physical part 1 Flashcards
1
Q
glacial definition
A
when there is lots of glaciers in middle and high latitudes.
Lasting tens of thousands of years
2
Q
inter-glacial definition
A
period of less glaciers due to climate warming
10,000 years
3
Q
quaternary definition
A
period of time
the last 2.6 million years
4
Q
when was holocene
A
last 11-12,000 years
5
Q
epoch definition
A
geological time period
smallest category
6
Q
ice age definition
A
period of cold climate
7
Q
cryosphere definition
A
the frozen water part of the Earth’s atmosphere
8
Q
ice sheet definition
A
on top of land
e.g. Antarctica
9
Q
sea ice definition
A
sits on top of the sea
10
Q
where are glaciers found
A
found in the mountains
11
Q
how much of the earth today is covered in ice
A
10%
12
Q
how often are ice ages
A
every 200 - 250 million years
13
Q
what was the last ice age called
A
quaternary ice age
14
Q
extent of ice from Britain from last ice age
A
-upto 2 miles deep
-melted in Britain about 11,500 years ago
-this ice shaped most of out landscape
15
Q
what are system comprised of
A
- inputs
- stores
- throughputs
- outputs
16
Q
are glaciated landscapes open or closed?
and why?
A
open systems
Energy and matter can enter as inout and leave as output
17
Q
stores in a glacier
A
-ice
-water
-debris accumulation
-movement of ice - due to gravity
18
Q
inputs of a glacier
A
-potential energy - height/gravity
-kinetic energy - from wind
-thermal energy - from sun
-precipitation
-deposition, weathering, mass movements, avalanches
19
Q
outputs of a glacier
A
-sediment - deposition and erosion
-calving
-ablation - melting, evaporation, sublimation
20
Q
energy inputs in a glacier system
A
-thermal from sun - evaporation
-gravitational potential energy - ice mass are elevated
-kinetic energy - debris and snow as avalanches
-geothermal heat energy - at base of glacier
21
Q
energy throughputs in glacier system
A
-gravitational energy - ice moves down hill
-frictional heat energy - ice movement - increase temp
-release of latent heat - when meltwater freezes
22
Q
energy stores in a glacier
A
gravitational potential energy - stored in rock
23
Q
what is energy outputs in a glacier
A
when energy leaves glacial system in form of heat
24
Q
material inputs in a glacier
A
precipitation of snow/rock debris
e.g. form avalanche
25
material throughputs in a glacier
movement of snow, ice, meltwater, and rock debris
26
material stores in a glacier
storage of ice, meltwater, and rock debris above, beneath or below the glaciers
27
material outputs in a glacier
water vapour, water, ice, rock debris and Aoelian (by wind) processes
28
Flows of solar energy through the glacial system
-evaporation and sublimation (output)
-without this there would be no snowfall
29
flows of variations in solar energy in a glacial system
determines differences in high latitudes 'v' low latitude glaciers - greater sow accumulation (more glacier)
30
flows of wind energy in a glacial system
importance in role of 'snow blow' and snow formation and at local scale.
31
flows of gravity through a glacial system
provide potential energy. determine flow of kinetic energy as ice/rock debris flows downhill.
32
flows of geothermal energy through a glacial system
influence gravitational energy available - causing uplift.
might also provide meltwater at base of glacier encouraging movement
33
system feedback in glacial system
characterised by feedback.
if [inputs=outputs] then the system is at equilibrium, i.e. glacier stays same size.
glaciers are dynamic equilibrium - 'self regulates'
34
positive feedback definition
a change creates a response in the system reinforces the effect of the original change. - amplifying that change and creating a 'snowball effect' which leads to new state of equilibrium
34
negative feedback definition
system will self-regulate to re-establish stability through counteracting the change and will maintain a state of equilibrium
35
albedo definition
expression of the ability of the earths surfaces to absorb the suns rays
water absorbs more light (lower albedo)
ice absorbs less light (higher albedo)
35
what is the mass balance / glacial budget
the glacier system constantly adjusts to the changes in the balance between accumulation and ablation
36
the balance year for calculating net balance
Time from minimum mass of one year to the minimum mass of next year
37
positive mass balance
when accumulation is greater than ablation.
