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 force ( τ_b), as given by the equation:

τ_b = ρ_igh sin α_S

Where ρ_igh is the density of the ice (ρ_i), 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.

α_S 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.

See more information on how glaciers flow here.