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 as small as Mars. 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 were formed in a manner similar to that in which the Hawaiian Islands came into being on Earth, namely from a hot balloon of material which rises from the deep interior of the planet and forms land on the surface. The size of these volcanoes suggests that, Mars had already cooled off and formed a crust thick enough to hold up the large volcanoes without allowing them to sink as they formed.
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