Earth's Longest Mountain Range Is Almost Entirely Underwater

The longest mountain range on Earth is one you have almost certainly never seen. The mid-ocean ridge winds 40,389 miles around the globe, and about 90 percent of it lies under the ocean.

The mid-ocean ridge in satellite-captured bathymetric data of the western Atlantic Ocean basin. It stretches around the globe like the seam of a baseball. Credit: NOAA.

Where the seafloor is made

The ridge is a system of mountains and valleys that criss-crosses the globe like the stitches on a baseball, and it is built by the movement of the Earth's tectonic plates. Where the great plates push apart, magma rises to fill the gap, forming mountains and valleys along the seafloor. As the crust spreads, new ocean floor is created — a process that literally renews the surface of the planet.

The largest volcanic feature on Earth

Look at a map of the world's volcanoes and you will see that most of them lie along the edges of this system. The global mid-ocean ridge is the largest single volcanic feature on Earth, made up of thousands of individual volcanoes and volcanic ridge segments that erupt from time to time.

Sources

Based on "What is the longest mountain range on Earth?" from NOAA's National Ocean Service, a work of the United States government in the public domain.