Few things illustrate the dynamic and tentative nature of scientific investigations like the ongoing quest to locate the Pink and White Terraces at Lake Rotomahana. As an intriguing science mystery, the terraces have it all – worldwide fame, a recently discovered 19th century diary, sophisticated technology and puzzling photographic evidence. The quest to find the terraces also provides a fitting story about how science works – as the investigations take circuitous, contradictory and surprising investigative paths.
Background information about the terraces
In the mid-1800s, the Pink and White Terraces were considered to be the eighth wonder of the natural world. They attracted visitors from around the globe, which was an incredible feat considering the difficulty of travel to New Zealand. As well as being beautiful, the formations were the largest silica terraces in the world.
Each terrace resembled a staircase-like cluster of pools that descended into Lake Rotomahana. The White Terraces, known as Te Tarata (the tattooed rock), were the larger of the two wonders and covered about 8 hectares of land. The fan-shaped cascades dropped in a series of 50 large steps, covering a distance of about 240 metres. The Pink Terraces, known as Ō-tū-kapua-rangi (fountain of the clouded sky), covered 2 hectares and had warm, clear pools.
The terraces were in a remote inland location. Most of what we know about the terraces’ appearance comes from paintings and black and white photographs. Surprisingly, the exact location of the terraces was not publicly recorded.
Mount Tarawera erupted on 10 June 1886. Millions of tonnes of volcanic ash, mud and rubble covered the area. The original Lake Rotomahana was significantly altered. A portion of the lake floor was ejected, and the newly formed Rotomahana crater filled with water to form the current lake. It was widely believed that both terraces were destroyed.
The serendipitous nature of scientific research
In February 2011, a joint New Zealand-American initiative mapped the bottom of Lake Rotomahana. Their purpose was to investigate the extensive geothermal activity under the lake.
The project scientists were surprised when underwater scans revealed images of crescent-shaped terraced structures in about 60 metres of water. The location of the terraces corresponded to the position of the Pink Terraces prior to the eruption. They scanned the area two more times and were reasonably certain they had located the bottom two tiers of the Pink Terraces – as explained in the article Portion of Pink Terraces revealed underwater.
The team returned to Lake Rotomahana in 2012 to undertake further sonar and seismic surveying. Their seismic survey showed that a substantial portion of the Pink Terraces appeared to have survived the 1886 eruption and was sitting at the bottom of Lake Rotomahana, covered by 2 metres of sediment.
The detailed map showed ridges and other features that were originally above water and can be matched to old paintings and photographs of both the pre-eruption and post-eruption landscape.
The team did note that the cascading and scalloped shapes of the Pink Terraces had proved challenging to image as the seismic signals had been scattered by the many hard surfaces at different angles. Read about the project and the high-tech equipment they used in the article Pink and White Terraces under 2 metres of sediment.
The fate of the White Terraces was still unknown as they were in a part of the lake that was significantly disturbed by the eruption.
Nature of science
A hallmark of science is that it is subject to revision when new information is presented or when existing information is viewed in a new light.
New information, new observations and new inferences about the terraces
In 2010, research librarian Dr Sascha Nolden found Ferdinand von Hochstetter’s 1859 field diary. The New Zealand Government employed Hochstetter to make a geological survey of the new territory. He travelled to the terraces with a party of surveyors and artists. Over 28–30 April 1859, Hochstetter completed an azimuth compass survey and made sketches and other observations in his field diary.
Dr Nolden translated Hochstetter’s field notes from Hochstetter’s native German to English and, in 2016, passed the information on to researcher Rex Bunn. Using forensic cartography and reverse engineering, Bunn and Nolden reconstructed the historic Lake Rotomahana over a modern topographic map. Their findings (inferences) are that the terraces are buried on land, not in the lake. Bunn estimates he can pinpoint the locations with a margin of error of 35 metres.
