La Soufrière’s Good Friday 1979 eruption marked by explosion

St Vincent’s La Soufrière volcano heralded the 42nd anniversary of its Good Friday 1979 eruption with a classic, dramatic explosion that sent a towering mushroom cloud of ash and rock splinters miles into the air.

It has been five days since the volcano has been shooting its gas-rich magma out of the crater, sometimes in towering ash columns, or in sending pyroclastic flows down its slopes.

The interspersed tremors accompanied by explosions or venting have been changing pattern over the days; but last night, the volcano had a relatively quiet time.

The University of the West Indies scientists monitoring the volcano said Tuesday that Soufrière has blasted away the heavy domes at the summit and used a lot of energy. They speculate that a new cap or dome may be forming.

But they predicted that the magma still had enough energy/gas inside of the volcano’s vent and that the pressure would build up and blast away the material that is blocking its vent.

The volcano did just that, exploding at 6.30 Tuesday morning.

UWI volcanologist Professor Richard Robertson, who leads a team of UWI Seismic Research Centre scientists on the island, said: “The explosion that we had this morning wasn’t as energetic as the one that we had in the beginning, telling us again that it didn’t have, even though it broke the cap, it didn’t have as much energy as when it started out.

“So the amount of gas-rich magma that you have there … that is at the surface… is probably being used up.”

If the volcano continues to follow the same pattern, the scientists expect to see some indication that it’s trying to grow a dome or form a cap.

“Now whether or not it builds up enough pressure and does what it did this morning, which is remove it and have an explosion, that’s possible,” Professor Robertson said, “or it’s possible that the cap/dome becomes thick enough to stop it, and the volcano doesn’t have the energy to breakthrough.

“We wouldn’t be surprised in the coming days that instead of having these very vigorous, really high plumes with fine ash being produced, what we would tend to have more of are these discreet explosions like we had this morning which for volcanologists, we would call it a classic Vulcanian explosion where you have a punching of material up into the air.”

In time, they hope there will be a period when they’re fairly certain the volcano won’t explode, and it would be relatively safe to “get the stations back up so that in case we get into a vigorous period again and we lose stations, we will have enough eyes in the mountain.”

Nevertheless, Professor Robertson stressed that the volcano may appear to others over the next weeks or hours to be “quieter” but “It’s still a pretty dangerous volcano”.

He said: “It can still explode, and do serious harm to the areas in its close reach. The size of the explosions will depend on the energy/amount of gas in the magma wanting to come out.

“So I would suggest to people don’t let down your guard, keep your guard up, don’t do anything stupid and let’s remain safe and keep the record that we have of nobody being killed from this eruption.”

La Soufrière’s second volcanic eruption in the 20th Century began on April 13 1979 after 10 months of a mild build-up. A series of strong vertical or Vulcanian explosions between April 13 and 26 generated ash falls, pyroclastic flows and mudflows.

There were no casualties, in marked contrast to the May 6 1902, eruption which killed 1,680 people, decimating the Carib community on the island’s northern coast. The blast occurred just hours before the biggest of a series of eruptions on Martinique’s Mount Pelee, culminating in the deadliest in Caribbean history, which wiped out the town of Saint-Pierre, killing all but one of its 28,000 inhabitants.

La Soufrière is but one of 19 live volcanoes on 11 eastern Caribbean islands. Two of them are located underwater near Grenada, including the recently active Kick ‘Em Jenny off the island’s northern coasts.

The Soufrière Hills in Montserrat remains the most active of all, which has erupted continuously since 1995, destroying the capital of Plymouth and killing at least 19 people in 1997.
(BT/Searchlight Newspaper)