How volcanoes explode in the deep sea

Most volcanic eruptions take place unseen at the bottom of the world's oceans. In recent years, oceanography has shown that this submarine volcanism not only deposits lava but also ejects large amounts of volcanic ash.

"So even under layers of water kilometers thick, which exert great pressure and thus prevent effective degassing, there must be mechanisms that lead to an 'explosive' disintegration of magma," says Professor Bernd Zimanowski, head of the Physical-Volcanological Laboratory of Julius-Maximilians-Universität (JMU) Würzburg in Bavaria, Germany.

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Underwater volcanic eruptions and magma flows on the sea floor have been seen for the first time ever thanks to video captured by NOAA. James Williams talks to the lead scientist on the project to learn the story behind the explosive images.

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