Axel Heiberg Island, Canada
Hva er en isbre ?
Hvorfor beveger isbreene seg ?
• Isbre = snø og ismasse i bevegelse
• Isen er deformerbar – ”brød-deigen”
• Isen endrer egenskaper med trykket
(istykkelsen)
• Isen glir
Folgefonna
Alaska – flytbevegelse - midtmorener
Surface velocity us is partly caused by gliding ug and partly deformation ud
Gliding/sliding varies considerably – deformation is almost constant
(depending on slope and thickness)
 
u
 A  n  A  ( gh sin  ) n
y
us = ug + ud
Sprekker på breer i
Norge – Svalbard - Antarktis
50
Bondhusbreen - Folgefonna
Bondhusbreen, Folgefonna
Bondhusbreen - Folgefonna
Bondhusbreen
Helikopterplatform
Bondhusbreen
Tunnellsystemet under Bondhusbreen
Bondhusbreen - tunnellsystem
Isen deformeres
Isen
deformeres
Is er en seig
masse som endrer
egenskaper med
trykk og
temperatur
Glens flow law deformation of ice:
 
u
 A  n  A  ( gh sin  ) n
y
Liquids:
 
u
 A   A  ( gh sin  )
y
Department of geosciences
Deformation rate h = 160m
Glens flow law: ė = A τⁿ
Closure rate:
dr/dt = A (P/n)ⁿ
dr/dt ~ 100-150 mm/d
If P = ρgh = 14 bar, n = 3:
A = 0.36 y-1 bar-1
or 11.4 * 10-15 s-1kPa-3
- twice as high as Peterson
Nigardsbreen still
INSTITUTT FOR GEOFAG
advanced
inI OSLO
2004
UNIVERSITETET
Artificial roche moutonne (Rundsva) with a boulder in
the ice
Boulder crossing
Rock wall pressures - water opening- temperatures
Rock crushing
Ice
Rock
Hvordan eroderer breene ?
• Skuring
• Knusing
• Plukking
Erosjon – transport – avsetning
INSTITUTT FOR GEOFAG
UNIVERSITETET I OSLO
INSTITUTT FOR GEOFAG
UNIVERSITETET I OSLO
Rundsva
Skuring, brunhud, plukking
Svenske skjærgården
Plucking