Oceanic ridges with hydrothermal vents / fields

Oceanic ridges with hydrothermal vents / fields are one of the 5 deep-sea habitats listed by OSPAR as threatened and / or declining.

Throughout the deep oceans, there are vast mountain ranges extending for more than 75000 km. These huge structures form the largest mountain range on earth, the mid-ocean ridge system. Here, planetary scale processes of crust formation, plate separation and global heat loss occur. On a smaller scale, these ridges form the setting for one of the most unusual and least-understood habitats on earth, the deep-sea hydrothermal vents.

Hydrothermal vents or black smokers are fissures in the ocean floor which eject hot, mineral-rich water. These cracks in the seafloor allow seawater to circulate and reach temperatures of up to 400� C while the intense pressure of several thousand metres of seawater prevents the water boiling. This super-heated water spews out of chimneys created of deposited minerals. The water is highly acidic, contains high concentrations of toxic compounds and minerals, and contains almost 2-3 times the amount of salt in the surrounding seawater.