In some areas of Papua New Guinea, people are facing an unusual problem. Floating volcanic rocks make 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 May 9, the eruption has produced large quantities of pumice, a light, porous volcanic rock that floats on the ocean surface.
Reports Since Manus Province in the northeast of the country, pieces of pumice accumulate along the coasts and rivers in enormous “rafts” 2 to 5 meters thick. In some localities, residents report be able to to walk where there was previously open water.
It’s a strange sight, but not unprecedented. Underwater eruptions have produced similarly large pumice rafts before, and experience from these events suggests that the disruptions faced by Manus communities could persist for months or even years, long after the eruption of Titan Ridge itself has ended.
A white plume and gray rafts of pumice spread from the underwater volcano Titan Ridge. Image from the European Space Agency.
For many communities in Manus, small boats are essential for accessing fishing grounds, neighboring villages, markets, schools and health services. When these transportation routes become difficult to use, the consequences go far beyond the inconvenience.
Billy Joseph, PNG Disaster Minister described growing concerns over food security and access to essential supplies.
The ocean forms the backbone of Manu’s livelihood, providing daily sustenance and the main source of income through the sale of seafood. In some villages, residents have begun manually removing pumice from shorelines and waterways in an effort to restore access to fishing grounds and avoid long-term damage to local areas. fisheries.
Titan Ridge is not the first underwater eruption to generate vast pumice rafts. In 2021, the underwater eruption of Fukutoku-Oka-no-Ba Southern Japan produced large quantities of floating pumice which drifted to the Nansei Islands, notably Okinawa. There, pumice clogged 71 ports and marinas, damaged hundreds of ship engines, disrupted ferry services and affected the tourism and fishing industries. THE economic cost in Okinawa Prefecture alone, the amount exceeded 515 million yen.
Japan had extensive transportation infrastructure, alternative supply chains, and substantial federal resources for cleanup and recovery. The cleanup effort used heavy machinery on land and sea and removed more than 110,000 cubic meters of pumice from ports and beaches, at an additional cost of more than 1 billion yen.
Despite its scale, the cleanup was of little use. Most of the pumice rafts were not washed away until the following spring due to changing seasonal winds.
While pumice from the 2021 Fukutoku-Oka-no-Ba eruption caused major disruptions to ports, ferries and tourism in Japan, Manus’ reports highlight another concern: potential impacts on food security and livelihoods of communities that directly rely on the ocean. These impacts may persist much longer than expected.
Even after the eruption subsides, pumice already floating on the ocean will continue to move around the area for months or even years. To understand why, it helps to understand how pumice behaves.
Pumice forms when gas-rich magma erupts and cools quickly. The escaping gas leaves behind countless small holes, creating a rock porous enough to float. Individual pieces of pumice clump together to form enormous floating rafts covering hundreds or even thousands of square kilometers.
Many people think that floating pumice quickly becomes waterlogged and sinks. Research by my colleagues and myself shows the opposite. Previous underwater eruptions show that some pumice stones can stay afloat for years. Ocean currents, winds, and storms can repeatedly redistribute pumice across large areas of the ocean, moving it between coastlines and islands long after an eruption has ended.
After the 2012 underwater eruption Le Havre Volcano north of New Zealand, pumice traveled thousands of kilometers across the Pacific, reaching Queensland about eight months later and even Tasmania more than a year later. So even after Titan Ridge erupts, we can expect already produced pumice to float in the area for months or even years.
Humans won’t be the only ones affected. Entire ecosystems could suffer.
A few months after the Fukutoku-Oka-no-Ba eruption in Japan in 2021, scientists observed dead farmed fish with stomachs full of pumice, indicating that some species may mistake floating pumice for food. The same researchers also documented pumice rafts crossing fringing coral reefs, temporarily reducing light levels and physically colliding with shallow-water coral colonies.
Research following the eruption of Hunga Tonga-Hunga Ha’apai in Tonga in 2022, this suggests another possible ecological impact. Satellite observations showed that volcanic particles suspended in seawater reduced light penetration through the water column, potentially affecting coral reefs and other marine ecosystems that rely on sunlight.
It is not yet clear whether similar impacts will occur in Papua New Guinea. However, these observations suggest that marine ecological effects may extend beyond immediate disturbances.
For now, the immediate concern remains the disruption of fishing, water and food security, and boat transport for essential services in Manus province. But the people of Manus are only tackling the first stage of the problem.
Pumice rafts pose an unusual volcanic hazard because their impacts do not necessarily end when an eruption stops. Japan’s experience shows that once pumice enters coastal waterways, there are few easy solutions.
This article was originally published on The conversation. Read the original article. 