Deep Sea Hydrothermal Vents

Deep Sea Hydrothermal Vents

A hydrothermal vent is a fissure in the planet's surface through which geothermally heated water erupts.



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Deep-sea hydrothermal vents are fissures in the seabed from which geothermally heated water erupts. Similarly to geysers and hot springs occurring on dry land, deep-sea hydrothermal vents form as a result of volcanic activity.

At the bottom of the oceans, volcanic activity occurs along oceanic plate boundaries, or at hotspots. The greatest number of deep-sea hydrothermal vents are found along divergent oceanic plate boundaries, that is, along mid-ocean ridges.

Rift valley

Mid-ocean ridge


Along mid-oceean ridges, seawater seeps into the oceanic crust through fissures of the seafloor, where it is heated by the upwelling magma. The temperature of the heated water can exceed 400°C (752°F), at which temperature water is normally in the gas phase. However, due to the high hydrostatic pressure at this depth, the superheated water exists here either in its liquid form or in a state where it has both gas and liquid-like properties.

In this state, water in the vent can hold a lot more dissolved minerals than cold seawater. When the erupting superheated water mixes with the cold, near-freezing seawater, it cools down rapidly. The solution becomes oversaturated, and its mineral content precipitates. This makes it appear like a cloud of smoke emitting from the seafloor.

The precipitating minerals may deposit around the opening of the vent and form a chimney-like structure. This chimney can grow quite rapidly and reach up to 60 m (196.85 ft) in height.

The color of the rising water depends on the dissolved minerals: black color indicates the presence of iron and sulfur, while barium, calcium or silicon-containing minerals color the water white. Hence the names black and white smokers.


The hot, highly acidic, sulfide-rich seawater around the vents is a toxic environment for most life forms. Amazingly, however, hydrothermal vents are surrounded by a great variety of organisms.

The foundation of the ecosystem of hydrothermal vents are chemosynthetic bacteria that obtain energy by oxidizing sulfur and its compounds, mainly hydrogen sulfide, in order to produce organic substances.

The bacterial mats then attract other organisms. Some animals, certain crustaceans for example, feed on the bacteria. Others have a symbiotic relationship with the bacteria living inside their bodies which provide nutrients for them. Such animals include certain clams and worms. Predators, such as octopuses, also settle around the hydrothermal vents.

The ecosystems around hydrothermal vents do not depend on sunlight, their formation is based on chemical and heat energy obtained directly from the Earth's crust.

Giant tube worm

"Yeti crab"


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