Minor Relief Features

Apart from the above-mentioned major relief features of the ocean floor, some minor but significant features predominate in different parts of the oceans. These are thermal vents of various types, gas vents, submarine caves, and channel-like depressions.

Mid-Oceanic Ridges

A mid-oceanic ridge is composed of two chains of mountains separated by a large depression. The depression, the central rift zone, contains trenches (the deepest parts of the ocean), mountains, and volcanoes.

Several types of mid-oceanic ridges exist, including volcanic rift zones, extensional fracture zones, and transform fault systems. These are often found in clusters oriented along the cardinal directions.

Submarine Canyons

Submarine canyons are deep valleys, some comparable to the Grand Canyon of the Colorado river (photo of Hudson Canyon) found on land.

These canyons are undersea features which occur along tectonically active mid-ocean ridges. They are created when plates drift apart creating gaps between them that fill with sediment creating a canyon.

Guyots

Guyots are seamounts that have built above sea level. Erosion by waves destroyed the top of the seamount resulting in a flattened shape.

Due to the movement of the ocean floor away from oceanic ridges, the sea floor gradually sinks and the flattened guyots are submerged to become undersea flat-topped peaks.

Atoll

An atoll is a ring-shaped coral reef, island, or series of islets. An atoll surrounds a body of water called a lagoon. Sometimes, atolls and lagoons protect a central island.

Channels between islets connect a lagoon to the open ocean or sea. Atolls develop with underwater volcanoes, called seamounts.