La Soufrière Scientific Update: Multiple Lahars Detected While Volcano Remains In A State Of Unrest

Lahar spotted in Wallilabou Valley, St Vincent as rainfall remobilizes the La Soufrière Volcano ash. (Paul Cole – Plymouth University, May 3rd 2021)

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), the seismic network recorded signals from multiple lahars for a period of about six hours starting around 9 AM. These lahars most likely took place in all the valleys around La Soufrière. The most intense lahars occurred between 11:00 AM and 12:00 PM based on the UWI SRC’s advisory.

The SRC says 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, hybrid and volcano-tectonic earthquakes have been recorded and there was no further tremor. The volcano continues to be in a state of unrest.

Volcano-tectonic (VT) earthquakes represent the brittle failure of rock – similar to that of tectonic quakes that occur along tectonic faults. Long-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.

Measurements of the Sulphur Dioxide (SO2) flux at La Soufrière were carried out with the help of the coastguard off the west coast yesterday. Measurements yielded an average SO2 flux of 1036 tons per day.

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)

According to the UWI SRC, the volcano continues to erupt. Explosions with accompanying ashfall, similar to or larger, can occur with little or no warning impacting St Vincent and neighboring islands.

The alert level remains red. The National Emergency Operations Center continues to be fully functional operating on a twenty-four-hour, around-the-clock basis. NEMO will continue to provide regular updates as they continue to monitor the Volcano.

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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