A rock dredge is designed to collect rock samples from the sea floor.
It comprises a heavy metal bag, which is 1 m in diameter, and a “mouth” fitted with tough teeth which can break any rock that it comes into contact with.
Once in place on the sea floor, the boat pulls on the dredge and its teeth break off pieces of rock which are collected in the chain-mail bag.
Three dredges are available on L'Atalante and the Pourquoi Pas? and two on the Marion Dufresne.
The set-up is as follows:
- Circular dredge (1 m diameter, 150 kg)
- 12 m of chain, mesh diameter 25 mm (total weight 200 kg)
- Swivel, WLL 12 tonnes
- Vessel’s deep-water cable (which can be protected using a sacrificial pendant).