Giant pumice raft might help boost habitats
Michael and Larissa Hoult were sailing from the Vava’u islands of Tonga to Fiji in the South Pacific Ocean when they saw it – a ‘‘total rock rubble slick’’ extending for miles around them. The rocks, some the size of marbles and others as big as basketballs, bumped against their boat and clogged their rudders.
‘‘It was quite eerie, actually,’’ Larissa Hoult told CNN. ‘‘The whole ocean was matte.’’
The couple had sailed upon what scientists call a pumice raft, a mass of floating, porous rock that forms when a volcano erupts from the ocean floor. The hot lava, full of gas bubbles, cools in the ocean water and produces pumice, which floats to the surface above the eruption.
The raft spotted by the Hoults has been compared in size to Manhattan, Washington and 20,000 football fields.
The Hoults had received an August 14 email warning of pumice fields, which had been spotted by other sailors and detected from space by Nasa satellites. By the evening of August 15, they were surrounded by the rocks and their sulfur smell, they said in a post on the Facebook page that tracks their sailing and surfing adventures.
‘‘The rocks were kind of closing in around us, so we couldn’t see our trail or our wake at all,’’ Michael Hoult told CNN. ‘‘We could just see the edge where it went back to regular water – shiny water – at night.’’
They posted photos of their discovery to Facebook, and in the week since have received homework assignments from scientists and university professors looking for photos and specimens of the pumice the Hoults collected.
Among them was Scott Bryan, a geologist and associate professor at Queensland University of Technology, who has been studying underwater volcanic pumice for two decades, he told the Australian Broadcasting Corporation.
This mass, he told ABC, is slowly floating toward Australia’s coastline – where in seven to 12 months it could arrive with a host of marine life ready to potentially revive the badly damaged Great Barrier Reef.
‘‘In this 150-odd square kilometres of pumice out there right now, there’s probably billions to trillions of pieces of pumice all floating together, and each piece of pumice is a vehicle for some marine organism,’’ Bryan told ABC.
Organisms such as algae, barnacles, snails, crabs and possibly even corals could attach themselves to the pumice raft, serving as a ‘‘natural mechanism for species to colonise, restock and grow in a new environment,’’ Bryan said.
Warming waters, caused by climate change, have caused devastating bleaching to the Great Barrier Reef, which stretches 2200 km off the coast of Australia and is the world’s largest coral reef. When ocean heat waves drive nutrient-rich algae from coral cells, they lose their color and begin to die. There are degrees of severity to the bleaching that coral reefs are facing, but the warmer the waters stay – and the longer the nutritious algae stays away – the greater the threat.
The pumice raft has the potential to deposit new, healthy coral around the reef, Bryan said.
‘‘It’s just one way that nature can help promote regeneration,’’ he told ABC.