Report on White Island (New Zealand) — 3 July-9 July 2013
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 3 July-9 July 2013
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2013. Report on White Island (New Zealand). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 3 July-9 July 2013. Smithsonian Institution and US Geological Survey.
37.52°S, 177.18°E; summit elev. 321 m
All times are local (unless otherwise noted)
On 9 July GeoNet Data Centre reported that over the previous few weeks very small volcanic earthquakes occurred at White Island approximately every 70 seconds; the hundreds of small bursts created a unique daily pattern on the seismograph. The pattern of the volcanic earthquakes changed over time; the tremor bursts changed in size and frequency and sometimes merged into continuous tremor. Neither increased gas emissions nor changes in the hot lake and recently-erupted lava dome suggested that the process creating the earthquakes, possibly fluid moving through a crack, was occurring at depth. The Volcano Alert Level remained at 1 (on a scale of 0-5) and the Aviation Colour Code remained at Green (on a four-color scale).
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.