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The mid-ocean ridge is the longest mountain range on Earth, stretching roughly 65,000 kilometres across the planet.
Mountains are often imagined as dramatic peaks rising above sea level. Yet Earth's most extensive mountain system lies mostly underwater. The mid-ocean ridge winds through the world's oceans, tracing a network of geological boundaries on a truly global scale.
A mountain system across the seafloor
According to NOAA, the mid-ocean ridge extends for about 40,389 miles, or 65,000 kilometres. Around 90 percent of it is underwater. Its broad, connected pattern has sometimes been compared with the seams of a baseball, wrapping around the planet instead of forming a single straight line.
How the ridge is built
The ridge marks places where tectonic plates move apart. As the crust separates, molten rock rises and cools, adding new material to the ocean floor. The process of seafloor spreading creates mountains, valleys and volcanic features over immense periods of geological time. Much of the planet's volcanic activity is associated with this linked system.
Why it changes our view of Earth
Maps of land alone can hide some of the planet's most important structures. The mid-ocean ridge illustrates how oceans cover an active and changing landscape. Scientists study it to understand plate tectonics, the creation of ocean crust and the forces that reshape Earth's surface.
Sources and further reading
Editorial note: This article explains documented research and links to the primary institutions used to verify its central claims.