Report on Rotorua (New Zealand) — 31 January-6 February 2001
Smithsonian / US Geological Survey Weekly Volcanic Activity Report,
31 January-6 February 2001
Managing Editor: Gari Mayberry
Please cite this report as:
Global Volcanism Program, 2001. Report on Rotorua (New Zealand). In: Mayberry, G (ed.), Weekly Volcanic Activity Report, 31 January-6 February 2001. Smithsonian Institution and US Geological Survey.
38.08°S, 176.27°E; summit elev. 757 m
All times are local (unless otherwise noted)
The IGNS wrote, "On Friday 26 January at about 1530 to 1540, a muddy hot pool (Spring 721) erupted violently in the largest hydrothermal eruption in Kuirau Park since 1966. Blocks of rock debris and mud were blasted to a height of about 100 m. Blocks up to a meter in diameter were blown over 50 m from the vent, with fragments up to 10 cm landing over 100 m away. The steam cloud from the eruption was visible several kilometers away." The eruption deposited debris 120 m to the E of the vent and ~30 m to the W. The original hot pool was about 3 meters in diameter; the newly formed crater was about 10-12 m in diameter.
Geological Summary. The 22-km-wide Rotorua caldera is the NW-most caldera of the Taupo volcanic zone. It is the only single-event caldera in the Taupo Volcanic Zone and was formed about 220,000 years ago following eruption of the more than 340 km3 rhyolitic Mamaku Ignimbrite. Although caldera collapse occurred in a single event, the process was complex and involved multiple collapse blocks. The major city of Rotorua lies at the south end of the lake that fills much of the caldera. Post-collapse eruptive activity, which ceased during the Pleistocene, was restricted to lava dome extrusion without major explosive activity. The youngest activity consisted of the eruption of three lava domes less than 25,000 years ago. The major thermal areas of Takeke, Tikitere, Lake Rotokawa, and Rotorua-Whakarewarewa are located within the caldera or outside its rim, and the city of Rotorua lies within and adjacent to active geothermal fields.