The Mid-Atlantic Ridge hosts numerous hydrothermal fields (colored dots). Logatchev, Rainbow and Saldahna are underlain by variable mixtures of deeper crustal rocks (gabbros and peridotite) and both Logatchev, Rainbow host high-temperature black smokers. The other fields are also sites of black smokers, but are hosted on volcanic rocks. Lost City is currently the only known hydrothermal field composed solely of carbonate chimneys. Image courtesy of University of Washington.