Identifying the world’s largest volcano is complex because the answer depends entirely on how “largest” is defined. Volcanic size can be quantified in several distinct ways, meaning scientists cannot point to a single, undisputed winner. The largest may be the mountain that stands highest above sea level, the one that rises highest from its base, or the one that contains the greatest total volume of material. This means the title is split between contenders that each dominate a specific metric of scale.
How Volcanoes Are Measured
Volcanologists use three primary metrics to determine the size of a volcanic structure. The most common measurement is elevation, which is the height of the summit above sea level. This is the simplest measurement to take and often determines the “highest” peaks familiar to the general public.
A more geologically meaningful metric is the true vertical rise, which measures the distance from the volcano’s base on the ocean or land floor to its summit. This figure accounts for the entire mountain structure, regardless of whether the base is submerged or buried. Volume or mass is calculated by estimating the total amount of rock contained within the mountain, typically expressed in cubic kilometers. This metric speaks to the sheer bulk of the volcano.
The World’s Most Massive Volcano
By the metric of total mass and volume, the largest active volcano on Earth is Mauna Loa, located on the island of Hawaiʻi. This giant shield volcano is estimated to contain a volume of approximately 75,000 to 80,000 cubic kilometers of rock. Its massive structure accounts for more than half of the surface area of the island.
While the summit of Mauna Loa stands at 4,169 meters (13,679 feet) above sea level, this is only a fraction of its true height. The volcano’s slopes descend thousands of meters to the seafloor, and its base has depressed the Earth’s crust another 8 kilometers beneath the ocean floor. Measuring from its deep base, the mountain rises an astonishing 9,170 meters (30,085 feet), making it taller from base to peak than Mount Everest is from sea level.
The title of “most massive” was briefly challenged by the Tamu Massif, a colossal underwater feature in the Pacific Ocean. However, research concluded that Tamu Massif is likely a complex of overlapping volcanic structures rather than a single shield volcano. This reinforces Mauna Loa’s position as the single active volcanic edifice with the greatest mass and volume.
The World’s Highest Peaks
When size is determined by elevation above sea level, the record belongs to Ojos del Salado, a mountain straddling the border between Chile and Argentina. This peak is recognized as the highest active volcano in the world, reaching an elevation of 6,893 meters (22,615 feet).
Ojos del Salado is a composite volcano, or stratovolcano, situated high in the Andes mountain range. Its great height is primarily a function of its location on an existing, elevated continental mountain chain. Although its total volume is significantly smaller than that of the Hawaiian giants, its prominence is due to the stacking of viscous lava flows and ash layers high above the surrounding terrain.
Why Size Matters: Type and Activity
The difference in size records is intrinsically linked to the two main types of volcanoes they represent: shield volcanoes and stratovolcanoes. Mauna Loa is a classic shield volcano, built from highly fluid, basaltic lava that flows easily and spreads out over vast distances. This low-viscosity lava creates broad, gently sloping sides, which allows the volcano to achieve its immense volume and base width over millions of years.
In contrast, Ojos del Salado is a stratovolcano, formed by thick, viscous lava and layers of ash and rock fragments. This sticky material does not travel far before solidifying, resulting in the steep, conical profile that contributes to its great height above the ground.
While Mauna Loa’s activity is characterized by relatively non-explosive, effusive lava flows, its most recent eruption occurred in late 2022. Ojos del Salado is considered active due to persistent fumarolic activity, which involves the emission of steam and gases from the mountain, but it has no confirmed eruptions in historical times.