Back in 2013, Tamu Massif — a giant underwater volcano off the coast of Japan — stole Hawaii’s crown as the largest single volcano in the world. But it’s not a true single volcano at all.

Researchers published a paper in 2013 in the journal Nature Geoscience concluding that Tamu Massif was a giant “shield volcano” — even bigger than Hawaii’s Mauna Loa, which rises 30,085 feet (9,170 meters) from the ocean floor and covers thousands of square miles with its ancient, solidified magma flows. Now, in a new paper, researchers conclude that the 2013 paper was wrong, and Tamu Massif isn’t a shield volcano. The crown, according to this new research, returns to Mauna Loa.

Shield volcanoes form when a single volcanic plume spills enough lava over time, and that lava spreads far enough, to form a bulge-shaped mountain around the volcano’s opening. Mauna Loa is a shield volcano. So are most of the much smaller volcanoes in Iceland. (Cone-shaped volcanoes, like Mount St. Helens, aren’t shields but “stratovolcanoes.”) In 2013, researchers thought that Tamu Massif formed in this same way. But the new paper suggests they’re wrong.

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