Report on White Island (New Zealand) — March 1987
Scientific Event Alert Network Bulletin, vol. 12, no. 3 (March 1987)
Managing Editor: Lindsay McClelland.
White Island (New Zealand) Continued ash emission
Please cite this report as:
Global Volcanism Program, 1987. Report on White Island (New Zealand). In: McClelland, L. (ed.), Scientific Event Alert Network Bulletin, 12:3. Smithsonian Institution. https://doi.org/10.5479/si.GVP.SEAN198703-241040.
37.52°S, 177.18°E; summit elev. 321 m
All times are local (unless otherwise noted)
Several ash eruptions have occurred since geologists visited the crater on 3 February. Emissions occurred both before and after the M 6.3 earthquake on 2 March, and heavy steaming was observed on 3 March.
When geologists returned on 28 March, new ash covered at least the E half of the island to a maximum measured thickness of 20 cm, burying the 25 January block deposit E of 1978 Crater. Ash was predominantly lithic with a minor fresh magmatic component. Congress Vent had enlarged 2-3 times in diameter and expanded W across the floor of 1978 Crater, forming a vertical-walled, flat-floored, circular shaft ~50 m deep. On 28 March, ash and high-pressure gas emission was occurring from a several-meter-wide, sub-horizontal, pipe-like opening in the NW wall. The pipe remained incandescent red during an hour of observation. Temperatures of two fumaroles E of 1978 Crater were measured on 28 March: one had decreased from 343 to 180°C since 3 February and the second had increased from 244 to 280°C.
Significant tremor was recorded on the White Island seismograph 17 February-11 March and 21-22 March. Small to moderate low-frequency volcanic earthquakes (B-type) dominated activity during periods without tremor. A few high-frequency volcano-tectonic events accompanied the B-type events. Small earthquakes, possibly eruption (E-type) were recorded on 20 February, and 23, 26, and 27 March. On 28 March a small E-type earthquake that was followed by 10 minutes of low-amplitude tremor was associated with a moderate ash eruption between 1000 and 1020 during the geologists' visit.
Geologic Background. Uninhabited 2 x 2.4 km White Island, one of New Zealand's most active volcanoes, is the 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 summit crater appears to be breached to the SE, because the shoreline corresponds to the level of several notches in the SE crater wall. Volckner Rocks, four sea stacks that are remnants of a lava dome, lie 5 km NNE. Intermittent moderate phreatomagmatic and strombolian eruptions have occurred throughout the short historical period beginning in 1826, but its activity also forms a prominent part of Maori legends. Formation of many new vents during the 19th and 20th centuries has produced 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.
Information Contacts: I. Nairn, NZGS Rotorua.