Glaciation Flashcards
Holocene epoch
last 11,700 years
the Pleistocene epoch
from 11,700 year to 1.8 million years bp
define eccentricity
earths orbit moving from more elliptical to circular over 100,000 years changing the amount of solar radiation received by the sun considering the dominant factor
define obliquity
tilt of the earths axis varies from 21.8° to 24.2° and back again over 41,000 years changing the intensity of sun radiation received at the poles so the greater the tilt, the greater the difference between summer and winter
define precession
the earth wobbles on its axis over 21,000 years causing long-term changes to when different seasons occur along the earths orbit
what is stadial
short sharp drop in global temperates where glaciers re-advance
what is interstadial
a short sharp increase in global temperatures where glaciers retreat
define temperate glaciers
in high altitude areas outside polar regions, water can exist as a liquid below 0, preventing the glacier from freezing to its bed having lots of debris in the basal layer
define polar glacier
occur in high latitudes, particularly in Antartica and Greenland. the glacier remains frozen at the base
difference between continuous, discontinuous and sporadic permafrost
-continuous permafrost is in the coldest parts of the world and can extend downwards hundreds of metres. —-discontinuous is more fragmented and thinner.
-sporadic occurs at margins of periglacial environments and is usually very fragmented and only a few metres thick.
-the biggest difference between them all is their depth as they range from hundreds of metres to a few metres
nivation
the combination of freeze-thaw and meltwater erosion
frost heave
the concentration and cracking of rapidly freezing soils
suction
the migration of sub-surface water to the ‘freezing front’
solifluction
the mass movement of the active layer downslope
freeze-thaw
the 9% expansion of water upon freezing
associated landform of wind erosion
loess
associated landform of solifluction
solifluction lobes
associated landform of nivation
nivation hollow
associated landform of freeze-thaw
block fields, scree
associated landform of frost heave
ice wedges, patterned ground, pingos
associated landform of suction
ice lenses, pingos
external factors that influence rate of accumulation and ablation
temperature, precipitation type and amount, latitude and altitude
what factors influence glacier movement
friction, temperature, gradient and underlying rock
glacial erosional processes
abrasion- where rocks and stones become embedded and are then rubbed against the bedrock and rock faces as the glacier moves
plucking- where rocks and stones become frozen to the base or sides of the glacier and are then tears rocks away as the glacier moves leaving a jagged landscape.
associated glacial erosion processes
freeze-thaw and meltwater
four different glacial landform environments
periglacial, glacial, marginal and proglacial
what is a rouche moutonnees
a small bare outcrop of rock shaped by glacial erosion, with one side smooth and gently sloping(abrasion upslope) and the other steep, rough, and irregular(plucking downslope).
landforms of cirque glacier
cirques, aretes, pyramidal peak
landforms of valley glaciers
u-shaped valleys, truncated spurs, hanging valleys, ribbon lakes
landforms of ice sheet scouring
basins, knock & lochans, roche moutonnees
how does a cirque form
snow and ice accumulate in a nivation hollow where nivation processes enlarge and deepen it
as more ice accumulates over time it compacts into glacier ice and begins to flow- a cirque glacier is formed
what happens during a cirque
freeze-thaw weathering loosens material which is entrained and gathers and sub-glacial basal ice.
the rotational flow of the glacier deepens the hollow through abrasion
whilst plucking of the back wall erodes the cirque backwards, creating a steep, arm-chair shaped hollow. deposition can take place where flow is weakest and a lip can form on the edge of the cirque
how are basins created
created where large ice sheets take advantage of differential rates of erosion of rock, deeply eroding the weaker rock to create basins which are subsequently filled by water
how is knock and lochan created
topology occurs as the ice sheet advances it preferentially erodes through the ice sheet, scouring areas of dense jointing more than areas without joining
The 2 glacial deposition processes
Lodgement and ablation
Define lodgement
Beneath the ice mass, subglacial debris being carried,become lodged, occurs when friction is greater than drag force
Define ablation
Material is deposited as the glacier melts
Upland landforms and characteristics
Moraines- large glacial deposits.
Drumlin-oval or egg shaped hill
Low land landforms and characteristics
Erratics - boulders picked up by ice and deposited
Till plains- an extensive plain
What is supragcacial hydrology
Water on glacier formed by ice melting in summer
Flows off, into a number of cracks similar to ordinary river system.
What is englacial hydrology
Structures in the ice (crevasses), allow water to penetrate in ice
Characteristics of fluvioglacial deposits
Smaller, more rounded, sorted horizontally, stratified vertically
What are kames and kames terraces and how are they formed
K- Material collects within a depression When the glacier melts completely, the material is left on the valley floor. This leaves a mound fine material
Kt-during the summer, meltwater streams are formed at the side of the glacier, which deposit material. a flat, linear deposit of sediment at valley sides
Values of glaciated landscapes
Cultural, economic, environmental, biodiversity, natural systems
2 example environmental values
Maintain a gene pool of wild organisms to ensure genetic variety
Arctic and Antarctic environments are living labs
2 example economic values
Farming, tourism
2 biodiversity values
Tundra covers 8 million km 2
Permafrost increases fragility
how do glaciated landscapes maintain natural systems
75% of all freshwater is locked up as ice
the UN estimates that 40% of the global population could be affected by the changes to meltwater regimes in Asia
Permafrost may currently hold 1500 billion tones of carbon
3 natural threats
Lahars, glacial outburst, avalanches
What is a glacial outburst
A powerful flood, resulting from a bursting subglacial lake
How does tourism affect active temperate environments
Both winter and summer sports put pressure on the environment in the form of various types of pollution, though most resorts attempt to minimise the impacts through renewable energy and recycling.
