Pumice strewn across Coast beaches was caused by an underwater volcano eruption - about 18 months ago

IT is not every day that you see remnants of an underwater volcano strewn across the Gold Coast's otherwise pristine beaches.

Pumice stones have been washing up on Gold Coast beaches. Lena Rubitschung, 16, from Switzerland, found these chunks at the S...

IT is not every day that you see remnants of an underwater volcano strewn across the Gold Coast's otherwise pristine beaches.

Pumice stones have begun washing-up along Gold Coast beaches in the past two days after an underwater volcano off the coast of New Zealand erupted creating the largest pumice raft seen in 50 years.

The buoyant, white stones are littered across beaches along the east coast of Australia and the best place to look for the rock is along the line of high tide.

Gold Coasters were among many Australians to find the stones at the coast yesterday.

The volcanic eruption created a 20,000 sq km raft which eventually spread roughly 4 million sq km while it broke up, although the stones did not travel as far as Swiss exchange student Lena Rubitschung did to get to the Gold Coast.

The 16-year-old has been on the Gold Coast for about five months and expected pristine beaches and friendly locals when she came to Australia, not fist-sized pumice stones littered across the sand.

"I love the beach," she said.
"I try to get to the beach every day.

The New Zealand eruption formed a 20,000 sq km raft that eventually spread about 4 million sq km as it broke up.

The porous pumice floats because it is formed when frothy lava solidifies, trapping tiny bubbles of air.

Queensland University of Technology researcher Scott Bryan has said it was the largest pumice raft in the past 25 to 50 years, eclipsing even that caused when Krakatoa in Indonesia erupted in 1883.

Dr Bryan said the pumice was teeming with marine hitchhikers, including barnacles, molluscs, anemones, bristle worms, hydroids and crabs and showed how places such as the Reef came to have so many species.

The raft had travelled about 4000km and most of the pumice on the northern beaches is the size of small pebbles but some of its pieces are about the size of a closed fist.

Dr Bryan said the pumice was the result of an eruption by the Havre Seamount in July last year in the Kermadac Islands, north of NZ.

"Pumice rafts are the only process in evolutionary history that can transport species fairly rapidly - up to 30 kilometres per day - across deep oceans that would normally act as geographic barriers," Dr Bryan said.

"In the past, we've seen rafts become home to micro-communities of more than 80 species including corals, and sometimes the weight of the hitchhikers is so great that it causes the pumice to sink."

The Seamount eruption went unnoticed for two weeks until a keen-eyed tourist flying back to NZ from Samoa saw the pumice from an aircraft.