Report on White Island (New Zealand) — 9 December-15 December 2015
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 9 December-15 December 2015
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2015. Report on White Island (New Zealand). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 9 December-15 December 2015. Smithsonian Institution and US Geological Survey.
37.52°S, 177.18°E; summit elev. 321 m
All times are local (unless otherwise noted)
On 10 December the GeoNet Data Centre reported that minor unrest continued at White Island based on results from recent routine monitoring. During the previous week scientists visited the island and detected continuing (over the previous three months) ground deformation and a small increase in CO2 soil gas flux. Small temperature increases were also measured at the hottest fumarole and from the lake water. Volcanic tremor levels fluctuated, but overall showed a consistent rise over the last two months; they remained below those observed in 2012 when unrest was stronger and small eruptions occurred. Airborne gas measurements revealed an increase in CO2 and a decrease in SO2 gas fluxes. The Volcanic Alert Level remained at 1 and the Aviation Colour Code remained Green.
Geologic Background. Uninhabited 2 x 2.4 km White Island, one of New Zealand's most active volcanoes, is the 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 summit crater appears to be breached to the SE, because the shoreline corresponds to the level of several notches in the SE crater wall. Volckner Rocks, four sea stacks that are remnants of a lava dome, lie 5 km NNE. Intermittent moderate phreatomagmatic and strombolian eruptions have occurred throughout the short historical period beginning in 1826, but its activity also forms a prominent part of Maori legends. Formation of many new vents during the 19th and 20th centuries has produced 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.