Olympus Mons is supported by a thick lithosphere. The extraordinary size of Olympus Mons is likely because Mars lacks mobile tectonic plates. Unlike on Earth, the crust of Mars remains fixed over a stationary hotspot, and a volcano can continue to discharge lava until it reaches an enormous height. 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
Tectonics of Mars in elevation than the southern highlands, and have a much lower crater density, indicating a younger surface age. The underlying crust is however thought to be the same age as that of the southern highlands. Unlike the southern highlands, magnetic anomalies in the northern plains are sparse and weak. The Tharsis plateau, which sits in the highland-lowland boundary, is an elevated region that covers roughly one quarter of the planet. Tharsis is topped by the largest shield volcanoes known in the solar system. Olympus Mons stands 24 km tall and is nearly 600 km in diameter. The adjoining Tharsis Montes