Available Weekly Reports
13 May-19 May 2009
In early May, scientists from an NSF (RIDGE and MARGINS Programs) and NOAA (Ocean Exploration Program) sponsored cruise on the University of Washington vessel, the R/V Thompson, traveled to the Lau-Tonga region. This rapid-response expedition was undertaken after strong indications of submarine eruptive activity had been detected during a November 2008 NOAA Vents Program expedition. On 6 and 7 May, team members used the Jason 2 ROV to observe eruptions from two vents of West Mata, a small submarine volcanic cone in the northeast Lau Basin, about 200 km SW of Samoa. Explosive activity occurred from one end of a 5-m-long fissure at Hades vent, at a depth of 1,208 m, while pillow lavas erupted from the other end of the fissure. Glowing bubbles up to a meter in diameter also issued from the fissure. The Prometheus vent, a cinder cone located near the summit and about 100 m N of Hades, erupted explosively with nearly continuous lava fountains that ejected tephra into the water. Both vents were often obscured by sulfur gas emissions, but incandescence was visible for minutes at a time.
Sources: NOAA Vents Program
13 May 2009Back to Top
Summary of eruption dates and Volcanic Explosivity Indices (VEI).
|Start Date||Stop Date||Eruption Certainty||VEI||Evidence||Activity Area or Unit|
|2008 Nov (in or before)||2009 May (in or after)||Confirmed||0||Historical||Prometheus and Hades vents|
West Mata, a submarine volcano rising to within 1174 m of the sea surface, is located in the northeastern Lau Basin at the northern end of the Tonga arc, about 200 km SW of Samoa. West Mata volcano lies about 7 km west of another submarine volcano, East Mata; both lie at the northern end of the Tonga arc, north of the historically active Curacoa submarine volcano. The two volcanoes were discovered during a November 2008 NOAA Vents Program expedition, and West Mata was found to be producing submarine hydrothermal plumes consistent with a recent or lava effusion. A return visit in May 2009 documented explosive and effusive activity from two closely spaced vents, one at the summit, and the other on the SW rift zone.