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Southern Hemisphere (South Atlantic Ridge): Northern Hemisphere (North Atlantic Ridge):

The islands on or near the Mid-Atlantic Ridge, from north to south, with their respective highest peaks and location, are: This trench, however, is not regarded as the boundary between the North and South American Plates, nor the Eurasian and African Plates.

Near the equator, the Mid-Atlantic Ridge is divided into the North Atlantic Ridge and the South Atlantic Ridge by the Romanche Trench, a narrow submarine trench with a maximum depth of 7,758 m (25,453 ft), one of the deepest locations of the Atlantic Ocean. This rift marks the actual boundary between adjacent tectonic plates, where magma from the mantle reaches the seafloor, erupting as lava and producing new crustal material for the plates. The Mid-Atlantic Ridge includes a deep rift valley that runs along the axis of the ridge for nearly its entire length. In Iceland the Mid-Atlantic Ridge passes across the Þingvellir National Park, a popular destination for tourists

The ridge is central to the breakup of the hypothetical supercontinent of Pangaea that began some 180 million years ago. The discovery of this worldwide ridge system led to the theory of seafloor spreading and general acceptance of Wegener's theory of continental drift and expansion in the modified form of plate tectonics. Ewing, Heezen and Tharp discovered that the ridge is part of a 40,000-km (25,000 mile) long essentially continuous system of mid-ocean ridges on the floors of all the Earth's oceans. In the 1950s, mapping of the Earth's ocean floors by Bruce Heezen, Maurice Ewing, Marie Tharp and others revealed that the Mid-Atlantic Ridge had a strange bathymetry of valleys and ridges, with its central valley being seismologically active and the epicenter of many earthquakes. The existence of such a ridge was confirmed by sonar in 1925 and was found to extend around Cape Agulhas into the Indian Ocean by the German Meteor expedition.

A team of scientists on board, led by Charles Wyville Thomson, discovered a large rise in the middle of the Atlantic while investigating the future location for a transatlantic telegraph cable. The existence of the ridge and its extension into the South Atlantic was confirmed during the expedition of HMS Challenger in 1872. A ridge under the northern Atlantic Ocean was first inferred by Matthew Fontaine Maury in 1853, based on soundings by the USS Dolphin.