The Mid-Atlantic Ridge hosts numerous hydrothermal vent fields. Logatchev,
Rainbow, and Saldahna are underlain by variable mixtures of deeper crustal rocks
(gabbro and peridotite) and both Logatchev and Rainbow host high-temp black
smokers. The other fields are also black smokers but are hosted on volcanic
rocks. Lost City is the only known field composed of carbonate chimneys.