Volcanic hazard: Floating volcanic rock disrupting life in Papua New Guinea

Rebecca Carey

People in parts of Papua New Guinea are facing an unusual crisis. Floating volcanic rock is making boat travel difficult, blocking access to fishing grounds and disrupting daily life in coastal communities.

The source of the pumice is the ongoing Titan Ridge eruption from an underwater volcano in the Bismarck Sea. Since 9 May, the eruption has produced vast amounts of pumice — a lightweight, porous volcanic rock that floats on the ocean surface. Reports from Manus Province in the northeast describe chunks of pumice accumulating along coastlines and waterways in enormous rafts two to five metres thick. In some locations, residents report being able to walk where there was previously open water.

Submarine eruptions have produced similarly vast pumice rafts before, and experience suggests the disruption facing Manus communities could persist for months or even years, long after the Titan Ridge eruption itself has ended. For many Manus communities, small boats are essential for accessing fishing grounds, neighbouring villages, markets, schools and healthcare services. When those transport routes become blocked, the consequences extend well beyond inconvenience.

PNG Disaster Minister Billy Joseph has described growing concerns regarding food security and access to essential supplies. The ocean serves as the backbone of Manus livelihoods, providing daily sustenance and income through seafood sales. In some villages, residents have begun manually clearing pumice from shorelines to restore access to fishing grounds and prevent longer-term damage to local fisheries.

In 2021, the submarine eruption of Fukutoku-Oka-no-Ba south of Japan produced large quantities of floating pumice that drifted to Okinawa. There, pumice clogged 71 harbours, damaged hundreds of vessel engines, disrupted ferry services and affected tourism and fishery industries. The economic cost in the Okinawa Prefecture alone exceeded 515 million yen.

Japan had extensive transport infrastructure, alternative supply chains and substantial federal resources for recovery. The cleanup effort employed heavy machinery and removed more than 110,000 cubic metres of pumice at an additional cost of more than 1 billion yen. Despite its scale, the cleanup was only somewhat useful; most pumice rafts only washed away the following spring with the change in seasonal winds.

While the Japanese eruption caused major disruption to infrastructure, reports from Manus highlight a different concern: the direct impact on food security and livelihoods. These impacts may persist far longer than expected. Even after the eruption ends, the pumice already floating on the ocean will continue to move through the region for months to years.

Ecosystems may also suffer. Months after the 2021 Japan eruption, scientists observed dead farmed fish with stomachs full of pumice, indicating that some species mistake the rock for food. Researchers also documented pumice rafts passing across fringing coral reefs, temporarily reducing light levels and colliding with shallow-water coral colonies.

For now, the immediate concern remains the disruption to fishing, food security and essential boat transport in Manus Province. However, the people of Manus are dealing with only the first stage of a long-term problem.