What is the tallest volcano in the solar system?
Quick answer
Olympus Mons on Mars is the tallest known volcano in the solar system. It rises about 22 km (13.6 miles) above the surrounding plains, nearly 2.5 times the height of Mount Everest, and is about 600 km (370 miles) wide, roughly the size of Arizona.
How big is Olympus Mons?
| Olympus Mons (Mars) | Mauna Kea / Mauna Loa (Earth) | Everest (Earth) | |
|---|---|---|---|
| Height | ~22 km above its base | ~9–10 km from the seafloor | 8.8 km above sea level |
| Width | ~600 km | ~120 km | — |
| Type | Shield volcano | Shield volcano | Not a volcano |
It’s so wide and gently sloped that if you stood on it, the curve of Mars would hide the summit; it would look like a long, gradual hill.
Why did it grow so big?
| Reason | Explanation |
|---|---|
| No moving plates | On Earth, tectonic plates move volcanoes off their hot spots, creating chains like Hawaii. On Mars, the crust stayed still, so lava kept piling up in one place |
| Lower gravity | Mars’s gravity is only about 38% of Earth’s, so mountains can grow taller before collapsing |
| Long history | Eruptions continued for hundreds of millions of years |
Is it still active?
Some lava flows on Olympus Mons appear relatively young in geological terms, perhaps tens of millions of years old, but there’s no sign of current eruptions.
Other giant mountains
- Rheasilvia, a peak inside a crater on the asteroid Vesta, is similar in height and may rival Olympus Mons.
- Mauna Kea is Earth’s tallest mountain measured from base to peak, at about 10 km, though much of it is underwater.
Mars has two other famous features: Valles Marineris, a canyon about 4,000 km long, and its red dust. Thinking of visiting? See how long it takes to travel to Mars. Earth’s highest peaks are listed in the highest mountain in South America.
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