Powerful explosive eruption at La Soufriere volcano, ash to 12 km (40 000 feet) a.s.l., St. Vincent and the Grenadines

Powerful explosive eruption at La Soufriere volcano, ash to 12 km (40 000 feet) a.s.l., St. Vincent and the Grenadines

A powerful explosive eruption took place at La Soufriere volcano, St. Vincent and the Grenadines at 12:41 UTC (08:41 LT) on April 9, 2021, producing an ash column that rose up to 12 km (40 000 feet) above sea level. This is a culmination of the seismic activity that began on April 8.

Ashfall was reported on the flanks of the volcano and surrounding communities, including Chateaubelair and Petite Bordel.

Ash cloud to 3.3 km (11 100 feet) a.s.l. is moving WNW and to 12.2 km (40 000 feet) a.s.l. to ENE, the Washington VAAC said at 18:11 UTC.

The explosive eruption is likely to continue for days and possibly weeks.

Areas to be affected by pyroclastic flows and surges will be communities in the red and orange zones, UWI-SRC volcanologists said at a press conference held at 15:00 UTC today.

Communities across mainland St. Vincent will experience varying degrees of ashfall. The Grenadines may also be affected.

The Barbados Met Servies reported that light ashfall can be expected in approximately two hours - around 21:00 UTC. St. Lucia and Grenada may also experience ashfall in the coming hours.

The ash plume may cause flight delays.

Ash on the ground can cause discomfort in persons suffering from respiratory illnesses and will impact water resources.

Images courtesy UWI-SRC and Dr. Thomas Christopher

Ash produced by the eruption at La Soufriere volcano at 13:50 UTC on April 9, 2021. Credit: NOAA/GOES-16, RAMMB/CIRA, TW

Another explosion took place at around 19:00 UTC, with ash column estimated at approximately 4 km (13 100 feet) a.s.l.

Second explosive eruption on April 9, 2021. Credit: UWI-SRC

Second explosive eruption on April 9, 2021. Credit: UWI-SRC

This is the culmination of a significant increase in activity at the volcano detected on April 8, 2021, which has prompted The Government of Saint Vincent and the Grenadines to raise the volcanic alert level to Red and issue an evacuation order for communities in the Red volcanic hazard zone.

The UWI-Seismic Research Centre (UWI-SRC) scientific team recorded six separate bands of volcanic tremor throughout the day.

This new type of seismic event has not yet been observed since the beginning of the eruption in December 2020, UWI-SRC said. The seismic signal recorded is usually associated with the movement of magma and fluids close to the surface.

Ash venting was also observed during the most recent tremor episode.

Images courtesy UWI-SRC

Geological summary

Soufrière St. Vincent is the northernmost and youngest volcano on St. Vincent Island. The NE rim of the 1.6 km (1 mile) wide summit crater is cut by a crater formed in 1812.

The crater itself lies on the SW margin of a larger 2.2 km (1.3 miles) wide Somma crater, which is breached widely to the SW as a result of slope failure.

Frequent explosive eruptions since about 4 300 years ago produced pyroclastic deposits of the Yellow Tephra Formation, which blanket much of the island.

The first historical eruption took place in 1718; it and the 1812 eruption produced major explosions.

Much of the northern end of the island was devastated by a major eruption in 1902 that coincided with the catastrophic Mont Pelée eruption on Martinique.

A lava dome was emplaced in the summit crater in 1971 during a strictly effusive eruption, forming an island in a lake that filled the crater prior to an eruption in 1979.

The lake was then largely ejected during a series of explosive eruptions, and the dome was replaced with another. (GVP)

Featured image courtesy UWI-SRC and Dr. Thomas Christopher

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