The real Mount Doom… and the real Mount Doom; Volcanoes in Taupo, New Zealand

As a research geologist I get to focus on some interesting topics, especially related to volcanoes, geothermal systems, and gold and ore formation. The three are more interconnected than you would initial think, as most gold deposits are formed via the interaction of hot hydrothermal fluids with their surrounding rocks.

So at the beginning of my studies I was lucky enough to get to participate in a field trip to the active Taupo Volcanic Zone (TVZ) in the North Island of New Zealand. Visiting vigorously active geothermal sites and young volcanoes, we made our way through the TVZ. And of course, being in the land of Middle Earth (and being a huge Lord of the Rings fan) I had to check out some iconic movie locations too 🙂

With so much wonderful geology, and equally amazing scenery, I will have to break my trip up in two blogs. This part is a look at the volcanoes of the Taupo Volcanic Zone. We will make our geological journey from south to north, from the volcanoes of Tongariro that were used as the Mount Doom in Lord of the Rings, to the astonishing active volcanic White Island, that could as well be the Real Mount Doom. The second part you can check out here, and is all about the geothermal systems (plus a quick stop in Hobbiton).

New Zealand’s “Mount Doom” Volcanoes

The Taupo Volcanic Zone (TVZ) is a volcanic arc-back-arc system resultant from the westward subduction of the Pacific Plate below the North Island of New Zealand. Being a relativity young arc (<1.6 Ma), the TVZ is distinguished from other modern volcanic arcs by its anomalous high heat flow, voluminous rhyolite volcanism and widespread geothermal activity. The TVZ is compositional segmented into a northeast and southwest andesite-dominated sector with composite cones and no calderas, and a central rhyolite-dominated segment. The whole TVZ zone extends ~250km from White Island at the northern tip, to the south end where lies the Tongariro Volcanic Centre (Cole 1978; Wilson et al 1994; Cassidy et al 2009).

The Tongariro Volcanic Centre is a young, active, complex of multiple andesite-dacite volcanic cones constructed over a period of 275,000 year. One of the major volcanoes at Tongariro is the perfectly-shaped stratovolcano of Mount Ngauruhoe, which is a parasitic cone to Tongariro.

Mount Ngauruhoe was the main stand-in backdrop for Mount Doom in the Lord of the Rings movies filmed at Tongariro. With a little extra CGI help of course 😉

Another site that was the host of many scenes walking around Mordor and Mt. Doom in the Lord of the Rings was Mt. Ruapehu. This is the largest active, predominantly andesitic volcano in the TVZ. Made up of multiple flows, you can see the boundaries of each andesite flow as it has autoclastic breccia on the top and bottom. The red staining is also an indication of a sub-aerial volcanic eruption as Fe-oxide reacted with atmospheric oxygen.

And finally, in the distance lies a lonely mountain…

Moving from the south to the very northern tip of the Taupo Volcanic Zone, we go offshore into the Bay of Plenty, and encounter the spirited White Island. White Island is among the most active and accessible andesite-dacite stratovolcanoes in the world.

The island is a place that seems out of this world, with acidic, bright green crater lakes, high temperature fumaroles and acid springs. In fact, it even has native sulfur flows, just like what would be on the surface of Saturn’s moon, Titan.

Ash layers on the ground record histories of hydrothermally altered, and fresh, ash falls. White Island’s internal active hydrothermal system may even be a modern example of an high-sulfidation style epithermal mineral deposit with its high metal fluxes and acid-oxidizing condition (Hedenquist et al., 1993; Giggenbach and Sheppard 1989). Though no Lord of the Ring scenes were filmed here (for obvious safety reasons), it isn’t hard to imagine White Island as a current, earth equivalent of Mount Doom.

Final thoughts

The volcanoes of the Taupo Volcanic Zone on the north island of New Zealand are nothing short of remarkable. From exploring the recent lava deposits and mountain peaks, to being immersed in the heart of a steaming volcanic caldera, the TVZ is truly a breath taking area that exhibits the raw power of molten earth. Next up will be part two of this journey through the Taupo Volcanic Zone… time to check out the boiling muds and hot geysers of the active geothermal systems in the centre of the TVZ, plus another Lord of the Rings stop, Hobbiton!

-Stephanie

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