BRADES, Montserrat (GIU) -- The Scientific Advisory Committee (SAC) met for its annual session from October 22 to 24 at the Montserrat Volcano Observatory (MVO).
During the meeting (SAC 17), SAC members and scientists from MVO and the Seismic Research Centre discussed monitoring data and recent activity of Soufriere Hills Volcano, including the 22-23 March 2012 event.
According to Sonja Melander, outreach officer for the MVO, “A hazard assessment was conducted to determine the probability of volcanic hazards affecting areas around the Soufriere Hills Volcano. This was done by applying the SAC’s usual method of quantitative risk assessment using expert opinions on the probability of various scenarios occurring. The expert opinions are collected and combined using a formal method called expert elicitation.”
The SAC 17 team released their preliminary report and met with community members on Wednesday evening in Salem to discuss it.
The full text of the report follows:
“During the past year there were two very brief episodes of ash venting and increased gas release, on 23 March and 8 August 2012. Seismic events that occurred on 23 March included some of the largest earthquakes caused by the volcano since the eruption began.
“These two episodes did not lead to renewed lava production and it is now 32 months since the last extrusive phase, easily the longest such pause in the eruption. A few small pyroclastic flows, caused by minor collapses of the dome towards Tar River and Gages Valley, have occurred and hot gases have continued to escape through the dome, which remains a large hot mass liable to collapse.
“MVO’s monitoring of ground motion, gas emission and seismicity is consistent with continuing activity of the volcanic system at depth. The inflation of the island, seen throughout this pause, continues, though at a lower rate in recent months. The rate of sulphur dioxide emission is steady but lower than the long-term rate. In late August and September, small, low-frequency earthquakes, possibly indicative of magma motion, were seen for the first time since lava extrusion ceased in 2010.
“The volcano remains capable of renewed activity but there are no immediate precursory signs of this.
“The hazard from pyroclastic flows and surges in the lower Belham Valley, which had declined in our last assessment, remains at a similar level to that of one year ago. Pyroclastic flows can occur at any time without warning and consequently the threat to people working in or visiting Plymouth remains,” the report reads.