Black smokers are sea bed hydrothermal vents which are rich in dissolved minerals. When the superheated mineral saturated water enters the cold sea the minerals are precipitated out which form a tall chimney structure, one chimney in the Pacific reached 40m tall. Black smokers are rich in sulphurs and sulphides which can form ore deposits eg manganese. Blacksmokers were originaly discoverd by a small submarine called Alvin in 1977. Not ony were they a completely new geological discovery but the smokers were found to support their own ecosystems of organisms which relied on the warm nutrient rich waters rather than a photosynthesis based ecosystem. The deepest blacksmokers are found 5000m down in the Cayman trough.