Deepest and most explosive underwater eruption ever seen happening near Samoa hotspot

October 20, 2011 – SAMOA – An underwater volcano bursting with glowing lava bubbles — the deepest active submarine eruption seen to date — is shedding light on how volcanism can impact deep-sea life and reshape the face of the planet. Submarine eruptions account for about three-quarters of all of Earth’s volcanism, but the overlying ocean and the sheer vastness of the seafloor makes detecting and observing them difficult. The only active submarine eruptions that scientists had seen and analyzed until now were at the volcano NW Rota-1, near the island of Guam in the western Pacific. Now researchers have witnessed the deepest active submarine eruption yet. The volcano in question, West Mata, lies near the islands of Fiji in the southwestern Pacific in the Lau Basin. Here, the rate of subduction — the process in which one massive tectonic plate dives under another, typically forming chains of volcanoes — is the highest on Earth, and the region hosts ample signs of recent submarine volcanism. “It was absolutely stunning and exciting, something we’d never seen on the seafloor before,” researcher Joseph Resing, an oceanographer at the University of Washington in Seattle, told OurAmazingPlanet. This submarine eruption is the deepest seen yet, about 2,200 feet (700 m) deeper than NW Rota-1. This was deeper than scientists had expected to see explosive eruptions. Water pressure goes up the further down you go, “so as pressure goes up, the ability of gas as it comes out of magma to cause explosions is diminished, and the thought was that you wouldn’t get explosive eruptions below about 1,000 meters (3,300 feet),” Resing said. Eruptions at centers of ocean floor spreading — where the majority of eruptions on Earth happen — generally seem to occur in relatively short episodes lasting hours to months, but West Mata appears to have erupted near continuously since it was first observed in 2008. This might be because magma is focused there, instead of being spread across many volcanoes at once. “However, this is a question that we don’t currently know the answer to,” Resing said. –OAP