White Island (Whakaari) Volcano

White Island (Whakaari) is the summit of a volcano of the same name rising 321m from the sea in the Bay of Plenty, 50km from the coast of the North Island, New Zealand. Whilst the dimensions of White Island are about 1.6 x 2 km, the base of the volcano extends over an approximate area of 16 x 18km at a depth of 300-400m. The volcano, which is estimated to be 200000 years old, is at the SW end of a chain of seamounts which represent the NE section of the Taupo Volcanic Zone. White Island is principally composed of two overlapping stratocones. Remnants of the extinct Ngatoro Cone make up the NW quarter of the island, whilst the rest is made up of the active Central Cone. Volckner Rocks, 5km NNW of the island are a further visible part of the complex and are considered to be the remains of a large lava dome. Both stratocones were emplaced by a succession of andesite / dacite lava flows and pyroclastic deposits. To date, 22 layers of lava have been identified, seperated by layers of non-coherently erupted pyroclastic materials (for details see Cole et al., J. of Petrology 41(6), p.867-895, 2000). The deposits suggest that activity has involved phases of high levels of lava extrusion, seperated by phases of minor basaltic-endesetic explosive activity as witnessed in historical times.

White Island viewed from SE, Nov. 2007.	White Island with Volckner Rocks behind (top right), Nov. 2007

No deposits attributable to White Island have been found on the mainland, and there is no evidence for any major explosive event at the volcano. Hence, White Island has had little impact on populated areas. Nevertheless, it has been suggested that it is in principle capable of a large eruption, since gas and heat output levels suggest a sizeable magma body underneath. A large eruption could deposit large amounts of ash and pumice, yet the primary hazard could be the induction of Tsunamis which could threaten coastal communities. Similarly, collapse of part of the volcanic ediface could occur at any time and cause tsunamis as witnessed at island volcanoes such as Mount Augustine or Stromboli. For extensive discussion of the potential human impact of W.I. volcano, see "Volcanic Hazards at White Island" by Cole, Nairn and Houghton.

The historically active crater encompasses three subcraters (Western, Central and Eastern). The Eastern subcrater which is open to the sea shows only minor geothermal activity. The Central and Western subcraters have been the sites of numerous small to moderate explosive eruptions from varying vents, many of which have been obscured by erosion and subsequent activity. For example, eruptions in Central subcrater formed "Noisy Nellie" crater in the early 1940s, several small pits in 1980 and "Donald Duck" crater in 1988. Western subcrater has undergone numerous changes in the last 100 years. Notable craters formed in 1933, 1962-65, 1968-69 and 1971. However, these occupied sites within the perimeter of the larger crater formed during the 1976-1982 eruptions which has subsequently been modified by further eruptions and is now known as the 1978/90 crater complex. This crater is presently the site of the acidic lake.

White Island Western Subcrater with Lake, Nov. 2007	White Island Crater Lake, Nov. 2007

A complete chronological list of eruptive activity in the past decades is too extensive to be included here, yet a summary of the most notable events is provided (see monthly reports of Smithsonian Global Volcanism Program for more detail (1977 onwards)). A phase of heightened activity occurred from 1976-1982, with further significant activity reported for various periods until 1992. Phreatomagmatic, magmatic, aswell as strombolian eruptions were witnessed during this period. Lengthy periods of ash emission were observed at different points from various vents. Particularly large explosions with visible incandescence and producing sizeable ash columns up to 6km high were reported on 25.08.1977, resulting in base surges affecting much of the crater floor. A similar event occurred in July 1978. From Dec.-Jan. 1979, large volumes of ash were erupted during numerous eruptive events. In early 1981, numerous large phreatomagmatic explosive eruptions left numerous ballistics scattered up to 600m from the crater. On 25.01.87, a powerful phreatic eruption occurred during an otherwise quiet period. The eruption was without warning, but was preceeded by a M4.7 earthquake centered 400km N of the island. Numerous ballistic blocks 1m in size were thrown 500m from the vent and 5cm long pyroclastics fell on a boat 1km away. A large ash column with lightning was also observed. 1987 and 1988 produced several further events of slightly lower magnitude. Phases of more or less intense tephra emission were observed intermittently during the period from 1986-1992. Strombolian activity was observed during late 1991 when it is thought that the conduit extended down to the top of a magma body at 300-400m depth. This phase ended abruptly in January when it is assumed that part of the conduit wall collapsed, thereby covering the magma body. This change was marked by the largest seismic event recorded at White Island up to that date. Poor visibility hindered observations, yet a nearby yacht had its sails coated in mud and ashfall was reported on the mainland. In 2000 there was a shorter period of increased activity involving significant ash emission and a new explosion crater was formed during a magmatic eruption on 27 July. Since 2002 little significant activity has occurred. Lake temperatures have risen substantially in 2007, leading to increased evaporation and lower water levels. This could be a precursor of renewed activity. Fumarolic activity has persisted with various intensities since historic records began. Carbon dioxide and sulphur dioxide are the predominant gases involved.

