La Soufrière, St. Vincent – SCIENTIFIC UPDATE 22/04/21 6:00 PM
1. Seismic activity at La Soufrière continued the pattern established after the explosive activity on 18 April.
2. Small long-period and hybrid earthquakes continued to be recorded, with their rate of occurrence gradually increasing.
3. High-level seismic tremor started at 11:09 am, generated by explosive activity, and lasted for about 20 minutes.
4. A vertical explosive eruption plume rose slowly above the crater eventually reaching a height of about 8 km.
5. During the initial stages of the 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.
6. Tremor continued, at a lower level, for the next two hours as La Soufrière continued to vent ash.
7. 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
8. 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).
9. 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.
10. Explosions with accompanying ashfall, of similar or larger size, can occur with little or no warning impacting St. Vincent and neighbouring islands.
11. The volcano is at alert level Red.
12. Visit the International Volcanic Hazard Health Network for volcanic ash information and resources:
Photo caption: Time-lapse video of the explosion on 22/04/21 from the camera at Belmont Observatory, St. Vincent. Note pyroclastic density current on western flank early on. The flow took 5 minutes to reach the sea (average speed 33km/he).
Credit: The UWI Seismic Research Centre
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NEMO St. Vincent and the Grenadines
API – The Agency For Public Information: St. Vincent and the Grenadines
Department of Emergency Management
NEMO Saint Lucia
CDEMA – Caribbean Disaster Emergency Management Agency