Undiscovered volcanic features could lie hidden not far from the Bay of Plenty coastline – and a new seafloor survey stands to reveal them.

The Royal New Zealand Navy's inshore patrol vessel Hawea is helping carry out a detailed scan of the ocean floor, where new features – possibly including two caldera volcanoes – may lie buried beneath thick sediment.

"There appears to be volcanic edifices out there that are a little poorly defined," said project leader Dr Cornel de Ronde, of GNS Science.

The 10-day probe, a collaboration between the NZ Defence Force and GNS, will help researchers better understand how the Taupo Volcanic Zone extends out from the Bay of Plenty coast.


The area is notably home to New Zealand's most active volcano, White Island, which rises up 1.6km from the seafloor.

The survey will cover about 30,000 sq km and extend between East Cape and Coromandel Peninsula and out as far as White Island, 48km from the coast – an area equivalent in size to the province of Otago.

Image / GNS Science/NZDF
Image / GNS Science/NZDF

It will augment the seafloor bathymetry of the region that has been collected in recent years, mostly by Niwa.

Scientists are using special instruments to collect gravity and magnetic measurements that can clearly recognise geological features such as lavas and volcanic rocks on and under the seafloor.

Commonly, these structures can be buried by sediments or obscured by faults and other seafloor structures.

A magnetometer will be towed behind the ship and a gravimeter will collect measurement from a fixed position inside the ship.

De Ronde said the survey would greatly enhance the understanding of the volcanic history of the offshore region.

"Over many years scientists have made detailed observations and measurements of subsurface volcanic structures right up to the Bay of Plenty coast," de Ronde said.


"But the area between the coast and White Island is pretty much a void in scientific terms.

"We are very grateful to the NZDF for offering their support to remedy this."

De Ronde said the end result would be a detailed geophysical map showing seafloor
geophysical structures.

The Hawea's commanding officer, Lieutenant Brock West, said the NZDF had a long-standing relationship with scientific organisations.

"We recognise that this scientific survey is valuable and we are pleased that we can help enable it."

Scientists to discuss offshore tsunami, quake threats

Meanwhile, two leading Japanese scientists will this week discuss Japan's catastrophic 2011 Tohuku earthquake and tsunami, and its early warning system.

In talks in Wellington and Napier, Dr Yoshihiro Ito, a scientist from the University of Kyoto, will speak about what scientists have learnt from the Tohoku earthquake – and what those insights mean for New Zealand.

"The 2011 Tohoku earthquake occurred offshore of Japan, along a subduction zone similar to the subduction zone that lies off the East Coast of New Zealand," Ito said.

"We are attempting to learn more about how these subduction zones behave."

One way was by using an offshore cabled network of seismometers and seafloor pressure instruments that measured movement of the seafloor right along the Japanese coast – a topic that will be covered by Dr Kimihiro Mochizuki, of the University of Tokyo's Earthquake Research Institute.

Mochizuki will detail the development of Japan's offshore-cabled observation systems and how these can be used for early warning for earthquakes and tsunami.

The EQC has just funded research looking at whether an early warning system could work in New Zealand.

Ito and Mochizuki are currently working alongside New Zealand scientists to study the Hikurangi Subduction Zone that marks the boundary of the Pacific and Australian tectonic plates.

It was arguably New Zealand's most significant active fault and capable of generating a magnitude 8 plus earthquake that, along with widespread ground shaking, could trigger a tsunami, coastal uplift, landslides and liquefaction.

"Given these leading Japanese scientists will be in New Zealand, it is a great opportunity to hold these science talks so that people can come and learn from Japan's experiences," said Kate Boersen, of the collaborative project East Coast LAB.

Talks will be held at Victoria University's Rutherford House this Wednesday at 6pm and at Napier's National Aquarium of New Zealand at 6pm on Thursday.