Being a shield volcano, Olympus Mons has a very gently sloping profile. The average slope on the volcano's flanks is only 5°. Slopes are steepest near the middle part of the flanks and grow shallower toward the base, giving the flanks a concave upward profile. The shape of Olympus Mons is distinctly asymmetrical—its flanks are shallower and extend farther from the summit in the northwestern direction than they do to the southeast. The volcano's shape and profile have been likened to a "circus tent" held up by a single pole that is shifted off center.