Figure 36.15 Olympus Mons. (a) Overhead view

(a) Olympus Mons, the largest volcano in the solar system, is a shield volcano, similar to volcanoes in Hawaii. The central edifice of Olympus Mons has a summit caldera 24 km above the surrounding plains. Surrounding the volcano is an outward-facing scarp 550 km in diameter and up to 6 km high in places. In other places, it is hidden under lava flows cascading out into the surrounding lava plains. This cliff is unique among the giant shield volcanoes on Mars. Beyond the scarp is a moat filled with lava, most likely derived from Olympus Mons. The rough, crinkly areas around Olympus Mons form the Olympus Mons Aureole. Both the Aureole and the basal cliff are poorly understood, but their origins may be related: one theory holds that the basal cliff was formed by many large landslides and that the Aureole marks material piled up at the bottom of these landslides. (NASA/JPL)

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