Spotlight on undersea volcanos

A team of top scientists from New Zealand and the US is heading to the Bay of Plenty this week to gather data on underwater volcanos on the Kermadec arc.

Over the next three weeks, remotely operated submersibles will scour the sea bed to the north-east of the region in an attempt to gain a greater understanding of the hostile environment.


The autonomous submersible Sentry will collect terabytes of data at a time.

In a NZ first, the target seafloor volcanoes – Macauley Caldera and nearby Giggenbach – will be investigated extensively at close range.

The 18-day voyage is scheduled to depart Auckland today (March 3), and is built around the regular Navy supply trip to Raoul Island on HMNZS Wellington. This particular voyage will support GNS Science, the Department of Conservation, and the Meteorological Service.

The project is a collaboration involving GNS Science, the Royal New Zealand Navy and US-based Woods Hole Oceanographic Institution, which owns and operates the autonomous underwater vehicle Sentry.

Sentry will be deployed from HMNZS Wellington for its day-long missions to skim over the seafloor and gather data to build detailed three-dimensional maps of the kilometre-deep caldera, and measure up to 12 different chemical and physical parameters of the ocean and the seabed.

It will return to the ship after each mission to download terabytes of data, have its batteries recharged and be programmed for its next deployment. It is scheduled to make eight dives during the voyage, covering around 10 square kilometres of seafloor per dive.

Both Macauley Caldera and Giggenbach are within 100km of Raoul Island and are actively venting hot water and gases on the seafloor. Both volcanoes have been investigated by surface ships on previous voyages.


The Macauley Caldera.

The voyage is part of a long-term GNS Science programme to build detailed maps and collect geological data, including hydrothermal venting, at about 30 major submarine volcanoes in the Kermadec Arc, which runs between Bay of Plenty and Tonga, says project leader Dr Cornel de Ronde.

It is Sentry's second visit to New Zealand. During a GNS Science-led voyage in 2011, it gathered detailed information on four other submarine volcanoes northeast of White Island.

'Sentry is the ideal vehicle for obtaining comprehensive information and understanding on the seafloor and the environment around these submarine volcanoes,” says Cornel, a marine geologist at GNS Science.

'It provides the appropriate level of detail on the geology of the seafloor, the hydrothermal systems, deep-sea habitats and the occurrence of mineral deposits.”

The project is part of a multi-year research programme by GNS Science to map and understand tracts of seafloor in New Zealand's vast offshore territory.

New Zealand has sovereign rights over an area of seafloor totalling 5.7 million square kilometres - equivalent to 14 times the size of California or one percent of the Earth's surface.

The area is largely unmapped and unexplored. The New Zealand landmass is just four percent of this submerged area – sometimes referred to as the continent of Zealandia.


The undersea volcanoes of the Kermadec arc.

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