Mount Ruapehu

At the top of Ruapehu there is a lake. It sits right where the volcano erupts.

Scientists check the lake's temperature.

DOC explains that Te Wai ā-moe, Ruapehu's Crater Lake, fills the volcano's vent. Scientists sample its water and gases every month and measure its temperature.

When Ruapehu erupts, water from the lake can be thrown out. It rushes down the valleys like a flash flood, mixing with ash, rocks and snow. This fast volcanic mudflow is called a lahar, and DOC says it is the main volcanic hazard on Ruapehu.

DOC: the Summit Hazard Zone is a 3 km radius around Te Wai ā-moe/Crater Lake, which fills Ruapehu's vent. Lahars, the main volcanic hazard, form when eruptions eject lake water that flows at speed down valleys as a flash flood, mixing with ash, rocks and snow; they can also form when heavy rain remobilizes volcanic debris, and large ones have traveled well beyond the volcano's slopes.

GeoNet: volcanologists sample the crater lake's water and gas, and airborne gas, monthly; recent bulletins track its temperature and gas output.

Ruapehu erupted in 1995 and 1996. Ash fell on the land around it.

Today, scientists watch the volcano closely.

GeoNet says the most notable of the 1995-1996 eruptions came on 23 September 1995, when the volcano threw rocks and plumes of hot ash and steam into the sky, and lahars surged down into the Whangaehu River. The eruptions emptied the crater lake. A new lake began to fill in 2003, and in March 2007 the dam of volcanic debris holding it failed, sending a lahar down the Whangaehu Valley.

GeoNet watches Ruapehu with web cameras, seismographs, microphones and GPS stations, working with DOC.

GeoNet (2020): the 1995-1996 eruptions peaked on 23 September 1995 with ballistics, plumes of hot ash and steam and lahars into the Whangaehu River; later eruptions spread ash, and the sequence removed the crater lake and modified the rim and outlet. The new lake, filling from 2003 to about nine meters above the outlet behind a debris dam, broke out in March 2007 as a dam-break lahar.

Monitoring (with DOC): three web cameras, 10 seismographs, six microphones that detect explosions and nine continuous GPS stations. In October 2026 GeoNet kept Ruapehu at Volcanic Alert Level 1 (minor unrest), noting fluctuating low-to-moderate tremor.

Golden and red tussock grass covers big areas of the park.

Blue ducks swim in fast mountain streams.

DOC says large areas of Tongariro National Park are covered in golden and red tussock grasses, and many alpine plants, like mountain daisies and gentians, flower in summer. Much of the forest is mountain beech, which grows above 1,000 meters.

The endangered whio, or blue duck, lives on fast-flowing streams in and around the park, and North Island brown kiwi live in its forests.

DOC (Tongariro National Park flora and fauna): a wide diversity of alpine plants, many flowering in summer (purple parahebe, mountain daisies, buttercups, eyebrights, gentians); golden and red tussocks over large areas, now invaded by introduced heather; mountain beech forest above about 1,000 m with podocarps below; orchids; sundews in tarns formed because volcanic ash is rather impermeable.

Birds include the endangered whio (blue duck) on fast streams, North Island brown kiwi in the forests, pipits, sometimes seen above 1,600 m, and, rarely seen, kākā, kārearea (falcon) and kākāriki.

If you are in a valley and the volcano erupts, climb to higher ground.

Always follow the park's safety signs.

DOC says eruptions can happen at any time with little or no warning. Before visiting, check the volcano's current status and the advice for your track.

If an eruption happens, DOC says to move away from it and out of valleys, sideways to higher ground such as a ridge, because a lahar can rush down a valley like a flash flood. If you see flying rocks or an ash cloud coming, shelter behind a bank or ridge and cover your head with your pack.

DOC at Risk Management Stage A (Alert Level 1): do not enter within 700 m of the center of Te Wai ā-moe/Crater Lake; do not camp within 1.5 km of it, on the Summit Plateau or in valleys; choose campsites on high ground away from lahar paths.

In an eruption: move away and out of valleys, sideways to a ridge; shelter behind a bank or ridge from flying rocks or an ash cloud and cover your head with your pack; at Whakapapa, sirens warn people to move out of lahar paths.