From Narooma to Bermagui to Tathra, locals and visitors have been wondering where all this very light, volcanic rock has come from.

Reports from Tathra came in on Thursday of piles of the pumice pebbles at the boat ramp and a slick of the rocks floating off the cliffs.

But we are not alone with reports of the pumice being washed up as far north as Rockhampton, Queensland.

And it is not a new phenomenon with pumice events back in 2007 and then 1984.

Queensland University of Technology researcher Scott Bryan is a world expert in pumice rafts and has been reported in various media outlets on this latest event.

He narrowed down the source was the Havre Seamount that erupted, spewing out a huge volume amount of lava, creating a raft of porous volcanic rock estimated to be more than 20,000sq km in size.   

According to Wikipedia, the Havre Seamount is located near the L'Esperance and L'Havre Rocks in the Kermadec Islands of New Zealand, around 800 km north-east of Tauranga, New Zealand.

Little was known about the seamount until the 2012 Kermadec Islands eruption and resulted in subsequent scientific visits to the site to investigate the seamount.

The Rockhampton Morning Bulletin reported this month that according to Great Barrier Reef Marine Park Authority, the raft travelled more than 4000km across the Tasman and the Coral seas.

In December, pieces were also found on Rainbow Beach on the Fraser Coast, the Bulletin reported.

Now the pumice has floated all the way down the East Coast washing up on Sydney, Wollongong and now Far South Coast beaches.

This is not new and Daniel Dasey posted a blog on the Sydney Morning Herald website back in January 2007.

Back then hundreds of tonnes of the frothy rock, produced by volcanoes, also made it to our shores after seismic activity in the South Pacific near Tonga.

Apart from giving a lift to exotic forms of coral and bemusing swimmers, the rock back then and now is not expected to have a major impact on the environment.

“This also happened in 1984,” said marine researcher Leon Zann, who back in 2007 had just returned to Australia after three years as Professor of Marine Studies at the University of the South Pacific in Fiji.

“I was in Tonga at the time and it took six months for the pumice to reach Australia.”

In August 2006, the crew of the yacht Maiken were travelling to Australia from San Francisco when they encountered a massive raft of pumice at least 16km wide.

They later travelled towards a huge steam cloud on the horizon and were able to approach to within 1.5km of a volcanic island being created by lava piling up on the ocean floor.

“You could clearly see the three mounds creating a crater with one side breaking off opening up towards the sea,” crew member Frederik Fransson said.

“It looked like a big island made of black coal.”

Mr Zann said pumice spewed up by the volcano back then had travelled the 600km west to Fiji in about two months. In some locations it was thick on the shore and caused yacht engines to lose traction.

Mr Zann said it was believed pumice could help coral species spread by ferrying larva over great distances.

Pumice deposits on the shoreline also give ocean researchers an indication of how far up the beach high tides can extend.