Scientists say latest La Soufrière explosion typical of destruction of lava dome

The Seismic Research Centre (SRC) of the University of the West Indies (UWI), Thursday night said that the earlier eruption of the La Soufrière volcano is typical of the growth and destruction of lava domes.

The SRC said the volcano, which began erupting on April 9, had a “vertical explosive eruption” at 11:09 am (local time) generated by explosive activity, and lasted for about 20 minutes.

“A vertical explosive eruption plume rose slowly above the crater eventually reaching a height of about eight kilometres. 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,” the SRC said in its evening bulletin.

It said seismic activity at La Soufrière continued the pattern established after the explosive activity last weekend and that small long-period and hybrid earthquakes continued to be recorded, with their rate of occurrence gradually increasing.

“Tremor continued, at a lower level, for the next two hours as La Soufrière continued to vent ash. 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 SRC, which has a team of scientists monitoring the volcano, said 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). 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,” the SRC said, adding “explosions with accompanying ashfall, of similar or larger size, can occur with little or no warning impacting St Vincent and neighbouring islands.”

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