must survive under the snow to re-remerge and flower quickly once temperatures rise again in the spring
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how is the water cycle maintained through the tundra
Water storage – approximately 75% of all the freshwater of the world is locked up in ice – glaciers contain nearly 2% of all water overall
During the summer months, meltwater provides a water source for settlements down stream, creating storage in lakes and rivers. For example, the Alps known as the ‘water towers of Europe’ transport an average of 216km3 of water a year to nearby regions
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what is arctic amplification
The Arctic region is now warming twice as fast as the global average, this phenomenon is known as Arctic Amplification
This is a positive feedback loop
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how is the carbon cycle maintained through the tundra
The extensive areas of permafrost and tundra peat are major areas for soil carbon and methane storage – as much as 14% of the Earth’s carbon is stored in permafrost
Currently the Arctic remains a carbon sink – meaning it absorbs more carbon than it releases. This happens because the cold climate limits decomposition of organic matter
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how can periglacial environments create a negative feedback loop for the carbon cycle
Not all scientists agree that the melting permafrost will release carbon dioxide and methane
As permafrost thaws, carbon could remain in the soil to be used by new vegetation
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how can periglacial environments create posotive feedback loops for the carbon cycle
as permafrost thaws it could release these gases, contributing to atmospheric greenhouse gas levels
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what did scientists in Alaska's Arctic Long Term Ecological Research Site find in relation to the carbon cycle
set up artificial warming plots over 20 years, and found increased growth of shrubs at the expense of mosses, sedges and grasses
Measurements show no change in the amount of carbon below ground, which means that carbon released due to melting permafrost has been balanced by carbon in puts into the soil as a result of more plant growth and the decomposition of plant litter
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natural and human threats to glaciers
Both current glaciated and relict upland regions are hazardous
Human activities can also degrade and damage fragile glacial and periglacial environments and ecosystems
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natural threats
rock falls
avalanches
debris slides
glacial outburst floods
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human threats
leisure and tourism
reservoir construction
urbanisation
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avalanches
An avalanche exists where sheer stress exceeds sheer strength of a mass of snow located on a slope. While avalanches tend to follow well-known tracks and can often be predicted, they are nevertheless a significant hazard, usually killing around 200 people per year with most of these deaths in the Alps and the Rockies
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glacial outburst floods
A glacial outburst flood is a powerful flood caused by the sudden discharge of a subglacial or ice moraine dammed lake. There is potential for an outburst flood whenever meltwater collects behind an ice or moraine obstruction. These very large floods are a huge threat to people and property in inhabited mountain valleys
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leisure and tourism
Resorts in glaciated regions, particularly ski resorts attract large amounts of people each year, for example Zermatt in Switzerland attracts 2 million visitors per year. At the height of the ski season the resident population in Zermatt can be as high as 35,000. This creates a huge demand for energy and water and threatens environmental degradation due to urbanisation, increased noise and vehicle emissions and the expansion of ski areas
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reservoir construction
As glaciers store 69% of the world’s fresh water, many countries are tapping into this source, especially due to fears of summer water shortages due to glacial retreat. Within the Chinese side of the Tibetan Plateau there are nearly 37,000 glaciers, containing the largest volume of ice outside the polar regions and also giving birth to many rivers across Asia including the Ganges. Almost 2 billion people in more than a dozen countries depend on these ice fed rivers. China aims to build 59 reservoirs to capture and save the glacial run off for the future. Reservoir construction would require intense, heavy machinery and the clearing of land as well as irreversible damage to wildlife
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urbanisation
Traditionally, the development of settlements in relict glaciated areas has been for agricultural purposes, however in polar environments this is not the reason. Settlements in polar regions tend to be surrounded by nothing and tend to be built for resource exploitation purposes including whaling, mining and fishing. Inevitably there are issues with pollution and toxic waste as well as conflicts occurring between these outsiders and the native people. Regular contact from outsiders has reduced the chances of survival of traditional culture groups e.g. the Inuit in Greenland
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what 4 problems does rising visitor numbers in more extreme environments cause
soil erosion
deforestation
trampling
landslides
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what type of landscape is the lake disrtict
a relict glaciated landscape
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how many footpaths are there in the lake district
almost 200 miles to support the 16 million visitors each year
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how is the lake district under threat
both the landscape and ecology of the Lake District are fragile and under threat from overuse.
