Months after an undersea volcano erupted off southern Japan on Aug. 13, pumice stones and debris have been found floating on the shores of Batanes province over the weekend, the Philippine Institute of Volcanology and Seismology (Phivolcs) confirmed on Tuesday, Nov. 23.
"At 7:45 a.m. (Philippine Standard Time) of 23 November 2021 (Tuesday), the Batanes Provincial Disaster Risk Reduction and Management Officer (PDRRMO), Mr. Dhan Esdicul, reported to the DOST-Phivolcs Batanes Seismic Station that volcanic material have been washed onto the shores of Sitio Maydangeb, Ivana, Batanes Province. This was first noticed in coves of Batan and Sabtang islands on 21 November 2021 (Sunday)," Phivolcs said in its primer.
It noted that the Fukutoku-Okanoba Submarine Volcano, which is part of Japan's Volcano Islands in the Bonin Island, is located five kilometers (km) northeast of the island of Iwo Jima and over 2,000 km northeast of Batanes and Aparri, Cagayan.
As to how the pumice and smaller-graned volcanic ash reached the island-province, Phivolcs said the materials have been carried by ocean currents to the shores of mainland Japan and the Philippines.
Fukutoku-Okanoba Volcano's eruptions were first documented by the Japan Coast Guard on Aug. 13, during a flight observation that confirmed the eruption as well as the height of the eruption plumes.
Phivolcs said the massive underwater eruption ejected "tens of millions of cubic meters of pumice and other finer volcanic debris, or 'pumice rafts,'" which started washing up along coastlines of Okinawa Prefecture, Japan.
It defined pumice rafts as floating masses of buoyant porous rocks resulting from a submarine volcanic eruption.
"During the eruption, hot and gas-rich magma rapidly cools to form pumice rocks which then float and gather on the surface forming a raft," it added.
Hazards, possible damages from floating pumice
Phivolcs said that floating pumice stones could potentially damage passing boats, and may also harm the marine biodiversity.
"Pumice may abrade boats and other structures found on the sea. Similarly, pumice and fine volcanic material can infiltrate and cause damage to boat engines and disruption to fishing vessels," it pointed out.
It also noted that pumice and fine-grained ash material can block drainage pipes, while pumice rafts can obstruct sunlight, thus affecting the growth of marine life.
"Pumice or fine ashcan also be ingested by marine animals, leading to death; there have been reports of fish kill in some parts of Japan. Seawater contamination is possible, e.g. from leached volcanic sulfur," Phivolcs added.
Immediate action from national, local governments needed
Phivolcs advised local government units (LGUs) to coordinate with the Office of Civil Defense (OCD) to enlist the Philippine Coast Guard (PCG) in warning sea vehicles on the presence of pumice rafts as these pose hazards to marine vessels and aquatic activities.
The LGUs concerned were also asked to seek help from the PCG to implement containment measures such as the use of spill boom, use of nets/trawls, scooping via shovel loaders, boats.
Likewise, Phivolcs asked the Bureau of Fisheries and Aquatic Resources (BFAR) to test for seawater contamination around affected communities of Batanes Province, while LGUs need to mobilize barangay officials and their units, volunteers, and civil society to help monitor the beaches and note important information such as locality of occurrences, thicknesses and general areal coverage of volcanic deposits and date and time of observation in the coastlines.
"LGUs should look for a place to temporarily collect the pumice and explore long-term plans for proper disposal or use, (as well as) issue warnings and advisories against swimming in coasts with floating pumice," it added.
People are reminded to avoid swimming and other beach activities in the meantime as the pumice rafts reduce visibility when swimming underneath these and may cause abrasion injuries.
"This also safeguards against ingestion of seawater with potentially harmful substances such as sulfur and very fine ash that may have been brought by the pumice rafts," Phivolcs said.