The question of the world’s tallest mountain often leads to confusion because standard measurements focus only on the distance from the summit to the surface of the sea. This overlooks a mountain’s full geological structure. To find the true giant of the planet, it is necessary to look beyond the ocean’s surface and consider the vast submerged portions of these colossal landforms. This requires differentiating between a mountain’s height above sea level and its total size from its fundamental base.
Defining Height Versus Tallness
When geologists and cartographers discuss mountain measurements, they use two distinct metrics. The first, referred to as height or elevation, measures the vertical distance from a mountain’s summit to the mean sea level. This is the common standard used for all mountains visible on land, establishing their altitude relative to a global datum point.
The second metric, termed tallness, measures the mountain’s total vertical extent from its base to its summit. For continental mountains, defining the base is subjective, but for those that begin on the ocean floor, the base is clearly the point where the structure meets the abyssal plain. This base-to-summit measurement provides a more accurate representation of the mountain’s true physical size and mass. It is by this second metric that the world’s tallest mountain is found deep underwater.
The Tallest Mountain Measured From Base to Summit
The mountain that holds the title for the world’s greatest vertical extent is Mauna Kea, a dormant shield volcano located on the island of HawaiĘ»i. Measured from its true base on the Pacific Ocean floor to its peak, Mauna Kea reaches a total height of approximately 10,205 meters (33,480 feet). This makes the Hawaiian peak nearly a mile taller than the elevation of Mount Everest.
Mauna Kea’s summit rises to 4,205 meters (13,796 feet) above sea level, meaning that nearly 60% of its massive structure is submerged. Its colossal scale is also evident in its volume. The immense weight of the volcano has depressed the oceanic crust beneath it by several kilometers, emphasizing its sheer geological mass.
The Geological Forces That Submerge Mountain Bases
The submergence of Mauna Kea’s base results from specific geological processes associated with hotspot volcanism. Mauna Kea is a shield volcano, built up gradually over millions of years by countless flows of fluid lava erupting through a fixed point in the Earth’s mantle known as the Hawaiian hotspot. As the Pacific tectonic plate slowly moved over this hotspot, the continuous accumulation of lava created the massive, broad structure of the Hawaiian Islands.
The mountain’s sheer volume and weight force the base below the surrounding sea floor, a process known as isostasy. The volcano’s mass causes the relatively thin oceanic crust to flex and sink into the mantle, creating a surrounding depression called the Hawaiian Trough. This feature effectively lowers the mountain’s base even further below the original sea floor.
The Highest Peak Measured From Sea Level
In contrast to Mauna Kea’s total tallness, Mount Everest remains the undisputed holder of the title for the highest peak on Earth. The summit of Mount Everest, part of the Mahalangur Himal sub-range of the Himalayas, sits farthest above mean sea level.
The current accepted elevation, jointly measured and declared by China and Nepal in 2020, is 8,848.86 meters (29,031.7 feet) above sea level. Because Everest is part of a continental mountain range that sits atop a high plateau, its base is already thousands of meters above sea level. This difference in base elevation is why Everest is the highest mountain for climbers, while Mauna Kea is the tallest mountain from a purely geological perspective.