Seamount - A large, underwater volcanic mountain rising at least 1,000 meters above the surrounding seafloor.

Abyssal plain - Flat or gently sloping areas of the deep ocean floor, typically found at depths between 4,000 and 6,000 meters.

Abyssal hill - Small, underwater hills on the ocean floor, usually less than 1,000 meters in height.

Atoll - A ring-shaped coral reef, island, or series of islets surrounding a central lagoon, often found in warm, tropical waters.

Oceanic ridge - A continuous underwater mountain range formed by plate tectonics where new oceanic crust is created.

Trench - A deep, narrow depression in the ocean floor, typically found at convergent plate boundaries where one tectonic plate is forced beneath another.

Island arc - A curved chain of volcanic islands formed at a convergent boundary where an oceanic plate is subducted beneath another plate.

Island chain - A series of islands, often formed by volcanic activity or tectonic processes, arranged in a line or curve.

Gas hydrate (clathrate) deposit - A crystalline solid consisting of gas molecules, typically methane, trapped within a lattice of water molecules, found in permafrost or beneath the seafloor.

Guyot - A flat-topped, submerged volcanic mountain with a broad summit, typically formed by erosion and subsidence.

Hydrothermal vent - Openings in the ocean floor from which geothermally heated water emerges, often rich in minerals and supporting unique ecosystems.

Continental rise - A gently sloping accumulation of sediment at the base of the continental slope, marking the transition between continental and oceanic crust.

Continental slope - The steeply inclined region of the continental margin between the continental shelf and the continental rise.

Continental shelf - The shallow, submerged platform extending from the shoreline to the continental slope, characterized by relatively gentle slopes.

Submarine canyon - Deep, steep-sided valleys cut into the continental slope and shelf by underwater currents or geological processes.

Barrier reef - A coral reef separated from the mainland or island shore by a lagoon, often parallel to the coastline.

Rift zone - A region of Earth's crust where tectonic plates are moving apart, typically marked by volcanic activity and the formation of new oceanic crust.

Fracture zone - A linear zone of fractures in Earth's crust, often associated with tectonic plate boundaries or the movement of oceanic crust.