La Soufrière’s 32nd Explosive Eruption Included A Pyroclastic Flow

The La Soufrière Volcano erupts on April 22nd, 2021 as seen from the Belmont Observatory. (Dr. Ilias Papadopoulos, UWI SRC)

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), during the initial stages of this morning’s explosion, a base surge (pyroclastic density current, PDC) was seen moving down the western flank of the volcano. PDCs are hot (200°C-700°C), ground-hugging flows of ash and debris.

Seismic activity at La Soufrière continued the pattern established after the explosive activity on April 18th. Small long-period and hybrid earthquakes continued to be recorded, with their rate of occurrence gradually increasing. The high-level seismic tremor started at 11:09 am, generated by explosive activity, and lasted for about 20 minutes. Tremor continued, at a lower level, for the next two hours as La Soufrière continued to vent ash.

A vertical explosive eruption plume rose slowly above the crater eventually reaching a height of about 8 km.

Since the initial depressurization noted immediately following the April 9 explosive phase, the continuous GPS network has recorded a decrease in the overall rates of horizontal and vertical movement. The continuous GPS (Global Positioning System) network is used to track changes in ground shape on and around the volcano. As magma moves beneath the volcano, changes in pressure cause the volcano to change shape (inflate/deflate).

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. Its pattern of seismic activity over the last few days is typical of the growth and destruction of lava domes. 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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