Rising more than twice the height of Mount Everest, Olympus Mons dominates the landscape of Mars and holds the title of the largest volcano in the Solar System. Its massive size and unique structure continue to intrigue scientists, decades after its discovery.
With a height and a base spanning an area comparable to Poland, this ancient giant isn’t just a geological marvel. It’s a key to understanding Martian volcanic history. Its existence challenges what we know about planetary activity in the absence of tectonic plates.
The Volcano So Massive It Can Be Seen from Earth
The volcano is located in Mars’s western hemisphere, not far from the equator, where it looms as high as 26 kilometers above the surrounding terrain in some areas. As the NASA pointed out:
“It is 27 kilometers high, over 600 kilometers at the base, and is surrounded by a well-defined scarp that is up to 6 km high. The summit caldera (central depression) is almost 3 km deep and 25 km across.”
According to BBC Sky at Night Magazine, Olympus Mons is so prominent that it was visible from Earth long before space probes reached the Red Planet. Early astronomers once called the bright feature Nix Olympica, latin for “Olympic Snow”, based solely on telescope observations.
Its true form was only confirmed in 1971, when NASA’s Mariner 9 mission mapped Martian topography for the first time. Since then, Olympus Mons has remained one of Mars’s most studied, and misunderstood, features.
Towering and Wide: A Volcano Like No Other
Unlike the sharp, steep volcanoes often seen on Earth, Olympus Mons belongs to a category called shield volcanoes, which form through the steady outflow of low-viscosity lava. This type of lava spreads quickly and broadly, giving the mountain its gently sloping profile, similar to a flattened dome or a warrior’s shield.
Its surface area reaches approximately 300,000 square kilometers, making it larger than many entire countries. As reported, this vastness is a direct result of the way shield volcanoes grow, not through explosive eruptions, but through gradual, layered accumulation.
Mars Without Tectonics: A Lava-built Monument
The staggering height and volume of Olympus Mons are explained in part by Mars’s lack of tectonic plate movement. Unlike Earth, where shifting plates constantly change the positions of volcanic hotspots, Mars has a static crust, allowing lava to build up in the same location for millions of years.
According to the same source, Olympus Mons sits above a massive magma hotspot in the region known as Tharsis Rise. Since this hotspot hasn’t moved over time, repeated eruptions kept adding layer upon layer of lava at the same site, eventually forming the largest volcano known in the Solar System.
vBecause of the planet’s small size and relatively stable crust, Mars didn’t experience the type of volcanic drift that produces chains of volcanoes like those found on Earth. As a result, Olympus Mons grew higher and wider without interruption, a geological exception born from planetary conditions.
Dormant But Not Forgotten
While Olympus Mons is no longer erupting today, its last major volcanic activity occurred around 25 million years ago, which is considered relatively recent in geological terms. There are no photos of it erupting, as all known activity predates human exploration.
According to observations cited by Sky at Night Magazine, there may be much older volcanic layers buried beneath more recent flows, suggesting a long and complex eruption history. Still, its overall shape has remained remarkably preserved, thanks in part to the Martian environment, which lacks the water and wind erosion found on Earth.
In 2024, researchers detected traces of frost on Olympus Mons’s surface, equivalent to 60 Olympic swimming pools of water, a discovery that has reignited interest in the volcano.