The Mid-Atlantic Ridge is an underwater mountain range of the Atlantic Ocean that runs from Iceland to Antarctica, and is the longest mountain range on Earth. These mountain ranges are where tectonics plate pull apart, this pulling motion creates cracks in the ocean floor called rift zones. As the plates pull apart, magma rises to fill in the spaces. Heat from the magma causes the crust on either side of the rifts to expand, forming the ridges. The ridge was discovered by Bruce Heezen in the 1950s. The discovery of this ridge led to the theory of seafloor spreading and general acceptance of Wegener's theory of continental drift. According to plate tectonics, this ridge runs along a divergent boundary.

This ridge is an oceanic rift that separates the North American Plate from the Eurasian Plate in the North Atlantic, and the South American Plate from the African Plate in the South Atlantic. The ridge actually sits on top of the mid-Atlantic rise which is a progressive bulge that also runs the length of the Atlantic Ocean with the ridge resting on the highest point of this linear bulge. This bulge is thought to be caused by upward convective forces in the asthenosphere pushing the oceanic crust and lithosphere.

This divergent boundary first formed in the Triassic period when a series of three-armed grabens coalesced on the supercontinent Pangaea to form the Ridge. Usually only two arms of any given three-armed graben become part of a divergent plate boundary. The failed arms are called aulacogens and the aulacogens of the Mid-Atlantic Ridge eventually became many of the large river valleys seen along the Americas, and Africa (including the Mississippi River, Amazon River and Niger River).

See also

• Atlantis Massif