The Pink and White Terraces of Lake Rotomahana: What Was Their Fate After the 1886 Tarawera Rift Eruption?

Journal of Volcanology and Geothermal Research 314 (2016) 126–141

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Journal of Volcanology and Geothermal Research

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The Pink and White Terraces of Lake Rotomahana: what was their fate after the 1886 Tarawera Rift eruption?

C.E.J. de Ronde a,⁎,D.J.Fornarib,V.L.Ferrinic,S.L.Walkerd,B.W.Davya,C.LeBlanca,F.CaratoriTontinia, A.L. Kukulya b, R.H. Littleﬁeld b a GNS Science, 1 Fairway Drive, Lower Hutt 5010, New Zealand b Woods Hole Oceanographic Institution, 266 Woods Hole Road, Woods Hole, MA 02543, USA c Lamont-Doherty Earth Observatory, Columbia University, 75 Geoinformatics Centre, 61 Route 9W, Palisades, NY 10964-8000, USA d Paciﬁc Marine Environmental Laboratory, NOAA, 7600 Sand Point Way NE, Seattle, WA 98115-6349, USA article info abstract

Article history: The Pink and White Terraces that once stood regally on the shores of old Lake Rotomahana, and which were Received 1 December 2015 unique in their beauty as a natural wonder of the world, were regarded by the local Māori as a taonga, or treasure, Accepted 4 February 2016 because of the therapeutic qualities of the waters and their majestic appearance. The eruption of Mt. Tarawera on Available online 15 February 2016 June 10, 1886 is commonly cited as the cause of their demise, with the lake rapidly rising soon thereafter to drown the large, newly formed Rotomahana crater and other volcanic edifices shaped during the excavation of Keywords: the old lake. Thus, the effects of the eruption have been masked from onlookers for more than 125 years. Lake Rotomahana Pink and White Terraces However, application of state-of-the-art survey techniques usually applied in the marine realm to modern Side-scan sonar Lake Rotomahana, including AUV surveys with numerous sensors, seismic profiling, water column surveys and deployment of deep sea cameras, has provided a wealth of new information about the state of hydrothermal systems in the lake and the probable fortunes of the Pink and White Terraces. We believe that the majority of both sets of terraces were destroyed during the eruption. However, some tantalizing evidence remains for remnants from both sites to exist to this day. High-resolution bathymetric mapping of the lake floor clearly recognizes some features of the post-1886 landscape, including a prominent landmark known as The Pinnacle. If we accept the postulated location of The Pinnacle on a pre-1886 map of Lake Rotomahana, then we appear to have captured a photograph of one of the buttresses to a tier of the nearby White Terraces. More revealing, are side-scan sonar images of structures located in the correct position of the Pink Terraces with respect to The Pinnacle, albeit ~20 m deeper than expected if the pre-1886 lake level of 292 m above sea level is to be believed. This work clearly shows that the greater Pink Terraces hydrothermal system survived the eruption and is very active today, whereas that part of the system that supplied hydrothermal fluids to the White Terraces has largely ceased activity altogether. © 2016 Elsevier B.V. All rights reserved.

1. Introduction The eruption of Mt. Tarawera on June 10, 1886 ensured that the terraces would be resigned to history, as the devastating effects of the The famed Pink and White Terraces that once stood regally on the eruption through the bottom of the old lake changed the surrounding shores of old Lake Rotomahana (Fig. 1) were iconic not only for their landscape forever (de Ronde et al., 2016-a) and plastered the immediate unheralded beauty as a natural wonder of the world (Fig. 2), but also countryside meters thick with mud and debris (e.g., Pittari et al., 2016- because they represented one of the first focal points for the start of a). Within months of the eruption the new lake began to fill as the his- eco-tourism (Keam, 2016). The terraces were regarded by the local torical outlet for the old lake was dammed by debris; most of the new Māori as a taonga, or treasure, because of the therapeutic qualities of geothermal features were drowned within a few years and today the the waters and their majestic appearance. They developed a natural af- lake is ~120 m deep at its deepest point (de Ronde et al., 2016-b). Fortu- finity for, and with, the intrinsic values of these taonga that enhanced nately, due largely to the magnificence of the terraces and the rise of com- their own unique cultural identity. The terraces are also considered to mercial photography at the time, accurate records of their nature, setting, have represented the largest silica sinter deposits ever seen on Earth. and even intricate detail of individual terraces meant that at least they would never be forgotten. ⁎ Corresponding author. This paper focuses on the area encompassing the Pink and White E-mail address: [email protected] (C.E.J. de Ronde). Terraces with the aim of describing the impact the 1886 Tarawera

