Arsia Mons is one of the largest volcanoes in the solar system, located on the planet Mars. It stands about 20 kilometers (12 miles) high and spans approximately 250 kilometers (155 miles) in diameter. This shield volcano is part of the Tharsis volcanic region, which contains several other massive volcanoes. The formation of Arsia Mons occurred over millions of years through repeated lava flows. Its broad, gently sloping structure is typical of shield volcanoes, and it features a large summit caldera, which is a depression formed after a volcanic eruption. Scientists study Arsia Mons to understand the geological history of Mars and its volcanic activity.