The question of the world’s tallest volcano is complex because the answer depends entirely on the method used for measurement. Like any mountain, a volcano’s height can be quantified in several ways. Measuring the summit above sea level yields one result, while measuring the full structure from its true geological base to its peak gives a dramatically different answer. This difference splits the title between the highest point on a continental landmass and the largest total mountain structure emerging from the deep ocean floor.
Defining Tall: Measuring Height Above Sea Level
The most common metric for mountain height is the elevation of the summit above mean sea level. By this standard, the highest volcano in the world is Nevado Ojos del Salado, a massive peak in the Andes mountain range. Ojos del Salado, which straddles the border between Chile and Argentina, stands at 6,893 meters (22,615 feet) above the ocean surface. This stratovolcano is known for its steep, conical shape and contains the highest known crater lake in the world, situated at approximately 6,390 meters. Although it has not had a major eruption in over a millennium, it is considered active due to persistent fumarolic activity.
Defining Tall: Measuring Height from Base to Summit
When height is measured from the volcano’s true geological base to its highest point, the title shifts to an oceanic giant: Mauna Kea, located on the Island of Hawaiʻi. Its summit rises 4,205 meters (13,796 feet) above the Pacific Ocean’s surface. However, the vast majority of Mauna Kea is submerged beneath the waves, descending roughly 6,000 meters (19,700 feet) to the ocean floor. Measuring from this underwater base to the peak, Mauna Kea reaches a total height of approximately 10,210 meters (33,500 feet). This measurement makes it the tallest mountain on Earth by a significant margin, surpassing the elevation of Mount Everest above sea level.
Largest Volcanic Mass and Footprint
A third way to define the largest volcano is by sheer mass and volume, which identifies Mauna Loa. Mauna Loa is recognized as the largest active volcano on the planet in terms of volume and area covered. While its summit is slightly lower than Mauna Kea’s, its mass is far greater, accounting for more than half of the entire Island of Hawaiʻi. The volume of Mauna Loa is estimated to be at least 75,000 cubic kilometers (18,000 cubic miles). Furthermore, its weight has depressed the oceanic crust beneath it by an additional 8 kilometers. Considering this crustal depression, the volcano’s total height from its deepest geological root to its summit is about 17 kilometers (56,000 feet), confirming Mauna Loa as the most massive single mountain on the planet.
The Geology Behind Giant Volcanoes
The fundamental differences in the size and shape of these volcanic giants are explained by the type of magma that forms them. The two main categories are stratovolcanoes (like Ojos del Salado) and shield volcanoes (like Mauna Kea and Mauna Loa). Stratovolcanoes are found at subduction zones, where one tectonic plate slides beneath another, leading to the formation of silica-rich magma. This magma is highly viscous, meaning it traps gas easily and does not flow far from the vent. This process causes the eruption material to pile up in layers of ash and lava, resulting in the steep, conical profile and explosive eruptions.
In contrast, shield volcanoes formed over a stationary hotspot. The magma feeding them is basaltic and has very low viscosity, allowing it to flow great distances before hardening. This runny lava builds up in thin, broad sheets over millions of years, creating a mountain with a gently sloping profile that spans a massive footprint. The continuous, effusive nature of these eruptions allows shield volcanoes to achieve immense volumes.