Ruapehu eruption, 1996

Image: Thorvaldur Thordarson, GNS Science | ©

Introduction

Find out about volcanic hazards in Tongariro National Park and what to do in the event of an eruption.

Tongariro National Park is an active volcanic area. Eruptions can occur with little or no warning. The closer you are to the Park’s active volcanic vents, the higher the risk.

A network of volcanic monitoring equipment and early warning systems mitigate volcanic risk but cannot guarantee your personal safety. You are responsible for deciding the level of risk that is acceptable to you and planning your visit accordingly.

ngauruhoe-eruption-390.jpg
Ngauruhoe erupting in 1975

What to do

Before you go

  • Know where the volcanic hazards zones are
  • Consider whether you're comfortable with the volcanic risk associated with your trip. If you're uncomfortable, choose somewhere to go outside the Park's volcanic hazard zones.

In an eruption

  • Move immediately away from the eruption site, staying out of valleys
  • If you’re in a valley, move sideways to higher ground (a ridge top) – a lahar (fast moving volcanic mud flows) is possible.
  • If you see flying rocks, or a steam and ash cloud coming towards you, take shelter behind a bank or ridge and cover your head with your pack. 

If you hear sirens and voice messages

The Ruapehu Eruption Detection System (EDS) and Village Lahar Alarm Warning System (VLAWS) warn the public of lahar risk through sirens and voice messages.

Whakapapa ski area

  • Move immediately out of valleys and move sideways to higher ground (a ridge top)
  • Remain in a safe area on higher ground until advised by ski field staff to move.
  • If you are in a building or car park – stay put.
  • If you are in the Ruapehu Summit Hazard Zone, move down the mountain along ridges to the base area.
  • If you see flying rocks, or a steam and ash cloud coming towards you, take shelter behind a bank or ridge and cover your head with your pack.

Whakapapa village

  • Move immediately away from the Whakapapanui Stream to the eastern side of the Bruce Road. Buildings and facilities on the western side of the road – the Holiday Park, Hepi Terrace and the Tavern – are at risk from lahar.
  • Assemble at the Chateau Tongariro.
  • Stay at the Chateau Tongariro until advised by hotel or DOC staff to move.

Volcanic hazard zones

Ruapehu Summit Hazard Zone


Lahar deposit on Ruapehu, 1996

The Summit Hazard Zone on Ruapehu is a 3 km radius around Te Wai ā-moe/Crater Lake, which fills the vent of Ruapehu.

Flying rocks (ballistics), and fast-moving clouds of steam and hot ash, can occur during eruptions of Ruapehu. These are the most hazardous within the Summit Hazard Zone.

The main volcanic hazard to most visitors on Ruapehu is lahar. Lahars occur during eruptions when water in Te Wai ā-moe is ejected and flows at speed down valleys as a flash flood – mixing with ash, rocks and snow on its way down. There are multiple lahar paths through Whakapapa Ski Area, where a lahar warning system operates. Lahars can also occur when volcanic debris on the volcano’s slopes is remobilised during heavy rain.

Lahars can have impact beyond the Summit Hazard Zone – large events have travelled well beyond the slopes of the volcano.

The lahar of March 2007 occurred when a dam at the outlet of Te Wai ā-moe, created by eruption materials from the 1995 and 1996 eruptions, collapsed and released a deluge of water that flowed down the primary lahar path of Ruapehu – the Whangaehu Valley on the eastern side of the mountain.

Reducing the risk

The closer you are to Crater Lake and the longer you stay, the higher the risk you are exposed to. DOC recommends:

  • Not entering the area 700 m from the centre of Crater Lake
  • Not camping or overnighting in the area 1.5 km from the lake’s centre.
  • Not camping or overnighting on the Summit Plateau or in valleys – select camp sites on high ground away from the potential path of lahars. If you’re in a valley when an eruption occurs move immediately to higher ground.

Map of areas recommended not to enter or camp (PDF, 3,474K)

Ski area hazard zones

Whakapapa Village hazard zones

Tongariro Hazard Zone

The Tongariro Hazard Zone is a 3 km radius from each of the three active vents of Mt Tongariro – Te Maari, Red Crater and Ngāuruhoe. These vents have all been active within the last 150 years. The most recent eruption occurred from Te Maari in 2012.

Flying rocks (ballistics) and fast-moving clouds of steam and hot ash are the main volcanic hazards on Tongariro.

The Tongariro Alpine Crossing and Tongariro Northern Circuit both pass through the hazard zone. Even when the tracks are open, volcanic risk is present. If you are uncomfortable with this risk, choose a different track.

Tongariro hazard zone map

Tongariro Alpine Crossing electronic warning signs

Electronic warning signs will be deployed on the Tongariro Alpine Crossing if volcanic risk increases. These signs will indicate whether the track beyond the sign is open or closed, based on the level of volcanic risk.

If the electronic light signs are deployed and flashing red, the track is closed due to increased volcanic risk – turn around and go back the way you came.

Volcanic alert level system

The system evaluates the current level of volcanic unrest or eruption of the volcanoes in Tongariro National Park. The Volcanic Alert Level is set by GeoNet, based on volcano monitoring data from the Park. There are six Volcanic Alert Levels, ranging from no volcanic unrest, through two levels of volcanic unrest, to three levels of volcanic eruption.

For more information and to see the current Volcanic Alert Levels for the volcanoes of Tongariro National Park, see Volcanic Alert Levels (GeoNet website)


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