alert bulletin: Oct 9 2007, 10:00 am - Ruapehu Volcano

Science Alert Bulletin RUA-07/08 - Ruapehu volcanic activity update: Alert Level reduced to Level 1

GNS scientists have continued to monitor the activity at Ruapehu since the eruption on September 25. As no further eruptions have occurred since then the Alert Level is now being lowered to Level 1.

Data from Crater Lake sampling and airborne surveys to analyse gases in the volcanic plume have shown a response to the eruption on September 25, as has the seismic activity recorded by the GeoNet equipment.

The Crater Lake temperature has risen slightly (13 to 19 °C), the SO₂ flux has shown no change, while the CO₂ flux has increased slightly. The lake chemistry shows a slight increase in magnesium, while there is little change in chloride concentrations. There has been a small increase in the background level of volcanic tremor, but almost no volcanic earthquakes. These observations are consistent with the volcano's hydrothermal system responding to an eruption through it. The hydrothermal system has not stabilised as yet and the possibility of further activity remains at the volcano. Any further eruptions may also occur without warning.

The Department of Conservation in conjunction with GNS Science has developed guidelines for access to the mountain and maps showing areas at risk from volcanic activity. Visitors are encouraged to follow these. View Map Here

The Alert Level is now reduced to Level 1 (departure from typical background surface activity, signs of unrest) and will continue to be re-assessed regularly.

Brad Scott
Duty Volcanologist