Black smoker hydrothermal vent at the northwest caldera site of the Kermadec volcanic island arc, South Pacific Ocean. Black smokers are seabed volcanic vents where minerals dissolve in water superheated by magma (molten rock). The minerals precipitate out on contact with the cold surrounding water, producing 'smoke'. The minerals form crusts around the vents, causing them to grow into tall chimneys over time. Deep sea vents such as this provide an unusual habitat that some organisms are able to exploit.