Landsys Flashcards
glacial landsystem model
utilises kleman 1996’s inversion principle= flipping evidence on its head approach. application of conceptual models to glacial landforms in the opposite way of the solving the genetic problem in order to determine th form and dynamics of the glacier
element- unit– ls
gs landsystem evans def
‘templates for interpreting very complex landscapes formed by different glaciation styles’
clark 1997
highlights need to focus on whole systems rather than research small areas in order to create effective reconstructions
surge glacier
Raymond 1987: ‘multi year oscillations between extended periods of normal motion and brief periods of comparatively fast motion’- up to 100 times
–. active phase lasts 5-10 years every 10-200 years
q phase = no movement really
- ice on the run (qui 2017) -spending spree bank account
evans et al (1999)- 8 landform types associated with surge glaciers
active phase:
- flutes formed
- overidden moraines
- cupola hills created
- composite ridges
- due to extreme proglacial thrusting
- blowout structures
- due to evacuation of pressurised water
Q-phase
- hummocky moraines
- extreme thrusting in a phase leaves bands of debris and ice so when ice melt happens = hummocky moraines left - outwash tracks
- lots of deposition of Glaciol-fluvial sediments - concertina esker
- often overprint flutes
- formed by mw outwash which deforms eskers - csr
Kleman 1996 assumptions
inversion concept
- basal sliding requires thawed bed
- subglacial lineations require basal sliding
- subglacial lineations aligned to ice flow
- frozen bed conditions = minimal landscape change
evans and rea 1996
recognise 3 overlapping zones of surge glacier land system
a) outermost zone- limit of surge-zone fo thrust block moraines
b) intermediate zone- patchy chaotic hummocky morain
c) inner zone= flutings , csrs and concertina eskers
evans et al 2007
Bruarjokull surging glacier se iceland
- used aerial photography to identify diagnostic landforms of surging glacier landystem
- TBMs + push moraines, overrides TBM, concertina eskers, CSRs, flutings, hummocky moraines and pitted outwash
- identify biggest surge was in 1890 = 10km advance or 5m/hour
Knudsen 1995
concertina eskers
kleman inversion problem
analysis of glacial geomorphology in a conceptual framework
- extraction of ice sheet properties and dynamics from glacial geomorphology
- 5 dims, 3 of space and then time and process components
- main tool = recognition of swarms/flowsets- coherent directional landforms
kleman 2006
problem of cold based glaciation0 no direct evidence of glaciation - relict landscapes –> still produce mw so mw landforms related to marginal drainage
- -> klemans argues ice streams = useful concept but should be broken into dif types under inversion principles
- topographically governed, transient, or ephemeral
evans and rea 1999
ice land- eyjabakkajokull
-TBM found at margins but these can be produced by non surge in permafrost regions- not unequivocal sign
-concertina eskers- emanate from margins- knudsen 1995 formed by shortening of pres surge sinous eskers by compression however more likely they are formed in Q phase by high discharge
- CSR = prominent networks found in Bruarjokull foreland = eyjabbajokull
- hummocky moraines- requérez lots of sediment subglacial to surface by thrusting–> cited as evidence for surging in LIS but cannot solely be used as non surge with high debris provision can from them also
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stokes 2013
paleo ice streams
- bennet describe ice streams as ‘arteries’ of ice sheet = drain 90% of ice
- Alley et al recognise PIS should leave behind a recognisable geomorphic signature
clark 1993
MSGLS er >10
stokes and clark 1999
PIS glacial landsystem model
- > 150km long and >20km wide
- highly convergent flow patterns
- rapid velocity- elongated bedforms
- abrupt lateral margins
- evidence of deformed til
