glaciation

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73 Terms

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inputs

energy from the sun, precipitation, rock debris

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outputs

meltwater, sediment deposition

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transfers

erosion and transportation processes, which move ice and rock around the system

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Steady-state equilibrium

changes in accumulation and ablation do not vary much from the long-term average conditions

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metastable equilibrium

the glacier changes from one state of equilibrium to another due to an event causing a change in conditions

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dynamic equilibrium

the state of equilibrium changes over a longer timescale than metastable equilibrium

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positive feedback

increases the initial change: e.g
increase in snoww cover --> more solar energy, reflected, creating cooler temperatures --> more snow

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negative feedback

global warming increases evaporation and cloud cover --> more solar energy is reflected, creating cooler temperatures

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eccentricity

elliptical orbit changes to more circular and back again over a 100,000 years, varying the amount of solar radiation reaching earth

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axis tilt

varying from 21.8 to 24.4 over a period of 41,000 years, changing the amount of solar radiation at the poles

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wobble

earth wobbles on its axis over a 20,000 year cycle, changing the time of year when it is closet to the sun

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pleistocene (Quaternary period)

2.5 million - 11,500 years ago,

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holocene (Quaternary period)

11,500 years ago to today, which is the present interglacial period

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little ice age

glacial oscillation between 1350 and 1850

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cold based glaciers

  • occur in high latitudes
  • ice temperature below pressure melting point
  • basal ice is frozen to bedrock
  • most movement by internal deformation
  • little erosion due to lack of movement
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warm based glaciers

  • occur in temperate regions
  • temperature at base at pressure melting point
  • heat from earth adds to melting
  • meltwater assists movement of glacier
  • actively eroding and transporting
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polythermal glaciers

cold-based in the upper region and warm-based lower down

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shear stress

the downslope force due to gravity resulting from the build-up of an ice mass

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internal deformation

intergranular flow - under pressure the ice crystals move relative to each other

laminar flow - ice crystals move along parallel layers within the glacier

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basal sliding

enhanced basal creep - basal ice deforms around irregularities in the bedrock surface

regelation slip - basal ice deforms under pressure caused by obstacles; once past the obstacle the meltwater refreezes

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subglacial bed deformation

softer rock and unconsolidated sediments are not strong, so the weight of the ice in a glacier can cause the sediments to deform. As the sediments change shape, the ice on top moves with them

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compressional flow

a reduction in gradient results in a slowing of movement. The ice thickens, crevasses close and thrust faults develop in the ice

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extensional flow

an increase in gradient results in accelerated movement. The ice thins and crevasses form

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ice sheet

an ice dome, several kilometres thick, submerging the topography beneath

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ice shelf

a large area of floating glacier ice extending from the coast

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ice cap

a smaller version of an ice sheet covering an upland area

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ice field

ice covering an upland area, but not burying topography

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valley glacier

a glacier confined between valley sides

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Piedmont glacier

a valley glacier that fans out over a flatter area at the end of the valley

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cirque glacier

a small glacier filling a hollow on the side of a mountain

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distribution of ice cover

today - 10% of earth's land area
85% of all glaciers are in Antarctica

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freeze-thaw

repeated freezing and thawing of water, expanding cracks in rocks and eventually causing fragments to break off and fall on to the glacier

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abrasion

debris embedded in the glacier base scrapes the bedrock as it moves

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plucking

ice freezing on to valley sides, floor and bedrock pulls away rocks as it moves

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subglacial fluvial erosion

meltwater flowing at the base of a glacier erodes rock the same way as surface streams. Pressure causes streams to flow faster, increasing erosion potential

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factors affecting glacial erosion

  • basal thermal regime
  • ice velocity
  • ice thickness
  • bedrock permeability
  • bedrock jointing
  • debris characteristics
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supra glacial

debris from weathering falls from valley sides onto the glacier

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englacial

debris falls into crevasses and is moved within the glacier

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subglacial

basal ice freezes around material and drags it along by traction. Englacial material moving to the base and plucking adds to the amount

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ablation till

unsorted, angular material deposited by melting ice. Stones show no preferred orientation

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lodgement till

rounded, subglacial material deposited by a moving glacier. The long axis of stones is orientated in the direction of movement

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deformation till

weak bedrock is deformed by ice movement

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terminal moraine

a high ridge across a valley deposited as a glacier retreats from the furthest point reached

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recessional moraine

a series of ridges across a valley behind a terminal moraine, marking a stationary period in ice retreat

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lateral moraine

weathered material falls on to a glacier from valley sides. When the ice melts it deposits a ridge parallel to the valley sides

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medial moraine

two lateral moraines combine along the centre of glacier surface when valley glaciers merge. As ice melts it is deposited along the middle of the valley

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push moraine

when glaciers begin advancing again, the debris at the snout is pushed into a ridge

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erosion - fluvioglacial processes

subglacial streams are under pressure and fast flowing, eroding bedrock especially by abrasion

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transportation - fluvioglacial processes

high-energy meltwater streams have the capacity to transport large sediment loads

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deposition - fluvioglacial processes

when I loses energy it deposits material; rounder than glacial deposits, sorted by size, distinct layers

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periglacial

the edges of glacial areas, where repeated freezing and thawing modify the landscape

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permafrost

soil and rock that is below O degrees celsius for at least 2 years

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continuous permafrost

a.layer of frozen ground that can be hundreds of metres deep

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discontinuous permafrost

a thinner, fragmented layer of frozen ground

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sporadic permafrost

an isolated mass of permafrost in unfrozen ground

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active layer

the surface layer up to 3m deep, which thaws in summer and refreezes during the winter

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pingos

a dome-shaped mound of earth up to 70m high and 500m in diameter, with an ice core

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mass movement

the downward movement of materials due to gravity

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rapid mass movement

rockfalls and landslides change the profile fo a glacial valley

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rapid glacier melt

volcanic activity causes large-scale melting, resulting in flooding and rapid mudflows

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Arête example

Helvellyn range

<p>Helvellyn range</p>
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corrie/tarn example

red tarn

<p>red tarn</p>
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U shaped valley example

Ullswater valley

<p>Ullswater valley</p>
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Ribbon lake example

Ullswater

<p>Ullswater</p>
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Roché mountonnée example

Norfolk island

<p>Norfolk island</p>
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Truncated spur example

Walla crag

<p>Walla crag</p>
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What countries were in the alpine convention 1995

8 countries

  • France
  • Switzerland
  • Liechtenstein
  • Italy
  • Slovenia
  • Austria
  • Germany
  • Monaco
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what are the 8 protocols of the Alpine convention

  • mountain farming
  • energy
  • mountain forests
  • conservation of nature + countryside
  • Transport
  • Tourism
  • soil conservation
  • spacial planning and sustainable development
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Hohe Tauern - Austria

  • largest protected area in alps
  • Grossglockner glacier --> 3000m
  • 4000 types of fungi
  • 20,000 animal species
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What is done to make Hohe Tauern sustainable

  • donation of land use
    footpaths well maintained
  • Gardonna Mountain Resort --> eco hotel
  • public transport = free
  • protection of ski areas --> cow's graze in summer
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GLOF

glacial lake outburst flood

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impacts of GLOF's

affects fresh water, agriculture, livelihood

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GLOF case study = Dig Tsho (Butan - 1994)

  • increase in depth due to melting ice caused moraine dam to break
  • village flooded 7 hours after dam break
  • 2m deep, 200km away from source