Definition: A hydrothermal vent found on the ocean floor. The vents are formed in fields hundreds of meters wide when superheated water from below the Earth's crust comes through the ocean floor. The superheated water is rich in dissolved minerals from the crust, most notably sulfides, which crystallize to create a chimney-like structure around each vent. When the superheated water in the vent comes in contact with the cold ocean water, many minerals are precipitated, creating the distinctive black color. The metal sulfides that are deposited can become massive sulfide ore deposits in time.
