Monday 31st January

Today's contributor: Jon Copley

SHRIMP, our towed camera system, spent most of today traversing the seafloor of the middle ridge at Three Sisters at between 1100 and 1300 m deep, allowing us to inspect the marine life down there, and look for promising sites for deploying the megacorer.

"SHRIMP-HD", now "pimped" with an HD camera and laser scale system from Isis

Paul, our expedition Chief Scientist, has offered a useful analogy for surveying with SHRIMP: go to the top floor of a house, lean out of a window, and dangle a matchbox on a long string down to just above the ground outside. Then drag that matchbox in a consistent grid pattern over the patio, without crashing it, while bouncing up and down on a bed upstairs. It is a testament to the skills of the bridge officers driving the ship, and the SHRIMP team controlling the winch, that the task seems effortless.

The seafloor that we surveyed today varied from a flat plain dotted with brittle stars and occasionally their cousins, the sea cucumbers, to rocky outcrops festooned with octocorals that looked like bottle-brushes. The rocky outcrops were old "pillow basalts" - solidified flows of lava that once squeezed out of the seafloor like toothpaste from a tube. In general, however, the volcanic features that we saw looked "old and cold", consistent with the lack of definitive signs of venting found by our CTD survey.

"SHRIMPshack": mission control, inside two modified cargo containers on the aft deck

After hauling SHRIMP back aboard in the early evening, we sent down the megacorer to collect sediment samples from two areas identified by the dive. Although we haven't found vents in this area, that result may help us understand the evolution of the volcanic ridges in Bransfield Strait. But absence of evidence isn't evidence of absence, and so the sediment cores will allow the geochemists to check those ideas.

January 2011


February 2011