A huge raft of volcanic rock has been spotted floating in the South Pacific Ocean, and it’s due to reach Australian waters in a matter of months. Strange as it sounds, this is good news – scientists say the pumice will help restock the ailing Great Barrier Reef with coral and sea creatures collected during its voyage.

The “raft” is made up of pumice, a porous type of rock that has such a low density that it can float on water. The rock was produced in underwater volcanic eruptions on August 7 near the island of Tonga. Pumice rafts like these happen fairly regularly in the area, perhaps every five years or so, but this one is particularly big – it reportedly stretches for 150 km2 (58 mi2).

An up-close look at the raft came a few days later, when Australian sailors Michael Hoult and Larissa Brill, of Sail Surf ROAM, entered the rocky field. En route to Fiji on their catamaran, the couple reported that they came across the pumice raft on August 15, and reported it to authorities as a hazard for other vessels.

Hoult and Brill said that the slick extended as far as they could see, and was made up of rocks ranging from marble-sized to basketball-sized. A video shot by another sailor, Shannon Lenz, shows an eerie, undulating surface that looks like gravel but moves like ocean.

The two sailors collected samples of the pumice for Professor Scott Bryan, a geologist at the Queensland University of Technology, as well as scientists from other institutions. The raft is now drifting east, and is expected to float past New Caledonia, Vanuatu, and other islands before reaching Australian waters in about seven or eight months’ time.

And when it does, the pumice will most likely bring a treasure trove of life with it. The porous structure of the coral gives tiny organisms plenty of places to latch onto to make the long journey.

“At the moment the pumice will be bare and barren but over the next few weeks it’s going to start getting organisms attached to it,” says Bryan. “Then they’re going to grow and diversify, to ultimately wash up here in Australia.”

This boost of life should help replenish the Great Barrier Reef, which has been struggling in recent years due to climate change. The Reef suffered back-to-back bleaching events in 2016 and 2017, which killed off large swathes of coral. And sadly, its ability to recover has been called into doubt.

Scientists have hatched many plans to try to help, using robots to deliver coral “babies” and kill off coral-destroying pests, designing floating films that could cool waters, and altering the seawater chemistry to pre-industrial conditions.

Now, with the rocky raft incoming, it looks like nature itself is lending a hand to the restoration efforts. The pumice is floating down at just the right time of year, during the main coral spawning season. Hopefully that means more passengers will jump aboard.

“It’s the right timing,” says Bryan. “So it will be able to pick up corals and other reef building organisms, and then bring them into the Great Barrier Reef. Each piece of pumice is a rafting vehicle. It’s a home and a vehicle for marine organisms to attach and hitch a ride across the deep ocean to get to Australia.”

Scientists will continue to track the huge pumice raft as it continues its journey over the next few months. Check out the video shot by Shannon Lenz below.

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