World’s largest volcano lurks beneath Pacific Ocean

The most massive volcano in the world, with a footprint the size of New Mexico, crouches in the dark depths of the western Pacific Ocean. With its hollowed peak lying beneath 2 kilometers of water, Tamu Massif, a basaltic mound, may rival the largest known volcano in the solar system: Mars’ Olympus Mons.

A team led by oceanographer William Sager then of Texas A&M University bounced sound waves off the deep-sea mountain to measure its size.

The researchers report online September 5 in Nature Geoscience that Tamu Massif forms a broad, rounded dome rising 4 kilometers from the seafloor and stretching 450 by 650 kilometers across. Core samples that the researchers extracted from the volcano’s slopes showed that, during its prime 145 million years ago, the ancient mound spewed lava sheets 23 meters thick.