Hydrothermal vents form in mid-ocean ridges where tectonic plates are spreading apart and seawater percolates down fissures and is heated by hot magma. They were first seen in 1977 in the Galapagos Islands by scientists who discovered that bacteria were converting toxic vent materials into usable energy for other organisms that had never been seen before.
In areas where the Earth´s plates are spreading apart, seawater circulates under the ocean´s crust and is heated. When the heated water rises again to the ocean floor´s surface, it is vented as plumes.
The hottest, darkest plumes are black, rich in sulfur and can reach heights of up to 18 stories tall. White plumes are cooler and smaller in size and contain barium, calcium and silicon.