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

The Pink and White Terraces that once stood regally on the shores of old Lake Rotomahana, and which were unique in their beauty as a natural wonder of the world, were regarded by the local Maori as a taonga, or treasure, because of the therapeutic qualities of the waters and their majestic appearance. The eruption of Mt. Tarawera on 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 the old lake. Thus, the effects of the eruption have been masked from onlookers for more than 125 years. However, application of state-of-the-art survey techniques usually applied in the marine realm to modern 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 similar to 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. (C) 2016 Elsevier B.V. All rights reserved.