Jun 28 1995 - Ruapehu Volcano

The temperature of Ruapehu Crater Lake at depth has apparently remained above the 47°C recording limit of the ARGOS satellite recording system since the last Science Alert Bulletin on 27 April 1995. A lake surface temperature reading of 38 °C was obtained by a Department of Conservation staff member on June 17, but the lake temperature has not been measured directly since then. Starting at approximately 14:00 on June 26 and finishing at approximately 13:40 on June 27, an episode of intense volcanic tremor was recorded on the Dome seismometer (near Crater Lake), as well as at the Chateau and Ngauruhoe instruments. However, there has been no significant increase in the acoustic noise levels recorded by the ARGOS system in the Crater Lake. The tremor strength is such that further heating of the lake may occur in the near future, and we consider that the volcano remains capable of eruptive activity at any time. Further significant episodes in tremor or increases in acoustic noise level will result in further Science Alert Bulletins being issued.

Alert Status

Based on the above information we recommend that the Alert Level at Ruapehu volcano be maintained at Level 2, and recommend that restrictions on access to Crater Lake Basin be maintained.

C.J.N. Wilson
Volcanology Programme Leader