Report on Ruapehu (New Zealand) — 29 June-5 July 2016
Smithsonian Institution / US Geological Survey
Weekly Volcanic Activity Report, 29 June-5 July 2016
Managing Editor: Sally Sennert.
Please cite this report as:
Global Volcanism Program, 2016. Report on Ruapehu (New Zealand) (Sennert, S, ed.). Weekly Volcanic Activity Report, 29 June-5 July 2016. Smithsonian Institution and US Geological Survey.
39.28°S, 175.57°E; summit elev. 2797 m
All times are local (unless otherwise noted)
On 5 July GeoNet reported that the elevated activity at Ruapehu had declined; gas emissions returned to baseline levels, volcanic tremor decreased to levels detected in the second half of 2015, and the temperature of the summit Crater Lake had declined from a high of 46 to 23 ºC. The Volcanic Alert Level was lowered to 1 (minor volcanic unrest) and the Aviation Colour Code was lowered to Green.
Geological Summary. Ruapehu, one of New Zealand's most active volcanoes, is a complex stratovolcano constructed during at least four cone-building episodes dating back to about 200,000 years ago. The dominantly andesitic 110 km3 volcanic massif is elongated in a NNE-SSW direction and surrounded by another 100 km3 ring plain of volcaniclastic debris, including the NW-flank Murimoto debris-avalanche deposit. A series of subplinian eruptions took place between about 22,600 and 10,000 years ago, but pyroclastic flows have been infrequent. The broad summait area and flank contain at least six vents active during the Holocene. Frequent mild-to-moderate explosive eruptions have been recorded from the Te Wai a-Moe (Crater Lake) vent, and tephra characteristics suggest that the crater lake may have formed as recently as 3,000 years ago. Lahars resulting from phreatic eruptions at the summit crater lake are a hazard to a ski area on the upper flanks and lower river valleys.