gain of ice i.e. in winter
results in glacier advancing
38
negative mass balance
ablation is greater than accumulation.
loss of ice i.e. in spring or summer
glacial retreat (maybe)
39
equilibrium in glacier system
accumulation= ablation
glacier remains stable equilibrium
if net balance is negative, it moves under gravity
40
what are the two zones a glacier can be divided into?
accumulation zone
ablation zone
separated by the equilibrium line altitude (balance of inputs and outputs)
41
accumulation zone
where accumulation exceeds ablation
42
ablation zone
where ablation exceeds accumulation
43
factors influencing the growth of ice sheets
- accumulation of snow and ice formation
- climate - cold winter - hot summer
- further snow - gradually snow turn into ice, fern, Neve, glacial ice
- aspect - direction the glacier is facing
44
factors influencing the decay of ice sheets
- ablation
- summer temperature is higher
- outputs exceed inputs
- loss of ice resulting from calving
45
sublimation
when ice changes directly from ice to water vapour without being a liquid.
Specific case of vaporisation
46
temporal differences in mass balance
change
short term variations
long term variations
47
short term variations
instant, day, monthly, year
mass balance varies throughout the year, glaciers typically get more accumulation in winter and more ablation in summer
48
long term variations
100s, 1000s of years
cumulative mass balance is mass of glaciers at stated time, relative to mass at earlier time.
These measurements give us detailed info about climate change
49
what does glacier analysis show
the vast majority of European glaciers are receding, with the rate of recession accelerating since the 1980s
50
precipitation in high latitude areas
high pressure areas/bands with low levels of clouds and low precitipation
51
precipitation in high altitude areas
increase in altitude means clouds may condense and result in precipitation
52
Lithology definition
what rocks are made of
e.g. limestone, granite, basalt, sandstone
53
Cracks in rocks
-more rocks means more easily eroded
-jointing (stress)
-bedding (water build up in between layers)
-faulting (techtonic plate movement)
54
Impact of climate on glaciers?
- wind
- precipitation
- temperature
55
How does wind affect glaciers?
- can carry erosion, transportation, and deposition
- known as aeolian processes
- can shape glaciated landscapes
56
How does precipitation affect glaciers?
-major input
- determine glacial mass balance
- vary seasonally
57
How does temperature affect glaciers?
- if temp rise above 0, there will be increase in ablation and higher outputs (mainly in summer months
- high latitude - temp might never rise above 0
58
Joints and faults
a fault is due to techtonic movement
joint is due to stress
59
Impact of geology on glaciers
- lithology - refers to physical and chemical composition of rock
- structure - properties of individual rock
60
impact of latitude on glaciers
-high latitude - cold dry climate, little seasonal variation - larger stable ice sheets (Greenland)
-low latitude but high altitude - variable temp and higher precipitation - more dynamic glaciers which shape the glaciers
61
impact of altitude on glaciers
- glaciers can be found in high latitudes due to reduction in temp with altitude
- decreases at rate 0.6C/100m increase in height
62
impact of relief on glaciers
- steeper the relief - the more potential energy (gravity) - glacier will have more energy to move downslope
63
impact of aspect on glaciers
- if slope is facing away from sun, temp might never go above 0C
- less melting
- more likely to have positive mass balance, so glacial advance
64
what is the snowline?
Where snow starts on a mountain varies depending on climate
65
what are the different types of glacier?
