ABSTRACT
Glaciers and ice sheets generally move very slowly, with speeds up to a few tens of meters per day at most. This suggests that in good approximation accelerations may be neglected so that Newton’s second law reduces to an equilibrium of forces. Forces applied to the surface of a volume element must balance the body force (gravity) that acts on the entire volume. To arrive at the balance equations, consider a small volume element in the glacier, centered at (x, y, z) with dimensions ∂x, ∂y, and ∂z as shown in Figure 3.1. It is convenient to choose the Cartesian coordinate system such that the z-axis is vertical and positive upward.
