Sediment coring is a common way of getting very detailed information about the layers of sediment below the seafloor. Sites for coring are usually chosen based on results of an earlier sidescan survey, where target areas have been identified. There are several different types of corer, depending on what sort of sediment is on the seafloor, and what sort of sample needs to be taken.
A coring device comprises a steel cable attaching the equipment to the ship's winch, weights to help drive the corer into the seabed, and a steel tube known as the core barrel, which is the part of the corer which is pushed into the seafloor.
Gravity coring uses the weight of the coring equipment to push the core barrel into the soft mud at the bottom of the ocean. Weights may be added to the top of the corer to make sure that the core barrel is pushed far enough into the seafloor sediment. Piston corers are similar, but they have a piston inside the core barrel which provides suction to help pull to sediments up into the core barrel. An average core is between 5 and 20 metres long.
Once the corer has been brought back on board the ship, the core is removed. Plastic tubes (rather like drainpipes) are used to line the core barrel and keep the sediment core in one piece when it is removed. Cores are split in half lengthways to reveal the layers of sediment inside.
Left: Bringing up the coring apparatus