A team of Kiwi, US and Australian scientists have sent one of the world's most advanced unmanned submarines to the bottom of the Pacific Ocean to explore a large and active underwater volcano.
GNS is on a two week mission with the New Zealand Navy and a team of American scientists and engineers to map the Macauley Caldera, which sits in the Kermadec Arc.
It is a vast but little-known part of New Zealand, home to the world's most hydrothermally active string of underwater volcanoes.
The unmanned underwater vehicle called The Sentry is diving more than one kilometre there, and is using sonar technology to scan the sea floor.
It has 12 sensors that can detect heat, which indicates hydrothermal or volcanic activity.
Project leader Cornel De Ronde says the Macauley Caldera is the size of Wellington Harbour.
"There is a cone about the size of Mount Eden that sort of out-crops on the eastern flank of this volcano and it's very very active."
There is considerable international interest in the Kermadec region, because of the active volcanoes and its near pristine ocean, which is a habitat to a large number of unusual sea animals.
Mr De Ronde says the Sentry gives a greater understanding of what's on the sea floor.
"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".
GNS turns 150
This expedition comes as GNS turns 150.
It was set up by the Government during the gold rush in 1865, as part of an effort to map New Zealand.
Its Chief Executive Mike McWilliams says it was one of the first geological agencies ever established.
"It was one of the earliest geological surveys set up to survey the land, make geological maps, and understand where the important resources were - which were gold and coal".
The agency is now recognised around the world for its work investigating earthquakes, tsunamis and volcanoes.
Now Mr McWilliams says GNS will focus on mapping New Zealand's vast territory or Exclusive Economic Zone.
Most of it lies undersea.
"Our next job for the next 150 years is to systematically map the resources, the hazards and most importantly the geological history of that other 95 percent of New Zealand that we claim, called Zealandia."
This latest mission to map the Macauley Volcano is part of the new GNS mission.