The northern hemisphere hosts several gigantic shield volcanoes that rise from the broad Tharsis "bulge" and from a smaller raised area in Elysium to the west.
Mars has the largest volcanoes known in the solar system. Olympus Mons, the largest on Mars , is 25 km high and has a volume between 50 and 100 times that of Mauna Loa, the largest volcano on Earth. At its summit lies an enormous caldera at least 80 km in diameter.
