Shield volcano Mars are very similar to the shield volcanoes on Earth. Both have gently sloping flanks, collapse craters along their central structure, and are built of highly fluid lavas. Volcanic features on Mars were observed long before they were first studied in detail during the 1976–1979 Viking mission. The principal difference between the volcanoes of Mars and those on Earth is in terms of size; Martian volcanoes range in size up to high and in diameter, far larger than the high, wide Hawaiian shields. The highest of these, Olympus Mons, is the tallest known mountain on any planet in the solar
Arsia Mons the three Tharsis Montes volcanoes, it is the only major Tharsis volcano south of the equator. The volcano is in diameter, almost high (more than higher than the surrounding plains), and the summit caldera is 110 km (72 miles) wide. It experiences atmospheric pressure lower than 107 pascals at the summit. Excluding Olympus Mons, it is the largest known volcano in terms of volume. Arsia Mons has 30 times the volume of Mauna Loa in Hawaii, the largest volcano on the Earth. The caldera of Arsia Mons was formed when the mountain collapsed in on itself after its reservoir of