Tongariro erupts

Mt Tongariro has, throughout of lifetime at least been the least active of the volcanoes on the Central Plateau.

Until late last night; Stuff reports:

Volcanic activity at Mt Tongariro could continue for weeks, months or even years after Tongariro rumbled to life after being dormant for more than 100 years last night.

Last night's eruption was a total surprise, so "we have to expect the unexpected", GNS volcanologist Michael Rosenberg said.

The mountain erupted at 11.50pm, sending ash across roads and prompting a potential threat warning for central North Island regions.

The eruption threw rocks and spewed ash from the Te Mari craters, near Ketetahi hot springs, on the northern side of the mountain, GNS Science said.

WITNESS ACCOUNTS

Truck driver Tama Coker was heading across the Desert Road while the eruption was happening and said the noise was like a train.

"There was a big flash," he said.

"I thought it was lightning and then it started raining sand. It was pretty thick. I heard it rumbling like a train."

Coker said that when he drove through the Desert Road he could not see the white lines on the road.

"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.

"It's something I'll probably never see again in my lifetime."

He said the sand-like ash had covered his truck, and the sign writing on the trailer was barely visible.

Local resident David Bennett who lives on the southern shores of Lake Rotoaira, about 6km away from the eruption,  said he heard and saw the mountain erupt just before midnight last night.

He considered himself fortunate no rocks landed on his house last night.

"There were rocks being thrown out. It was like thunder and lightning and fireworks," Bennett said.

There was a lot of ash on State Highway 46 this morning - the roadway linking the Desert Road with the Whakapapa Ski Field.

"It was spectacular. There were rumbling sounds and thunder and lightning coming out from the base of the eruption," Mr Bennett said.

There were no cars in the Tongariro Crossing Carpark when he visited the area  this morning, Bennett said.

He  said there were about 12 houses on the southern shores of Lake Rotoaira and when the mountain erupted locals made sure all the residents living in the area were safe.

His house is situated about five kilometres away from the roadway leading to the northern end of the Tongariro Crossing.

A few locals did drive to the Hirangi Marae in Turangi but most just stood and watched the spectacular show.

"It's a volcano. If it goes. It will go. We'll all be vapourised. Ruapehu and Ngauruhoe have erupted regularly over the years. Now it is Tongariro's turn."

Bennett understood nobody overnighted at the Ketetahi Hut at the northern end of the Tongariro Crossing last night and that the Ketetahi Springs area had not been affected by the eruption.

He also understood a new vent had opened up near the Te Maari Crater area on Mount Tongariro. 

GNS scientists noticed an upsurge of activity at Tongariro in the last couple of weeks, but the scale of last night's eruption was completely a bolt from the blue. And it may be the first of a few more; read on:

Civil Defence said volcanic activity could pose a threat to Waikato, Hawke's Bay, Gisborne, Manawatu-Whanganui, Bay of Plenty and Taranaki.

People living in those areas were advised to stay indoors with all the windows and doors closed and listen to the radio for updated emergency information and instructions.

It was the first eruption to happen on the mountain in more than 100 years, but if past trends are anything to go by, it could be the first of many more to follow, Rosenberg said.

Eruptions happened intermittently from 1855 through to 1897, and it could not be ruled out that this was the start of a prolonged period of activity in the area, Rosenberg said.

"We have to expect the unexpected. We really can't predict what this will lead to," Rosenberg said.

"This has taken us by surprise. It's gone from some little earthquakes that seemed to be tailing off, then all of a sudden this has gone boom.

"We really didn't expect that there would be an eruption apparently out of nowhere."

Teams from GNS would be assessing the volcano by air today and would be gathering samples of ash and rock. If they do not contain magma, then it is indicative that magma has not broken the surface, and may soon do so, Rosenberg said. 

All this excitement, and we're far away from home! Fortunately, we have excellent internet access at our accommodation, so we'll be able to follow this turn of event. It certainly does bring back memories of the 1995 eruption on Mt Ruapehu which caused significant disruption around the central North Island.

But we are a volcanic country, so these kinds of events are to be expected from time to time, and Mt Tongariro has decided that her time is now.