In addition to seafloor life, researchers also study the geological structures which host that life. The VISIONS ‘05 expedition to the northeast Pacific in September 2005 studied the area around underwater volcanoes of the Juan de Fuca Ridge in the northeast Pacific Ocean. Here, at the boundary between two of Earth’s gigantic crustal plates, scientists are examining a vent system that releases ultra-hot water rich in sulfur compounds—and thereby supports a host of extreme life-forms. Such exotic undersea environments are formed by geological and thermal forces that have been characterized only in the past 40 years, and still hold many mysteries.