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Colorful Cobble

This tricolor rock resulted from volcanic activity along the Gakkel Ridge at the bottom of the Arctic Ocean between Russia and the North Pole. The black middle portion is the glassy outer rim of lava that once covered the entire rock. The outer crust is gone from the left side, and iron in the rock has been oxidized by contact with seawater—basically, it’s gotten rusty. The white on the right side is a thin veneer between the glassy outer rim, which cooled super fast, and inner layers, which cooled more slowly. The rock was collected on a Dive & Discover cruise in 2007 by CAMPER, a sampling sled deployed after scientists identify an area of interest on the seafloor.(Photo by Chris Linder, Woods Hole Oceanographic Institution)