Hydrothermal Vents

A hydrothermal vent is an underwater hot spring found on the ocean floor.

hydrothermal vents

They are commonly found near volcanically active places, areas where tectonic plates are moving apart, ocean basins, and hotspots. On land, these vents result in the formation of hot springs, fumaroles and geysers.

The study of submarine hydrothermal vents (hot springs) began in 1977 near the Galapagos Islands. Locally, many hydrothermal vents have been found along the Kermadec Arc associated with active submarine volcanoes.

Hydrothermal vents produce metal-rich chimneys, of interest in undersea prospecting, and provide an important environmental niche for life in the deep.

There are different types of chimney structures at these vents:

Black smokers – vents that emit dark particles with high levels of sulphur-bearing minerals, or sulfides. The dark colour is caused because dissolved minerals precipitate as tiny metal-rich particles, forming ‘smoke’. This is due to large differences in temperature between the discharging fluids (350°C) and the surrounding seawater (2°C), plus rapid changes in acidity and oxygen content.

White smokers – vents that emit lighter-coloured minerals, e.g. barium, calcium, and silicon. These vents also tend to have lower temperature plumes.

Hydrothermal plumes can be used to locate hydrothermal vents. Plumes form when the hydrothermal fluids exit vents on the seafloor and mix with the surrounding seawater. Learn about finding hydrothermal plumes.

The diagram below shows a typical submarine volcano that you might find along the Kermadec arc, with a plume forming above a hydrothermal vent.

hydrothermal vent diagram
Seawater modified by chemical exchange with the surrounding rocks (blue arrows) and gas-rich magmatic fluid (red arrows) mix before emerging at the seafloor. Manganese, iron, iron oxyhydroxide, carbon dioxide, hydrogen sulphide, methane and helium-3 are release into the black smoker plume as the hot hydrothermal fluids mix with cold seawater.