Taupo Volcanic Zone: Mount Doom – Ruapehu and Ngauruhoe

 

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That white mountain puffing dark gray ash in the foreground is Ruapehu. Ngauruhoe is part of the mountains in between Ruapehu and the tip of that lake (which is actually a supervolcano that we’ll talk about next week). (GNS Science)

Ruapehu and Ngauruhoe are two of the Taupo Volcanic Zone’s three stratovolcanoes (the other, as we’ve seen, is White Island).

Both have made cameo appearances, directly or indirectly, in Peter Jackson’s Lord of the Rings. In the real world, they are New Zealand’s two most active volcanoes.

There is so much volcanism on the North Island, per last week’s GNS Science guest videos, because it sits at a subduction zone.

At the Taupo Volcanic Zone, plate tectonic forces are spreading the North Island apart. Molten material from the depths easily finds its way up to the surface here.

Ruapehu

This 9,200-foot complex stratovolcano is New Zealand’s highest mountain. In the Jackson movies, its slopes stood in for Mount Doom and also the Emyn Muil.

Ruapehu is some 200,000 years old. Three vents have been active on it over the last 10,000 years. The currently active one is filled by a crater lake:
 

Ruapehu image from Photovolcanica.

Ruapehu image from Photovolcanica. (Text added.)

Most of Ruapehu’s frequent eruptions have been low on the VEI scale, but it has had at least four cone-building eruptions in the past. In 1995, and again in 1996, it cut loose with VEI 3 eruptions.

Geoff Mackley posted some raw video of the 1995 and 1996 eruptions on YouTube (and yes, there is a ski resort on the volcano).
 

The presence of water in the active vent makes Ruapehu eruptions quite explosive, of course.

It also increases the risk of lahars in which a slurry of water and ash pours down the mountain’s flanks. The volcano doesn’t have to be erupting at the time. Unstable material that has been damming up the crater lake may collapse and unleash the lahar.

This happened on Christmas Eve, 1953 – eight years after the volcano had last erupted. One hundred and fifty one people died.

Another lahar occurred a year after Ruapehu’s 2006 eruption. Again, the volcano was quiet. This time, fortunately, no one was hurt.
 

Ruapehu currently shows signs of unrest, but its aviation code is green. Its webcam is here.

Ngauruhoe

Technically, 7,500-foot Ngauruhoe is just a vent on the volcanic massif of Tongariro. There are more than a dozen craters on this 275,000-year-old massif.

Ngauruhoe first erupted about 2,500 years ago. It’s the youngest vent in the complex and has grown a beautifully symmetrical cone that towers some 3,000 feet over neighboring craters.
 

Mount Ngauruhoe rises behind Red Crater in the Tongariro volcanic complex.  (GeoNet)

Mount Ngauruhoe rises behind Red Crater in the Tongariro volcanic complex. It is the most active volcano here, but Red Crater also has erupted during recorded history. (GeoNet)

The most recent eruption at Tongariro was at Te Mari craters in 2012. Ngauruhoe last erupted in 1977, a VEI 1. Eruptions in 1972 and 1975 were stronger at VEI 3. Like Ruapehu, it erupts frequently, but with a little more intensity. Its biggest known eruption was a VEI 5 some 2,500 years ago.

Currently the Tongariro complex is showing a little unrest, but Ngauruhoe is quiet. The Ngauruhoe webcam is here.

You can also watch both Ruapehu and Ngauruhoe here.

Ngauruhoe, like other peaks at the Tongariro massif, is highly tapu to the Maori people. For this reason, Peter Jackson wasn’t allowed to film there. Instead, he used images of Ngauruhoe as a base for models and CGI works of Mount Doom.

You can climb this volcano, however.

Its summit offers beautiful vistas of the surrounding volcanic complex and the world, as this video posted by Nick Estelrich shows.
 

As mentioned above, New Zealand’s North Island is spreading apart in the Taupo Volcanic Zone. This allows magma to rise up to the surface. Sometimes that happens on quite a large scale.

The world’s last supereruption happened here, at Taupo, 27,000 years ago. Next week, we’ll wrap up this series with a look at Taupo and its super-playmates, Rotorua and Okataina calderas.

 
 


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Categories: Sunday morning volcano

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