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Lifting a thin shelf of volcanic lava at a deep-sea hydrothermal vent revealed a warm, fluid-filled cavity crowded with adult tubeworms and other animals. The discovery, made by a remotely operated vehicle on the East Pacific Rise, shows that vent life can occupy spaces beneath the visible seafloor—not just the chimneys and rock surfaces scientists can see.
What did scientists find beneath the seafloor?
At the Fava Flow Suburbs vent site near 9°50′N on the East Pacific Rise, researchers found animals living in shallow cavities under thin lobes of volcanic lava. The site is about 2,515 meters below the ocean surface. A 2024 study in Nature Communications describes this as the first reported discovery of animal life excavated from shallow subseafloor cavities at deep-sea hydrothermal vents.
The team examined six cavities. Five, each about 10 centimeters high, were visibly inhabited. They contained adult tubeworms as well as mobile animals, making this more than a discovery of microbes living in porous rock.
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The cavity animals included adult Oasisia alvinae tubeworms with tubes up to 20 centimeters long—the longest reported for that species—and adult Riftia pachyptila up to 50 centimeters long. Researchers also found mobile fauna including Paralvinella, limpets, Neomphalus, Nereis, Archinome, and other polychaete worms and gastropods.
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Some tubeworms had reproductive organs. Two males contained sperm and two females contained large eggs. That suggests reproduction may occur below the seafloor, although the observations do not establish how often it happens or how many animals reproduce there.
How did the ROV get beneath the lava?
The researchers used the remotely operated vehicle SuBastian to investigate the rock at the vent site. Rather than excavating a large trench, the team drilled and widened small holes, sampled vent fluid, suction-sampled organisms, and lifted whole lava shelves. Raising a thin shelf exposed the cavity beneath it.
That approach let the team inspect spaces hidden from ordinary observation of the seafloor surface. The Associated Press described the operation as an underwater robot overturning volcanic slabs to reveal life below the vents; the peer-reviewed study reports the drilling, sampling, and lifting methods.
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For the five visibly inhabited cavities, Bright and co-authors reported these measurements in their 2024 Nature Communications study:
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| Measurement | Reported value |
|---|---|
| Maximum temperature | 18.1 ± 7.1 °C |
| pH | 6.1 ± 0.4 |
| Salinity | 33.8 ± 0.4 |
The researchers also measured sulfide and oxygen. The values are not given here, so no specific concentrations can be stated. These measurements describe the observed cavities at this site; they are not a standard profile for every hydrothermal vent or subseafloor habitat.
How might animals live and move beneath a vent?
The authors propose that cold seawater enters porous volcanic rock in a recharge zone, mixes with warmer hydrothermal fluid, and flows back out through cracks. That circulation could carry larvae into the cavities, where they might settle and grow. Some animals may also crawl through cracks between cavities and the seafloor.
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This proposed pathway connects the visible vent community with a hidden habitat in the crust. The study directly observed animals in cavities, but larval transport through the fluid circulation is an explanation proposed by the authors, not a directly tracked journey.
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It expands the known habitat of vent animals
Hydrothermal vent food webs do not depend on sunlight. Many vent animals host dense bacterial symbionts that use reduced chemicals for energy and fix carbon. Finding animals beneath the visible seafloor means the habitat available to vent communities may extend into the volcanic crust, changing how scientists estimate local and regional geochemical fluxes.
It adds a habitat to consider in conservation
The authors argue that the discovery strengthens the case for protecting hydrothermal vents, including from potential impacts such as deep-sea mining. The cavities’ three-dimensional extent has not been quantified, however, so this finding does not establish how much habitat exists or what a particular disturbance would affect.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Does this mean all hydrothermal vents have animals underneath them?
No such conclusion follows from one site. The observation was made at Fava Flow Suburbs on the East Pacific Rise, and the study says the cavities’ full three-dimensional extent is unknown. Further observations are needed to determine whether similar animal colonies occur beneath vents elsewhere. The discovery establishes that animals can live in these shallow subseafloor cavities; it does not show that every vent has the same community or that there is a known global population.
Could this help explain life beyond Earth?
It is relevant as an example of how life can occupy a hidden environment without sunlight, using chemical energy associated with fluid and rock. That makes it an interesting comparison for thinking about potentially habitable environments elsewhere, but the finding is evidence about Earth only. It does not demonstrate extraterrestrial life or establish that another world has the same conditions.
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