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Olympus Mons
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The solar system's largest known volcano Olympus Mons on Mars topographic map of Mars Mars: Tharsis province
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The solar system's largest known volcano
The solar system's largest known volcano Olympus Mons, Mars's tallest volcano, imaged by the Mars Global Surveyor spacecraft on April 25, 1998. North is to the left. Water-ice clouds are visible to the east (top) against the bordering escarpment and above the plains beyond. The central caldera, about 85 km (53 miles) across, comprises several overlapping collapse craters.

Olympus Mons

volcano, Mars
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Olympus Mons, volcano on the planet Mars, the highest point on the planet and the largest known volcano in the solar system. Centered at 19° N, 133° W, Olympus Mons consists of a central edifice 22 km (14 miles) high and 700 km (435 miles) across. Around its perimeter an outward-facing cliff ascends as high as 10 km (6 miles) above the surrounding area. At the summit is an 85-km- (53-mile-) diameter crater, or caldera, comprising several mutually intersecting craters. For comparison, the largest volcano on Earth, Mauna Loa, Hawaii, measures 120 km (75 miles) across at its widest extent and rises 9 km (5.6 miles) above the ocean floor. Broad, gradually sloping flanks and the presence of numerous long flows and lava channels identify Olympus Mons as a shield volcano and suggest that it was built up from eruptions largely of fairly fluid basaltic lava. Its tremendous size has been attributed to the stability of the Martian crust and to a long accumulation time, possibly more than a billion years.

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The Editors of Encyclopaedia BritannicaThis article was most recently revised and updated by Amy Tikkanen.
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