May 5, 2010

May 5th Synopsis

We have now been at sea one week, already half-way through this expedition to the Lau Basin. During this first part of the cruise our main scientific objectives have been to search for new volcanic activity, as well as to verify whether or not volcanoes visited on past cruises are still active. Two methods of exploration have been used. The first is a suite of sensors on board a CTD-rosette sampler system that is lowered from the ship, which enables us to detect hydrothermal and volcanic activity on the seafloor. The second method is a camera sled that is towed near the seafloor, providing images of lava flows, biota, and hydrothermal vents.

Up to this point our operations area has been the Mata group of volcanoes. West Mata, the volcano that was erupting lava onto the seafloor during our last visit in 2009 is still extremely active (see our blog entries from the 2009 expedition link on the right side of this page). The hydrothermal system at East Mata is also still emitting hydrothermal fluids. The main focus area has been the "North Matas", an area not previously explored by our group. CTD tows have been executed across all of the northern Matas and all but one have a hydrothermal signal. In addition 2 camera tows on the northern Matas reveal hydrothermal vent biota, as well as extinct and active sulfide chimneys.

Camera tow image of chimneys on one of the northern Matas.
The chimneys in this image don't appear to be emitting hydrothermal fluids.

Biota in the region of the previous chimney image.
Crab species, shrimp and urchins are present.

CTD towyo over one of the North Mata volcanoes.
Orange and red colors indicate high particle concentrations over the summit.

The NE Lau basin appears to be one of the most magmatically active place on earth. Our previous research shows evidence of extensive volcanism in the region. Many areas are covered with relatively young lava flows. So, in addition to looking at the Mata group of volcanoes, we also performed 4 camera tows over some of those lava flows. When magma is erupted on the seafloor and is cooled by hydrothermal activity, it releases a rare elemental tracer, helium (3He). A large helium anomaly exists throughout the region, the source of which is unknown. In an effort to better identify the source, three CTD vertical casts were acquired in the area of the Tonga trench. This long-term project is one we will continue to pursue.

At this point we have performed 14 CTD operations, 8 of those have been tow-yos and 6 have been vertical casts. 7 camera tows have been completed. Stay tuned.