What are some methods used to investigate the seafloor?
Sonar methods and core sampling
The seafloor can be investigated using acoustic waves that are reflected by the sediments and rocks creating a kind of acoustic picture of the seafloor features.
Depending on the energy (how strong) and frequency of the emitted signal it is possible to penetrate at different depth within the sediment cover of the seafloor thus obtaining a stratigraphy of the structures present. It is as looking through the layers of the deposits covering the seafloor.
If needed it is also possible to collect some cores of the seafloor deposits using a gravity corer which can be described as a vertical hollow tube that dives through the water under its own weight and then penetrates the sediments collecting them.
Deeper samples can be collected by drilling the seafloor with specialized equipment.
Finally optical images of the seafloor features can be recorded using underwater cameras towed or as part of robotic systems.
In shallow water (usually less than 100 meters or 300 ft) scuba divers can map the seafloor with similar methods used for mapping on dry land.