An international expedition, including University of Otago researchers, is gaining striking new views of an underwater volcano in the Kermadec Islands, which recently produced a floating pumice island the size of Israel.
Otago University geology researcher Associate Prof James White is aboard the United States research vessel Roger Revelle, which is based at Scripps Institute in San Diego, California.
The huge raft of floating pumice, which was discharged in 2012, attracted wide international interest and was tracked by satellite images back to Havre, an underwater volcano about 700km northeast of the Bay of Plenty.
The expedition is investigating the biggest recorded explosive eruption of a submarine volcano in history.
Prof White said this ''very exciting cruise'' was also the first time ''anywhere on Earth'' that a remotely operated undersea vehicle had been used to investigate a recent ''large explosive submarine eruption''.
''Because of this, almost every observation made will be a first of its kind in some ways,'' he said.
The Havre submarine volcano ranges in depth from 650m at its shallowest to 1.6km below sea level.
The Mapping, Exploration, and Sampling at Havre (Mesh) expedition is using two US deep diving robotic underwater craft, including the remotely operated ''Jason'', which streams video images back to the surface via a fibre optic cable. Prof White, Otago PhD student Arran Murch and researchers from GNS Science are among the scientists exploring the Havre caldera - a cauldron like volcanic feature - to detect changes resulting from the 2012 eruption.
Researchers had already observed pumice in blocks, ''many the size of cars'', strewn around on the upper rim of the caldera, where a group of small lava volcanoes had also formed, Prof White said in an interview.
The expedition continues until April 17.