Allis, R.G. 1984 The 9 April, 1983 steam eruption at Craters of the Moon thermal area, Wairakei. : . Report / Geophysics Division 196 25 p
Abstract: A steam eruption occurred at Craters of the Moon thermal area, Wairakei, on April 9, 1983. The eruption was the fourth in a series of eruptions from one crater (G) since 1978. At the height of the eruption, pumice clasts were thrown up to 60 m above the ground surface, and fine ejecta was deposited up to 120 m from the crater. Between 1000 and 2000 cubic m of material was ejected, with most of this originating from the crater floor. The maximum depth of the crater is now about 15 m, making it the deepest crater in the Craters of the Moon thermal area. Most of the ejecta was probably erupted during a three hour period, although an intense steam discharge continued afterwards. The eruption fluid appeared to be dry steam discharging into the floor of the crater. The most likely cause of the eruption is an increased steam flow into the bottom of the crater G prior to the eruption. This would have caused an increase in the subsurface steam pressure, until the load pressure was exceeded and the eruption commenced. Barometric pressure, earthquakes, and self-sealing mechanisms were probably not the cause of the eruption. However this, and several other eruptions in the Taupo area, have occurred after several months of abnormally dry weather have been terminated by several days or weeks of wet weather. Possibly an increase in the near-surface soil saturation influenced the time of the eruption
