A gigantic fleet of floating rocks, spewed up from an underwater volcano in the Pacific Ocean, floated across the waves for thousands of miles. Eventually, it made it all the way to Australia, then started on a new project: revitalizing the world’s largest (and very threatened) coral reef system. This unlikely chain of events may sound somewhat incredible, but it’s an entirely true story – one that has played out dramatically over the last year, while highlighting the surprising, largely unseen ways in which Earth’s natural environmental systems intersect with one another.
Stranger still, it’s not the first time this has happened. An eruption in 2001 from the same submarine seamount – a nameless volcano, simply dubbed Volcano F or 0403-091, located near the Vavaʻu islands in Tonga – produced a similar rocky flotilla, which also voyaged on the currents to Australia over the space of a year. When this phenomenon occurs, it creates what’s called a pumice raft – a floating platform composed of countless chunks of buoyant and highly porous volcanic rock. Each one of these small rocks attracts marine organisms, including algae, barnacles, corals, and more. These tiny travelers end up hitching a ride across the ocean, and they can help seed and replenish endangered coral systems at their ultimate destination: for many, the Great Barrier Reef.
“Each piece of pumice has its own little community that has been transported across the world’s oceans – and we have had trillions of pieces of this pumice floating out there following the eruption,” says geologist Scott Bryan from the Queensland University of Technology in Australia.”Each piece of pumice is a home, and a vehicle for an organism, and it’s just tremendous. The sheer numbers of individuals and this diversity of species is being transported thousands of kilometers in only a matter of months is really quite phenomenal.” Bryan knows a thing or two about these pumice migrations. He’s been studying the volcanic rafts for 20 years, investigating the 2001 eruption, its 2019 successor (which started washing up on Australian shores in April), and other underwater eruptions as well.
His most recent study, published last month, examined the 2012 eruption of the Havre Seamount, also in the South Pacific – estimated to be the largest underwater volcano eruption ever recorded, broadly equivalent to the most powerful volcanic eruption on land in the 20th century. That event produced a gigantic raft of pumice rock that ended up dispersing over an area twice the size of New Zealand – in addition to littering the seafloor with giant chunks of pumice the size of vans. –Science Alert