Classroom@Sea » Cruises

Exploring a crater between Cook and Thule Islands

On Saturday at mid-day we arrived to an incredibly beautiful place: the South Sandwich Islands. We approached them in the fog, but as we were getting closer, two of the large islands, Cook and Thule, appeared ahead of us, covered in ice, snow and clouds. In the afternoon, the clouds cleared and the landscape was spectacular: snowed-covered peaks, glaciers running down to the sea, steep black slopes and a beach with a penguin and seal colony. This is a unique place to work!

We have been working between the two islands, in a crater at around 600 m depth. We first did several CTDs to look for potential hydrothermal plumes and take some water samples to measure the concentration of methane in the water, which will help us understand if there are vents in the seafloor. There was a plume signal and so we deployed SHRIMP with its video cameras to have explore the sea bed in the crater. The seafloor was covered with sediment and had large amounts of decaying algae that have fallen from the coast. These algae are a good source of food for the animals living in the deep sea, so all the algae were covered in animals like sea stars and large ribbon worms (nemerteens) eating them. We did not find hydrothermal vents in this survey, but we could only have SHRIMP flying over the seafloor for a few hours, as we had to leave the islands before dark. However, the work we have done today will allow us to come back and conduct a more detailed survey of the crater.