The first deep-sea hydrothermal vents were discovered in 1977. During a February 17, 1977 dive of the research submersible Alvin at the Galápagos Rift, scientists directly observed hot vent fluids and a thriving biological community on the seafloor.
The discovery overturned the assumption that deep-ocean ecosystems ultimately depended on sunlight-driven photosynthesis. Instead, bacteria around the vents use chemosynthesis, obtaining energy by oxidizing chemicals such as hydrogen sulfide released in the vent fluids. These microbes support dense communities containing giant tubeworms, clams, mussels, crabs, and other specialized animals.
There is a subtle historical distinction behind this date. Scripps researchers had gathered photographic, mapping, and temperature-anomaly evidence along the Galápagos Rift in 1976, and scientific papers describing vents appeared in 1977. The direct observation and sampling of the living vent ecosystem also happened in 1977. Black smokers—higher-temperature vents that emit dark mineral particles—were discovered later, in 1979, on the East Pacific Rise.