In 1886, New Zealand’s Mount Tarawera blew its top, the explosion taking with it the nearby Lake Rotomahana, along with the Pink and White Terraces, a series of quartz geothermal pools that once stair-stepped their way down the side of the mountain into the lake.
In the following years, a number of craters reformed Lake Rotomahana, but the Terraces, an international tourist attraction and one of the natural wonders of the world, appeared to be gone for good.
That is until last year, when researchers claimed they had determined the location of the geothermal pools. According their work, published in The Journal of the Royal Society of New Zealand, the geothermal pools might be buried under the ash on land, raising the tantalizing possibility that they could be dug back out. But before you get too excited, Michael Daly at Stuff.co.nz reports that a new study has put the kibosh on that idea, suggesting the terraces are, indeed, lost forever, leaving behind just a few remnants at the bottom of the lake.
After the 1886 explosion, people lost track of just where, exactly, the Terraces were located. But between 2011 and 2014, researchers from Woods Hole Oceanographic Institution and GNS Science of New Zealand used Autonomous Underwater Vehicles to look at the bottom of the lake to map its geothermal features, creating a 3D map of the area. The scans revealed what appeared to be some of the Terraces covered in sediment near the location where they were believed to have existed.
In 2016, the team published its results, which concluded that the Terraces were mostly destroyed by the eruption. However, that same year, another group of researchers began working with the diaries of a 19th-century geologist named Ferdinand von Hochstetter, which included an 1859 compass survey of the location of the geothermal pools. After comparing the coordinates with old maps of the former lakebed, they concluded in a study last summer that the Terraces were not on the bottom of the lake, but were likely still partially onshore, buried under tens of feet of ash and soil. The local iwi people, who consider the Terraces a sacred site, raised the idea of excavating the landmarks. The GNS team, however, continued to insist the terraces were lost.
To be sure, GNS took another look, examining an 1881 photo of the Terraces taken from across the lake, allowing them to approximately triangulate the geothermal pools’ former position. They also examined bathymetry maps of the ancient lake, finding distinct shoreline features that match with what we know about the Terraces. “We've re-examined all of our findings from several years ago and have concluded that it is untenable that the Terraces could be buried on land next to Lake Rotomahana,” Cornel de Ronde, lead author of the paper in the Journal of the Royal Society of New Zealand, says in a press release.
The GNS team’s research shows that the eruption of Tarawera expanded the depth of Lake Rotomahana by almost 200 feet and increased the lake’s area by a factor of five. “The destruction of the majority of the Terraces is perhaps not surprising given that the 1886 eruption was so violent it was heard in Auckland and in the South Island,” says de Ronde, “The blast left a 17km-long [10.6 mile] gash through Mount Tarawera and southwestwards beneath lake.”
De Ronde calls the idea of digging for the Terraces at the edge of the lake “fruitless.” For their part, the iwi people are waiting to make a decision about whether to look for the Terraces on land or not until another expected paper on the Terraces is released. “As we have stated previously, the iwi is in no position to say where the actual location of the terraces is until all of the research has been completed," Tuhourangi Tribal Authority chairman Alan Skipwith tells Daly. “Any decisions made will need to be ratified by the iwi as the site is sacred to our people.”