Hydrothermal vents are fissures in the ocean floor from which geothermally heated water emerges. First discovered in 1977 near the Galápagos Rift, they overturned the assumption that all life on Earth ultimately depends on sunlight.
How they form
At mid-ocean ridges, tectonic plates pull apart and seawater percolates down through cracks in the seafloor. Heated by magma chambers below, the water reaches extreme temperatures, dissolves minerals, and rises back through vents — emerging as dark, mineral-rich plumes.
"We were absolutely stunned. There were mussels, clams, crabs — a whole community in the total absence of sunlight." — Robert Ballard, 1977
Chemosynthesis: sunlight-free energy
Unlike surface ecosystems, vent communities are powered by chemosynthesis. Specialised bacteria oxidise hydrogen sulphide (H₂S) from the vent fluid, converting it into organic carbon — forming the base of an entire food web in permanent darkness.
Known vent fields
| Name | Location | Depth (m) | Type |
|---|---|---|---|
| Lau Basin | Pacific | 1,900 | Black smoker |
| Lost City | Atlantic | 800 | White smoker |
| Lucky Strike | Mid-Atlantic | 1,730 | Black smoker |
| Kairei | Indian Ocean | 2,450 | Black smoker |
| ASHES | Juan de Fuca Ridge | 1,540 | White smoker |
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Notable inhabitants
Riftia pachyptila (tube worm)
Growing up to 2 metres in length, tube worms are among the fastest-growing marine invertebrates. They have no mouth or digestive system — instead hosting billions of sulphur-oxidising bacteria in a specialised organ called the trophosome.
Yeti crab (Kiwa hirsuta)
Discovered in 2005 near Easter Island, the yeti crab cultivates mats of bacteria on its hairy claws. It is thought to "farm" these bacteria as a food source, waving its claws through vent plumes to seed their growth.
Pompeii worm (Alvinella pompejana)
Among the most heat-tolerant animals on Earth, Pompeii worms live in tubes attached directly to vent chimneys, with their tails at temperatures of up to 80°C.