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Report on Whakaari/White Island (New Zealand) — October 1989

Whakaari/White Island

Scientific Event Alert Network Bulletin, vol. 14, no. 10 (October 1989)
Managing Editor: Lindsay McClelland.

Whakaari/White Island (New Zealand) Tephra ejections; possible new vent

Please cite this report as:

Global Volcanism Program, 1989. Report on Whakaari/White Island (New Zealand) (McClelland, L., ed.). Scientific Event Alert Network Bulletin, 14:10. Smithsonian Institution. https://doi.org/10.5479/si.GVP.SEAN198910-241040

Whakaari/White Island

New Zealand

37.52°S, 177.18°E; summit elev. 294 m

All times are local (unless otherwise noted)

Phreatic block and ash ejections have continued since ... fieldwork on 31 July (SEAN 14:07). Small explosion-type earthquakes recorded 20 and 29 August, and periods of high-amplitude tremor in early-mid-September probably marked ejections of new lithic blocks, lapilli, and ash found on the crater floor in October. On 11 September, the crew of a fishing boat reported two dark mushroom clouds rising 500 m above the summit. This eruption coincided with low-amplitude tremor, but no discrete earthquakes were recorded.

When geologists visited the crater 11 October, new, gray, fine ash covered the main crater floor. Since 31 July, 280 mm of new tephra had accumulated on 1978 Crater rim, and 115 mm at a site roughly 200 m to the SE. No fresh magma was detected. Impact crater shapes suggested that blocks ejected to ~150 m E and SE of 1978 Crater had originated from a new vent within Congress Crater. This crater, previously funnel-shaped with walls dipping steeply into Hitchhiker vent, had deepened since July and had a flat floor. Gullies deepened to the E (away from Hitchhiker), suggesting that a new vent was obscured from view beneath the E crater wall.

Donald Duck crater was slightly enlarged and emitted clouds of light yellow gas, the first seen at White Island. The crater rim was lightly dusted with fine (<0.5 mm) bubble walls and spherules of yellow sulfur. Ash from the vent had largely buried the June 1989 block field as far as 100 m SE. R.F. Crater appeared unchanged since 31 July, with a near-flat floor and black, fountaining, muddy water, briefly visible through vapor clouds.

Background seismicity was steady in August with as many as 7 A-type and 16 B-type events/day. On 2 September a sequence of >100 high-frequency events (M < 3.5) were located ~13 km W of White Island at l-2 km depth. Medium-frequency tremor was recorded throughout September. By late September, seismicity had decreased to <3 A- or B-type events/day, and continued at a low level throughout October.

Deflation of the Donald Mound-1978 Crater area, almost continuous since mid-1987, has apparently resumed after a possible brief pause in July. Fumarole temperatures and gas emission had generally decreased, with only one fumarole (Noisy Nellie) showing high-pressure discharge of clear dry gas.

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, P. Otway, and B. Scott, NZGS Rotorua.