Olympus Mons: Mars's Giant Volcano

Olympus Mons is the largest known volcano in the Solar System, a shield volcano on Mars. Its quoted height depends on the reference point: NASA gives about 27 km from its base, while its summit stands more than 21 km above a Martian elevation datum. It is an extremely broad volcano with gentle slopes. Mars’s lower gravity and the absence of present-day moving lithospheric plates—which on Earth carry crust away from magma sources—likely helped large lava piles accumulate. This is a broad explanation, not a complete reconstruction of the volcano’s history.