Activities such as walking, climbing and camping can lead to footpath erosion, trampling and littering, which challenges the areas resilience
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how can walkers create issues in the lake district
Walkers destroy vegetation and compact soil, which reduces infiltration rates
The exposed soil is also more easily washed away by heavy rain (rainfall is high in the Lake District)
Gullies may then form along footpaths, which channel even more water and cause further erosion.
When walkers try to avoid badly eroded sections of footpath, they inevitably end up widening them
Increased storms (as a result of climate change) are likely to worsen the problem
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how many visitors does the lake district have each year
over 16 million
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how does the local economy of the lake district benefit well from tourism
local economy benefits hugely from this influx, for example in 2014, visitors spent about £1.1 billion, which helped support local businesses
Many services that benefit tourists also benefit local people e.g. better public transport and roads). Some of the money tourists bring in is also used to protect the environment that visitors come to see.
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how many jobs does tourism provide in national parks
Tourism provides over 16,000 jobs in the National park, as well as boosting the local economy through the multiplier effect
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what is the multiplier effect
the ways in which development creates an upward spiral, so that investment and spending both increases employment and leads to further economic activity.
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what is the sagamartha national park
includes Mount Everest. It’s an active glaciated area with a fragile ecosystem. It is a destination for mountain tourism and is home to over 6000 Sherpa* people. It has an enormous environmental and cultural value, but faces a range of threats.
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what are the threats to the sagamartha national park
tourism
climate change and shrinking glaciers
avalanches
deforestation and landslides
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why has deforestation been caused in sagamartha national park
farming
use of firewood as fuel
clearing forested areas to build roads, reservoirs etc
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what has happened in sagamartha national park as a rresult of deforestation
less than 30% of Nepal forests remains
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what are the consequences of deforestation in sagamartha national park
Loss of wildlife habitats and biodiversity
Erosion of exposed soils leading to infertile soil as nutrients are washed away
Increased risk of landslides
Disruption of the water cycle
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whats happened with tourism in sagarmatha national park
tourist industry in the Park is largely in the hands of the Sherpa people
Tourism has boosted the local economy, leading to improved standards of living, better healthcare, education and infrastructure
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environmental damage and socio economic change in sagamartha national park as a result of the tourist industry
Footpath erosion and the construction of illegal trails
Water pollution
Problems with waste disposal
Increased demand for forest products as well as new hotels and lodges
Changes to the Sherpa way of life
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what is happening to most of the worlds current glaciers
are retreating
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how much ice mass have glaciers on the eastern slopes of the rocky mountains lost
between 25 and 75% of their mass since 1850.
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whats happened to glaciers in Tajikstan, central asia
1949 in Tajikistan, Central Asia, glaciers covered 18,500km2 of land: in 2012 they covered only 11,000km2, a decrease of 38%
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what % of the himalayan glaciers are in rapid retreat
85% of the Himalayan glaciers are in rapid retreat: e.g. the Khumba Glacier (one of the highest in the world at the base of Everest) has retreated over 5km since 1953.
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areas in Peru and Bolivia covered by glaciers shrunk by what % over the last 30 years
25%
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what are the 4 changes to the hydrological cycle that could impact glacial recession
meltwater
river discharge
sediment yield
water quality
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do receeding glaciers produce more or less meltwater
more
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what affect does increasing meltwater have on rivers
lot of cases glaciers feed rivers, for example rivers in Asia such as the Mekong (flows through Laoes, Thailand, Vietnam, China, Cambodia and Myanmar), Yangzte (China), Brahmaputra (India), Ganges (India) and Hwange Ho (China) are all fed by Himalayan glacial meltwater. An increase in meltwater means a loss of a steady supply in the future, which for the rivers mentioned could have huge implications for China and India’s populations. In India the reduction of glacial meltwater flowing into the Ganges-Brahmaputra system is likely to result in at least 500 million people facing water shortages, with nearly 40% of India’s irrigated land being affected.
