Start survey on the South section of the East Scotia Ridge
We are now on the E9 segment of the East Scotia Ridge, just below 60ºS!
As in the northern section, we have started our survey conducting a detailed swath bathymetry of the area, to have good maps of the seafloor. The are of the ridge that we are studying is especially interesting because the ridge has a crater in the middle. This crater was formed either by a volcanic eruption, like the craters in volcanoes on dry land, or because a lava lake collapsed when the moulted lava retreated below it into the magma chamber. The result is a beautiful crater of 1.5 km diametre, with the top of its walls at 2400 m depth and the centre of the crater at 2750 m depth. You can see a bathymetric map that Ali has made with the swath data.
Once we had a good map of the seafloor, we started our CTD tow-yo survey. The CTD was deployed in one side of the crater and the survey started, looking for the changes in the CTD data that indicate the presence of “cloudy” water. There were no hydrothermal plume signals in the crater. We searched all night outside the crater as well, but with not much luck....but then, just at breakfast time, things started getting exciting! The CTD monitors started showing increased LSS signals (indicating higher concentration of particles) and a lower transmissometre signal (which measures the amount of light that goes through the water). This is indicating that down there there is a large beautiful hydrothermal plume, so the smokers can not be very far! When we had the CTD in the plume, Doug fired some bottles from the CTD to take water samples for chemical analyses. Once the CTD was on board, there was a rush of activity as the water needs to be taken into the lab quickly and analysed or preserved, for example by freezing it, for analysis later. Doug analysed the methane in the water and Sarah the iron, while David froze water samples to study its nutrients composition and Alex filtered several litres of water from each sample to later analyse the bacteria in the water.