The largest volcano in the solar system is on Mars. It’s called Olympus Mons, and it’s about 13.6 miles (22 kilometers) high—nearly three times the height of Mount Everest! Its base is so wide (370 miles or 600 kilometers across) that it could cover the entire state of Arizona. Because of Mars’ low gravity and lack of tectonic plate movement, this volcano grew to such colossal proportions.
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