Human activity threats to upland active and relict landscapes
Resource exploitation- oil in Alaska
Tourism- footpath erosion
Climate Change
Environmental impacts of human activities
Soil erosion (r)
Changes to hydrological cycle (a)
Thawing permafrost (a)
Invasion of species due to warming(a)
Economic impacts of the environmental consequences
Decline in agriculture productivity
Decline in tourism as a result of environmental degradation
Decline in tourism from warming
Increased energy insecurity
Who are the players in management approaches
Local government
National government
Conservationists
NGOs
International organisations
Local people
Describe do nothing on the spectrum of management
Allows economic activity to flourish
Allow cold environments to be exploited for whatever resources
Describe sustainable management on the spectrum of management
Used resources to benefit the existing community
Conserve resources for future generations
Describe comprehensive conservation on the spectrum of management
Aims to protect and conserve glacial and periglacial environments as wilderness
Organised eco-tourism and eco-farming
Exploitative activities not permitted
Factors that influence management strategy
Population densities
Stakeholders(players)
Legislative frameworks
Mandatory legislation is most effective
What is the alpine convention
An international treaty between alpine countries for the sustainable development and protection of the Alps
How do crevasses form
Tension cracks caused by the bucking of the glacier as it flows over a rock step
what are lateral moraines
Lateral moraine forms at the edge of the glacier and consists of rock fragments from the side of the valley
what are medial moraines
Medial moraine is found in the middle of a glaciated valley and is formed by the merging of two sets of lateral moraine
where do terminal moraines form
forms at the furthest end of the glacier and marks its maximum advance
what are recessional moraines
Recessional moraine is similar to terminal moraine, but these mark locations where the glacier may have paused in its retreat, allowing deposition to occur.
what are drumlins
oval-shaped small hills and form in previously glaciated lowland area. From their distribution, it is possible to work out the direction of glacier movement.
what is an interglacial
a relatively warm period of several thousands of years in which glaciers predominately retreat
what is calving
the breaking up of glacial ice, that extends over oceans, creating ice bergs
what is glacier mass balance
the net difference between accumulation and ablation over the course of one year
what does proglacial mean
the environment directly in advance of a glacier
how many were killed at south base camp Everest by a 7.8 magnitude earthquake
22
how much have glaciers shrunk in the last 50 years
13%
how can you reduce tourism in Sagarmatha national park
limit the number of permits given to climbers
reduce group sizes
what are ice contact landforms
kame
kame terrace
esker
what are proglacial landforms
outwash plain
kettle hole
proglacial lake
varves
what is the difference between ice contact landforms and proglacial landforms
ice contact result from the deposition of material carried by the ice
proglacial result from deposition by meltwater beyond the glaciers snout
what is an esker
a long, narrow ridge of deposits. sub-glacial streams carry large amounts of rock debris due to their high hydrostatic pressure, as glacier melts deposited at a consistent rate
what is an outwash plain
a flat expanse of debris in front of glacier snout. as meltwater streams emerge from the glacier they gradually lose their energy and deposit their debris load. coarse sands first then clay later
what is a kettle hole
a circular depression. as the glacier retreats, detached blocks of ice remain, meltwater streams cover them in deposits, so when the ice melts a depression is left
what is a proglacial lake
a lake formed at the snout of the glacier. formed by the damming action of a terminal or recessional moraine
in the little ice age where did glaciers advance and why did it not become an interstadial
advanced in the north and south hemisphere
and was stopped by the industrial revolution
what factors affect glacier movement
size (greater thickness=greater pressure)
altitude (snowfall increases)
variations in mass balance
slope
lithology
how many people will be affected if meltwater regimes change in Asia
the UN estimates that 40% of the global population could be affected by the changes to meltwater regimes in Asia
how many of the Himalayan glaciers are retreating
70%
how are landscapes vulnerable from uncertain futures of climate change
forest dieback: rainforests could change into less productive farmland
how will the water cycle be impacted from the uncertain futures of climate change
if the thermohaline circulation changes the this could change how oceans and atmosphere transfer heat energy, causing greater warming and more ice melt
what human action leads to uncertain futures of climate change
governance- decisions
conflict
population growth
technology
what physical systems lead to uncertain futures of climate change
residency times
feedback mechanisms
tipping points
thermohaline circulation
What are varves and how are they formed
Found in the deposits of glacial lakes
Consist of two distinct layers of sediment, one being lighter coloured sand material and the other dark clay material
