The deep sea has long been likened to a terrestrial desert. In some ways the analogy is useful, writes marine biologist Cindy Lee Van Dover, for the oceanic floor, like many arid regions of the earth, is low in biomass. She adds, "What life there is, though, is remarkably diverse," sometimes numbering hundreds of species in a single square meter of mud. That deep-sea diversity is nowhere more pronounced than in the thermal vents that often occur where tectonic plates meet, marked by great lava fields and even active volcanoes (three-quarters of which are underwater). Located, among other places, along the great mountain ridges of the Laurentian Abyss and the Marianas Trench, these vents harbor strange creatures found nowhere else--giant clams and mussels, for example, and 2-meter-long "tubeworms" whose internal organs house sulfur-oxidizing bacteria. Discovered only in 1977, these hydrothermal vents, which vary markedly from ocean to ocean, have excited much attention among researchers. Some scholars now believe that life originated in these fiery environments, which have yielded relict species of barnacles, crinoids, and mollusks hitherto known only from the fossil record. Examining the ecology and geochemistry of the planet's deep-sea vent systems, Van Dover presents a wide-ranging, interdisciplinary, and highly accessible survey of these mysterious places.