Before yesterday, the new TOBI experienced technical problems. He had to be back on board to make necessary repairs. This led us to advance the dredging planned for more later.
dredging permits, such as drilling, sampling the seabed material. While drilling back a column of rock at a specific point, dredging retrieve blocks torn from the shallow sea floor along a profile.
The operation involves dragging a net behind the ship ballasted. Its opening is serrated to hang blocks beyond. A thinner tube collects non indurated sediments (clays, sands). The cable tension is monitored along the profile. It shows when the net reaches or leaves, or when the substance is retained by a rock surface roughness. In the latter case, the value of the voltage gradually increases and then decreases sharply if the blocks are detached. The amplitude of these peaks provides information on the importance of taglines and thus the likely quantity of material recovered. A profile is generally made up the slopes of lines underwater.
blocks back on board the dredger are then sorted and inventoried. They are photographed and weighed. Samples are separated by type and weighed. The most interesting are cut, numbered, photographed and described.
To date we have completed 5 dredging. The profiles are located south of the ridge axis south-west Indian plate Antarctica reliefs type "smooth seafloor" assumed. Varying amounts of rock were recovered, ranging from tens to hundreds of kilograms per drag. They have uncovered more or less serpentinized peridotite, sediment, sedimentary breccias, gabbros ... and a fish.
Stéphane Rouméjon
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