New Zealand: A Land Shaped by Volcanoes

Ruapehu Volcano

Volcanic activity in Tongariro National Park began about 2 million years ago and continues to this day. The activity of Mount Ruapehu is intense. This active gray volcano in New Zealand is located in the national park, in the center of the North Island.

From time to time, the volcano stirs, releasing gas and heating the crater water. On September 25, 2007, the volcano expelled rocks over two meters in diameter during the eruption. Mount Ruapehu, the highest mountain on the North Island, stands at 2,797 meters, and its summit crater filled with water is one of the most active in the world.

Major spectacular eruptions occurred in 1995 and 1996, covering the snowy slopes of the mountain and the entire surrounding area with ash. This is why scientists closely monitor its activity and maintain a high alert level on Ruapehu, as well as on White Island and Tongariro. On Mount Ruapehu, above 1,600 meters, the volcanic terrain combines with perennial snows and the only glaciers on the island. The walls of the summit caldera are permanently snow-covered, making the crater lake one of the most beautiful landscapes in Tongariro National Park.

The mountain has the shape of a circular cone with steep slopes and numerous fluvio-glacial valleys. The steep slopes of Mount Ruapehu are conducive to the formation of numerous waterfalls, such as the Waitonga Falls, which are about forty meters high. Despite sufficient rainfall (≈1200 mm/year), the very windy climate, low humidity, and gravelly and sandy soils have produced a desert-like environment in the volcanic zone of Taupo, a mix of moraines, limestone scree, and sparse vegetation, including mosses, lichens, or scattered shrubs.

N.B.: A stratovolcano is a volcanic mountain formed by the accumulation, over successive eruptions, of lava flows and layers of ash. The stratovolcano is an explosive volcano characterized by very steep slopes and the presence of a dome at the summit, composed of very viscous lava filled with gas. Examples include Mount Etna in Sicily, Kilimanjaro in Tanzania, Merapi on the island of Java in Indonesia, and the Ngauruhoe volcano in New Zealand.

Ngauruhoe Volcano

Ngauruhoe is a very young stratovolcano located in Tongariro National Park, the first national park created in New Zealand. It is listed as a UNESCO World Heritage Site.

Mount Ngauruhoe is an active stratovolcano in New Zealand, located in the Central Plateau of the North Island. Ngauruhoe is entirely built from layers of lava and tephra; in reality, it is a secondary cone of Tongariro.

The cone rises to a height of 2,291 meters, making it the highest peak in the Tongariro Massif, although Ngauruhoe is generally considered a separate mountain geologically. It is also the youngest and largest of the dozen cones in the great Tongariro volcanic massif.

The eruptive vent of Mount Ngauruhoe formed only 2,500 years ago, while the massif has been building over the last 300,000 years.

This gray volcano frequently erupts, emitting pyroclastic flows and lahars, making it the most active volcano in New Zealand. Its summit is a double collapse crater; the shallow Red Crater contains a smaller crater filled with solidified lava. The interior of the volcanic vent is a scree of andesite, a gray volcanic rock commonly found in the volcanism of the Pacific Ring of Fire.

Its last eruption occurred on July 4, 1977, and was of low magnitude. The New Zealand Geological Survey reported observing an ash column 900 meters high above the summit of Ngauruhoe.

Taranaki Volcano

Taranaki Volcano (Egmont), at 2,518 meters, is the second-highest mountain on the North Island and the most imposing stratovolcano in New Zealand. It is located at the southwestern tip of the North Island, near the city of New Plymouth.

It is a magnificent stratovolcano with a regular conical shape, like Mount Etna in Sicily. The Taranaki mountain formed through the repeated superposition of lava flows and pyroclastic deposits (ash, cinders, blocks).

This young volcano, which emerged from the waters 70,000 years ago, has seen avalanches of ash, pyroclastic flows, and limestone scree flow down to the sea.

The exact date of the last eruption cannot be determined because the volcano is too young for radiocarbon dating. Vulcanologists are somewhat concerned, and seismographs and GPS receivers continuously monitor the perimeter of the volcano to measure any expansion or tilting, which could indicate the beginning of a collapse.

The current cone is approximately 10,000 years old and has 4 lava domes on its lower northern and southern slopes.