An Etymological Dictionary of Astronomy and Astrophysics

An immense chain of underwater mountains that runs down the middle of the Atlantic Ocean. The MAR, approximately 500-1000 km wide, extends 16,000 km from Iceland to the Antarctic Circle. The MAR is so high that it actually rises above sea level in many places, forming volcanic islands. The Azores, Ascension, St. Helena, and Iceland all arise from this great Atlantic range.
The chain results from the movement of the continental plates. As these plates slowly separate, they leave gaps in the → Earth’s crust. This allows molten rock from beneath the Earth’s crust to reach the surface and forms a ridge. The MAR is a part of the global → mid-ocean ridge system.

See also: → mid-; → Atlantic; → ridge.