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Olympus Mons(ŏ-lim -pŭs) A lofty volcanic peak on Mars, located in the planet's northern hemisphere at 18.6° N latitude and 134.0° W longitude. It is the largest volcano on Mars and possibly the largest in the Solar System. With an estimated age of 200 million years, it may be younger than the volcanoes on the Tharsis Ridge. It has a base more than 600 km across and rises to a 90 km diameter caldera at an elevation of 26 km above the surrounding plains. Around much of the base is an escarpment up to 6 km high. This giant feature is an important influence on Martian weather. For comparison, the largest volcano on Earth, Hawaii's Mauna Loa, rises only 9.3 km from its 120-km diameter base on the floor of the Pacific Ocean. See also Mars, volcanoes.
Olympus Mons[ə′lim·pəs ′mänz]
The largest volcano on Mars; it is approximately 360 miles (600 kilometers) across at its base and stands approximately 16 miles (26 kilometers) above the surrounding terrain. Also known as Nix Olympica.