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Largest Volcano on Earth Is Found Beneath Pacific Ocean

How big is the world’s largest volcano? The answer is bigger than the British Isles. Recently, researchers from University of Houston announced the discovery of the world’s largest volcano, called Tamu Massif, from Shatsky Rise in northwest Pacific Ocean. The new findings have been published in the journal Nature Geoscience.

The enormous mound, the Tamu Massif, possesses more than 310,000 square km and dwarfs the previous record holder, Hawaii’s Mauna Loa. William Sager, the lead author of the study and a geologist at the University of Houston, said that the Tamu Massif is only 25 percent smaller than Olympus Mons on Mars, which is the biggest volcano in Earth’s solar system.

The researchers noted that the Tamu Massif is an extinct volcano. It erupted for a few million years during the early Cretaceous period and has been extinct since 144 million years ago.


Height and width comparison between Tamu Massif, Mauna Loa and Olympus Mons. *Image source: Nature.

Although it spreads in a large area, the Tamu Massif is a “shorty”— it’s 400 miles (650 kilometers) wide but only about 2.5 mile (4km) tall. Sager said:” The slopes are very shallow. If you stand on this thing, you would have some difficulties telling which way was downhill.” This is might because the lava erupted form the Tamu Massif has high effusion velocity so it can flow farther.

The top of the Tamu Massif is around 6,500 feet (1,980 meters), thus this volcano sits below the ocean surface and has been hidden for years. Sager and his colleagues have been studying Shatsky Rise for decades, seeking to solve the puzzle of oceanic plateaus. However, “Structures that are under the ocean are really hard to study,” said Sager.

Tamu Massif

A 3D map of the Tamu Massif. *Image source: William Sager

However, the researchers painstakingly collected lava samples from Tamu Massif and analyzed seismic survey data and finally understood how the great volcano formed. They found that lava flows dipping away from the summit of the volcano, suggesting that Tamu Massif is a single volcano. Large quantities of lava from mantle flows from a volcano crater around the central area and moves along the slope for hundreds of miles and eventually flows into near basin. As time passes, wide but relatively plain volcano with shield shape forms.

The researchers point out that the new findings could help constrain models of how oceanic plateaus form. Oceanic plateaus are largest igneous rock on earth but how they are formed has long been controversial.  Some researchers believe plums of magma from deep in the mantle punch through the crust, flooding the surface with lava. Other scientist think that pre-existing weaknesses in the crust, such as tectonic-plate boundaries, provide passageways for magma from the mantle, the layer beneath the earth’s crust. Shatsky Rise formed atop a triple junction, where three plates pulled apart. Sager emphasizes that in order to explain ocean plateaus, people need to know how big volcano like Tamu Massif forms in one spot and delivers this kind of magma supply in a short time.

Moreover, other oceanic plateaus, such as Ontong Java Plateau, located north of the Solomon Islands in the southwest Pacific Ocean, could be awaiting discovery. Volcano like Tamu Massif might offer some clues for scientists and help them better demonstrate earth’s interior activity mechanism.

Source: Nature;Science 2.0; LiveScience