More than 70% of volcanic activity occurs underwater with much of it hidden from human view by seawater. But in 2012, passengers on a flight over the Pacific Ocean saw something odd: a big chunk of floating pumice rock, signaling an underwater volcano had erupted. A new paper published in the journal Science Advances details that 2015 exploration and its surprising discoveries.

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The Largest Underwater Volcano Explosion, We Almost Missed | Mach | NBC News