GeoNet reported that the deadly 9 December eruption at White island modified the active crater area. The basin previously containing a hot acidic lake was mostly filled by debris with numerous, isolated ponds after the event. During overflights observers identified three main vents within a 100-square-meter area. Volcanic tremor significantly increased at around 0400 on 11 December and was accompanied by vigorous steaming and localized mud jetting from the active vent area. By the early evening tremor was at the highest level recorded since the 2016 eruption. On 12 December the Volcanic Alert Level was lowered to 2 (since no more eruptions had occurred since 9 December), though the Aviation Color Code remained at Orange. Later that day tremor levels decreased but remained very high compared to normal levels. Energetic steam-and-mud bursts continued from the active vent area. Gas emissions had increased compared to 10 December measurements. Tremor levels continued to decline during 12-13 December and then significantly dropped later on 13 December. During an overflight on 13 December observers noted small-scale gas jetting and steam bursts from the active vents. High heat flow was confirmed by a glow emanating from the vent area in overnight webcam images during 12-15 December; high-temperature (more than 200 degrees Celsius) volcanic gas was being emitted at a high rate when observed during an overflight on 15 December. GeoNet noted that data from various measurements suggested a magma source not far below the surface, possibly as shallow as tens of meters deep. According to the New Zealand Police the death toll from the 9 December eruption was 15, with two people still missing.

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.

Sources: GeoNet, New Zealand Police