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Images: Earth's Complex Complexion

Working in the ice-covered Arctic Ocean in 2001, scientists and crew aboard the maiden voyage of the U.S. icebreaker Healy successfully—and surprisingly—were able to perform 200 dredge operations along the Gakkel Ridge, collecting some 4,000 seafloor rock samples. (Henry Dick.)

The 2001 AMORE (Arctic Mid-Ocean Ridge Expedition) collected SeaBEAM sonar data to create this detailed 1,000-kilometer (620-mile) bathymetric map of the Gakkel Ridge.


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Volcanic activity at mid-ocean ridges creates new seafloor crust that spreads outward to cover 70 percent of Earth's surface. Recent expeditions have led to the discovery of an entirely new type of mid-ocean ridge. Instead of two classes of ridges—fast-spreading and slow-spreading—there is now a third, ultraslow. Ultraslow-spreading ridges, which may make up one-third of the global ocean ridge system, have distinctive characteristics. Like other mid-ocean ridges, ultraslow ridges have areas where magma rises from the mantle and erupts at the seafloor to create new ocean crust. But in between, there are also amagmatic zones, where solid slabs of mantle rock rise directly to the seafloor.

Scientists had predicted that the Gakkel Ridge was spreading far too slowly to promote volcanism, but an expedition in 2001 found surprising evidence for active volcanoes and hydrothermal vents.

The new U.S. icebreaker Healy performed splendidly on its maiden voyage to the Arctic Ocean in 2001 to explore the Gakkel Ridge—the deepest and slowest-spreading ridge on Earth. (Henry Dick.)