Whakaari / White Island (, , lit. "the dramatic volcano"), also known as White Island or Whakaari, is an active andesite stratovolcano situated from the east coast of the North Island of New Zealand, in the Bay of Plenty. The island covers an area of approximately , which is just the peak of a much larger submarine volcano.
The island is New Zealand's most active cone volcano, and has been built up by continuous volcanic activity over the past 150,000 years. The nearest mainland towns are Whakatāne and Tauranga. The island has been in a nearly continuous stage of releasing volcanic gas at least since it was sighted by James Cook in 1769. Whakaari erupted continually from December 1975 until September 2000, and also erupted in 2012, 2016, and 2019.
Sulphur was mined on the island until the 1930s. Ten miners were killed in 1914 when part of the crater wall collapsed.
A large eruption occurred at 14:11 on 9 December 2019, which resulted in 22 fatalities, including two people who were missing and ruled to be dead by a coroner. Twenty-five survivors were injured, many critically and with severe burns. Forty-seven people were reportedly on the island when it erupted. A second eruption closely followed the first.
Geography Whakaari / White Island is an irregular oval in shape, with a length (northwest–southeast) of and a width of , and covers an area of approximately . It lies in the Bay of Plenty from the North Island mainland, due north of the town of Ōpōtiki and north-northeast of Whakatāne. The island's active crater lies slightly southeast of the island's centre, and contains an acidic lake. The crater has a sharp rim to the northwest, with its highest point (also the island's highest point) being the Mount Gisborne in the west. The Mount Percival forms the northern part of the rim. An older vent, the Mount Ngatoro, lies to the northwest."Whakaari / White Island," topomap.co.nz. Retrieved 16 December 2019. The exposed island is only the peak of a much larger submarine volcano, which rises up to above the nearby seafloor.
The island is generally rugged, with cliffs surrounding most of the coast. The only exceptions are to the southeast of the crater, where ash and boulder slopes descend to Te Awapuia Bay (also known as Crater Bay), the site of derelict buildings and the island's wharf. This bay lies between a prominent headland, Troup Head, at the island's southeastern extreme, and the island's southernmost point, Otaketake, which is the site of one of the island's gannet colonies. Another colony exists at Te Hokowhitu, the cliff which forms much of the western coast of the island.
Several rock reefs and islets are located along the island's northeast coast, and there is also a rock reef at Troup Head. A small islet, Club Rocks, lies south of Otaketake Point. It consists of a set of four sea stacks rising to more than above sea level. In addition, four sea stacks collectively known as Te Paepae o Aotea or Volkner Rocks lie northwest of Whakaari / White Island. Three of these sea stacks rise precipitously from the sea floor (less than below sea level) to a maximum height of m above sea level. The fourth sea stack is just an eroded stump.
Climate
Geology Whakaari / White Island is an andesite–dacite stratovolcano that consists of two overlapping volcanic cones, which are the Ngatoro and Central cones. The Ngatoro Cone is extinct and partially eroded. The amphitheatre-shaped Central Cone is an active cone. The crater of Central Cone is open to the southeast as the result of major, past flank landslides involving hydrothermally altered rock and past phreatic and phreatomagmatic eruptions. the Ngatoro Cone and Central cones are both constructed of alternating layers of lava flows, tuffs, agglomerates, tephra, igneous dikes, and breccias. Some of these strata have been altered to varying degrees by highly corrosive and acid hydrothermal fluids and gases.Cole, J.W., Thordarson, T. and Burt, R.M., 2000. Magma origin and evolution of White Island (Whakaari) volcano, Bay of plenty, New Zealand. Journal of Petrology, 41(6), pp.867–895.Moon, V., Bradshaw, J. and de Lange, W., 2009. Geomorphic development of White Island Volcano based on slope stability modelling. Engineering Geology, 104(1–2), pp.16–30.Jimenez, C., 2015. Magmatic-hydrothermal system at White Island volcano, North Island, New Zealand. in M. Calder, ed., pp. 35–46, JCU SEG Student Chapter New Zealand, North Island Field Trip 2015 Guide Book. Queensland, Australia: James Cook University SEG Student Chapter, Society of Economic Geologists, Inc.
The modern crater floor of Whakaari / White Island lies less than above sea level and is largely covered by material from the 1914 debris avalanche. The main crater contains three coalescing sub-craters. The sub-craters are aligned NW-SE within the amphitheatre-shaped Central Cone. The open sea breaches the south-eastern crater wall in three places to form Shark, Te Awapuia, and Wilson bays, which Troup Head and Pinnacle Head separate from each other. Long-lived, semi-continuous, weak, hydrothermal explosions, similar to those occurring in the Western sub-crater today, are regarded to have formed these three bays as hydrothermal explosion craters.
