inputs
energy from the sun, precipitation, rock debris
outputs
meltwater, sediment deposition
transfers
erosion and transportation processes, which move ice and rock around the system
Steady-state equilibrium
changes in accumulation and ablation do not vary much from the long-term average conditions
metastable equilibrium
the glacier changes from one state of equilibrium to another due to an event causing a change in conditions
dynamic equilibrium
the state of equilibrium changes over a longer timescale than metastable equilibrium
positive feedback
increases the initial change: e.g increase in snoww cover --> more solar energy, reflected, creating cooler temperatures --> more snow
negative feedback
global warming increases evaporation and cloud cover --> more solar energy is reflected, creating cooler temperatures
eccentricity
elliptical orbit changes to more circular and back again over a 100,000 years, varying the amount of solar radiation reaching earth
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
wobble
earth wobbles on its axis over a 20,000 year cycle, changing the time of year when it is closet to the sun
pleistocene (Quaternary period)
2.5 million - 11,500 years ago,
holocene (Quaternary period)
11,500 years ago to today, which is the present interglacial period
little ice age
glacial oscillation between 1350 and 1850
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
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
polythermal glaciers
cold-based in the upper region and warm-based lower down
shear stress
the downslope force due to gravity resulting from the build-up of an ice mass
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
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
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
compressional flow
a reduction in gradient results in a slowing of movement. The ice thickens, crevasses close and thrust faults develop in the ice
extensional flow
an increase in gradient results in accelerated movement. The ice thins and crevasses form
ice sheet
an ice dome, several kilometres thick, submerging the topography beneath
ice shelf
a large area of floating glacier ice extending from the coast
ice cap
a smaller version of an ice sheet covering an upland area
ice field
ice covering an upland area, but not burying topography
valley glacier
a glacier confined between valley sides
Piedmont glacier
a valley glacier that fans out over a flatter area at the end of the valley
cirque glacier
a small glacier filling a hollow on the side of a mountain
distribution of ice cover
today - 10% of earth's land area 85% of all glaciers are in Antarctica
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
abrasion
debris embedded in the glacier base scrapes the bedrock as it moves
plucking
ice freezing on to valley sides, floor and bedrock pulls away rocks as it moves
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
factors affecting glacial erosion
basal thermal regime
ice velocity
ice thickness
bedrock permeability
bedrock jointing
debris characteristics
supra glacial
debris from weathering falls from valley sides onto the glacier
englacial
debris falls into crevasses and is moved within the glacier
subglacial
basal ice freezes around material and drags it along by traction. Englacial material moving to the base and plucking adds to the amount
ablation till
unsorted, angular material deposited by melting ice. Stones show no preferred orientation
lodgement till
rounded, subglacial material deposited by a moving glacier. The long axis of stones is orientated in the direction of movement
deformation till
weak bedrock is deformed by ice movement
terminal moraine
a high ridge across a valley deposited as a glacier retreats from the furthest point reached
recessional moraine
a series of ridges across a valley behind a terminal moraine, marking a stationary period in ice retreat
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
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
push moraine
when glaciers begin advancing again, the debris at the snout is pushed into a ridge
erosion - fluvioglacial processes
subglacial streams are under pressure and fast flowing, eroding bedrock especially by abrasion
transportation - fluvioglacial processes
high-energy meltwater streams have the capacity to transport large sediment loads
deposition - fluvioglacial processes
when I loses energy it deposits material; rounder than glacial deposits, sorted by size, distinct layers
periglacial
the edges of glacial areas, where repeated freezing and thawing modify the landscape
permafrost
soil and rock that is below O degrees celsius for at least 2 years
continuous permafrost
a.layer of frozen ground that can be hundreds of metres deep
discontinuous permafrost
a thinner, fragmented layer of frozen ground
sporadic permafrost
an isolated mass of permafrost in unfrozen ground
active layer
the surface layer up to 3m deep, which thaws in summer and refreezes during the winter
pingos
a dome-shaped mound of earth up to 70m high and 500m in diameter, with an ice core
mass movement
the downward movement of materials due to gravity
rapid mass movement
rockfalls and landslides change the profile fo a glacial valley
rapid glacier melt
volcanic activity causes large-scale melting, resulting in flooding and rapid mudflows
Arête example
Helvellyn range
corrie/tarn example
red tarn
U shaped valley example
Ullswater valley
Ribbon lake example
Ullswater
Roché mountonnée example
Norfolk island
Truncated spur example
Walla crag
What countries were in the alpine convention 1995
8 countries
France
Switzerland
Liechtenstein
Italy
Slovenia
Austria
Germany
Monaco
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
Hohe Tauern - Austria
largest protected area in alps
Grossglockner glacier --> 3000m
4000 types of fungi
20,000 animal species
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
GLOF
glacial lake outburst flood
impacts of GLOF's
affects fresh water, agriculture, livelihood
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