The Atlantic’s spine is Earth’s longest mountain chain’s heart
The Mid-Atlantic Ridge is a divergent plate boundary on the Atlantic floor and part of the planet’s longest mountain range. North of the Azores triple junction it parts North America from Eurasia and Africa; farther south it splits Africa from South America along a seismically alive rift.
Matthew Fontaine Maury inferred a North Atlantic rise from USS Dolphin soundings in 1853; HMS Challenger confirmed its southward run in 1872 under Charles Wyville Thomson. Nineteen-fifties seafloor maps by Marie Tharp, Bruce Heezen, Maurice Ewing and colleagues showed a valley-and-ridge bathymetry whose central rift hosts many earthquakes—and revealed the ridge as one segment of a roughly 40,000-kilometre global mid-ocean system. Thomson's team had stumbled on the rise while scouting a route for a transatlantic telegraph cable. Sonar confirmed it in 1925, and the German Meteor expedition traced it around Cape Agulhas into the Indian Ocean. The global picture that emerged fed seafloor-spreading theory and won acceptance for Wegener's drift idea in its plate-tectonic form.
Magma wells along that axial rift, erupting as lava that builds new crust for the plates on either side. Near the equator the Romanche Trench, plunging to 7,758 metres, divides North Atlantic Ridge from South Atlantic Ridge without itself marking the North–South America or Eurasia–Africa plate edges. Island peaks riding the chain include Beerenberg on Jan Mayen (2,277 m), Iceland’s Hvannadalshnúkur (2,109.6 m), Pico in the Azores (2,351 m), and Tristan da Cunha’s Queen Mary’s Peak (2,062 m).
Ascension, Saint Helena, Gough, and Bouvet add lower summits on the southern limb; Saint Peter and Paul Rocks barely clear 22.5 metres. The chain runs from its junction with the Gakkel Ridge northeast of Greenland down to the Bouvet triple junction, and the plates it separates drift apart at an average of about 2.5 centimetres a year. It crosses Iceland as the Neovolcanic Zone, with the Reykjanes Ridge offshore to the southwest. The boundary was born in the Triassic, when three-armed rifts merged across Pangaea; the arms that failed, called aulacogens, later guided great river valleys including the Mississippi, the Amazon and the Niger.
Source: Mid-Atlantic Ridge
