On 20 December, GeoNet Data Centre reported that the spiny lava dome at White Island had not changed during the previous 10 days. No changes to the lava dome were noted when scientists compared photos taken on 19 December to previous ones, but several small lakes occupied parts of where a large lake was before August. The highest temperature reading from the lava dome was 187 degrees Celsius, the hot lake to the S was at least 71 degrees and upwelling strongly, and the cool lake on the N side of the dome was 35 degrees. The Alert Level remained at 2 (on a scale of 0-5), and the Aviation Colour Code remained at Orange (second highest on a four-color scale).

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.

Source: GeoNet