Fig. 1. Map of Lake Rotomahana showing the location of the pre-1886 lakes Rotomahana and Rotomakariri (dark blue), superimposed on the modern lake area (light blue; modiﬁed from Nairn, 2002; old Lake Rotomahana outline taken from Keam, 2016;seeFig. 3); asterisks mark the location of the Pink and White Terraces with respect to pre-1886 Lake Rotomahana. Inset shows location of Lake Rotomahana (at end of arrow tip) within the North Island of New Zealand. LR, Lake Rotomahana; TVZ, Taupo Volcanic Zone.

eruption had on the terraces, and to determine if any part of those terraces and indeed, the hydrothermal system that fed those terraces, survived that cataclysmic event (cf. Simmons et al., 1993).

2. Pink and White Terraces (pre-1886)

The sinter terraces of Lake Rotomahana were each remarkable in their own right, but to have two such examples occurring on the marginsofonelakewasunprecedented,asitistoday(Fig. 2A). The White Terraces, or Te Tarata in Māori (meaning “the tattooed rock”), were fan-shaped with an opening angle of 60°, situated on the northeastern side of old Lake Rotomahana where they draped over the slopes of a ridge dropping down to the lake (Fig. 3; Keam, 2016). They stood ~100 ft. (30.5 m) above the lake level, with a distance from the crater at the summit of the terraces to their base of ~800 ft. (~244 m), spanning ~525 ft. (~160 m) at their widest point and covering an area of approximately 7 ac (~2.8 ha; Martin, 1888; Keam, 2016, and references therein). The sinter formed from cascading, thermal waters that originated at the Te Tarata cauldron at the summit of the terraces. As their name would suggest, the White Terraces were glistening white and comprised about ﬁfty rel- atively larger terraces with many other smaller terraces that commonly formed adjoining steps between the larger ones (see below and Fig. 4). The Pink Terraces, or Otukapuarangi in Māori (meaning “fountain of the clouded sky”) were situated on the western side of the old lake, located in a narrow, steeply sloping valley fed at the top by the Otukapuarangi cauldron (Figs. 1–4A). They were smaller than the White Terraces, standing ~85 ft. (26 m) above the lake with a frontage of 140 ft. (43 m), spanning a distance of ~495 ft. (~151 m) and covering an area of about 5 ac (~2 ha; Martin, 1888; Keam, 2016,andreferences therein). These terraces had a distinctive pink hue to them (Fig. 2A) and Fig. 2. A. Painting of the Pink Terraces (foreground) and White Terraces (background) although the origin of the color is uncertain, the most likely explanation with Mt. Tarawera in the far distance. Note the height of the Pink Terraces with local is trace elements in the silica such as Fe3+ or Sb (cf. silica sinter at Maori nearby for scale. Otukapuarangi cauldron is steaming at the top of the terraces, on the far left-hand side. Note also the arcuate promontory just beyond (east of) the Pink Champange Pool, Waiotapu; Weissberg, 1969; Pope et al., 2005), though Terraces. View is towards the NE. Facsimile of a painting entitled “The Pink & White effects due to microorganisms are a possibility. Terraces” by J.B.C. Hoyte (1835–1913). B. Black and white photograph looking upslope Terraces at both locations form lobes (arcuate in plan view, convex of the White Terraces from almost its base, with steam rising from Te Tarata cauldron at out) with steps that are coated with overﬂow deposits of silica saturated, the summit. At the base of the terraces there is a suggestion that some older tiers might near-neutral pH chloride water. Complex patterns occur where individual be submerged beneath the lake level at the time the photograph was taken. Photograph taken by C. Spencer (“Pink and White Terraces”) between 1880 and 1886, now housed terraces intersect (Fig. 4B). Closer inspection shows that they have bul- in Te Papa (New Zealand's National Museum). bous buttresses (overhangs) with evidence for both sub-horizontal Download English Version: https://daneshyari.com/en/article/4713010

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