This Giant Raft of Volcanic Rock Could Help Heal the Great Barrier Reef

An underwater volcanic eruption created a huge raft that will evolve into a traveling habitat for many sea creatures.
Pumice raft, August 2019. Image: NASA​
Pumice raft, August 2019. Image: NASA

An enormous raft of volcanic powder is floating across the South Pacific Ocean, and may eventually end up enriching the Great Barrier Reef with nutrients and new lifeforms.

This expanse of pumice—a type of glass-rich volcanic debris—was belched up a few weeks ago by an undersea volcano located about 30 miles northwest of the Tongan island of Vava’u. It currently stretches for 58 square miles, an area the size of Staten Island.


Sailors on the 48-foot catamaran Roam encountered the raft on August 9, and posted incredible video footage of the floating rock the following week.

“We sailed through a pumice field for 6-8 hours, much of the time there was no visible water,” said Roam crew member Shannon Lenz in the video description. “It was like ploughing through a field. We figured the pumice was at least 6 inches.”

Satellite imagery of the raft captured by NASA’s Landsat 8 satellite a few days later revealed that it was slowly breaking apart as it drifted across the South Pacific.

Massive pumice rafts are a relatively rare sight, but they are not unprecedented. In 2012, for instance, an immense raft of 10,000 square miles was formed off the coast of New Zealand.

While these rafts create hazards for vessels, they are a boon to marine life in much the same way that volcanic eruptions on land nourish terrestrial ecosystems. In fact, some scientists have speculated that pumice rafts may have played a major role in the origins of life on Earth.

These floating structures attract corals, algae, worms, and other seafaring species, which often evolve into thriving habitats. That could be good news for Australia’s Great Barrier Reef, which is where the raft is projected to wind up in about a year.

The Great Barrier Reef has experienced devastating biodiversity losses in recent decades, as corals die off in the warming waters caused by human-driven climate change. If chunks of the raft do make it to the reef, they could temporarily reinvigorate it by transplanting fresh healthy corals to the environment, according to Scott Bryan, a geoscientist at Queensland University of Technology.

"This is a potential mechanism for restocking the Great Barrier Reef," Bryan told the BBC.

"Based on past pumice raft events we have studied over the last 20 years, it's going to bring new healthy corals and other reef-dwellers."

Ultimately, though, the Great Barrier Reef will only be saved if humans curb greenhouse gas pollution, which is the major factor driving the warming of the oceans. Pumice rafts have helped seed new life around the globe for eons, but these unique habitats cannot preserve vulnerable ecosystems without our help.