The mid-ocean ridge is the longest mountain range on Earth, formed mainly along oceanic spreading centers.
It is a connected global system of underwater mountains extending for more than 60,000 kilometers. At divergent plate boundaries, magma rises as plates separate, cools, and creates new oceanic crust. This process is called seafloor spreading.
Most of the ridge lies beneath the oceans, so it is far less familiar than mountain ranges visible on land. Volcanic activity, hydrothermal vents, and shallow earthquakes commonly occur along its crest.
The term does not identify one isolated ridge. It describes the worldwide network, which includes named sections such as the Mid-Atlantic Ridge and the East Pacific Rise.