By Sacha Harwood
Mt Tongariro erupted overnight after laying dormant for more than 100 years.
The mountain cast an ash cloud over much of the central North Island with Volcanic activity expected to continue for weeks.
Air New Zealand said some flights could be cancelled or delayed after the ash plume reportedly reached 6,000 meters.
Nearby residents heard loud explosions and saw “glowing hot blocks” after a earthquake lasting around five minutes, volcanologist Brad Scott told Radio New Zealand.
“To be honest we didn’t see anything in the latest data up until last night that indicated it was ready to erupt,” he said.
Scott said Tongariro is the smallest of the three volcanic mountains in the central North Island plateau and is constantly monitored by scientists.
There have been no further eruptions or earthquakes, Scott said, but more activity is expected now the craters have broken through.
Truck driver Tama Coker said the noise was like a train and visibility was poor as he was driving the Desert Road when the eruption took place.
“There was a big flash,” he told stuff.
“I thought it was lightning and then it started raining sand. It was pretty thick. I heard it rumbling like a train.”
“I could just see the yellow glare on the mountain. I only had visibility of about 10 to 15 feet in front of me. It was a bit scary.”
Police closed the island’s main highway linking Wellington and Auckland due to poor visibility as ash spread across the roads causing potential warnings for the central North Island areas.
Civil Defense have warned people nearby should stay indoors because of the potential threat from the ash cloud stretching around 250 kilometers from either coast of the North Island.
No immediate casualties have been reported and police have since reopened the road.