Photograph by Al Giddings
A cloud of hydrothermal fluids streams from a black smoker, or mineral chimney, along the Mid-Ocean Ridge off the west coast of Mexico. Black smokers are common to spreading zones in plate boundaries. Chimneys are made of lead, iron, manganese, and zinc sulfides, through which spew superheated ocean water. They also harbor exotic life-forms, far below the reach of sunlight.