Report on Whakaari/White Island (New Zealand) — March 1992
Bulletin of the Global Volcanism Network, vol. 17, no. 3 (March 1992)
Managing Editor: Lindsay McClelland.
Whakaari/White Island (New Zealand) Continued vigorous explosive activity
Please cite this report as:
Global Volcanism Program, 1992. Report on Whakaari/White Island (New Zealand) (McClelland, L., ed.). Bulletin of the Global Volcanism Network, 17:3. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN199203-241040.
37.52°S, 177.18°E; summit elev. 294 m
All times are local (unless otherwise noted)
Explosive activity continued through early March from Wade and TV1 Craters.... Distinct emissions of gray and reddish ash were observed during regular visits to the island and from nearby fishing vessels. A larger event on 20 February produced a tall plume (estimates ranged up to 5,000 m) and ejected blocks and juvenile bombs. Numerous E-type seismic signals were recorded through mid-Mar.
Observations. On 3 February, R. Fleming (Waimana Helicopters) noted gray ash, not present during a 1 February visit, covering the W and SW walls of the main crater. Two eruption columns were reported the next day, the first at 0740 by R. Pollack (MV Pursuit), and a stronger one at 1318 by V. Froude (Dept of Conservation; MV Takapu). Froude observed another eruption column at 0737 on 5 February. TV1 Crater was the source of a light gray ash cloud, 50-100 m high, during an island visit at 1040-1730 on 7 February. Ash again emerged from TV1 during a 12 February visit. Light pink-brown ash emission began at about 1229, and increased slightly during the afternoon. The next day, Fleming reported the emission of red ash from TV1 (at 1530). Strong red ash emissions were reported at 1900-2000 by John Baker (MV Ma Cherie). Wade Crater, inactive earlier in the month, erupted light pink-red ash during a 17 February visit (1030-1546), while TV1 emitted only white steam.
The eruption on 20 February began abruptly at about 1004 without any visible precursors. The initial dark eruptive pulse rose rapidly from TV1 Crater, accompanied by an uprushing noise. Ballistics, white lithic blocks, and dark (not visibly incandescent) juvenile bombs, were ejected to 400-500 m height. Another 3-5 more-dilute, block-free pulses of activity occurred over the next 5 minutes, feeding a high convective plume that traveled SSE. By 1010, several observers along the Bay of Plenty coast had seen the eruption cloud, estimating heights of 1,600-5,000 m. R. Martin and M. Stringfellow (Bay of Plenty Regional Council staff) measured elevation angles of 4.8-5°, yielding column heights of 4,200-4,300 m. Fleming estimated that the initial eruptive pulse rose 1,700-1,800 m before expanding. By 1020, activity had decreased to an ash-free, very weakly convoluting, low eruptive plume. High levels of steam and gas emission continued for 1.5 hours after the explosion, before a dramatic decrease in mid-afternoon.
Voluminous light-brown ash emissions completely obscured the main crater during an afternoon visit on 27 February. On 1 March, thick dark ash emissions were reported by Pollack at 0847. Wade Crater erupted a cloud of pink/brown ash 500-700 m high while TV1 emitted white steam, during a visit at 1125-1515 on 3 March. Nearly continuous ashfall occurred E of the crater. Maximum particle sizes were ~1 mm. Occasional roaring and thumping noises were heard. Fumarole temperatures ranged to >300°C, and analyses of gas samples showed high gas/water ratios, with one sample yielding a strong magmatic signature. The floor of May 91 Crater was nearly flat, reaching 30-35 m below its SE rim. During a 5 March visit at 1020-1605, Wade emitted a weak ash-tinged plume and conspicuously blue fume, accompanied by loud, pulsating degassing noises. Dense ash-free steam from TV1 often obscured half of the 1978/90 Crater Complex. No ash was observed during a 10 March visit, although a steam plume rose to 300-400 m.
Seismicity. B-type seismicity increased from 5-6 events recorded daily 18-24 January to >15/day 1-5 February, while the daily number of recorded A-type earthquakes remained at 2-4. Medium-frequency volcanic tremor began on 6 February. B-type earthquakes declined sharply in number, and were absent from records on 12-17 February. Volcanic tremor amplitude increased after 11 February to a peak on 16 February, coinciding with an 11-hour period (15-16 February) when 4-6 microearthquakes were recorded per minute. Tremor, predominantly medium-frequency (4-7 Hz) with occasional lower frequency signals lasting 1-5 hours, declined to background levels by 21 February. The level of seismic activity remained similar (0-6 A-type and 0-5 B-type events daily) through 3 March, when a swarm of >40 B-type events was recorded.
E-type (eruption) events were recorded every several days during late January-early February [six from 30 January-4 February], were rare in mid-February [one on 14 February], then occurred almost daily from late February through mid-March [20 from 20 February-15 March, with seven on 29 February]. The event that accompanied the production of the large ash-laden column on 20 February was similar to, but larger than, the 17 January seismic event. Of the two predominant varieties of E-type signals during this period, the more common had a low-frequency onset followed by a high-frequency coda; the other was dominantly high-frequency and had a more impulsive onset.
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: I. Nairn and B. Scott, DSIR Rotorua.