Mudflows on all flanks of the volcano – Stewart
The activity level has remained very quiet at La Soufrière for a week now, but a dangerous hazard associated with the volcano, mud flows, are carrying material down the valleys as the rains pour down.
“The volcano itself has been quiet, we had very few of the volcanic earthquakes that we were used to; no tremor is taking place. So, the volcano remains quiet which is good.” volcano seismologist Roderick Stewart of the University of the West Indies(UWI)-Seismic Research Centre(SRC), and Montserrat Volcano Observatory(MVO) indicated yesterday, April 29.
Since the last explosion on April 22, all reports have been almost silent on the seismic front, and there have been no further explosions.
Also, during the NBC program yesterday morning, the scientist noted that while they wouldn’t say as yet that the volcano is going to back to ‘sleep’; it is quietening down.
They continue to watch, “very carefully for any reversal of that”.
Stewart also indicated, “I suspect we will be using the opportunity in the next few weeks to install some new equipment that’s replacing some of the stuff that was destroyed in the eruption and watching closely to see if anything indicates a restart of activity, that’s really our major task in the coming months.”
While giving an update yesterday, the scientist informed, “The big activity over the last 24 hours is overnight we’ve had several lahars (or mud flows) on, I think, all the flanks of the volcano.”
Lahars or mud flows are fast moving floods of water, rock, ash and debris, and they flow down the river valleys, while sometimes extending onto flatter ground. Because of the material they contain, such as trees and rocks, they pose a significant danger. Persons may lose their lives if caught in one.
“..We suspect there are lahars in all the main drainage valleys and that these may have caused quite a lot of damage as they pass down from the volcano to the sea,” the scientist informed.
The signals were dying down at the time of the program but could pick up again every time the rain falls.
Some sounds heard over Wednesday night/Thursday morning caused people to take to social media and ponder whether La Soufrière had exploded once again. However, this was not the case.
“…We heard noises here as well, at Belmont. It is actually the lahars going on, and thunder and lightning, associated with the rain,” Stewart explained.
The lahar brings “trees down with it, and the amount of material that has been brought down, any time the lahar goes round the bend or goes over some topography, it will make thumping noises basically, and these can be heard quite a long way away.”
Professor Richard Robertson was in the field at the time that Stewart was speaking, and relayed that in the Richmond area of North Leeward, many trees were brought down because the lahars are erosive.
“In one place he says the river bank has been moved back by about 10 meters, that’s 30 feet, it’s eroded into the river bank,” Stewart said.
Robertson had also observed steam coming from the lahar in some areas, signifying that they were warm, from hot deposits around the volcano.
“…Another hazard that people should be aware of. Sometimes on the road, you’ll see there’s flooding on the road, there’s some fast moving water and it’s maybe only six inches deep,” Stewart noted, and people think they can drive through this.
“…but the water, because it’s got material in it, is incredibly powerful and can actually sweep vehicles away,” he said.