Underwater volcano spews exotic lava

Charles Harvey, contributor

This video, taken a kilometre down in the south-west Pacific Ocean near Tonga, shows an exotic type of volcanic lava normally associated with the birth of a subduction zone.

Boninite forms when mantle rock reacts with hydrothermal fluid and then melts. It typically forms during the early stages of subduction, when one tectonic plate is forced below another.

The lava contains huge quantities of super-hot steam, carbon dioxide and sulphur. When the molten rock hit the cool, dense waters of the Pacific, these gases cause explosions that fragment the new rock, creating the characteristic pillow and bubble shapes seen in the video.

"Observing the eruption in real time was a rare and special opportunity, because we know so little about how submarine volcanic activity behaves," says Robert Embley of the National Oceanic and Atmospheric Administration, and co-author of the research.

"This is one of only a handful of glimpses of the process we've had to date and is the first time we've actually observed natural submarine light from the glowing magma."

Journal reference: Nature Geoscience DOI:10.1038/ngeo1275

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