The Atlantic Vents With Two Kinds of Fire
Two hydrothermal vent fields have been found inside a vast Atlantic fault system. Their plumbing appears to combine volcanic heat with a second engine hidden in mantle rock.
The Discovery
An international expedition has found two hydrothermal vent fields in the Doldrums Megatransform and Fracture Zone, a 600-kilometre system of faults cutting across the Mid-Atlantic Ridge. They are the first known vent fields discovered in and around this remote system, roughly 1,300 kilometres off north-eastern Brazil.
The findings were reported by Schmidt Ocean Institute and expedition lead MBARI. Ship sonar narrowed the terrain, an autonomous vehicle mapped it at one-metre resolution, and the remotely operated vehicle SuBastian supplied visual confirmation and samples.
What Makes Them Strange
Initial observations indicate that both fields have hybrid plumbing. Ordinary volcanic heat operates alongside serpentinization, a reaction in which seawater meets exposed mantle rock and releases heat and chemical energy. Only a handful of mixed systems like this are known.
- The larger field covers about 99,000 square metres.
- It contains 23 vents, including 13 active black smokers.
- Fluids reached 280°C at a depth of roughly four kilometres.
- A smaller, weaker field lies 170 kilometres away.
Two engines are feeding life in one of the Atlantic's darkest rooms.
The Implications
Researchers saw evidence of fluid circulation along faults, fractures and scarps during every remotely operated dive across the Doldrums system. That suggests transform faults may move far more seawater through oceanic crust — and host more hydrothermal activity — than scientists previously recognised.
The hybrid interpretation is based on the expedition's initial observations. Laboratory work on the collected rock, fluid and biological samples still has to resolve how the two heat-producing processes interact.
What Happens Next
The fields support shrimp, mussels, crabs and anemones whose food webs begin with chemosynthetic microbes rather than sunlight. Comparing those communities with vents on the neighbouring Mid-Atlantic Ridge may reveal how deep-sea animals cross huge gaps between temporary habitats.
The Doldrums were not empty. They were an overlooked circulation system, breathing seawater through the crust.