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New Zealand scientists are investigating an undersea volcanic eruption which has created a large "pumice raft" 400km west of Raoul Island.
GNS Science vulcanologist Craig Miller told AAP that the Royal New Zealand Air Force had provided photographs of the pumice raft and New Zealand's National Maritime Co-ordination Centre had reported a sea disturbance 100 nautical miles long and 25 nautical miles wide, located 400km west of Raoul Island.
It was originally thought that the undersea volcano Monowai had erupted, but it's northeast of Raoul Island.
Mr Miller said the pumice raft has been caused by an undersea eruption.
When magma flows into the sea it quickly cools and turns into pumice and then floats to the surface.
Asked if the undersea eruption was linked to the eruption of Mt Tongariro and an eruption on White Island this week he said: "It's all along the same boundary but that is about where the link stops".
The navy vessel Canterbury has picked up samples of the pumice and GNS scientists are on board the vessel.
Raoul Island is part of Kermadec Islands and is 1100km northeast of New Zealand. The area is a known source of volcanic activity.