Nov 15 2004, 2:00 pm - Ruapehu Volcano

Moderate volcanic tremor recommenced at Ruapehu on November 3, and continues at varying levels. Volcanic tremor is not unusual at Ruapehu, but this is the strongest since April - May 2003. Since March 2004 the lake temperature has fallen from a high of 35°C, to below 16°C by August. The Crater Lake was visited on November 13 and the temperature had risen to 18.9°C, the first sign of an increase since August. A slight increase in the area of grey discoloured water over the active vents was also observed, suggesting convection is occurring but the lake is not fully mixed.

Ruapehu Crater Lake will often warm following periods of volcanic tremor, and the present observations are following that trend. Heating cycles are common at Ruapehu, occurring every 9 - 12 months and lasting 3 - 4 months. As the lake warms, steam plumes may be observed under favourable conditions.

As there is no change in activity the Alert Level for Ruapehu remains at Alert Level 1.

Brad Scott
Volcano Surveillance Co-ordinator