On 15 September GeoNet reported continuing but low levels of activity at Whakaari/White Island. Over the previous six weeks the team conducted three flights to measure gas emissions and one for visual observations. The data show that shallow magma was degassing at a high rate through an open, unobstructed system. Temperatures at the gas vents remained high (around 440 degrees Celsius), though that is 100 degrees less than when measured in July. Some of the gas vents had become larger and water had ponded on the crater floor. Continuing subsidence of the active vent areas and the S and W parts of Main Crater wall was indicated by deformation measurements. Volcanic tremor had been generally low, except for a short period in early August. The Volcanic Alert Level was lowered to 1 and the Aviation Color Code remained at Yellow.

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