In his diary, Hochstetter noted that his map was made over a large area with the use of a compass as his sole instrument. He said that he could make no pretensions to trigonometric exactness and that the map would be useful until a better and more complete map took its place.
What next for the terraces?
Bunn says the next step will be to survey the area using non-invasive ground-penetrating radar. If the imaging returns positive results, core sampling and excavation could follow. Those working on this project are volunteering their time and equipment.
In a 20 March 2018 radio interview, Bunn reported that the ground penetrating radar phase was not successful. However, the surveying technology leads his team to believe that each of the terrace springs appear to be next to the lake shore. Bunn believes that the upper sections of each terrace survived but the lower sections were fractioned off and are in the lake. A large piece of pink silica sinter found by the GNS researchers who were mapping the lake matches this location. In addition, a re-discovered third terrace – Te Tuhi’s Spring or the Black Terrace – and its crater are also located on land near the lake. The Black Terrace was documented by Hochstetter but was left off 20th Century maps. Rex Bunn says that his work is drawing to a close. Any decisions regarding drilling is up to the local iwi, who are the landowners.
In August 2018, GNS released a media statement saying its researchers stand by their earlier findings. GNS scientist Dr Cornel de Ronde is the lead author in a peer-reviewed paper which reports that a portion of the Pink Terraces may lie at the bottom of Lake Rotomahana and that the White Terraces were destroyed. Dr de Ronde says these findings are consistent with historic photographs and published maps by Ferdinand von Hochstetter.
In November 2018, NIWA scientists Andrew Lorrey and John-Mark Woolley published an article in the journal Frontiers in Earth Science. Their research confirms the findings of the GNS scientists. The research by NIWA was conducted at the request of the Tūhourangi Tribal Authority, the kaitiakitanga for Lake Rotomahana.
The journal Frontiers in Earth Science published a commentary by Rex Bunn, critiquing aspects of Lorrey and Woollery's 2018 article.
The Pink and White Terraces and the nature of science
Use this article, the two news articles Portion of Pink Terraces revealed underwater and Pink and White Terraces under 2 metres of sediment and other online information from Useful links (if desired) to explore the nature of science.
Suggested activities include:
Discuss the articles and research findings using questions from The nature of science as questions.
Student activities The extra piece and Scrambled sentence draw parallels to aspects of the nature of science. Do one or both of the activities and discuss how they reflect/parallel the findings of the different investigations regarding the Pink and White Terraces.
GNS scientists published a paper in the Journal of the Royal Society of New Zealand saying that the location of the White Terraces by Bunn and Nolden is untenable. Read about the GNS response in the Stuff article Search for the Pink and White Terraces: GNS scientists challenge lake shore claim.
Researchers have used the data from non-invasive scanning to locate the final burial site of the famous Pink and White Terraces, 132 years after the Mt Tarawera eruption engulfed them. Listen to researcher Rex Bunn in conversation with Radio New Zealand's Kathryn Ryan in this podcast – Pink and White Terraces Final Location Discovered. The RNZ article also includes survey maps and images of the area.
These Stuff articles expand on the information about Rex Bunn and Dr Sascha Nolden’s findings regarding the Pink and White Terraces. Researchers claim to have found the lost Pink and White Terraces and Next step to examine potential Pick and White Terraces site to go ahead.
Read about the joint GNS-US exploration of the terraces: The Pink and White Terraces of Lake Rotomahana: what was their fate after the 1886 Tarawera Rift eruption? and Multi-pronged investigation lays out the latest word on Lake Rotomahana.
Read The Journal of the Royal Society of New Zealand article Forensic cartography with Hochstetter’s 1859 Pink and White Terraces survey: Te Otukapuarangi and Te Tarata.
GNS Science has created a map of Rotomahana's lake floor. It shows floor features that have not been seen for more than a century, including the likely locations of the remnants of the Pink and White Terraces. This 2021 article from Stuff explains how the map was made. The GNS Science webshop is offering a free downloadable PDF version of the map.