In 1977, scientists exploring the Galápagos Rift along the mid-ocean ridge in the eastern Pacific noticed a series of temperature spikes in their data. They wondered how deep-ocean temperatures could change so drastically—from near freezing to 400 °C (750 °F)—in such a short distance. The scientists had made a fascinating discovery—deep-sea hydrothermal vents. They also realized that an entirely unique ecosystem, including hundreds of new species, existed around the vents. Despite the extreme temperatures and pressures, toxic minerals, and lack of sunlight that characterized the deep-sea vent ecosystem, the species living there were thriving. Scientists later realized that bacteria were converting the toxic vent minerals into usable forms of energy through a process called chemosynthesis, providing food for other vent organisms.

Hydrothermal vents are like geysers, or hot springs, on the ocean floor. Along mid-ocean ridges where tectonic plates spread apart, magma rises and cools to form new crust and volcanic mountain chains. Seawater circulates deep in the ocean’s crust and becomes superheated by hot magma. As pressure builds and the seawater warms, it begins to dissolve minerals and rise toward the surface of the crust. The hot, mineral-rich waters then exit the oceanic crust and mix with the cool seawater above. As the vent minerals cool and solidify into mineral deposits, they form different types of hydrothermal vent structures.

Hydrothermal vent structures are characterized by different physical and chemical factors, including the minerals, temperatures, and flow levels of their plumes. Black smokers emit the hottest, darkest plumes, which are high in sulfur content and form chimneys up to 18 stories tall, or 55 meters (180 feet). The plumes of white smokers are lightly colored and rich in barium, calcium, and silicon. Compared to black smokers, white smokers usually emit cooler plumes and form smaller chimneys. Vents with even cooler, weaker flows are often called seeps. They appear to shimmer because of differences in water temperatures or bubble because of the presence of gases, like carbon dioxide.

The study of hydrothermal vent ecosystems continues to redefine our understanding of the requirements for life. The ability of vent organisms to survive and thrive in such extreme pressures and temperatures and in the presence of toxic mineral plumes is fascinating. The conversion of mineral-rich hydrothermal fluid into energy is a key aspect of these unique ecosystems. Through the process of chemosynthesis, bacteria provide energy and nutrients to vent species without the need for sunlight.