Seafloor spreading is the process by which new oceanic crust is formed at mid-ocean ridges. As the plates move apart, magma rises from the mantle and cools to form new crust.

A divergent boundary is the boundary between two tectonic plates that are moving apart. At these boundaries, new oceanic crust is formed.

Hydrothermal vents are openings in the seafloor that release hot water and chemicals from the Earth's interior. These vents are often found near mid-ocean ridges and are home to unique ecosystems.

Subduction is the process by which oceanic crust is recycled back into the mantle. At convergent boundaries, one plate moves beneath another, carrying the oceanic crust down into the mantle.

Pelagic sediment is the layer of sediment that covers the seafloor. It is composed of fine-grained material that has settled from the water column.

Erosion is the process by which sediment is transported from land to the sea. It is caused by the action of wind, water, and ice.

Deposition is the process by which sediment is deposited on the seafloor. It occurs when the sediment is no longer being transported by wind, water, or ice.

Weathering is the process by which sediment is weathered into smaller particles. It is caused by the action of wind, water, and ice.

Biogenic sediment is the type of sediment that is composed of the remains of marine organisms. It includes the remains of plankton, fish, and other marine animals.

Authigenic sediment is the type of sediment that is composed of material that has been chemically precipitated from seawater. It includes minerals such as calcite, aragonite, and silica.

Terrigenous sediment is the type of sediment that is composed of material that has been transported from land to the sea. It includes sand, silt, and clay.

An echo sounder is an instrument that is used to measure the depth of the sea. It works by sending out a sound wave and measuring the time it takes for the sound wave to bounce off the seafloor and return to the instrument.

A side-scan sonar is an instrument that is used to create images of the seafloor. It works by sending out a sound wave and measuring the time it takes for the sound wave to bounce off the seafloor and return to the instrument.

A multibeam sonar is an instrument that is used to create three-dimensional images of the seafloor. It works by sending out a fan-shaped beam of sound waves and measuring the time it takes for the sound waves to bounce off the seafloor and return to the instrument.

A sub bottom profiler is an instrument that is used to study the layers of sediment beneath the seafloor. It works by sending out a sound wave and measuring the time it takes for the sound wave to bounce off the different layers of sediment and return to the instrument.