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Report on Whakaari/White Island (New Zealand) — February 1984

Whakaari/White Island

Scientific Event Alert Network Bulletin, vol. 9, no. 2 (February 1984)
Managing Editor: Lindsay McClelland.

Whakaari/White Island (New Zealand) Tephra eruption from new vent

Please cite this report as:

Global Volcanism Program, 1984. Report on Whakaari/White Island (New Zealand) (McClelland, L., ed.). Scientific Event Alert Network Bulletin, 9:2. Smithsonian Institution. https://doi.org/10.5479/si.GVP.SEAN198402-241040

Whakaari/White Island

New Zealand

37.52°S, 177.18°E; summit elev. 294 m

All times are local (unless otherwise noted)

A tephra eruption began at White Island in late December 1983. No significant activity had been reported since late 1981.

NZGS personnel reported that a ground inspection on 23 November and an aerial inspection on 27 November 1983 had yielded no evidence of eruptive activity. Airborne COSPEC measurements on the 27th showed an SO2 emission rate of 1,200 t/d. Voluminous steam colums above the island were observed from Pukehina Beach (~65 km SE) in late December-early January by two NZGS geologists. A pilot reported that the eruption column had changed from white to gray about 20 January. Photographs taken by a yachtsman who landed on White Island on 27 January showed a dense ash column.

During an aerial inspection on 2 February, crater conditions appeared similar to those shown in the 27 January photographs. Geologists who flew over the island (from 0944-1000) observed a gray-green ash layer on the main crater floor and the island's outer slopes. Ash appeared thickest on the N slopes. A white steam plume with a little light gray, fine ash was rising to 1.2-1.5 km above sea level. All eruptive activity appeared to come from a new vent (about 20 x 30 m and at least 50 m deep) that had formed at the site of a vigorous fumarole on the N margin of the older (SE) portion of the dumbell-shaped 1978 Crater complex. A small tuff ridge had been built up from the floor of 1978 Crater to the rim of the new vent. Impact craters and blocks up to 1 m in diameter were visible on the tuff ridge and throughout the complex, extending E to Donald Mound. Impact crater density decreased rapidly away from the vent. Fumarolic activity in other areas appeared to have declined from the level observed in November. At about 1200, after geologists left the area, a vigorous, dark eruption column was observed from many points along the coast of North Island, more than 50 km away.

During field work on 6 February, NZGS personnel observed little apparent change since their previous visit. No significant new ashfall was evident outside the rim of 1978 Crater. Small blocks (less than 10 cm in diameter) on the floor of the 1978 Crater complex were not ash-coated, suggesting recent ejection. All the blocks consisted of lithic andesite; some were altered. Moderate gas emission from the active vent was punctuated by occasional pulses of fine gray ash. More voluminous emissions occurred at about 1200 and 1530. Acid rain and a little ash fell on the geologists.

Post-November 1983 tephra thicknesses ranged from 60 mm about 150 m N of the new vent, to 15 mm about 350 m E, and 2 mm about 800 m E. Sand-sized material in new ash NE of the vent was dominated by abundant fresh plagioclase, pyroxene, some possible olivine crystals, and magnetite, with subordinate glass and minor amounts of lithic fragments. Considerable altered silt- and clay-sized material was also present in the ash. At a site closer to the vent, tephra from an earlier phase of the 1983-84 activity had the same crystal and glass components but a much larger proportion of altered lithic fragments.

At 762°C, the temperature of a fumarole E of Donald Mound was similar to that measured on 23 November 1983; temperatures below 700°C were measured on all other visits in 1983, 1982, and 1981. Inflation had continued in the Donald Mound area. The localized uplift area was about 400 mm across and centered on Donald Mound.

NZGS geologists returned to White Island on 17 February. Except for a small quantity of blocky ejecta around the E rim of the new vent, there was little evidence of recent eruptive activity. Fumarole temperatures remained high, and the Donald Mound area was still inflated.

Telemetry of seismic data, which stopped in late November, resumed 6 February. Between the 6th and 23rd, 6-30 low-frequency B-type volcanic earthquakes were recorded daily. There were more than 20 events/day, 9-15 February, and fewer than 15/day, 16-23 February. High-frequency volcano-tectonic earthquakes numbered fewer than 3/day except on 6, 7, 8, and 13 February when 13, 20, 12, and 11 events were recorded. Long-duration, wide-band, multiple-frequency earthquake sequences were recorded on 8, 9, 10, 11, 14, and 17 February. Similar sequences had previously been correlated with eruptive activity, but there was no visual confirmation of any eruption clouds associated with these events. Weak low- or medium-frequency tremor was recorded for 8-9 hours on 11 February.

Further Reference. Rose, W.I., Chuan, R.L., Giggenbach, W.F., Kyle, P.R., and Symonds, R.B., 1986, Rates of Sulfur Dioxide and Particle Emissions from White Island Volcano, New Zealand, and an Estimate of the Total Flux of Major Gaseous Species; BV, v. 48, p. 181-188.

Geological Summary. 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: I. Nairn, NZGS, Rotorua; W. Rose, Michigan Tech. Univ.