At a height of nearly 27km (16.7 mi), Olympus Mons on Mars is the largest known volcano in the Solar System and is almost three times as tall as Mount Everest’s height above sea level.It is over 20 times wider than it is tall. Olympus Mons is the youngest of the large volcanoes on Mars, having formed during Mars’s Amazonian Period. Olympus Mons is located between the northwestern edge of the Tharsis region and the eastern edge of Amazonis Planitia. It stands about 1,200 km (750 mi) from the other three large Martian shield volcanoes, collectively called the Tharsis Montes (Arsia Mons, Pavonis Mons, and Ascraeus Mons). The Tharsis Montes are slightly smaller than Olympus Mons.
Olympus Mons is the result of many thousands of basaltic lava flows. The extraordinary size of the volcano has been attributed to the lack of tectonic plate movement on the Red Planet. The lack of movement allows the Martian crust to remain fixed in place over a magma hotspot allowing repeated, large lava flows. The flanks of Olympus Mons are made up of innumerable lava flows and lava channels. Many of the flows have levees along their margins.
Olympus Mons lies at the edge of the Tharsis bulge, a vast volcanic plateau that is very ancient. The formation of Tharsis was likely complete by the end of the Noachian Period. At the time Olympus Mons began to form in Hesperian times, the volcano was located on a shallow slope that descended from the high in Tharsis into the northern lowland basins. Over time, these basins would have received large volumes of sediment eroded from Tharsis and the southern highlands. The sediments likely contained abundant Noachian-aged phyllosilicates (clays) formed during an early period on Mars when surface water was abundant.
As the largest volcano in the Solar System, Olympus Mons has been extensively studied. Those studies have been helped by the closeness of Mars. Those studies will continue into the future as will the exploration of the entire planet.
Olympus Mons, complete with escarpment and aureole. This 3D view of the complete volcano has been derived from US Mars Orbiter Laser Altimeter (MOLA) topographic data superimposed with the Mars Orbiter Camera (MOC) wide-angle image mosaic.