Report on Whakaari/White Island (New Zealand) — 1 August-7 August 2012
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 1 August-7 August 2012
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2012. Report on Whakaari/White Island (New Zealand). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 1 August-7 August 2012. Smithsonian Institution and US Geological Survey.
37.52°S, 177.18°E; summit elev. 294 m
All times are local (unless otherwise noted)
The GeoNet Data Centre reported that during 2011 and early 2012 White Island Crater Lake slowly evaporated, exposed steam vents, and formed two large muddy pools. Sometime between 27 July and 28 July, the lake level quickly rose 3-5 m. Vigorous gas-and-steam emissions through the new lake were observed from the air. Gas emission measurements on 1 August showed that sulfur dioxide had increased during the previous three months but carbon dioxide levels did not change.
Since early July there had been intermittent periods of volcanic tremor, including several hours early on 28 July and during 30-31 July. GeoNet noted that tremor was not uncommon at White Island but earlier in 2012 it had been at very low levels. A recent ground survey showed that the main crater floor was no longer subsiding and may have been slowly rising. The Alert Level remained at Level 1 (on a scale of 0-5), indicating signs of volcano unrest. The Aviation Colour Code increased to Yellow (second lowest on a four-color scale).
A particularly strong period of volcanic tremor was recorded during 4-5 August, and ended with an earthquake at 0454. Web camera images from between 0454 and 0457 showed an eruption from Crater Lake. This was the first time ash has been produced from White Island since 2000. [Correction: The last eruption occurred in 2001.] The Alert Level was raised to 2 and the Aviation Colour Code was raised to Orange. A steam plume rose from the crater on 5 August. Around 2330 on 7 August volcanic tremor sharply decreased to levels detected prior to the current episode of unrest. A few hours after this drop, the color of the plume changed from white to light brown, indicating more ash in the plume. Visual observations in the past few days showed that a small cone was building in the lake, around the main area of degassing.
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.