Atlantic Ocean

The Atlantic Ocean is Earth's second-largest ocean, covering approximately one-fifth of its surface. The ocean's name, derived from Greek mythology, means the "Sea of Atlas".

Ocean bottom

The principal feature of the bottom topography of the Atlantic Ocean is a great submarine mountain range called the Mid-Atlantic Ridge. It extends from Iceland in the north to approximately 58° south latitude, reaching a maximum width of about 1,600 km (1,000 miles). A great rift valley also extends along the ridge over most of its length. The depth of water over the ridge is less than 2,700 m (8,900 ft) in most places, and several mountain peaks rise above the water, forming islands. The South Atlantic Ocean has an additional submarine ridge, the Walvis Ridge.

Related Topics:
Topography - Mid-Atlantic Ridge - Iceland - Rift valley

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The Mid-Atlantic Ridge separates the Atlantic Ocean into two large troughs with depths averaging between 12,000 and 18,000 ft (3,700 and 5,500 m). Transverse ridges running between the continents and the Mid-Atlantic Ridge divide the ocean floor into numerous basins. Some of the larger basins are the Guiana, North American, Cape Verde, and Canaries basins in the North Atlantic. The largest South Atlantic basins are the Angola, Cape, Argentina, and Brazil basins.

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The deep ocean floor is thought to be fairly flat, although numerous seamounts and some guyots exist. Several deeps or trenches are also found on the ocean floor. The Puerto Rico Trench, in the North Atlantic, is the deepest. The Laurentian Abyss is found off the eastern coast of Canada. In the south Atlantic, the South Sandwich Trench reaches a depth of 8,428 m (27,651 ft). A third major trench, the Romanche Trench, is located near the equator and reaches a depth of about 24,455 ft (7,454 m). The shelves along the margins of the continents constitute about 11% of the bottom topography. In addition, a number of deep channels cut across the continental rise.

Related Topics:
Seamount - Guyot - Laurentian Abyss - South Sandwich Trench - Romanche Trench

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Ocean sediments are composed of terrigenous, pelagic, and authigenic material. Terrigenous deposits consist of sand, mud, and rock particles formed by erosion, weathering, and volcanic activity on land and then washed to sea. These materials are largely found on the continental shelves and are thickest off the mouths of large rivers or off desert coasts. Pelagic deposits, which contain the remains of organisms that sink to the ocean floor, include red clays and Globigerina, pteropod, and siliceous oozes. Covering most of the ocean floor and ranging in thickness from 60 m to 3,300 m (200 ft to 11,000 ft), they are thickest in the convergence belts and in the zones of upwelling. Authigenic deposits consist of such materials as manganese nodules. They occur where sedimentation proceeds slowly or where currents sort the deposits.

Related Topics:
Sediment - Continental shelves - Globigerina - Pteropod - Manganese nodule

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