This is an image of Olympus Mons.
Click on image for full size
The largest volcano in the solar system is Olympus Mons, shown in the image to the left. Olympus Mons is a Martian shield volcano. The altitude of Olympus Mons is three times the altitude of the largest peak on Earth, Mt. Everest, and is as wide as the entire chain of Hawaiian Islands. Measurements returned by Mars Global surveyor demonstrate the unbelievable size of Olympus Mons. Olympus Mons is a very large volcano for a body the size of Mars, given the fact that Mars is three times smaller than the Earth. The size of Olympus Mons suggests something special about the surface of Mars and how Mars cooled over time.
Mars has several other *very* large volcanoes. Some of them are located on top of a big bulge in the side of Mars called the Tharsis Ridge. The volcanoes built during this period were built in a manner similar to that in which the Hawaiian Islands came into being on Earth, namely by a hot plume, rising from the deep interior of the planet, which builds land on the surface. The size of these volcanos suggests that Mars had already cooled sufficiently to form a lithosphere thick enough to support large volcanoes without allowing them to sink.
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