The planet Mars has the largest volcano in the solar system, called Olympus Mons. Olympus Mons is a colossal shield volcano that rises about 22 kilometers (around 13.6 miles) above the Martian surface, which is nearly three times the height of Mount Everest. It spans about 600 kilometers (373 miles) in diameter, making it extremely broad as well. Its volume is about 100 times that of Earth's largest volcano, Mauna Loa. The unique size of Olympus Mons is due to Mars's lower gravity and lack of tectonic plate movement, allowing the volcano to grow enormously over millions of years.