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How does a dredge collect rock samples from the ocean floor?

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To collect rock samples from the ocean floor, researchers use a specialized dredge designed to be dragged along the seafloor.1

Unlike industrial dredges used for excavation or mining, a scientific bottom-dredge is constructed of sturdy steel plate, typically measuring 30 centimetres deep, 60 centimetres wide, and 90 centimetres long. The device features an open forward end to scoop up materials as it is pulled across the bottom. To ensure the collection of large rock samples, the aft end is equipped with a heavy grill made of round steel bars. If researchers need to collect finer-sized material, a screen of heavy hardware cloth is placed over this grill to prevent the loss of smaller specimens.1

This method is distinct from other sampling techniques, such as coring or the use of grabbing devices like "snappers," which are generally employed for collecting sediment rather than rock.1