A Hydrothermal Vent (sometimes called Black Smokers) occurs at the bottom of the deep ocean. The yellow is appropriate because is is sometimes called Sulphur Vents. In Sulphur Vents, bacteria grow on the sulphur, and animals eat the bacteria. Unlike everywhere else on earth, there is no sunlight and no plants for the rest of life to feed off. The Hydrothermal Vents are very hot.