Sep 18 2006, 3:00 pm - Raoul Island Volcano

Observations of earthquake activity close to Raoul Island, the water level and temperature in Green Lake and the degree of hydrothermal activity in the Green Lake crater area are no longer sufficient for signs of volcano unrest. The Scientific Alert Level is therefore reduced to Alert Level 0 (usual dormant or quiescent state).

Following the Raoul Island eruption on March 17 the Scientific Alert Level was increased to 2 (minor eruptive activity). By April 26 there had been no further eruptions and unrest was declining, so the Alert Level was reduced to 1 (signs of unrest).

Since April we have observed a continuing decline in unrest at Raoul Island:

1. There has been no significant nearby earthquake activity (within a distance of ~30 km of Raoul Island).
2. The water level in Green Lake has continued to drop and is now close to the pre-eruption level. On August 27, the lake temperature was 20.3°C, well within the seasonal range.
3. The level of ongoing hydrothermal activity (upwelling in Green Lake, nearby hot pools, and steaming ground) is now commensurate with that expected six months after an eruption like that in March.
4. Chemical analyses of samples recently collected from some of the features are typical of volcano-hydrothermal features in this environment.

The activity has now declined to where it is insufficient to maintain Scientific Alert Level 1 (signs of unrest) and the Alert Level is consequently reduced to 0 (usual dormant or quiescent state).

Steven Sherburn
Duty Volcanologist