Report on Whakaari/White Island (New Zealand) — January 1993
Bulletin of the Global Volcanism Network, vol. 18, no. 1 (January 1993)
Managing Editor: Lindsay McClelland.
Whakaari/White Island (New Zealand) Minor ash ejections; rapid deflation continues
Please cite this report as:
Global Volcanism Program, 1993. Report on Whakaari/White Island (New Zealand) (McClelland, L., ed.). Bulletin of the Global Volcanism Network, 18:1. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN199301-241040.
37.52°S, 177.18°E; summit elev. 294 m
All times are local (unless otherwise noted)
Minor ash emission was reported by helicopter pilot R. Fleming from a vent on the N floor of Wade Crater on 4 January. Eruption of blocks from a new vent under the S wall of the crater was observed on the same flight; no ejecta fell outside of the 1978/92 Crater Complex. The two vents were not significantly active the previous day, but gas emission was increasing. On 14 January, activity was observed from three sources in Wade Crater.
Fieldwork on 15 January revealed continuous ash coverage, with depths of 20-25 mm in some areas. No topographic changes within the 1978/92 Crater Complex were observed. An inclined vent on the S side of Wade Crater produced two types of activity. A steam column with minor ash content was emitted at about 1000, rising 200-500 m above the crater. Surtseyan style pulses with varying densities appeared at 1250 that rose 100-150 m. Individual blocks frequently broke away and could be heard rolling back into the vent. A steep unstable talus slope formed around the active vent. This vent appeared to occupy an area which showed some subsidence on 8 December.
There was no sign of new tephra or ejected blocks outside the 1978/92 Crater Complex during fieldwork on 21 January. A "lake" of viscous, black sludge in Wade Crater was erupting continuously from 3-4 points. The eruptions appeared to be generated by steam exploding through the sludge. Large lumps of sludge were thrown to 30 m, followed by larger explosions which sent debris up to 100 m high. No detonations were heard and there was no incandescence or fine ash emission observed at any stage of the eruptions. Fumaroles were active on the N and E sides of Wade Crater. TV1, Princess, and Royce craters were emitting fumes and low-pressure steam.
A levelling survey completed on 21 January again revealed rapid subsidence (-16.1 mm/month compared to -19.7 mm/month in the seven months prior to December) since 8 December on the W side of Donald Duck Crater. Geologists suggest a source depth of 100-150 m, with the rate of subsidence increasing since 1991. Medium-frequency volcanic tremors characterized seismicity through 15 January.
Geologic Background. The uninhabited Whakaari/White Island is the 2 x 2.4 km emergent summit of a 16 x 18 km submarine volcano in the Bay of Plenty about 50 km offshore of North Island. The island consists of two overlapping andesitic-to-dacitic stratovolcanoes. The SE side of the crater is open at sea level, with the recent activity centered about 1 km from the shore close to the rear crater wall. Volckner Rocks, sea stacks that are remnants of a lava dome, lie 5 km NW. Descriptions of volcanism since 1826 have included intermittent moderate phreatic, phreatomagmatic, and Strombolian eruptions; activity there also forms a prominent part of Maori legends. The formation of many new vents during the 19th and 20th centuries caused rapid changes in crater floor topography. Collapse of the crater wall in 1914 produced a debris avalanche that buried buildings and workers at a sulfur-mining project. Explosive activity in December 2019 took place while tourists were present, resulting in many fatalities. The official government name Whakaari/White Island is a combination of the full Maori name of Te Puia o Whakaari ("The Dramatic Volcano") and White Island (referencing the constant steam plume) given by Captain James Cook in 1769.
Information Contacts: B. Scott, C. Wood, and P. Otway, IGNS, Taupo.