The hydrothermal fluids exit the chimney and mix with the cold seawater. The
metals carried up in the fluids combine with sulfur to form black minerals
called metal sulfides, and give the hydrothermal fluid
the appearance of smoke. Many factors trigger this reaction. One factor is
the cold temperature, and another is
the presence of oxygen in the seawater. Without oxygen, the minerals would
In white smokers, the hydrothermal fluids mix with seawater under the seafloor. Therefore, the black minerals form beneath the seafloor before the fluid exits the chimney.
Other types of compounds, including silica, remain in the fluid. When the fluid exits the chimney, the silica precipitates out. Another chemical reaction creates a white mineral called anhydrite. Both of these minerals turn the fluids that exit the chimney white.
The white color comes from minerals that form when the fluid exits the chimney and mixes with seawater. Unlike the black minerals in black smokers, these minerals don't contain metals. (Click on the numbers to learn how black smokers and white smokers form.)
The chimneys grow bigger and bigger as long as fluid continues to flow out of them and the minerals continue to form. Scientists have observed some chimneys growing as fast as 30 centimeters per day. Chimneys, however, are fragile, and often collapse if they grow too big. (Click on the numbers to learn how black smokers and white smokers form.)