Whakaari / White Island and the sea stacks that form Club Rocks and Volckner Rocks are the emergent summits of a larger, , submarine volcano. It is known as White Island Volcano and has a total volume of . The bathymetry surrounding the emergent summit of Whakaari / White Island consists of a broad, sloping shelf extending from sea level to approximately depth. Steep margins define the extent of the submarine volcano at a depths of Duncan, A.R., 1970. The petrology and petrochemistry of andesite and dacite volcanoes in Eastern Bay of Plenty, New Zealand. Ph.D. thesis, Victoria University of Wellington, New Zealand. pp.362
The amphitheatre-shaped crater of the modern Central Cone is argued to have been created by the collapse of the former cone of the White Island Volcano to the southwest. Based on extrapolating 20 m GIS contour data to enclose the present crater and upwards with a maximum slope angle of 30°, the former pre-collapse summit was inferred to have been high. Side-scan and bathymetric data indicate possible debris flows associated with its collapse that can be traced back to the current crater on White Island. One of these debris flows exited the crater on the southern side of Troup Head and towards the southeast. It produced well-defined boulder-covered lobes on the seafloor. Another debris flow exited the modern crater on the northern side of Troup Head and through several submarine valleys towards the east into deep water. It produced boulder-covered valley-fill deposits. The latter debris flow was large enough to have produced a significant tsunami. As a result of the collapse of the former cone of the White Island Volcano, it is suspected to have generated a high tsunami that flooded the coast of Bay of Plenty as much as inland between 3,000 and 2,200 B.P.de Lange, W.P., Hansford, A. and Moon, V.G., 2006. Tsunami generation by island edifice failure at White Island and Motuhora Volcanos, New Zealand. In F. Foley, et al., eds., pp. 405–416. Earthquakes and Urban Development: New Zealand Geotechnical Society 2006 Symposium, Nelson, February 2006. New Zealand, Wellington: Institution of Professional Engineers.de Lange, W. and Moon, V., 2016. Volcanic generation of tsunamis: two New Zealand palaeoevents. in G. Lamarche et al., eds., pp. 559–567, Submarine Mass Movements and their Consequences: 7th International Symposium. Natural and Technological Hazards Research 41. Switzerland, Zurich, Springer Nature.
Volcanology
Whakaari / White Island lies in the northern end of the Taupō Volcanic Zone. The Taupō Volcanic Zone forms the southernmost segment of the -long Tonga–Kermadec–Taupō volcanic arc system and the Lau Basin–Havre Trough–Ngatoro Basin back-arc basin system.
Geological history
For the past few thousand years, Whakaari / White Island has been the location for an open, highly reactive hydrothermal system. This hydrothermal system expresses itself as hot springs and mud pools, fumaroles, and acid streams and lakes. The present centre for volcanic activity and outgassing is a large crater lake of boiling acidic waters located in the western subcrater. The intermixing mélange of marine waters, meteoric waters, and hot magmatic fluids generate acid brines, with pH as low as 2, that outgas and form numerous and often transitory hot springs and mud pools, fumaroles, and acid streams and lakes. The crater lake of boiling acidic water, which occupies the western subcrater, appears to vary in volume due to changing meteorological conditions and fluctuating levels of hydrothermal activity.Christenson, B.W., White, S., Britten, K. and Scott, B.J., 2017. Hydrological evolution and chemical structure of a hyper-acidic spring-lake system on Whakaari/White Island, NZ. Journal of Volcanology and Geothermal Research, 346, pp.180–211.Heap, M.J., Kennedy, B.M., Pernin, N., Jacquemard, L., Baud, P., Farquharson, J.I., Scheu, B., Lavallée, Y., Gilg, H.A., Letham-Brake, M. and Mayer, K., 2015. Mechanical behaviour and failure modes in the Whakaari (White Island volcano) hydrothermal system, New Zealand. Journal of Volcanology and Geothermal Research, 295, pp.26–42.Heap, M.J., Kennedy, B.M., Farquharson, J.I., Ashworth, J., Mayer, K., Letham-Brake, M., Reuschlé, T., Gilg, H.A., Scheu, B., Lavallée, Y. and Siratovich, P., 2017. A multidisciplinary approach to quantify the permeability of the Whakaari/White Island volcanic hydrothermal system (Taupo Volcanic Zone, New Zealand). Journal of Volcanology and Geothermal Research, 332, pp.88–108.
Although Strombolian activity occurred from the late seventies to the mid-eighties, explosive eruptions at Whakaari / White Island are typically phreatic or phreatomagmatic in style. The lava flows, ash, and pyroclastic flows produced by historic and prehistoric eruptions are andesitic and dacitic in composition. These eruptions also produce discrete craters within crater-fill deposits of the Central Cone. Since 1826, there has been a minimum of 28 phreatic or phreatomagmatic eruptions. In addition, prehistoric eruptions have also extruded lava. The lava flows from these prehistoric eruptions are exposed crater walls of the Central Cone. Whakaari / White Island's frequent activity and easy access attract scientists and volcanologists as well as many tourists. For example, this volcano provides a readily studied example of the type of volcanic magmatic–hydrothermal system involved in the generation of porphyry copper deposits.Hedenquist, J.W., Simmons, S.F., Giggenbach, W.F., and Eldridge, C.S., 1993. "White Island, New Zealand, volcanic-hydrothermal system represents the geochemical environment of high-sulfidation Cu and Au ore deposition", Geology, v. 21, pp. 731–734.Mandon, C. L., 2017. Volatile transport of metals in the andesitic magmatic-hydrothermal system of White Island, unpublished PhD dissertation. Wellington, New Zealand: School of Geography, Environment and Earth Sciences, Victoria University of Wellington. 209 pp.