GeoNet reported that minor ash emissions from the active vent area in Whakaari/White Island’s crater were visible in webcam images on 18 September. The Aviation Color Code was raised to Orange; the Volcanic Alert Level remained at 2. Minor light brown ash emissions were visible through the day, and rose no higher than 600 m above the volcano. Ash emissions were not visible beyond the island, but a steam plume was seen from the Bay of Plenty coast. A strong sulfur dioxide signal associated with the emissions was identified in satellite images that same day. One of the seismic stations began working again on 19 September and showed typical low-level seismicity, consistent with no visible ash emissions. GeoNet was unable to accurately characterize the ash emissions due to the lack of data from inoperable instruments and the semi-operational webcam on the island. They noted that the most likely cause was a small amount of magma moving into the shallow part of the volcano.

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