2024-02-11 09:32:02
those who have never seen The Lord of the rings (if anyone exists), perhaps they don’t know that the North Island of New Zealand – filming location for Peter Jackson’s epic fantasy trilogy – is absolutely full of volcanoes. This island, which houses the Taupō Volcanic Zone (TVZ), is nestled in the Pacific Ring of Fire and has more than two dozen impressive volcanoes, including Mount Doom itself: El monte Ngauruhoe.
But any volcanic area worth its salt also has a wide variety of impressive calderas, which are volcanic craters left by large eruptions. New Zealand also has a lot to offer in this geological category, as the TVZ includes two active boilers and six older ones. One of the best-known calderas is Lake Rotorua, the scene of its own fantastic legend: a Maori love story between a chief’s daughter and a local man of humble origins.
Now, Lake Rotorua is home to another fantastic story. But it is not a fantasy or a myth, but a mystery. Last week, a New Zealand research institute called GNS Science published incredibly detailed maps of Lake Rotorua that have never been seen before. The map, covering 33.7 square kilometers of the lake bed (about 68% of its total surface area), shows the geothermal dynamism still bubbling beneath the surface, details of an ancient river, and a surprisingly large negative magnetic anomaly in the southern end of the lake.
In statements to the website LiveScienceGNS Science senior scientist Cornel de Ronde compared the maps to wearing glasses for the first time: “You finally put on the glasses and you can see the fine print.”
The Rotorua caldera was first formed 240,000 years ago, due to a massive eruption that collapsed the lower magma chamber. Although the volcano has not erupted for 25,000 years, the lake continues to show the bubbling and stirring typical of the hydrothermal drama. Clouds of steam float on the surface, the water is full of sulfur and, from time to time, steam explosions occurlike popping a champagne cork.
However, volcanic rocks usually give positive magnetic readings, as they contain highly magnetic magnetite (hence the name). However, at the southern end of the lake, magnetic readings were mostly negative. The GNS Science team points out that this is probably due to the fact that the hot water of the hydrothermal system transformed the magnetite into pyrite (fool’s gold), whose magnetic signal is little or none. For this transformation to occur, the system must have been active for a long time.
Lake Rotorua’s popularity among tourists is not due to its warm, hot waters. At the bottom of the lake, the water remains at a cool temperature of 13.8° C due to the large volume of the lake itself. But although the hydrothermal action beneath this lake is not as explosive as that of Mount Doom or as humid as a Maori love story, it reveals a bit of the fascinating history of one of the most volcanically rich regions in the world.
Darren lives in Portland, has a cat, and writes/edits about sci-fi and how our world works. You can find his previous stuff at Gizmodo and Paste if you look hard enough.
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