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
Tohil Mons Tohil Mons Tohil Mons is a mountain on Io, one of Jupiter's moons. It stands at 5400 m (18,000 feet) and is located in the Culann–Tohil region of Io's antijovian hemisphere. It was named after the Mayan weather god Tohil. Tohil Mons is one of the most geologically complex mountains in the Solar System as the mountain shows evidence of forming from other mountains through tectonic and erosional processes, in combination with silicate volcanic rock or magma activity. The main massif of Tohil Mons has ridges and grooves, which indicate the presence of materials that have been tectonically displaced, including