Often, a site survey cruise precedes the main cruise to identify the best spots for the actual coring and to get the drill sites approved by bodies like IODP. In order to map the topography of the seafloor, a multi-beam echo sounder system is used, which is like a fanlike beam covering a huge swath of the seafloor. Additionally, sediment penetrating systems are employed, which shoot signals with varying energy pulses and wave lengths that hit the bottom and are differently reflected depending on the density of the layers, thus giving a detailed impression of the layering of the sediments.
Besides the seismics, autonomous underwater vehicles are often used for more local surveys. "To make sure we won't damage any living ecosystem, we drop an underwater camera to see the nature of the seafloor just around the potential drilling site" explained Gilbert Camoin from CNRS in Aix-en-Provence, who is the chair of EuroMARC's scientific committee as well as the project leader of CHECREEF (The Last Deglacial Sea-Level and Climatic Changes) and investigates coral reefs in both Tahiti and the Great Barrier Reef. Especially in the case of coral reefs, the regulations for drilling are very strict and pictures are taken before and afterwards. "There is no impact at all, when you pull up the pipes, the hole just collapses and it's even impossible to find it again" assured Camoin.
On the main cruise, the coring itself takes place as well as first measurements and part of the sampling, provided the type of ship allows for it. The cores are extracted in different ways, at different water depths and of differen
|Contact: Angela Michiko Hama|
European Science Foundation