The ocean floor along the Mid-Atlantic Ridge is lined with fields of hydrothermal vents, acting like huge billowing chimneys and creating centres for deep marine life.
At over 7,000 metres below the sea’s surface, you may think that the bottom of the Atlantic Ocean would be a quiet, dark place devoid of life: however, it is rimmed with rows of geothermal vents which support their own diverse ecosystems.
The Lost City is one of these fields – its extreme underwater conditions include high alkalinity (pH 9 to 11, as strong as ammonia solution) and temperatures of 40-90°C.
These conditions are created by a tall geothermal vents acting like chimneys reaching heights of up to 30 metres from the sea bed, gushing out high pressure geothermally heated water which is rich in methane and hydrogen.
The hollow towers, which are similar to geysers found on the surface, are formed by a chemical reaction between seawater and a mineral called peridotite found in the upper mantle of the Earth, the fluid section just below the hard surface crust.
Elsewhere along the sea floor, running along the Mid-Atlantic Ridge, very acidic hydrothermal vent structures called black smokers can be found, created by a different set of geo-chemical conditions at an average depth of 2,100 metres below sea level.
Perhaps surprisingly, these features are often hubs for life on the seemingly inhospitable sea bed: a profusion of bacteria provide food source for bivalves, shrimps, crabs, worms and even some types of fish, all of which exist without light at these great depths.
Away from these vents, the numerous deep-water life forms die and decompose into a thick, rich sediment known as pelagic ooze, which sustains a whole new ecosystem of marine organisms.
Exploring these alien environments at great pressures and depths is a real challenge for marine scientists, with work often carried out using ALVIN, a manned submersible vehicle built to withstand the harsh conditions at the bottom of the Atlantic.
First used to find and explore black smoker hydrothermal vents, ALVIN has undertaken 4,000 dives carrying 12,000 scientists to the relatively unexplored territory of the deep ocean.