|Present La Soufrière Alert Level:||YELLOW||The La Soufrière Volcano is restless. Seismicity and/or fumarolic activity are above the historical level at the volcano, or other unusual activity has been observed. This unusual activity will be specified at the time that the alert level is raised. This is level two of four.|
Professor Richard Robertson, the lead scientist monitoring La Soufriere, on Tuesday, warned that the volcano could erupt explosively again over the next seven days or so, if the current activities continue.
The La Soufrière Volcano has been erupting since April 9th, but the eruptions have gotten more infrequent, moving from every 12 hours or so, to over 41 hours apart in the case of the last eruption, on Sunday. To date, 31 discrete explosive eruptions have been recorded.
Robertson said that during the review period ending Tuesday morning, activities at the volcano, essentially continued as has been the case over the past few days, with the addition of having mudflows. Seismic activity continued the pattern established after the explosive activity on April 18, meaning that there continue to be small long-period, volcano-tectonic, and hybrid earthquakes, most of which aren’t felt. To date, there has not been any tremor activity since the April 19th eruption.
Professor Robertson also explained, “as we’ve said before, the volcano seems, in a sense, to be trying to grow a dome and it doesn’t succeed because it then has an explosion that destroys that dome. We expect at some point it might actually succeed and you may have a dome there. We don’t know if this week is the time it happens but if it doesn’t, then you, probably are going to have an explosion,” Robertson said.
Seismic signals have picked up on rockfalls. Robertson explained, “It is likely that as the dome grows, bits and pieces of it fall off and it generates a signal that we are having a rockfall. That’s possibly some of the reasons you get rockfall.” These seismic signals occur when a large rock or a large piece of volcanic material falls off the mountain and move down the mountainside. This movement generates vibrations that are detected by seismic instruments. Robertson also noted that it is possible to have rockfall anywhere in a volcano that is not related to dome growth.
Professor Robertson explained the gap between explosive eruptions is increasing with the relatively quiet periods also on the increase. But, what does this mean for the timing of future eruptions? Robertson added, that the volcano might succeed in building a dome, in which case “the chances of it capping the system, at least for a longer time would be there and you might, instead of having the explosion, have validation that you actually have a dome there. “And then it may take a little bit longer because it has more material to get out of the way if it is going to go explosive,” Robertson said.
“But the fact that you have them and you are beginning to have a few more is another indicator that you probably have the volcano growing or trying to — well, you have some sort of growth going on at the summit and that is a result of it, quite apart from the seismic signals that we are having.”
According to the UWI SRC, 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. Explosions with accompanying ashfall, similar to or larger, can occur with little or no warning impacting St Vincent and neighboring islands.
The alert level remains red. The National Emergency Operations Center continues to be fully functional operating on a twenty-four-hour, around-the-clock basis. NEMO will continue to provide regular updates as they continue to monitor the Volcano.
Official information will originate from St. Vincent and the Grenadines National Emergency Management Organization and the University of the West Indies Seismic Research Center.