hydrothermal vent, crack along a rift or ridge in the deep ocean floor that spews out water heated to high temperatures by the magma under the earth's crust. Some vents are in areas of seafloor spreading, and in some locations water temperatures above 350°C (660°F) have been recorded; temperatures at vents in the Cayman Trough in the Caribbean Sea have been measured at above 400°C (750°F). The deepest known vents are those of the Beebe Vent Field in the Cayman Trough, some 16,273 ft (4,960 m) below the sea surface. The hot springs found at hydrothermal vents leach out valuable subsurface minerals and deposit them on the ocean floor. The dissolved minerals precipitate when they hit the cold ocean water, in some cases creating dark, billowing clouds (hence the name "black smokers" for some of the springs) and settling to build large chimneylike structures.
Giant tube worms, bristle worms, yellow mussels, clams, and pink sea urchins are among the animals found in the unique ecological systems that surround the vents. All of these animals live—without sunlight—in conditions of high pressure, steep temperature gradients, and levels of minerals that would be toxic to animals on land. The primary producers of these ecosystems are bacteria that use chemosynthesis to produce energy from dissolved hydrogen sulfide. Some scientists believe such vents may have been the source of life on earth.
Hydrothermal vents were first discovered near the Galápagos Islands in 1977 by scientists in the research submersible Alvin. Vents have since been discovered in the Atlantic, Indian, and Southern oceans as well. Although a number of species found around the vents in each ocean are also found in other oceans, many of the species are unique to the particular region in which they are found.