Exploring undersea volcanoes

The Kermadec Arc

Scientists and university students from New Zealand, Britain and the United States have recently returned from an exciting 2-week sea voyage where they investigated 3 active submarine volcanoes in the Kermadec Arc, northeast of New Zealand.

The group explored 3 volcanoes – the Brothers, the Rumble II West and the shallow Rumble III. These volcanoes form part of a chain of about 90 volcanoes that rise from the ocean floor between New Zealand and Tonga. The volcanoes are mostly conical volcanoes – some as big as Mt Ruapehu. Some of them have large calderas indicating they were formed by powerful eruptions.

Underwater discoveries

The group discovered that one of the volcanoes, Rumble III, has erupted violently since it was last surveyed in 2007. The summit cone has collapsed, reducing the height of the volcano some 100m and filling the adjacent crater. Images taken by an underwater camera towed by their ship show strewn lava boulders covered by black volcanic ash near the new summit of the volcano.

Co-chief Scientist on the voyage Dr Cornel de Ronde of GNS Science says it was his 7th visit to the Brothers volcano in the past 10 years, with every visit producing new information.

On this visit, their ship deployed equipment over the Brothers volcano to analyse the vigorous hydrothermal plumes, rich with minerals, discharging from the seafloor vents. They wanted to detect any changes since the last time the vents were surveyed. Changes in the chemical make-up of the gases and hydrothermal fluids indicate changes in the magma system beneath the seafloor. Scientists are keen to know how quickly these changes occur, as it helps to understand the dynamics of submarine volcanic systems. On this trip, they also observed lower temperature acid vents that were covered in dense accumulations of long-neck barnacles.

Signs of life in extreme environments

A marine biologist with the Woods Hole Oceanographic Institution (United States), Timothy Shank, said he had been to more than 30 hydrothermal vent sites around the world and had not seen long-neck barnacles as dense or numerous as those at Brothers volcano.

“The question is, how do these animals manage to thrive in this incredibly extreme environment? New Zealand scientists are lucky having this wonderful natural environment right in their backyard.”

Real deal teaching!

Before discovering that Rumble III had erupted since it was last visited, the students had intended to study the interaction of sunlight, hydrothermal plumes and plankton, as the summit had been only some 230 metres below the sea surface.

But Dr de Ronde said that finding evidence of a catastrophic collapse at the summit of Rumble III volcano was an unexpected highlight of the voyage. He said that the eruption is consistent with the fact that a number of the 90 submarine volcanoes along the Kermadec Arc are highly active.

Expedition leader Professor Rick Keil of the University of Washington described the voyage as the opportunity of a lifetime for him and his students to carry out research with colleagues from GNS Science. “Unlike classroom teaching, this voyage was the real deal.”

The group travelled on an American ocean-going research ship, the RV Thomas G Thompson (RV stands for research vessel), which is owned and operated by the University of Washington.