Editing Atlantic Ocean (section)

== Geology and ocean floor ==
The Atlantic basin began forming when the supercontinent Pangaea broke apart during the Mesozoic Era. North America and South America moved away from Europe and Africa. Magma rose through the opening between the separating plates and cooled to form new oceanic crust. This process continues along the [[Mid-Atlantic Ridge]].

The Mid-Atlantic Ridge runs through the centre of the ocean from the Arctic region into the South Atlantic. It forms a long underwater mountain system above a divergent plate boundary. New crust forms along the ridge and moves outward on both sides. The spreading rate is slower than that of the East Pacific Rise, averaging about 2.5 centimetres each year.

Parts of the ridge rise above sea level to form islands. [[Iceland]] lies where the ridge intersects a volcanic hotspot. Other volcanic island groups formed where magma reached the surface away from continental margins.

Continental shelves extend from the surrounding land before descending along the continental slope. Sediment carried by rivers accumulates on the shelves and in deep submarine fans. Beyond the slopes, much of the ocean floor consists of abyssal plains covered by fine sediment. Submarine canyons cut through some continental margins and transport sediment into deeper water.

The Puerto Rico Trench formed near the boundary between the North American and Caribbean plates. It contains the deepest known point in the Atlantic. The South Atlantic also contains the [[South Sandwich Trench]], which formed where one oceanic plate descends beneath another.