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Mid-ocean Ridges

Bathymetric image of the East Pacific Rise, a mid-oceanic ridge located along the floor of the Pacific Ocean. (Image courtesy of Haymon et al., NOAA-OE, WHOI)

The mid-ocean ridge is a continuous range of undersea volcanic mountains that encircles the globe almost entirely underwater. It is a central feature of seafloor terrain that is more varied and more spectacular than almost anything found on dry land, and includes a collection of volcanic ridges, rifts, fault zones, and other geologic features.

At nearly 60,000 kilometers (37,000 miles) long, the mid-ocean is the longest mountain range on Earth. It formed and evolves as a result of spreading in Earth’s lithosphere—the crust and upper mantle—at the divergent boundaries between tectonic plates. The vast majority of volcanic activity on the planet occurs along the mid-ocean ridge, and it is the place where the crust of the Earth is born. The material that erupts at spreading centers along the mid-ocean ridge is primarily basalt, the most common rock on Earth.

Because this spreading occurs on a sphere, the rate separation along the mid-ocean ridge varies around the globe. In places where spreading is fastest (more than 80 millimeters, or 3 inches, per year), the ridge has relatively gentle topography and is roughly dome-shaped in cross-section as a result of the many layers of lava that build up over time. At slow- and ultra-slow spreading centers, the ridge is much more rugged, and spreading is dominated more by tectonic processes rather than volcanism.

Scientists study the physics, chemistry, and biology of mid-ocean ridges gain insight into how Earth works in very fundamental and often surprising ways.

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News & Insights

Wave Glider provides gateway to remote exploration

WHOI geochemist Chris German pairs an autonomous surface vehicle (ASV) called a Wave Glider with other vehicles to expand research here and on other Ocean Worlds

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News Releases


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WHOI in the News

The 40,000-Mile Volcano


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From Oceanus Magazine

7 Places and Things Alvin Can Explore Now

With its new depth rating of 6500 meters (4 miles), WHOI’s human-occupied vehicle (HOV) Alvin is set to take scientists places they’ve never explored in person

Racing an undersea volcano

Using AUV Sentry to make a high-resolution, near-bottom, seafloor map before the next volcanic eruption at the East Pacific Rise

How Is the Seafloor Made?

An ultrasound for the Earth? Using sound waves, a graduate student peers into the crystalline texture of the tectonic plates that cover our planet’s surface.

Pop Goes the Seafloor Rock

WHOI scientists used the human-occupied submersible Alvin and the autonomous underwater vehicle Sentry to explore a surprising discovery: gas-filled volcanic rocks on the seafloor that “pop” when brought up to the surface.

Deep-sea Detectives

Links to related materials Mid-Ocean Ridges—Articles, illustrations, and video showing how new seafloor crust forms Mapping the Seafloor with Multibeam Sonar Profile of Marshall Swartz Story of the SDSL Data-Link…