May 11, 2009

We Thought We’d Seen it All

Prometheus eruptive vent at the summit of West Mata (1208 meters)

Bob Embley: Co-Chief Scientist
Joe Resing: Chief Scientist

Five years ago we came across our first view of an active submarine eruption at NW Rota-1 volcano near Guam in the western Pacific. It amazed and astounded us to see volcanic bombs and gas bubbles being injected from Brimstone Pit (the volcanic vent). On our return visit in April of this year, we saw lava being extruded from the pit. We all felt very fortunate to witness these phenomena for the first time.

Hades eruptive vent at the summit of West Mata (1174 meters)

From results of our initial surveys in the NE Lau Basin in November 2008 we suspected something similar was occurring on West Mata, a small submarine volcanic cone in the northern Lau Basin, about 200 km southwest of Samoa. However, nothing prepared us for the sights we saw on the summit of this volcano - our first dive on the site today using the remotely operated vehicle Jason 2 nearly overwhelmed our senses with a collective gasp. Here, at a depth of 1208 meters (almost 4000 feet), we saw for the very first time pillow lavas flowing from a deep submarine volcano at a site we are now calling Hades. In contrast to Brimstone Pit, we could not approach close to this site because it was undergoing violent explosive activity and almost continuously shedding large blocks of lava as well as pillow flows. On our first approach we saw red glows from the extruding lavas up to 5-10 meters away from the vent!

We were due for another surprise. About 100 meters along the summit from Hades our sonar started showing some very strange echo returns from something to the north of us. As we turned toward it there was another billowing plume! Descending to this site another vent revealed itself as a cinder cone spewing volcanic bombs and ash! As we sat there, a red glow appeared and persisted for about 30 seconds as hot magma and gases were expelled. Wow! Have we seen it all yet? I very much doubt it!

Tomorrow we return to explore the site further…. Stay tuned.

All high-definition video by Advanced Imaging and Visualization Lab, copyright WHOI