Hot Spring, White Island Central subcrater	Mudpots, White Island central subcrater

Hot Spring, White Island Central subcrater	Fumarole, White Island Central subcrater	Mineral deposits, White Island Central subcrater

The history of ownership and exploitation of natural resources on White Island is arguably equally exciting as the volcano itself. The Maori visited W.I. regularly to harvest seabirds (Grey-faced Petrels) for food and sulphur was taken back to mainland settlements for use as a fertilizer. The 1st european to see W.I. was Cpt. Cook who observed it from a distance in 1769 and named it based on its appearance. The first european to land was Rev. Williams in 1826. Danish trader Tapsell bought the island from the Maoris in the 1830s, after which it was sold on several times. In 1874, Wilson, a judge at the Native Land Court, acquired a part-share of the island and began to mine small amounts of sulphur which was exported to Sydney. In 1883, another Aucklander named Johnson joined Wilson in established the "NZ Manure and Chemical Company". Wilson bought land at Sulphur Point in Tauranga (on the mainland) upon which a factory was built for producing sulphuric acid. Production was however abandoned in the wake of the 1886 Tarawera eruption which coated the island with a 2-3 cm thick layer of ash and raised fears that an eruption would occur at W.I. In 1898 production of sulphur ore was resumed and over a period of 4 years a total of over 5000 Tonnes was mined. After this, the best deposits were exhausted and the operation became uneconomical and was closed down.

In 1913, Brown and Mercer (UK with connections to Vancouver, Canada) purchased the island and established "The White Island Sulphur Co. of Vancouver". A boilerhouse with several retorts was erected on the island. Retorts are small ovens in which the sulphur ore is heated in order to extract sulphur from it. The operation was complicated. The retorts corroded unexpectedly fast and one worker was killed when a retort exploded. Also, the most readily accessible sulphur deposits had already been mined, so lakes on the crater floor were drained to access further deposits. In September 1914, disaster struck when the SW flank of the crater wall collapsed and the ensuing debris avalanche / lahar buried 11 mine workers and the mine infrastructure. Repeated search efforts found no trace of either. The event must have happened between the supply ship visits on 17. and 25. September. Whether the flank failure was related to an eruptive event (e.g. a phreatic eruption) and to what extent (if any) the mining operation in the crater played a role is not known. Apparently, explosions were heard on the mainland, and an increased smell of sulphur was reported. Mounds left by the collapse event are still visible and mark the locations of larger rocks from the flank.

1914 Collapse Scar (top middle)	Hummocks left by 1914 collapse on crater floor

Production was resumed again in 1923, when Mercer set up the "White Island Agriculture Chemical Co. Ltd". The company was floated with the assistance of Auckland Stockbroker George Raymond Buttle. The mining operation lasted for 10 years before bankrupcy in 1933. The remains of the reenforced concrete factory buildings on White Island are from this period.

Sulphur Bay (where water discoloured) and Gannet colony (left)	Ruins of 1923-1933 mining operation

Remains of retort in sulphur processing factory	Coroded machinery in sulphur processing factory	Sulphur storage bunker

In 1936, when the island was offered for sale, G.R. Buttle took the opportunity to buy it. In spite of attempts by the NZ government to buy the island, it has remained in the hands of the Buttle family to this date. In 1953 it was declared a private scenic reserve. Since 1995 access has been restricted and permits must be acquired by visitors. This provides a steady income to the owners. The island was already visited touristically in the 1860s when boats from the mainland would occasionally bring locals or day excursioners from the Northern Star Company cruise ships to see it. Boat and helicopter access is presently possible (e.g. from Rotorua with Volcanic Air Safaris (www.volcanicair.co.nz)). Visitors must be aware of the risk of unexpected phreatic explosive activity (see e.g. Jan. 1987 eruption). Nevertheless, such events are rare and White Island is well worth a visit.

For further information on New Zealands volcanoes, see sections on Ruapehu, Tongariro, Tarawera and Wai-O-Tapu geothermal area.

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