Giant of Mars: Olympus Mons Towers Over All Other Volcanoes

Olympus Mons on Mars rises about 21 kilometers (70,000 feet) and spans roughly 370 miles, making it the largest volcano in the solar system and, by some measures, the tallest mountain. Its gentle slopes and the thin Martian atmosphere mean the summit rises near space; its last major eruption is dated around 25 million years ago, so it’s considered dormant rather than extinct. The volcano grew large thanks to Mars’s low gravity, lack of plate tectonics, and a long eruptive history within the Tharsis region alongside other giant volcanoes, though the exact origin of its base cliffs and whether it could erupt again remain subjects of active research.