In some areas along the Mid-Ocean Ridge, the gigantic plants that form the Earth's crust are moving apart, creating cracks and crevices in the ocean floor. Seawater seeps into these openings and is heated by themolten rock, or magma, that lies beneat the Earth's crust. As the water is heated, it rises and seeks a path back out into the ocean through an opening in the seafloor. Yet this water does not boil because it is under so much pressure from the tremendous weight of the ocean above. When the pressure on a liquid is increased, its boiling point goes up.
Chimneys top some hydrothermal vents.
They spew mostly iron and sulfide, which combine to form iron monosulfide. This compound gives the smoker its black color. It reached the height of a 15-story building before it toppled. It is now actively rebuilding. There are many other reasons why scientists want to learn more about hydrothermal vents.