Abstract
Te Otukapuarangi (the Pink Terrace), Te Tarata (the White Terrace) and Te Ngāwhā a Te Tuhi (the Black Terrace) were massive siliceous sinter formations at Lake Rotomahana, New Zealand, that were ostensibly lost in the catastrophic 1886 Tarawera eruption. Previous work using an unpublished watercolour map and notes by Ferdinand von Hochstetter (1829-1884) have recently supported claims that the former Pink and White Terraces survived the 1886 eruption, and that they may be located under tephra adjacent to the modern lake margin. Divergent perspectives about the fate of Lake Rotomahana’s former sinter terraces suggest the reconstruction of New Zealand’s largest historic volcanic eruption is incomplete. We harnessed a wider amount of unique historic data recorded during Hochstetter’s 1859 survey than previously reported to hone the locations of the former Rotomahana sinter terraces. Volcanic landforms, the physical geography of the countryside, and former settlements are tied together via common sightings between sequential survey datums. Light detection and ranging (LIDAR) data supported the reconstruction of Hochstetter’s former survey and datum locations. Of significance, shared landmarks between the survey stations increased the confidence for resecting the 1859 datum position on the southern margin of former Lake Rotomahana. Hochstetter’s survey watercolour maps are part of a series drafted prior to a final version being professionally printed, and they do not portray a spatially accurate depiction of how sinter terraces and geothermal features around former Lake Rotomahana were arranged. As such, assertions of their superior cartographic nature are not well-founded, and application of them to provide former Terrace locations is compromised. The published pre-eruption map of Lake Rotomahana validates well against Hochstetter’s field diary measurements. When Hochstetter’s published map is orientated using reconstructed positions for survey datums at Lake Rotomahana, the former locations of the White and Pink Terraces lie entirely within the modern boundaries of the lake and not on land. The Black Terrace may have been destroyed and/or converted to an eruption crater, but may still exist on land (intact or in-part) west of Lake Rotomahana’s modern shoreline. This study demonstrates the value of historic cartography to improve understanding of volcanic processes.
Highlights
Environmental observations focused on monitoring volcanic landscapes provide our society with a basis for early warnings, disaster preparation plans, and response strategies for a range of eruption types
Our study focuses on information about Lake Rotomahana before the 1886 Tarawera eruption, which we use to relocate the sites of the former sinter terraces with respect to the modern landscape
Modern Lake Rotomahana was produced from the 1886 Tarawera eruption and it is one of many volcanogenic lakes located within the Taupo Volcanic Zone (TVZ), sitting astride the southern margin of the Okataina Volcanic Centre (Nairn, 1981, 2002; Cole et al, 2010; Leonard et al, 2010; Figure 1)
Summary
Environmental observations focused on monitoring volcanic landscapes provide our society with a basis for early warnings, disaster preparation plans, and response strategies for a range of eruption types. While the plinian-style activity on Mount Tarawera continued, there was further propagation of rift-aligned fissures beneath the Lake Rotomahana basin to Waimangu valley (Nairn and Cole, 1981; Walker et al, 1984; Keam, 1988, 2016; see Figure 1 for location and geology details). Eruptions along the Rotomahana-Waimangu rift extension generated a series of phreatomagmatic explosions that catastrophically evacuated, deepened and enlarged the former Rotomahana lake basin (along with other smaller lakes within that area) Volcanic products from this phreatomagmatic phase include “muddy” deposits and photography from the late nineteenth century suggested Lake Rotomahana’s Pink and White Terraces (Figure 2) were destroyed and/or buried during this severe event (Smith, 1886, 1887; Valentine, 1886; Thomas, 1888), despite persistence of a minority opinion of their survival (Nikora, 1936). Popular perspectives about the destruction and loss of The Terraces became solidified in the literature and entrenched in public sentiment after survivors passed away (Bunn and Nolden, 2016)
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