<P> Olympus Mons (/ əˌlɪmpəs ˈmɒnz, oʊ -, - ˈmɒns /; Latin for Mount Olympus) is a very large shield volcano on the planet Mars . By one measure, it has a height of nearly 22 km (13.6 mi or 72,000 ft). Olympus Mons stands about two and a half times as tall as Mount Everest's height above sea level . It is the tallest mountain in the Solar System . It is the youngest of the large volcanoes on Mars, having formed during Mars's Hesperian Period . It is currently the largest volcano discovered in the Solar System and had been known to astronomers since the late 19th century as the albedo feature Nix Olympica (Latin for "Olympic Snow"). Its mountainous nature was suspected well before space probes confirmed its identity as a mountain . </P> <P> The volcano is located in Mars's western hemisphere at approximately 18 ° 39 ′ N 226 ° 12 ′ E ﻿ / ﻿ 18.65 ° N 226.2 ° E ﻿ / 18.65; 226.2, just off the northwestern edge of the Tharsis bulge . The western portion of the volcano lies in the Amazonis quadrangle (MC - 8) and the central and eastern portions in the adjoining Tharsis quadrangle (MC - 9). </P> <P> Two impact craters on Olympus Mons have been assigned provisional names by the International Astronomical Union . They are the 15.6 km (9.7 mi) - diameter Karzok crater (18 ° 25 ′ N 131 ° 55 ′ W ﻿ / ﻿ 18.417 ° N 131.917 ° W ﻿ / 18.417; - 131.917) and the 10.4 km (6.5 mi) - diameter Pangboche crater (17 ° 10 ′ N 133 ° 35 ′ W ﻿ / ﻿ 17.167 ° N 133.583 ° W ﻿ / 17.167; - 133.583). The craters are notable for being two of several suspected source areas for shergottites, the most abundant class of Martian meteorites . </P> <P> As a shield volcano, Olympus Mons resembles the shape of the large volcanoes making up the Hawaiian Islands . The edifice is about 600 km (370 mi) wide . Because the mountain is so large, with complex structure at its edges, allocating a height to the structure is difficult . It stands 21 km (13 mi) above the Mars global datum, and its local relief, from the foot of the cliffs which form its margin to the northwest to its peak, is nearly 22 km (14 mi) (a little over twice the height of Mauna Kea as measured from its base on the ocean floor). The total elevation change from the plains of Amazonis Planitia, over 1,000 km (620 mi) to the northwest, to the summit approaches 26 km (16 mi). The summit of the mountain has six nested calderas (collapse craters) forming an irregular depression 60 km (37 mi) × 80 km (50 mi) across and up to 3.2 km (2.0 mi) deep . The volcano's outer edge consists of an escarpment, or cliff, up to 8 km (5.0 mi) tall (although obscured by lava flows in places), a feature unique among the shield volcanoes of Mars . Olympus Mons covers an area approximately the size of Italy, or about 300,000 km (120,000 sq mi). </P>

Which of earth's volcanoes olympus mons is most similar to in formation