An area of floating pumice 250 nautical miles in length and 30 nautical miles wide has been spotted along the Kermadec Arc, which lies around 1000 kilometres north-east of Tauranga.
An underwater volcano in the Kermadec Arc is believed to be responsible for releasing the pumice into the ocean.
Pumice released from an underwater volcano along the Kermadec Arc, 1000 kilometres north-east of Tauranga. Photos: Royal New Zealand Defence Force.
The Royal New Zealand Air Force’s Orion was on maritime patrol from Samoa to New Zealand on Thursday night when it spotted the “phenomenon” and relayed a message to the HMNZS Canterbury which is currently in the area doing a marine survey.
Lieutenant Tim Oscar, a Royal Australian Navy officer on a three year exchange with the Royal New Zealand Navy, saw what he describes as the weirdest thing he has seen in 18 years at sea.
“The lookout reported a shadow on the ocean ahead of us so I ordered the ship’s spotlight to be trained on the area.
“As far ahead as I could observe it was a raft of pumice moving up and down with the swell.”
Tim says the rock looked to be sitting two feet above the surface of the waves, and lit up a brilliant white colour in the spotlight.
“It looked exactly like the edge of an ice shelf.”
He says he had been briefed by GNS Volcanologist Helen Bostock the previous day when the ship first encountered an area of pumice from an undersea volcano.
“I knew the pumice was lightweight and posed no danger to the ship. None the less it was quite daunting to be moving toward it at 14 knots. It took about three to four minutes to travel through the raft of pumice and as predicted there was no damage.
“As we moved through the raft of pumice we used the spotlights to try and find the edge - but it extended as far as we could see.”
According to GNS Science the underwater volcano, Monowai, has been active along the Kermadec Arc and the pumice could be a result of that activity.