Hydrothermal vents, which are associated with areas seafloor spreading, may produce metalliferous muds. These muds are formed from the precipitation of metals in solution when the hot molten materials from the underlying crust come into contact with the cooler ocean water. Hydrothermal vents often support a characteristic community of organisms
which depend for their existence on bacteria that convert chemical energy into living matter. The bacteria in turn form the basis for the food chain of filter-feeding animals that comprise such communities.