KINGSTOWN, St. Vincent (CMC) — Volcanologist, Professor Richard Robertson is warning that while the explosions at La Soufriere volcano have been getting weaker and less frequent over the last two days, this does not mean that the eruption has ended.
“We are not convinced that the magma down there has all come up,” he said Wednesday evening on “Round Table Talk” on the state-owned VC3 cable channel.
“We are not sure how much [magma] it is and we are not convinced that it is completely up, that it is out, or that it has run out of steam,” he said, adding, “It will take us a little while to be sure it is really ended”.
The volcanologist, the lead scientist from the Seismic Research Centre (SRC) of the University of the West Indies (UWI) which is monitoring the volcano, said residents must remain on their guard, avoid the Red Zone, and take steps to minimise the impact of the ash.
He said the safe zones are expected to remain that way for the duration of the eruption.
The news comes even as Robertson and his team, as well as other professionals in the United Kingdom, had feared that the volcano had returned to “prehistoric” eruptions as occurred 15,000 years ago.
Such an eruption had the potential to turn St. Vincent into a “desert”, Robertson said.
After 42 years without any explosive activity, La Soufriere blew its cap on Friday morning, three months after it began to erupt effusively.
The 8:40 a.m. (local time/Atlantic Standard Time) eruption came a mere 15 hours after authorities issued an evacuation order, having been advised by Robertson that the monitoring team could not say that the volcano would not erupt in 24 to 48 hours.
The violent eruption sent plumes of ash 29,000 feet into the atmosphere, but was surpassed by an even more powerful one that same afternoon, which sent ash 50,000 feet into the sky.
Since then, there has been between “at least 29 discrete explosions or ash venting,” Robertson said, adding, “That’s a quite busy volcano.”
He said the last four discrete events took place over the last two days and, therefore, most of them occurred during the first three days of the eruption “when there was an almost continuous jetting of steam and ash.
“So it was quite busy Friday, Saturday, Sunday and it sort of reduced its rate.”
Roberson said volcanoes develop patterns and at La Soufriere it is almost as if the magma is in the chamber and “is trying to do something”.
The question is whether the magma contains enough gas to be jetted out. Therefore, the magma is moving jerkily in its attempt to get to the surface. As these jerky movements get more frequent, they then get bigger and produce tremors.
The size of the tremors increases and there is an exposition at the summit of either very gas-rich plume or one containing ash.