La Soufrière Scientific Update: Volcano Emitting 461 Tons Of SO2 Per Day

View of the La Soufrière Volcano and St. Vincent’s Leeward coastline. (Paul Cole, University of Plymouth)

Present La Soufrière Alert Level:ORANGEThere is a highly elevated level of seismic and/or fumarolic activity or other unusual activity. An eruption may begin with less than twenty-four hours’ notice.

According to the latest scientific advisory from the University of the West Indies Seismic Research Centre (UWI SRC), seismic activity at La Soufrière, St Vincent has remained low since the tremor associated with the explosion and ash venting around noon on 22nd April. In the last 24 hours, only a few long-period and volcano-tectonic earthquakes have been recorded.

Volcano-tectonic (VT) earthquakes represent the brittle failure of rock – similar to that of tectonic quakes that occur along tectonic faultsLong-period (LP) earthquakes are caused by cracks resonating as magma and gases move toward the surface. As the name suggests, a hybrid earthquake is somewhat a mixture between a VT and an LP. They tend to have impulsive starts but also contain a significant amount of low-frequency signals. They are thought to represent magma making its way to the surface at shallow depths and are often associated with periods of rapid dome growth.

Persistent steaming is observable from the observatory once the cloud cover is high enough and thermal anomalies continue to be detected by the NASA FIRMS alert system. These have been persistent since the April 22nd explosion. Thermal anomalies indicate that there is a source of heat within the crater and are most likely from a small body of magma left over, close to the floor of the summit crater.

Measurements of the sulphur dioxide (SO2) flux were done yesterday (20th May) and yielded an average SO2 flux of 461 tons per day. SO2 can be an indicator that fresh magma from a deeper source is being degassed.

Volcanic Hazard Map for the La Soufrière Volcano, St. Vincent (UWI SRC/NEMO)
Volcanic Hazard Map for the La Soufrière Volcano, St. Vincent (UWI SRC/NEMO)

The alert level is orange. The volcano continues to be in a state of unrest. Escalation in activity can still take place with little or no warning. Caution should be taken in crossing river valleys on the volcano due to the increased risk of lahars (mudflows) during periods of rainfall on the volcano.

For more information on coping and handling volcanic ash, the UWI SRC is directing people to the International Volcanic Hazard Health Network for volcanic ash resources.

Official information will originate from St. Vincent and the Grenadines National Emergency Management Organization and the University of the West Indies Seismic Research Center.

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