Tharsis Montes trio and Olympus Mons

Shaded relief image of Tharsis Montes and Olympus Mons derived from Mars Orbiter Altimeter data which flew on board NASA’s Mars Global Surveyor. The new data suggest that Tharsis Montes formed one by one, starting with Arsia Mons, possibly by the movement of a single mantle plume moving under the surface.