What is a Hydrothermal Vent?

Hydrothermal vent chimneys seen on the 2016 Deepwater Exploration of the Marianas aboard NOAA Ship Okeanos Explorer. Courtesy of NOAA OER.

Underwater volcanoes at spreading ridges and convergent plate boundaries produce hot springs known as hydrothermal vents. 

Scientists first discovered hydrothermal vents in 1977 while exploring an oceanic spreading ridge near the Galapagos Islands. To their amazement, the scientists also found that the hydrothermal vents were surrounded by large numbers of organisms that had never been seen before. These biological communities depend upon chemical processes that result from the interaction of seawater and hot magma associated with underwater volcanoes.

Hydrothermal vents are the result of seawater percolating down through fissures in the ocean crust in the vicinity of spreading centers or subduction zones (places on Earth where two tectonic plates move away or towards one another). The cold seawater is heated by hot magma and reemerges to form the vents. Seawater in hydrothermal vents may reach temperatures of over 700° Fahrenheit

Hot seawater in hydrothermal vents does not boil because of the extreme pressure at the depths where the vents are formed.