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effect of increasing meltwater
increase in meltwater could cause an increase in glacial outburst floods as deposited moraine can create glacial lakes which continue to increase in size until the moraine wall collapses, causing a catastrophic flood
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what did a glacial outburst flood cause in 1985
a 10-15 metre high surge of water and debris to flood down the Bhote Koshi and Dudh Koshi rivers in Nepal – destroying amongst many things the Namche Small Hydro Project
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how is river dishcarge effected by meltwater
Due to an increase in meltwater and the potential for more glacial outburst floods, river discharge will inevitably also be affected
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why do dicharge and meltwater increase during the summer
During the summer months where glacial ablation is at the highest during the year, meltwater and therefore discharge will increase – which will also increase sediment yield. An increased amount of sediment would mean water would increasingly become cloudy and sediment-laden, affecting the water quality.
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whats a stakeholder
People who are affected by or have an interest in something
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stakeholders for glaciated landscapes
conservationists
local and regional governments
global organisations
NGO's (non-governmental organisations)
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how are the challenges and conflicts posed by glacial landscapes managed
using a spectrum of management approaches
left end- do nothing total exploitation
middle-sustainable exploitation
right end- total protection no exploitation
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total exploitation
This is maximum economic exploitation without any protection of the natural environment. This is often the preferred approach of business and industry where there are large reserves of minerals, metals or fossil fuels that require open cast mining or large scale infrastructure. It causes significant conflict with conservationists and native people, who often depend on the natural landscape and live in harmony with it.
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eg of total exploitation
There are concerns that the Russian government will favour total exploitation of the Yamal Peninsula for gas, which could result in considerable environmental and cultural degradation.
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sustainable exploitation
This approach aims to find a balance between the need for resource exploitation and economic growth, and the need to conserve the natural environmental and indigenous cultures. It aims to take into account the interests of all stakeholders to reduce conflict, but this means it relies on compromise, which is often difficult to achieve.
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eg of sustainable exploitation
The Alpine Convention is a legislative framework that aims to achieve sustainable management of the European Alps.
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total protection
The aim is this approach is to completely conserve the natural environment, maintaining pristine conditions; the only form of exploitation may be limited scientific research and, possibly, carefully regulated tourism (such as eco-tourism). This approach is usually supported by conservationists, but may causes conflict with local people, businesses, industries and governments who wish to increase economic productivity through resource exploitation. Therefore this approach is most feasible in remote locations, which are either uninhabited or sparsely population, for example Antarctica, The North East of Greenland National Park and the Arctic National Wildlife Refuge in Alaska. It is enforced by national or international legal frameworks, such as the Antarctica Treaty.
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eg of legislative frameworks on an international scale
The Antarctic Treaty
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the antarctic treaty
Established Antarctic as a continent of peace and science, and set all pre-existing territorial claims of seven countries to one side.
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how many countries signed the Antarctic treaty
Signed by 60 countries, representing 89% of the world’s people
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positives of the antarctic treaty
Protects effectively by strict rules
No exploitation of the land
Support from 60+ countries
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negatives of the antarctic treaty
Disagreements could occur
Some countries aren’t signed up
More land claimed by some countries than others – more pressure for these countries not to use their ‘chunk’
Tourisms still allowed, trust in travel companies and education of tourists on how to protect area.
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another example of legislative framework on an international scale
The Alpine Convention
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the alpine convention
Part of the sustainable approach is to reduce carbon emissions
E.g. In Arosa, Switzerland an offsetting scheme for carbon emissions has been set up, this is to offset emissions generated by tourists. Tourists fill in a questionnaire
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positives of the alpine convention
Combines multiple countries who are working towards the same goal
Aims to create a balance between exploitation and protection
Tackles climate change
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negatives of the alpine convention
Tourists still allowed to visit area
Not all countries have ratified all of the protocols
Disagreements between communities about the lack of responsibility they have.
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eg of legislative framework on a local level
Zermatt switzerland
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posotives of zermatt switzerland
Car free areas
use of renewable energy
Water reused
Wildlife sanctuaries
Revegetating plants – covered 85% of priority areas
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negatives of zermatt switzerland
Local scale
Feared further degradation due to tourist numbers
Conflict between tourists and local people
Only on a local scale
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