Mid-Atlantic Ridge - Geology

Geology

For a general explanation of mid-oceanic ridges, see mid-oceanic ridge and seafloor spreading

The ridge sits atop a geologic feature known as the Mid-Atlantic Rise which is a progressive bulge that 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).

The ridge is about 2,500 meters (8,200 ft) below sea level, while its flank is about 5,000 meters deeper.

The Fundy Basin on the Atlantic coast of North America between New Brunswick and Nova Scotia in Canada is evidence of the ancestral Mid-Atlantic Ridge.