Low cloud has cleared giving scientists their first glimpse of Mt Tongariro from the air since the volcano erupted on Monday night.
Weather conditions improved on Wednesday morning allowing scientists to fly over the mountain which erupted about 11.50pm on Monday, spewing ash and prompting a threat warning for the central North Island.
GNS Science volcanologist Michael Rosenberg told NZ Newswire a number of new vents had been formed by the eruption on the northern side of the mountain.
"All we can do is keep analysing the seismic data and analyse ash and rock samples and piece together the puzzle," he said.
Rocks fell within 1km of the eruption, damaging Ketetahi Hut - one of four trampers' huts on the mountain - but there have been no reports of injuries.
Light ash fell as far away as Taupo and Napier, while the smell of gas - similar to the "rotten eggs" smell experienced in Rotorua - had drifted to Wellington.
Activity at the mountain settled on Tuesday, although on Wednesday steam was still billowing from Te Maari crater where the eruption took place.
GNS volcanologist Craig Miller earlier said there had been little change overnight and it was a "wait and see" situation.
It was far too early to say whether the volcano was returning to a sleeping state, like that between its last eruption in 1897 and Monday night.
"It will be probably weeks before we can start thinking about that sort of scenario," Mr Miller said.
Scientists believe the small-scale eruption was driven by steam rather than magma.
The resulting ash cloud caused some flights to be delayed or cancelled in the central North Island, but was blown offshore by Tuesday morning.
GNS Science had downgraded its aviation alert from red to orange but Tongariro Alpine Crossing, Tongariro Northern Circuit and all four huts on the mountain remained closed.