- ice sheets
- ice caps
- mountain ice caps
- ice field
- valley glacier
- corrie glacier
- piedmont glacier
- ice shelf
66
ice sheets
- e.g. Greenland and Antartica
- 96% of worlds ice is held here
- largest ice feature
- above 50,00km2
- only two exist
67
ice caps
- e.g. Vatajokull, Iceland
- huge, dome shaped masses of ice on high plateaus
68
Mountain ice caps
- e.g. Kilimanjaro, Tanzania
- mass of ice covering less than 50,00km2 on mountains
69
ice fields
- e.g. Patagonian Ice Field, Chile
- large area of interconnected glaciers with only tallest peaks (nunataks) exposed
70
Valley glacier
- e.g. Athabasca Glacier
- confined by valley sides
- follow course of existing river valley
- typically 10-30km long
71
Corrie valley
- small, on mountains
- N-NE facing
- cover area of 0.5 to 10km2
- gradually erode hollows through glacial erosion
72
piedmont glaciers
- e.g. Malaspina glacier, Alaska
- large lobes of ice
- form when glaciers spread out on reaching lowland areas and escapes confines of the valley
73
ice shelf
- e.g. Ross Ice Shelf, Antarctica
- extensions of ice sheets, reaching out over sea
- can be up to 1000, thick
74
tidewater glacier
a valley glacier that reaches the sea (small iceburgs)
75
iceburg
floating mass of ice thats been calved from snout of glacier
76
outlet glacier
glacier flowing out from an ice sheet, cap or field
77
Glacieret
small mass of ice in hollows, accumulated due to snow drifts and avalanches. Existed for two consecutive summers
78
Tributary glacier
small glacier flow into into a bigger one
79
Ice apron
small, steep, smooth glacial masses that cling to high mountainsides
80
how is snow made
- snow traps air when it falls and has low density - 0.1g/cm3
- snow accumulates and starts to compress. forces air out. Ice formation begins (diagenesis)
81
how long does it take for glacial ice to form in Alaska
within 5 years
82
how long does it take for glacial ice to form on Antarctica
150 to 200 years
83
what is polar
a cold environment, mainly covered in snow
84
what is temperate
a climate with no extreme temperature
85
example of a cold based glacier
Meserve Glacier (Antarctica)
86
characteristics of a cold based glacier
- high latitude - 66°N to 90°N or S of equator
- low relief
- temperates throughout -17°C
- glacier is frozen to the bed
- PMP is not reached so no meltwater
- movement of often a few metres a year
- limited ablation and accumulation - less seasonal variation and high pressure
- cold desert - less than 250mm of precipitation per year
- little erosion due to slow movement
- moves by intergranular flow or laminar flow
87
how do cold based glaciers move
- internal deformation:
intergranular flow
laminar flow
88
characteristics of warm based glaciers
- high altitude - 2000-3000m above sea level
- high accumulation in winter/ablation in summer (relief precipitation)
- basal temp is around 0°C which is PMP
- often steeper gradient
- may move up to 2-3m per day
- powerful erosion
- mainly moves by basal slippage
89
how do warm based glaciers move
basal slippage
90
what does basal slippage in warm based glaciers result in
- regelation slip
- creep
- glacial surge
91
Meserve Glacier (Antarctica) details
- small north flowing glacier in Antarctica
- 7km long
- tongues of the glacier terminate at almost vertical cliff
- basal temperature is -17°C
- silt rich basal layer - give distinct amber colour
- slow movement - 0-few mm a day as frozen to the bed
92
Athabasca glacier (Canada) details
- one of the 6 glaciers which flow out of Columbia ice filed in the Canadian Rockies
- moves at 2-3m per year
- approx 6km long
- 90-300m thick
- basal temp is at PMP
- most visited glacier - as close to the Icefields Parkway
- Retreated overall 1.5km
93
where do glaciers move fastest?
in the centre
94
where do glaciers move the slowest
moves more slowly at the base and sides as the ice might have frozen to the valley base and sides. Obstructions may have created frictional resistance
95
characteristics of ice
- when it's solid / rigid it will crack, forming crevasses
- when under steady pressure it will deform and behave like plastic
96
what is inter - granular flow? ( cold based glacier)
Individual ice crystals re-orientate and move in relation to each other
97
what is laminar flow? ( cold based glacier)
the movement of individual layers with the glacier (between annual accumulation layers)
98
what is regelation slip?
