New research finds missing link between active volcanoes

Rifting and volcanic activity in the Taupō Volcanic Zone (TVZ) is strongly related to the evolution of two ridges north-east of New Zealand which continue to move apart, according to new research led by GNS Science experts.

The research was led by Fabio Caratori Tontini of GNS Science, working with NIWA and GEOMAR in Germany and was published in the journal Nature Geoscience this week.

Around 5 million years ago, a submarine volcanic arc began to split in two forming the Havre Trough, bounded by the Colville Ridge to the west and the Kermadec Ridge to the east.

This area is related to the subduction of the Pacific Plate underneath the Australian Plate along the Kermadec Trench.

“For a long time we’ve known the TVZ is stretching by a few millimetres a year,” Dr Caratori Tontini says.

“We also knew the Havre Trough was similarly expanding, but scientists could not understand why the boundaries of the TVZ did not follow the Colville and Kermadec Ridges offshore.

“Our research has shown that actually, the Havre Trough is made of two distinct sections: a dormant western half and a much more active eastern half, representing two separate stages of evolution.

“The older western half was witness to a short-lived episode of seafloor spreading, similar to what is happening at the mid-ocean ridge that bisects the Atlantic Ocean.”

“By contrast, the currently active Kermadec arc volcanoes in the eastern half align perfectly with the TVZ,” co-author Dan Bassett of GNS Science says.

Dr Caratori Tontini says this wider context will help fine-tune what we currently know about volcanic hazards in the TVZ, given the part it plays in a wider system which includes submarine volcanoes in the Kermadec arc and their potential to generate tsunamis that could reach New Zealand’s coastline.

“This reminds us of the awesome forces that shaped New Zealand’s unique landscape –and how they will continue to do so in the future,” Dr Caratori Tontini says.

The GNS Science-led survey used geophysical data assembled over 15 years of study through ongoing collaboration with overseas institutions such as GEOMAR, and includes data from ships crossing the Havre Trough, satellites and aeroplanes.

Much of the recent data was collected onboard the NIWA research vessel Tangaroa using GNS Science’s own geophysical equipment, as part of a larger research effort to investigate hydrothermal systems associated with submarine volcanism, and their mineralisation.

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