Unrest at active volcano Mount Ruapehu in the Tongariro National Park has scientists wondering whether it will blow.
While GNS Science says an eruption is unlikely, scientists say it is hard to predict which way the volcano could go.
"I think it's important to recognise that Ruapehu is an active volcano that has erupted in the past and will continue to erupt in the future," Professor of Natural Hazards at Massey University and lead of a volcano research programme Jonathan Procter said in a statement to Science Media Centre.
Elevated levels of volcanic unrest continue at Mt Ruapehu as its crater lake belches carbon dioxide (CO2) at the second-highest level ever recorded at the site.
GNS says the increase in gas outputs and slowly rising temperatures at the stratovolcano suggest magma could be driving the unrest, increasing the chances of further activity.
Professor of geophysics at Victoria University Martha Savage told the Science Media Centre while GNS is correct in stating an eruption is unlikely, there is potential for one to happen.
"Volcanic eruptions are also somewhat like earthquakes, in that there are many, many more small ones than large ones. But it could be large."
Prof Savage said the volcano is "not hugely likely" to erupt soon but is much more likely to erupt now than it was a couple of years ago.
"The bottom line is, I would not let my children climb up Mt. Ruapehu now."
The Department of Conservation has issued a warning and closed the area 2km from the centre of Te Wai ā-moe (Crater Lake) to the public and concessionaires.
Prof Savage says the main takeaway is that the volcano is more active than it has been in around 15 years and definitely riskier than a few years ago.
On March 21, GNS increased the volcano's alert level to 2 which means there is moderate to heightened volcanic unrest, and potential for eruption hazards.
Prof Savage says a volcano's alert level can not reach level 3 until there is an eruption, but there have been eruptions while volcanos were under level 2.
Prof Procter says researchers, including himself, have looked into past events including the Mt Ruapehu eruption in 1953 to build scenarios off what might occur to have informed monitoring systems installed.
"Ruapehu has, in the past, been a prolific producer of lahars and we cannot ignore the events of 1953 where 151 people died from the impacts of lahar."
A lahar is a mixture of volcanic ash and debris that flow down from a volcano.
Prof Procter said the actions taken by DoC and GNS help mitigate any impacts from an eruption and raise public awareness.
