What is a hydrothermal vent?

As the continental crust is pulled apart, the magma injected along the spreading line forms basaltic ocean crust, marking the birth of a new ocean basin.
Along the central rift beneath the sea, hot magma close to the surface drives convection currents of seawater which circulate through the crustal rocks. This seawater leaches out metals from the newly-formed ocean crust, forming a solution rich in dissolved metals and minerals. This solution, known as hydrothermal fluid, is eventually jetted out onto the seafloor through a hydrothermal vent. The temperature of the fluid jetting out from these vents can be more than 300ºC.

As the hot mineralised solutions come into contact with the cold seawater, the metals are instantly drop out of solution (precipitate) as solid metal sulphides which form mineral deposits.

Certain types of hydrothermal vents are known as black smokers (pictured left) or white smokers, depending on their temperature, chemical composition, and colour.

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