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
Mons Huygens Mount Fuji, which overlooks Tokyo, Japan, is about altitude. Compared to the Andes, Mons Huygens would rank outside the hundred tallest peaks, being roughly the same height as Argentina's Cerro Pajonal; the peak is higher than any above sea level in Oceania, but base-to peak it is considerably shorter than Hawaii's Mauna Kea and its neighbors. Mons Huygens Mons Huygens is the Moon's tallest mountain (but not its highest point). It is about high and is located in the Montes Apenninus. The Montes Apenninus were formed by the impact that created Mare Imbrium. Adjacent is Mons Ampère to the west.