SCIENTISTS monitoring Mt Tongariro say there is a 50/50 chance it could erupt again.
The central North Island volcano spewed ash and rocks earlier this week, the first time it had been active in more than a century.
Volcanologists studying matter that had been sent out of the mountain kept a cautious two kilometre radius from the mountain’s crater, and found there was no fresh lava, only existing rock.
“It’s what you’d expect to see,” GNS volcanologist Brad Scott told APNZ.
“There’s still a 50/50 call as to it could stay as it is or it could enhance.”
They had also discovered during a flight over the mountain on Thursday that a couple of thousand tonnes of sulphur dioxide gas had been expelled, an indication that molten lava was bubbling inside.
“And whether or not that molten material carries on to the surface or stops where it is – we just don’t have any strong indications either way at the moment.”
More earthquake activity and increased volumes of gas coming out the crater could indicate an eruption was imminent.
Notice of an eruption could be up to a couple of weeks, “or it could be a lot shorter”.
“The mountain’s in an eruptive episode, it’s active, it could do what it pleases.”
Another GNS scientists, Mike Rosenberg, said both White Island, 51km north of Opotiki in Bay of Plenty, and Mt Tongariro were at low levels of activity, with small earthquakes continuing.
“White Island continues to produce the plume that sometimes contains a bit more ash than other times,” he said.
“Tongariro is about the same. People would have seen some very nice steam plumes.”
Calm weather and cold air allowing steam to rise meant the plume was visible.
Any larger eruption at Mt Tongariro was likely to be on a relatively small scale, similar to eruptions at Mt Ngauruhoe in the 1970s, GNS said.