Report on Whakaari/White Island (New Zealand) — 26 June-2 July 2019
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 26 June-2 July 2019
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2019. Report on Whakaari/White Island (New Zealand). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 26 June-2 July 2019. Smithsonian Institution and US Geological Survey.
37.52°S, 177.18°E; summit elev. 294 m
All times are local (unless otherwise noted)
GeoNet reported that earthquake swarms at White Island were recorded in May and beginning on 20 June. Even though both swarms were interpreted as fault activity and no unusual volcanic activity was observed, GeoNet increased monitoring of the volcano. Earthquake swarms can increase the likelihood of landslides.
A gas flight was conducted on 26 June because of the heightened monitoring and measurements were found to be 1,886 tons per day, three times the previous values measured in May. This was also the highest value recorded since 2013 and the second highest since regular measurements began in 2003. The Volcanic Alert Level was raised to 2 (on a scale of 0-5) and the Aviation Color Code was raised to Yellow. Two more gas flights found lower emissions values; sulfur dioxide flux was 880 tons per day on 28 June and 693 tons per day on 29 June. In addition, new measurements found no changes to fumarolic temperatures and modeling of ground deformation suggested the ongoing earthquake swarm was tectonic and did not reflect increased volcanic activity. The Volcanic Alert Level was lowered back to 1, with no change to the Aviation Color Code.
Geologic Background. 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.