Fichas
Glacier facts:
Fichas del conjunto (31)
- 1What is a glacierPerennial mass of ice and snow containing varying amounts of rock, debris, water and air which deforms under it own weight and flows downhill
- 2Which glacial geomorphologist suggested that basal lodgement of parcel could take place at low velocities equivalent to the rate of melting?Hallet
- 3In formerly glaciated areas, the orientation of rage and tail ridges is usually...Transverse to ice flow
- 4As a bedrock feature formed under thin, fast-flowing ice with evidence of joint removal on the lee side is known as...A Roche Moutonnee
- 5Glacieralised areas:10% glacerialsed
84%- Antartica
14% arctic
1.5%- continental
18 000BP- 30% earths surface was covered by ice - 6Different types of glacierIce sheet -50 000 km2
Outlet glacier- Shape of landscape shaped the glacial flows.
Tidewater glaciers
Piedmont glacier
Plateau ice field- topographically constrained.
Valley glacier
Cirque glacier
Hanging glacier - 7Density of snow and icefreshly fallen snow- 50- 200km m-3
firn- 400-830kg m-3
glacier ice - 830-910 kg m-3
pure ice- 917 kg m-3
pure water at 0 degrees- 1000kg m-3 - 8Mass balance gradientRate of change of net balance with altitude
Drives glacier motion:
high gradient- rapid glacier motion
low gradient- slow glacier motion
Continental climate- slow moving glacier- small wedge and low accumulation line.
Vice versa- maritime climate. - 9Thermal regimeIce temp.- 0- to -4 degrees
Pressure melting point leads to a lower melting point.
Rate- 0.072 degrees per MPa
Below 2km ice
pressure- 17.6MPa
Melting point - 1.27 degrees
Warm ice- warm or at the PMP
Cold ice- below the PMP.
With ^ depth- cold ice can ^ in temp. - 10H2O chaining stateSolid- liquid- 334 Jg-1 absorbed (melting)
Liquid - solid- 334 Jg released (freezing)
Liquid- gas - 2500 Jg -1 absorbed (evap.)
Gas- liquid 2500 jg -1 released (Condes)
Solid- gas- 2834 Jg-1 absorbed (Sublim.)
Gas- solid- 2834 g-1 released (deposition)
Melting 1g of ice lower the temp of 160g of ice by 1 degrees. - 11Cold based glacier most likely to occur:- ice is thin - les pressure -
Slow moving - less heat for friction
Cold climate- dissipate heat more efficiently - 12Warm based glacier most likely to occur:Ice is thick
Fast moving
Melt water percolation (release of latent heat). - 13Glacier flowUsually- 3-300 m yr-1
Jacobshavns Isbrae Greenland 8.36km yr-1
Meserve Glacier Antactica- 2m yr-1 - 14AbrasionBolton: abrasion related to: Effective (normal) pressure, Sliding velocity, Debris concentration.
Hallet- abrasion related to: Vertical velocity (basal melting), sliding velocity, debris concentration. - 15Quarrying / pluckingLarger-scale bedrock failure than abrasion
Exploits pre- existing weaknesses.
Favoured beneath thin- fast flowing ice.
Over bump= melts at front then refreezes- weakness- rip it out and entrain. - 16Melt-water erosionEffectiveness controlled by:
Erodibility of the rock...
Discharge regime (velocity etc.)
Sediment load....
sandblasting- 0.2mm diameter- high velocity etc.
Cavitation flow- 15ms-1 flow entering a widening channel at a high pressure - 17Glacial landforms:Micro- 1m
meso- 1m-1km
marco- 1km - 18Meso- Whale backProduced under thick ice
high normal pressure in
- Stoss side deposition.
abraded all the way across
slow ice
low amplitude relief - 19Meso- Roches moutonnes-Low normal pressure
-Promote abrasion on lee side.
-thin ice fast flowing ice
high amplitude relief - 20MacroMeltwater channels
Glacial troughs- U shaped valleys... - 21Effectiveness of glacial erosion....Average denudation rate across the is 43mm Ka-1
Average valley glacier denudation rate is 100- 5000mm Ka-1
Valley glaciers are extremely variable.... - 22Properties of glacial sediments- griansize & distribution
Last form - shape (relative of axes)
Roundness (how rounded/ angular are the corners)
Surface (e.g. striations)
Minor and Macro structure. - 23Passively transported sedimentModeratel wel sorted - pebble to bodler
VA A class
No striations
The amount of sediment depends on- Steepmess of valley sides
- Strength of rocks
- Exposed area above glacier - 24Actively transported sedimentSA R
Poorly sorted
Class with striations.
The amount of sediment depends on: Thelmal regime
Flow rate - 25Moraines- 3D depositive created by a glacier ( landforms)
Comprised of till. - 26LodgementThe friction on grain at bed of glacier is greater than the stress exerted by the ice.
Bouton- occurs at high pressure & can occur at high velocities
Hallet- Only occurs at low ice velocities ^ basal melting - 27Sub-glacial melt-outReleased of basal sediment in stagnant ice by melting of the ice b/w the grains
Close to the glacier margin - 28Types of subglacial depositional landforms-Flute- Parallel to ice flow
-Drumlins
-Esker- forma river which where filled by deposited sediments. - 29Moraines- passive sediment....Dump moraines- Dropped on tot ridge at the end of the glacier.
Lateral moraines .
Bifurcating ridges.
Ablation moraines- thin warm thick cold.
Englacial thrust moraines- sediment moves along the bottom of the glacier bed- then it is thrusted to the surface- different types of sediments. - 30McDougall (2001)Map the glacial landforms in the valleys.
Emphasis on ice-rmaognal moraines
Peri-Glaciate landforms observed on plateau - surfaces - no evidence of glaciation
Decay pattern centred on suits not valle heads. - 31Sediment movementCold-based glacier-moves sediment by internal defamation
Warm based on hard bed rock- basal sliding
Warm based on un-condsolidaton bed rock- deformation
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- SEM 1 resisit- Earth surafce processes Fichas sobre Glacier facts: , creado por Lucy Harris el 29/08/2018.
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