 Even life in the ocean depths, where sunlight cannot reach, was believed to obtain its nourishment either from consuming organic detritus rained down from the surface waters or from eating animals that did.However, in 1977, during an exploratory dive to the Galapagos Rift in the deep-sea exploration submersible "Alvin", scientists discovered colonies of assorted creatures clustered around undersea volcanic features known as black smokers.It was soon determined that the basis for this food chain is a form of bacterium that derives its energy from oxidation of reactive chemicals, such as hydrogen or hydrogen sulfide, that bubble up from the Earth's interior.