Author Topic: GNS alert bulletin: May 13 2008, 11:00 am - Ruapehu Volcano  (Read 881 times)

GNS alert bulletin: May 13 2008, 11:00 am - Ruapehu Volcano

GNS scientists are continuing to monitor Ruapehu. Elevated gas output, high lake temperatures and volcanic tremor continue to indicate elevated unrest at Ruapehu. It remains unclear if this is a sign of further eruptions in the near future. The volcano last erupted on September 25 2007 and the Alert Level remains at Level 1.

Data from the airborne gas measurements, seismic activity and Crater Lake temperature have continued to show variations since the September 25 2007 eruption.

The airborne gas plume measurements show the SO2 flux has gradually increased since last years eruption and the CO2 flux has varied. However the fluxes of both SO2 and CO2 gases have shown significant increases in our latest measurements (April 4 and May 7), being about ten times above the typical background.

The Crater Lake temperature has remained elevated and fluctuates between 34 and 36.8 C. The latest measurement was 34.4 C (April 26). Sustained heat from depth is required to keep the temperature this high for this length of time. It is believed that the source of this heat is magma within the volcano conduit. This magma is also producing the higher than normal gas flow and chemical changes.

The slight increase in the background level of volcanic tremor has continued, as have some short periods of stronger volcanic tremor. However volcanic tremor and changes in the level of tremor are very common at Ruapehu.

These observations are consistent with the volcano-hydrothermal system responding to recent eruptions and ongoing interaction with magma in the volcano conduit. The volcano remains in a status of unrest and the possibility of further activity remains at the volcano. If further eruptions occur, they may occur without warning. GNS Science will be making further observations this week.

The Alert Level remains at Level 1 (departure from typical background surface activity, signs of unrest) and will continue to be re-assessed regularly.
Brad Scott
Volcano Surveillance Co-ordinator