On average how long does it take for a glacier to build up before it starts to slowly move and slide? And how do Newton’s Laws affect a glacier the most?

Asked by Erik

Hi Erik,

The time taken for glacier ice to thicken sufficiently to start to move downslope will depend on:

  • The rate at which snow builds up
  • The slope of the ground.

Small, simple glaciers are driven by the gravitational driving forceτb), as given by the equation:

τb = ρigh sin αS

Where ρigh is the density of the ice (ρi), g is the acceleration due to gravity, and h is the thickness of the ice. This part of the equation is derived from Newton’s Second Law (F = ma), where the mass of the ice is the density times the height and the acceleration is the acceleration due to gravity.

αS is the ice surface slope. Steeper slopes tend to result in faster-flowing glaciers. The gravitational driving stress is resisted by basal and lateral drag against the valley floor and walls.

Driving and resisting stresses operating on a block of ice on an inclined slope.

See more information on how glaciers flow here.

About

I am a Senior Lecturer at Newcastle Univeristy, specialising in glaciology and glacial geology. I wrote and developed the AntarcticGlaciers.org website as part of an ongoing commitment to outreach, education and research impact. Read more about me at www.antarcticglaciers.org/bethan-davies.

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