A NZGS team visited White Island on 28 May. The active vent, in the smaller SE section of the dumbbell-shaped 1978 Crater, emitted a weakly convoluting, ash-poor eruption column, punctuated by occasional pulses of more vigorous ash ejection. Bombs up to 1 m in diameter were infrequently thrown above the vent, breaking open to reveal incandescent interiors. Sharp detonations were heard as often as every 3-5 seconds, but appeared to be related to gas release, not bomb ejection. The bottom of the steep-sided active vent was not visible, but it appeared to be more than 100 m deep. Fumarolic activity continued at several locations, but appeared to be at lower pressures and temperatures than during other recent visits. The temperature at one fumarole a few hundred m E of 1978 Crater had decreased to 410°C from 535°C on 25 January.

The entire main crater floor was covered by red tephra from the April-May eruptions. A pit dug 5 m from the edge of 1978 Crater (but not along the E-W axis of heaviest deposition) revealed 230 mm of April-May tephra overlying 110 mm of older compacted gray ash. Large ejecta were abundant within about 300 m of the vent, forming a discontinuous layer along the axis of deposition. Most of the large ejecta were low-density, dark brown, flattened or fusiform bombs with a slaggy breadcrust surface and cowdung or ribbon shapes. Bomb sizes were commonly ~0.3 m, but reached 2 m in longest dimension. Some apparently fresh, dense, and vesiculated glassy bombs were also observed. Large dense blocks of altered lithic material were often associated with impact craters.

A levelling survey over the main crater floor showed deflation of both 1978 Crater (at the W end of the main crater) and the SE portion of the main crater, relative to the NE section. This represents a continuation of the trend seen between the surveys of 7 December 1978 and 21-22 April 1979.

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: B. Houghton and I. Nairn, NZGS, Rotorua.