La Soufrière remains quiet – Dr Christopher

Seismic activity at La Soufrière remains low since the last explosion on April 22; while gas measurements continue to show a presence of Sulphur dioxide (SO2).

Speaking on the Round Table Talk on Wednesday, May 12, volcanologist, and gas specialist Dr Thomas Christopher indicated that “La Soufrière has been very quiet since the 22nd (April), it hasn’t really given us much to speak about which is definitely a good thing.”

They have recorded the odd sporadic earthquake with the seismic stations on the network.

“I think apart from that, the only highlight of what’s been happening is the gas measurements which have been going on and how we’re interpreting them,” he noted.

The recent measurements of average SO2 flux(mass) from traverses completed under the volcanic plume with the help of the coastguard, were averages of: 208 tons per day on May 9 on May 11, it was 252 tons per day.

More recent data in a question and answer post on the SRC’s facebook page indicated that on Thursday May 13, the reading was 721 tons per day.

This differs from the measurements taken on Sunday, May 2, which was showed a much higher average of 1036 tons per day.

The presence of the gas suggests that the volcano is active, as when they’re resting one shouldn’t see SO2 or very small amounts of it.  Recent gas fluxes were done by a local volunteer, Leanka Henry, who is being trained by Christopher to continue this aspect of the volcano monitoring in the hopes that she will continue.

“…But I think the good thing is that I think it’s safe to say that the volcano is less dangerous now than it was in the middle of April. So I guess that is basically related to why the hazard level has been relaxed and dropped back down to orange because it’s not in a violent state at the moment so people can get a bit closer to it now without their lives being in danger,” the scientist indicated.

Persons questioned whether the state that the volcano is in would be the “new norm”, to which Christopher reasoned that volcanos behave differently, and that unlike the way the Montserrat volcano operates, La Soufrière seems more along the lines of a heavyweight boxer “which comes at you really hard and beats you up really quickly and then goes away.”

“…I guess our main issue now is to try and figure out whether or not we think the danger has passed totally. Because we know it’s dropped off, but has it totally gone, that much we can’t say yet, but it’s definitely safer now than it was a month ago.”
The volcanologist also responded to questions on how they would determine whether the eruption has ended.

“…What we would look for is more or less what we call flat lines in some of the relevant data sets,” he stated. The seismics would be one thing to look at, but the volcano produced few earthquakes until March, although it had been growing a dome since late 2020.

“…seismics may not be the best one to choose because when it comes to earthquakes, this volcano is a bit sneaky,” Christopher noted.

They would also look at deformation indicative by a flat GPS, and Sulphur Dioxide measurements falling away to more or less zero.