When asked to think of the biggest mountain on Earth, we’d guess that most people think of towering Mount Everest, located in the Himalayas. But if you were to ask what the biggest volcano on Earth is, we’d bet that most people wouldn’t have a clue, perhaps not even knowing the distinction between a volcano and a mountain.
While all volcanoes are technically mountains, not all mountains are volcanoes. The difference lies in how each is created. While mountains form as a result of continental tectonic plates shifting and colliding, volcanoes are created from an eruption of magma from the Earth’s mantle, breaching the surface and continuing to grow with each lava flow. Volcanoes fade into mountains when they become extinct, meaning that magma no longer emerges from the volcano’s center.
Up until recently, the Hawaiian volcano Mauna Loa held the title of the world’s largest volcano, comprising an impressive 2,000 square miles in total volume. It is a shield volcano, so named for its wide, flattened appearance, resembling that of a soldier’s shield. These types of volcanoes are formed by highly fluid lava flowing steadily out from the center in all directions, making a new broad layer with each flow. And now science has discovered a new champion about 1,000 miles east of Japan, lying well out of sight at 6,500 feet below the surface of the Pacific Ocean: Tamu Massif.
Tamu Massif
Tamu Massif has been on the scientific radar for the last two decades, but it was originally thought to be a composite of several volcanoes in near proximity to each other that eventually became one entity, located on an oceanic plateau in the Pacific known as the Shatsky Rise. But recent studies of its seismic data revealed lava flows from one source in the volcano’s center spreading out in all directions, and core samples taken from various parts of Tamu Massif were all the same type and age of rock, which would not be possible if there were more than one volcanic entity that comprised the supervolcano.
The newly-crowned largest volcano on Earth dwarfs Mauna Loa with a dome of a staggering 100,000 square miles, and a base that plunges to around 4 miles beneath the Pacific. Its name comes from geology professor William Sagen, who was working at the Texas A&M University (TAMU) at the time he began studying the behemoth; massif is a scientific term for a large mountain.
Researchers believe that the volcano went extinct roughly 145 million years ago, just a scant million years after it began to form. The next step for scientists is to determine what caused Tamu Massif to form, starting with the source of the magma and how it made it to the surface in the first place. Discoveries made throughout the process could challenge what is currently understood about oceanic plateaus and may reveal more shield volcanoes like this one.
Until then, Tamu Massif will simply have to enjoy its status as a hidden giant on our ever-mysterious planet.
Images via National Geographic, Wikipedia
