Hydrothermal vent
Also called: Black smoker · Topic: Oceans: Hydrological Cycle, Relief of the Ocean Floor, Temperature and Salinity · NCERT: Beyond NCERT
Meaning
A hydrothermal vent is an opening in the sea floor, usually along a mid-oceanic ridge. Seawater seeps into cracks, is heated by the magma (molten rock) below, and gushes back out hot and full of dissolved minerals. When this water meets cold seawater, the minerals settle out as dark clouds, which is why vents are also called black smokers. Vents support life based on chemosynthesis, where microbes make food from chemicals instead of sunlight. Over time the minerals pile up as polymetallic sulphide deposits, which are rich in metals and are now wanted for deep-sea mining.
Example
Hydrothermal vents were first discovered in 1977 on the Galápagos Rift in the eastern Pacific. India holds an International Seabed Authority (ISA) contract to explore polymetallic sulphides on the Indian Ocean ridges.
Don't confuse with
- Polymetallic nodules: these are lumps of manganese, nickel, cobalt and copper that lie loose on the flat abyssal plains. Sulphide deposits form at vents on the ridges.