The Changing World

Black smoker

The erupting hot water is coloured black by the dissolved iron- and sulphur compounds it contains.

White smoker

The white colour is caused by minerals containing barium and calcium compounds and silicates.

divergent tectonic plate boundary

hydrothermal vent

Deep sea hydrothermal vents are fissures on the seafloor from which geothermally heated water emanates. Similarly to hot water springs ang geysers, seafloor hydrothermal vents are formed by volcanic activity. On the seafloor volcanic activity is most widespread along fault lines and around hotspots.

Deep sea hydrothermal vents are found in largest numbers along the boundaries of divergent tectonic plates, e.g. trenches.

Deep Sea Hydrothermal Vents

Seawater seeps down through the rocky crust deep enough to be heated by the hot magma to as much
as 400 ºC or above. Under the enormous pressure large amounts of minerals dissolve in the water. When the erupting hot water meets the near-freezing cold seawater, it cools suddenly and becomes over­saturated, causing the minerals to precipitate, which makes the water look smoke-like. The minerals settle on the floor around the vent, which gradually grows upwards, creating a chimney-like structure. These
can reach heights of up to 60 metres.

The hot, acidic water, rich in sulphides, is toxic for most living organisms, yet there is a thriving fauna around these vents. It is based on chemosynthetic bacteria, which produce organic material from sulphur compounds, thus providing nutrients for small crustaceans, and giant tube worms and molluscs as well, by living in symbiosis with them. These in turn attract predators, like octopuses.