Queensland University of Technology geologist Scott Bryan and colleagues studied the westward flow, or rafting, of pumice -- created when frothy molten rock cools rapidly and forms a lightweight bubble-rich rock that can float in water -- after volcanic eruptions in Tonga in 2001 and 2006.
Plants and tiny animals including corals latched onto the pumice as it was swept by ocean currents toward northeastern Australia, they found.
"The pumice raft created after the 2006 Home Reef volcano erupted in Tonga initially formed at least a 440 square kilometer (150 square mile) floating mass," Bryan said.
"This mass slowly broke up into streaks and millions to billions of marine organisms such as cyanobacteria, barnacles, mollusks, corals, anemones, and crabs began hitching a ride," he said.
When these tiny corals, coralline algae, anemones and other reef dwellers arrived in northeastern waters they became part of the Great Barrier Reef, he said.
"This is good news because we know the reef is being replenished as a result of volcanic activity in the southwest Pacific and volcanic activity is frequent with eruptions in the area occurring every five to 10 years," he said.