Published: Fri Jan 26 2001 1:00 AM
26 January 2001 - Eruption at Kuirau Park, Rotorua
On Friday 26 January about 3.30 to 3.40 PM NZDT, a muddy hot pool 2.5-3m diameter (Spring 721) burst into eruption, generating the largest hydrothermal eruption in Kuirau Park since 1966. These notes and comments are based on a visit on Friday evening, and again on Monday.
The eruption of blocks and mud was to about 100 metres height and produced a thick carpet of blocks and mud to the east, extending over 120m from the vent. The eruption was very directional. Very little ejecta is distributed to the west (maybe less than 30m from the vent). Blocks up to about 1 m diameter were projected over 50m from the vent, while blocks around 0.1 m or less diameter landed over 100m away. The crater formed is about 10 - 12m in diameter.
It was possible to recognise 4 eruption deposits on Friday evening, and this may give some insight into the eruption. These are:
The ballistic blocks appear to be present through almost all of the deposit. That is there are blocks that are clearly on top of all the muds, while other blocks are coated by mud with shelter zones on their leeward sides. Based on first impressions the dark grey liquid muds were erupted first, to the west. Then the main phase of the eruption commenced, ejecting muds and ballistic blocks to the east; this was followed by a smaller mud rich phase (no relationship with ballistics was ascertained), which was followed by a distinct ballistic shower, numerous centimetre-sized blocks are impacted into all the muds. The ballistics extend well beyond the muds to the north-east and it is not clear from first impressions the exact relationship to the muds.
Fallout of the mud layers has loaded all the trees and shrubs within the ejecta apron bending and breaking many of them.
B. J. Scott
Volcano Surveillance Co-ordinator