Mount Ngauruhoe, Central Plateau, North Island

“Mount Ngauruhoe is an active stratovolcano or composite cone in New Zealand, made from layers of lava and tephra. A stratovolcano, also known as a composite volcano, and is a tall, conical volcano built up by many layers (strata) of hardened lava, tephra, pumice, and volcanic ash.

Unlike shield volcanoes, stratovolcanoes are characterised by a steep profile and periodic, explosive eruptions. The lava that flows from stratovolcanoes typically cools and hardens before spreading far due to high viscosity. The magma forming this lava is often felsic, having high-to-intermediate levels of silica (as in rhyolite, dacite, or andesite), with lesser amounts of less-viscous mafic magma. Extensive felsic lava flows are uncommon, but have travelled as far as 15 km (9.3 mi).

Stratovolcanoes are sometimes called “composite volcanoes” because of their composite layered structure built up from sequential outpourings of eruptive materials. They are among the most common types of volcanoes, in contrast to the less common shield volcanoes. Two famous stratovolcanoes are Krakatoa, best known for its catastrophic eruption in 1883 and Vesuvius, famous for its destruction of the towns Pompeii and Herculaneum in AD79.

Mount Ngauruhoe is the youngest vent in the Tongariro volcanic complex on the Central Plateau of the North Island, and first erupted about 2,500 years ago. Although seen by most as a volcano in its own right, it is technically a secondary cone of Mount Tongariro. It lies between the active volcanoes of Mount Tongariro to the north and Mount Ruapehu to the south, to the west of the Rangipo Desert 25 kilometres to the south of the southern shore of Lake Taupo.

Maori Legend
Has it that the volcano was named by Ngātoro-i-rangi, an ancestor of the local Māori iwi, Ngāti Tūwharetoa. Local traditions say that Ngātoro-i-rangi called volcanic fire from his homeland Hawaiki that eventually emerged at Ngauruhoe. The name either commemorates his slave whose body was thrown into the volcano or refers to the insertions (ngā uru) of his hoe (paddle-like staff) into the ground.

Ngauruhoe is no longer showing signs of any significant unrest and the Volcanic Alert Level has been reduced to zero (typical background activity). A significant increase in earthquake activity in May 2006 prompted the alert level to be raised to one (signs of volcano unrest). Over the next two years GeoNet recorded an average of 5 to 30 earthquakes a day close to Ngauruhoe, though the maximum daily number was as high as 80.

Since mid-2008 the number of volcanic earthquakes close to Ngauruhoe has declined to the background level. Regular measurements of volcanic gas levels and the temperature of a summit gas vent have failed to record any significant changes over the last two and a half years. “Since mid-2008 the number of earthquakes has returned to a typical level of a few per week” GNS Science accordingly reduced the alert level for Ngauruhoe to Level 0 on 2 December 2008.

Mount Ngauruhoe was used as a stand-in for the fictional Mount Doom in Peter Jackson’s The Lord of the Rings movie trilogy, achieving worldwide exposure. The mountain is usually climbed from the eastern side, from the Mangatepopo track. From the Mangateopopo hut to the base of the mountain takes a steady 1 1/2 hour walk; the first 45 minutes are suitable for children or older people.

The track then climbs very steeply to the base of the climb. In summer the climb is difficult due to the loose tephra that gives way underfoot. In winter, snow consolidates the tephra. As the slope is about 45 degrees, kicking steps is essential, and this requires fitness. After rain, the snow may be covered by ice that is treacherous. Ice axes, crampons and ropes are recommended in mid winter.”

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