Tamu Massif, World’s Largest Volcano Discovered Under Pacific Ocean, Is 60 Times Larger Than Mauna Loa, Scientists Say

Scientists say that an underwater volcano, previously believed to be a collection of small volcanoes, is the largest ever discovered on Earth, and it has stripped the title from the previous record holder, Mauna Loa.

According to Nature World News, new research confirms that the inactive submarine shield volcano located about 1,000 miles east of Japan, dubbed Tamu Massif by scientists at the University of Houston in Texas, was formed by a single volcanic source. The research, published in the current issue of Nature Geoscience, places Massif’s size at approximately 120,000 square miles -- for comparison, that's roughly the size of Poland, New Mexico and the Sonoran Desert. Mauna Loa in Hawaii, which is still active, is 2,000 square miles.

Tamu Massif makes up the largest feature of the Shatsky Rise, an oceanic plateau in the Pacific Ocean that came into existence, scientists believe, as a result of volcanic-eruption activity that occurred between 130 and 145 million years ago.

William Sager, a professor of Oceanography at the University of Houston, who led the research, said the volcano’s colossal size isn’t the only unique thing about it: Its low, broad structure -- a distinguishing feature of shield volcanoes -- suggests that the lava that formed it flowed from distances much greater than the flow distances of lava that formed many other volcanoes.

"It's not high, but very wide, so the flank slopes are very gradual," Sager said. "In fact, if you were standing on its flank, you would have trouble telling which way is downhill. We know that it is a single immense volcano constructed from massive lava flows that emanated from the center of the volcano to form a broad, shield-like shape. Before now, we didn't know this because oceanic plateaus are huge features hidden beneath the sea. They have found a good place to hide."

"Its shape is different from any other submarine volcano found on Earth, and it's very possible it can give us some clues about how massive volcanoes can form," Sager said. "An immense amount of magma came from the center, and this magma had to have come from the Earth's mantle. So this is important information for geologists trying to understand how the Earth's interior works."

Sager explained that researchers were finally able to identify the source of the basalt that former the volcano, by collecting data and samples. "We knew it was a big mountain, some sort of volcanic mountain, but oceanic plateaus are very large features hidden beneath the ocean and it's very hard to study them," he said. "The main thing was the imaging we were able to do a few years ago, but without sort of the ground truth provided by samples that we drilled out of this thing, we wouldn't have had nearly as compelling a result."

However, Sager wouldn’t rule out the possibility that other volcanoes, similarly believed to be part of a series, could prove to be single volcanoes.

“Tamu Massif is the biggest single shield volcano ever discovered on Earth,” Sager said. “There may be larger volcanoes, because there are bigger igneous features out there such as the Ontong Java Plateau, but we don’t know if these features are one volcano or complexes of volcanoes.”