Explore the Largest Known Volcanoes

Volcanoes continually change Earth and other worlds. Here, an ash plume billowing out from Iceland's Eyjafjallajokull volcano, April 2010. Arni Frioriksson/Wikimedia Commons

Volcanism is one of the major forces that shape many worlds in the solar system. For example, this geological process continually "paves over" the surface of Io, one of Jupiter's moons. It's also reshaping the planet Venus beneath its thick blanket of clouds.

Not all volcanoes spew rock. Ice volcanoes operate on the moons of Europa (at Jupiter) and Enceladus at Saturn, and may well be changing the distant world, Pluto. Our home planet, Earth, has volcanoes on every continent and its landscape has been significantly changed throughout history by volcanism. Here is a look at the six largest volcanoes in our solar system. 

Olympus Mons

largest volcano in the solar system
Olympus Mons on Mars is the largest known volcano in the solar system. NASA

The largest known volcano in the solar system is actually on the planet Mars. Its name is "Olympus Mons" and it towers some 27 kilometers above the planet's surface. This giant mountain is a shield volcano and if it existed on Earth, it would tower over Mount Everest (the tallest mountain on our planet).

Olympus Mons is on the edge of a huge plateau called the Tharsis Bulge. It was built up by continual lava flows over millions of years, and contains several other volcanoes. The mountain is the product of continuous lava flows that occurred beginning about 115 million years ago and continuing until about two million years ago.

It now seems to be dormant. Planetary scientists do not know if there is still any activity deep within the volcano. That knowledge may have to wait until the first humans can walk the planet and do more extensive surveys.

Mauna Kea

Mauna Kea
Mauna Kea, on the Big Island of Hawai'i, as seen from orbit. While it is dormant, and hosts a number observatories, it is theoretically possible this mountain could erupt again. NASA

The next-largest volcanoes are on our own home planet Earth. The tallest one is called Mauna Kea, and it rises up nearly 4,267 meters above sea level on the Big Island of Hawai'i. However, there's more to Mauna Kea than meets the eye. Its base is deep beneath the waves, some six thousand meters. If Mauna Kea were all on land, it would tower up higher than Olympus Mons at an astounding 10,058 meters.

Mauna Kea was built up over a hot spot. That's a plume of heated melted rock called magma that rises up from Earth's mantle and eventually reaches the surface. Over millions of years, the plume has spurred the build-up of the entire Hawaiian Island chain. Mauna Kea is a dormant volcano, meaning that it hasn't erupted in well over four thousand years, so it may not be centered directly over the plume any longer. However, that doesn't mean it won't erupt again.

It could wake up someday, even though most of the activity on the island is now dominated by the Kilauea shield volcano on the slopes of nearby Mauna Loa.

Mauna Kea is home to a collection of astronomical observatories and is protected as both a research park and a historical site.

Ojos del Salado

Ojos del salado volcanoes
The Ojos Del Salado volcanic range in South America tower between two countries. USGS

Mauna Kea may be the tallest volcanic mountain when measured from base to summit, but another mountain claims the highest elevation if measuring from the sea bottom. It's called Ojos del Salado, and it rises up to 6,893 meters above sea level. This enormous mountain is located in South America, on the border between Argentina and Chile. Unlike Mauna Kea, Ojos del Salado is not dormant. Its last major eruption was in 1993 and it continues to rumble quietly.

Tamu Massif

tamu massif
Tamu Massif, (named after Texas A&M University), is under the Pacific Ocean's waves a thousand miles from Japan. It sprawls across the sea bottom and is still being mapped. USGS

One of the largest volcanoes on Earth wasn't even discovered until 2003. It remained such a well-kept secret largely due to its location deep in the Pacific Ocean. The mountain is called Tamu Massif, and it rises up about four kilometers from the sea floor. This extinct volcano last erupted 144 million years ago, during the geologic time period known as the Cretaceous. What Tamu Massif lacks in height it more than makes up in the size of its base; it sprawls across 191,511 square kilometers of the ocean bottom.

Mauna Loa

Mauna Loa erupting in Hawai'i
A view of a 1986 eruption of Mauna Loa on the Big Island of Hawai'i. USGS


Two other volcanoes are in the "Big Mountains" hall of fame: Mauna Loa on Hawai'i and Kilimanjaro in Africa. Mauna Loa was built up the same way that its sister peak Mauna Kea was, and towers some four thousand meters above sea level. It's still active, and visitors are warned that eruptions can take place at any time. It has been erupting almost continuously for more than seven hundred thousand years and is considered the largest volcano in the world by mass and volume.

Like Mauna Kea, it's a shield volcano, which means that it has been built up layer by layer through eruptions through a central lava tube. Of course, smaller eruptions do break out through vents in its flanks. One of its more famous "offspring" is the Kilauea volcano, which began erupting some three hundred thousand years ago. Volcanologists once thought it was merely an offshoot of Mauna Loa, but today Kilauea is considered a separate volcano, cuddled up next to Mauna Loa.


Mt Kilimanjaro
Mount Kilimanjaro in Africa, as seen from space. NASA

Mount Kilimanjaro is a massive and tall volcano in Tanzania in Africa that towers nearly five thousand meters above sea level. It's actually considered a stratovolcano, which is another term for a very tall volcano. It has three cones: Kibo (which is dormant but not dead), Mawenzi, and Shira. The mountain exists within the Tanzania National Parks. Geologists estimate that this massive volcanic complex began erupting some two and a half million years ago. The mountains are nearly irresistible to mountain climbers, who have swarmed its flanks since the 19th century.

Earth has hundreds of volcanic features, many much smaller than these massive mountains. Future explorers to the outer solar system, or even to Venus (if they should ever be able to descend close enough to see its volcanoes), will find exciting possibilities for volcanic activity out in the universe, as well. Volcanism is an important force on many worlds, and on some, it has created some of the most beautiful landscapes in the solar system.