Scientists exploring the depths of the Pacific Ocean have uncovered a rare and bizarre geological phenomenon that is challenging long-held assumptions about how Earth’s ocean floor works. More than 1,300 metres beneath the surface, near an active volcanic zone off Papua New Guinea, researchers discovered a deep-sea site where two normally incompatible geological systems are operating side by side.
The discovery was made during a deep-sea expedition in mid-2023, when scientists used a robotic submersible to explore the seafloor near Lihir Island. The team found a location where superheated hydrothermal vents and cooler methane-rich hydrocarbon seeps exist within just centimetres of each other, creating a chemical and biological environment never documented before in the deep ocean.
The site has been named Karambusel and was officially described in a study published in Scientific Reports in December 2025 by researchers from the GEOMAR Helmholtz Centre for Ocean Research Kiel. Scientists have identified it as the world’s first confirmed hybrid system where hydrothermal venting and hydrocarbon seepage occur together.
Hydrothermal vents are typically driven by magma deep beneath the Earth’s crust, heating seawater and enriching it with metals before it escapes through the seafloor. Hydrocarbon seeps, on the other hand, release gases such as methane produced from the breakdown of buried organic matter over long periods. Until now, these two systems were thought to occur separately due to their different geological origins.
At Karambusel, researchers observed shimmering hot fluids reaching temperatures of around 51 degrees Celsius erupting less than a metre away from cold methane-dominated gas emissions. This unusual proximity suggests that the vent system draws from both magmatic heat and sedimentary gas sources deep within the crust, challenging existing models of seafloor fluid circulation.
Chemical analysis revealed that the fluids are rich in metals such as arsenic, mercury, antimony and thallium, elements often associated with gold-bearing mineral systems on land. Gas samples showed that methane made up more than 80 percent of the released gases, an exceptionally high concentration for a hydrothermal environment. Scientists determined that this methane is thermogenic, formed through heat-driven decomposition of organic material rather than microbial activity.
Despite the extreme and toxic chemistry, the site supports thriving biological communities. Researchers documented at least 23 species of large organisms, including mussels, tubeworms, vent crabs and dense microbial mats. These organisms rely on chemical energy rather than sunlight, drawing sustenance from both methane and sulphide-rich fluids. The diversity and biomass suggest the system may have been active for thousands of years without being detected.
The discovery also raises serious conservation concerns. Karambusel lies in a mineral-rich region close to existing mining operations on Lihir Island and within areas licensed for potential seabed mineral exploration. Scientists warn that deep-sea mining or waste disposal in the region could irreversibly damage this fragile and unique ecosystem before it is fully understood.
Researchers say Karambusel offers a rare natural laboratory for studying how geology, chemistry and life interact in extreme environments. At the same time, they stress that its scientific value highlights the urgent need for stronger protections for deep-sea ecosystems that remain largely unexplored but increasingly exposed to industrial pressure.