Oct 4 2011, 10:00 am - Ruapehu Volcano

The annual test of the Ruapehu Eruption Detection System was successfully conducted on September 29. Currently the temperature of the Crater Lake at Ruapehu is 17-20 °C, while hydrogen sulphide gas flux has increased and has recently been noted by people on the volcano.

On September 29 an annual test of the Eruption Detection System (EDS) was conducted by the Department of Conservation, GNS Science and Ruapehu Alpine Lifts (RAL). The system was found to be functioning well, with RAL staff responding quickly and effectively. As with previous tests the vast majority of members of the public responded appropriately and quickly got to higher ground above the bottom of the valleys safe from possible lahars.

The temperature of the lake peaked at 41 °C on March 1 and fluctuated around 38-39 °C during March before declining through April-May, rising slightly in June and then declining again. Over the past seven weeks, the Crater Lake temperature has been steady at around 17-20 °C. Crater Lake was visited in September 29 for sampling and the temperature was 17.6 °C.

In recent weeks the amount of hydrogen sulphide gas from the lake has increased, and this has often been reported by the public on the mountain. This is consistent with a cooler lake, when the heat flow is partially sealed and the processes tend to produce more sulphur gas.

GNS Science volcanologists continue to monitor this and other volcanoes. Ruapehu remains an active volcano and future eruptions may occur with little or no warning.

The Volcanic Alert Level remains at Level 1 (departure from typical background surface activity, signs of unrest) and the Volcanic Aviation Colour Code is Green (volcano is in normal, non-eruptive
state).

Brad Scott
Volcano Surveillance Coordinator