Gravity corer

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Use of a gravity corer from the research ship

The gravity corer is a marine geological sampling device. With it, sediment cores can be “punched” out of the seabed .

description

The gravity corer usually consists of a set of weights made up of individual lead or steel disks (approx. 1 to 3 t in total). This is connected at the bottom with a pipe adapter. Steel pipes (usually 8 to 13 cm in diameter) are attached to it, which can be connected to one another with sleeves and thus form a continuous steel pipe . PVC pipes (so-called liners) are pushed into this tube. The tube ends at the bottom with a core catcher . Gravity cores are composed of 5 m segments with a maximum length of 30 m; the length is determined by the nature of the seabed. Previous gravity cores have been designed in such a way that the liner pipes extend to the flange on the weight set. The disadvantage here is that when the weight set penetrates the sediment, the sample surface remains in the weight set and is flushed out. The IOW patented a solution in which the liner pipe extends to the end of the device and is also closed pressure-tight with a flap. Thus you get the complete core, in addition to the core catcher, a vacuum is used to secure the core. For the most undisturbed sampling of soft sediments, a box-shaped variant, the box plumb bob (15 × 15 or 30 × 30 cm cross-section) is often used.

functionality

The gravity corer is lowered (lowered) to the sea floor hanging on a wire rope and is pressed into the bottom by its own weight. The sediment penetrates the liners. The core catcher prevents the sediment from slipping out again when the plumb bob is then pulled up (heave). The plumb bob is stored horizontally on deck (of the ship). After the core catcher is removed, the sediment-filled liners can be removed. They contain a sequence of sediment layers and are processed into samples in the laboratory .

Sediment core drawn with a gravity corer

See also

reference