On 12 December GeoNet reported that larger steam-and-gas plumes were recently being emitted from Whakaari/White Island. During an overflight on 5 December scientists observed a vivid white steam-and-gas plume rising from the vent area with no detected ash. There were no new ash deposits in the crater or on the island, and the plume was relatively cool at 150 degrees Celsius. During 1500-1800 on 10 December a larger steam-and-gas plume was visible in images from webcams located at Whakatane and Te Kaha, as well as in satellite images. Additional larger plumes were sometimes visible when weather conditions allowed during 10-12 December. Sulfur dioxide emissions detected by satellite had generally increased during the previous two weeks. During a gas monitoring overflight on 14 December scientists observed the emissions changing to include more ash content. The gas data showed increases in sulfur dioxide and carbon dioxide emissions, possibly indicating the start of a new eruptive episode. On 16 December the Aviation Color Code was raised to Orange (the second highest level on a four-color scale). The Volcanic Alert Level remained at 2 (on a scale of 0-5). GeoNet stated that the Alert Levels were reflective of the current level of activity, but there was uncertainty due to the current lack of consistent, usable, real-time monitoring data.

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