A hydrothermal vent is an opening in the seabed of the Earth by which geothermal energy escapes. Sea water enters, becomes very hot, and rises. The hottest ones carry many black chemicals, and are called black smokers. Scientists have found fewer white smokers. Heat escapes from underground in many places. If they are on land, they are usually hot springs, geysers, or fumaroles. Many archaea and bacteria live near hydrothermal vents. They support giant tube worms, clams and shrimp, and many other eukaryotes. The earliest known life forms are thought to have lived near such vents.