Please enable JavaScript.
Coggle requires JavaScript to display documents.
Glacier Deformation (Strain (= measurement of distortion / volume change,…
Glacier Deformation
Strain
= measurement of distortion / volume change
experienced over time by rock/ice volume
i.e. time-dependent response
Strain
vs Time
Initial elastic strain
(A-B)
Ice experiences a little deformation when loaded
Elastic
i.e. completely recoverable - returns to original shape
Instantaneous
i.e. no time-dependence
Deforms a few %
Primary, secondary & accelerating stages (B-E)
Later increments deformation / strain
=
Time-dependent
i.e. curve shifts to right
Correspond to transformations in ice crystallinity
Tertiary creep
(E-F) = interesting
Steady state reached
Deforms at constant strain rate
Once ice starts to flow down gravitational potential
Recovery & recrystallisation processes = active
Polycrystalline
= solid composed of crystallites of varying size & orientation
i.e. randomly oriented wrt eachother
How ice deforms when loaded ?
Strain vs Time plot
also: log strain rate vs log strain plot
Ice as
analogue
Quartz & ice = similar crystallographically
Ice = analogue for silicate mineral deformation in crust
Stress & creep accomodated by
Propagation of dislocations through crystal lattice
∴ fabric development in ice as lattice shape is rearranged
Strain rate
how fast material deforms - deformation rate
units = s-1
i.e. relative rate length change over time wrt itself
cancels itself out over time
Glaciers deform on microscale
to accomodate creep induced by gravitational potential of ice mass
Dominant mode ice deformation
=
Slip on basal 0001 plane
(dislocation glide)
Dislocation
= linear defect in a crystal lattice i.e. rock/ice
Stress acting on ice body
Ice mass subjected to body forces
reflect gravitational potential experienced by ice mass
causes creep motion
How does a glacier accomodate creep associated with its weight ?