glacier melts to go over an obstacle and then refreezes on the other side (due to pressure)
99
what is creep? (warm based glacier)
if ice encounters a large obstacle on bedrock floor, it's put under increased strain and so deforms plastically and flows or creeps around the obstacle
100
what is bed deformation (warm based glacier)
when ice is carried by saturated bed sediments moving beneath it. The water is under high pressure, carrying the ice above it
101
what is sheer?
pressure from above along with slip
102
what are crevasses a result of?
a) friction between glacier and valley sides and bed
b) tensions within the ice when there is a change in gradient
103
what are crevasses
A deep tensional crack which can form in glacial ice. Rarely more than 30m deep
104
what are the different types of crevasses
- marginal crevasses
- transverse crevasses
- longitudinal crevasses
- radial crevasses
105
Marginal crevasses
Result of friction along valley sides as ice advances
106
transverse crevasses
extend across glacier at steepening of gradient - common at 'ice falls'
107
longitudinal crevasses
valley becomes wider and ice surface widens to fill the valley
Long crevasses
108
how much does water expand when frozen?
8-9%
109
what is frost shattering weathering
- water trapped in rock pores will freeze and expand at very low temperature
- expansion causes stress which causes rock to disintegrate to small bits
110
what is pressure release
- as melting causes a reduction in the weight of overlaying ice, the underlying rock expands
- it fractures parallel to the surface
- these fractures (dilation) are sometimes known as pseudo-bedding planes
111
what is chemical weathering
weathering through chemical reactions/ change can produce weak residues of materials from rock which is then easily removed by erosion
112
when is chemical weathering particularly importanr
when meltwater is present and in contact with rock
113
what are the types of chemical weathering in a glacial environment
- oxidation
- solution
- carbonation
- hydration
- hydrolysis
114
what is carbonation
- carbonic acid reacts with calcium carbonate in rock (limestone) to produce calcium bicarbonate
115
what is oxidation
- minerals in rock react with oxygen
- either O2 in water or air
116
what is hydrolysis
minerals in rock can undergo a chemical reaction when in contact with water.
It's the hydrogen in water that causes this
117
what is solution
any process where a mineral dissolved in water is known as solution
Some become soluble when water is more acidic
118
what is hydration
when water molecules are added to rock minerals, they create minerals of a larger volume
Causes flaking
119
how likely is biological weathering in glacial areas
generally of low significance because plant and animal activity are limited by the low temperatures
120
what are the two types of biological weathering
- tree roots
- chelation (organic acids)
121
tree roots - biological weathering
- the roots grow into cracks / joints in the rock, they exert pressure, forcing the rock apart
122
chelation - biological weathering
- as plant and animal litter decomposes, organic acids are released
- causes soil to become more acidic
- react with minerals and break rock down
123
equilibrium definition
refers to a stable state where inputs and outputs are balanced and the system remains constant over time
124
example of equilibrium in glaciers
if accumulation of snow and ice = ablation, the glacier doesn't advance or retreat.
- the position of the glacier and the equilibrium line are unchanged
125
dynamic equilibrium definition
- refers to a state of balance where the system adjusts to changes in inputs and outputs
- maintaining a long term balance but with fluctuations in the short term
126
example of dynamic equilibrium in glaciers
- over time, glacier adjusts to climate changes
- if temp means more ablation, glacier will retreat temporarily
- if there is more snow, and less melting, it can restabilise
127
example of positive feedback
albedo melting feedback
128
initial change, feedback response, and outcome of albedo melting feedback (positive feedback)
- warmer temperature increase surface melting on the glacier, exposing darker ice or underlying rock
- darker surface absorbs more solar radiation (low albedo), further increasing temp and melting
- melting more, so faster glacial retreat
129
negative feedback example
glacier thinning and reduced ice flow
130
initial change, feedback response, outcome of glacier thinning and reduced ice flow (negative feedback)
- rising temp cause glacier thinning, reducing its mass and volume
- movement decreasing, slowing glaciers flow. limits ice in ablation zone and therefore reduces mass flow
- glacier adjusts to new conditions, stabilizing mass balance
