During 2 December fieldwork, geologists observed continued emission of fine red ash from Hitchhiker vent, similar to October and November. Near the vent, ~55 mm of ash had accumulated since 16 November, but only 1-2 mm of new ash had been deposited ~250 m to the SE. No fresh magma was detected in the ash; vesicular scoria fragments were last noted on 14 October. The new fumarole on the W floor of 1978 crater, first seen on 16 November, was emitting a jet of high-pressure white vapor at about a 45° angle. Small fumaroles were also noted for the first time on the floor of the western subcrater, below the 1914 landslide scar.

A deformation survey showed that subsidence had occurred in a broad zone, centered roughly 150 m E of Hitchhiker vent, since the previous measurements on 15 June. Magnetic data showed positive changes exceeding 200 nT in the same general area, interpreted to show significant cooling centered at 100-150 m depth. Temperatures of fumaroles in and near the area of subsidence had dropped substantially since June (Blue Duck, 775°C in June/565° in December; Donald Mound, 420/354°; Noisy Nellie, 280/226°). Seismicity has remained similar since mid-October, characterized by medium- to high-frequency volcanic tremor and microearthquakes. Maximum daily numbers of A-type (4) and B-type (23) events were associated with three small explosion earthquakes on 17-18 October.

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: J. Cole, Univ of Canterbury, Christchurch; I. Nairn, B. Scott, P. Otway, and D. Christoffel, NZGS Rotorua; B. Christenson, DSIR Chemistry, Wairakei.