Report on Tongariro (New Zealand) — 3 December-9 December 2008
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 3 December-9 December 2008
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2008. Report on Tongariro (New Zealand). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 3 December-9 December 2008. Smithsonian Institution and US Geological Survey.
39.157°S, 175.632°E; summit elev. 1978 m
All times are local (unless otherwise noted)
The Alert Level for Tongariro was lowered to 0 (typical background activity) on 2 December. The number of volcanic earthquakes declined to background levels since mid-2008. In addition, regular measurements of volcanic gas levels and the temperature of the summit gas vent showed no changes over the previous two and a half years.
Geologic Background. Tongariro is a large andesitic volcanic massif, located immediately NE of Ruapehu volcano, that is composed of more than a dozen composite cones constructed over a period of 275,000 years. Vents along a NE-trending zone extending from Saddle Cone (below Ruapehu volcano) to Te Mari crater (including vents at the present-day location of Ngauruhoe) were active during several hundred years around 10,000 years ago, producing the largest known eruptions at the Tongariro complex during the Holocene. North Crater stratovolcano, one of the largest features of the massif, is truncated by a broad, shallow crater filled by a solidified lava lake that is cut on the NW side by a small explosion crater. The youngest cone of the complex, Ngauruhoe, has grown to become the highest peak of the massif since its birth about 2500 years ago. The symmetrical, steep-sided Ngauruhoe, along with its neighbor Ruapehu to the south, have been New Zealand's most active volcanoes during historical time.