An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

Of, living in, or produced by the ocean.

→ ocean; → -ic.

That part of the → Earth's crust underling most of the Earth's surface which is covered by the oceans. It has a remarkably uniform composition (mostly ~ 49% SiO₂) and thickness (mostly ~ 7 km). The ocean floor is the most dynamic part of the Earth's surface. As a result, no part of the oceanic crust existing today is more than 200 million years old, which is less than 5% of the age of the Earth itself. New oceanic crust is constantly being generated from the → upper mantle by sea-floor spreading at → mid-ocean ridges, while other parts of the oceanic crust are being recycled back into the mantle at subduction zones.

→ oceanic; → crust.

Any section of the narrow, continuous submarine mountain chain through all the world's oceans. The oceanic ridge constitutes the most extensive mountain ridge on Earth, more than 65,000 km. Perhaps the best-known part of the ridge system is the → Mid-Atlantic Ridge.

→ oceanic; → ridge.