No dome visible at La Soufrire during observation flight
KINGSTOWN, St Vincent (CMC) — Scientists monitoring the La Soufrire volcano said that white steam could be seen venting near continuously from several locations on the crater floor, no dome is visible, although a spine could be seen through the clouds.
The Seismic Research Centre (SRC) of The University of the West Indies (UWI) said that an observation flight on Monday with fixed-wing aircraft was hindered because “visibility was poor, with clouds blocking the crater for much of the time”.
The SRC said that the volcano continues to erupt and that its pattern of seismic activity over the last few days is typical of the growth and destruction of lava domes.
“Explosions, with accompanying ashfall of similar or larger magnitude, can restart with little or no warning,” it said, noting that seismic activity at La Soufrire has been low after the tremor associated with the explosion and ash venting on April 22.
“Only a few long-period, hybrid and volcano-tectonic earthquakes were recorded and there was no further tremor,” the SRC said, adding that “the volcano is at alert level red”.
The lead scientist, Professor Richard Robertson, said that “things have been relatively quiet, since the explosion on the 22nd [of April], while seismologist Roderick Stewart said that during all the explosions there were a variety of different volcanic earthquakes, namely volcano tectonic, long period and hybrid.
Stewart said it is difficult, as a seismologist, to compare the level now to before the explosion started.
He noted that between December, when the volcano began erupting effusively, and February, when a then small dome was growing inside the crater, the only seismic signal was from the one signal at the summit.
That station was destroyed in the eruption this month, so it is quite difficult to say if the volcano is quieter than it was before the explosive eruption or if it is at the same level.
“There may well be a dome growing and we can’t pick up the seismicity because we will only get it near the summit. But, overall, it’s been remarkable the change in the level of activity after that last explosion. It’s gone back to virtually silent.”
Robertson said that some of the key stations are not reporting any events, and reiterating that something could be happening at the volcano that is not being detected seismically.
“The plan is… Rod is going up on a plane today to have a peep in the crater to see if we can confirm what we think might be happening, which is [that] there might be a dome growing,” Robertson said.
“There is a suggestion from interpreting some samples that there might be a dome there and the way in which the seismicity that we don’t have suggests that, that might be the case or simply that nothing is there and it is just simply quiet.”
He said the monitoring team might not be able to confirm this until Tuesday, adding that, hopefully, Stewart would be able to see inside the crater during his flight, and then the team would be better able to explain to the public what is happening.
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