La Soufriere seismicity reacts to heavy rains- scientist

Anytime it rains heavily, heightened seismicity is recorded at the Soufriere volcano as was the case over the last weekend.  

 On Wednesday, Lloyd Lynch, lead Scientist with the University of the West Indies Seismic Research Unit (UWI-SRC), monitoring the volcano said that over the last three days the seismicity was down from a slight increase they saw over the weekend.  

 Speaking on ‘Eyeing La Soufriere’ programme on NBC Radio, Lynch said it is their thinking that the 40 events recorded over the weekend, after the system went down to below 10 events per day in the early parts of last week, was because of the high level of rainfall.  

  “So we had the uptick over the weekend which coincided with the rainfall, and it seems to be going back now over the last three days. We had 25 events on Monday, 22 the day before and 20 over the last 24 hours, so it is settling back down it seems,” Lynch said attributing the uptick to the heavy rainfall and the interaction with the hydrothermal system.  

 Last week, Lynch explained that precipitation may be interacting with magma at the summit and creating phreatic eruptions.  

 These eruptions occur when magma heats ground water or surface water. The extreme temperature of the magma (anywhere from 500 to 1,170 °C) causes near-instantaneous evaporation of water to steam, resulting in an explosion of steam, water, ash, rock, and volcanic bombs.   

Lynch noted on Wednesday that they are now focused on getting the summit stations rebuilt and a helicopter flight to the summit on Monday showed a completely different terrain than what existed prior to the explosive eruptions.
   
“So we had the reconnaissance flight on Monday, and I thought that the furniture was rearranged, but after speaking to Dr. Stinton, who is back to do surveys, he has been studying the dome growth, the whole house has been rebuilt so that is what it is like up there,” Lynch said.   

Dr. Adam Stinton is a Volcanologist attached to the UWI–SRC. 

 Lynch said they hope to have Dr. Stinton go up to the summit ,as he is the best person to assess the change and explain the implications of these changes at the summit.  

Last week, Lynch explained the importance of proper monitoring as he stressed that decreasing volcanic risk involves a multi-prong approach. He said that with this in mind, it is important to improve the level of monitoring and surveillance.  

By doing his he said, scientists will be able to detect, at an early stage, a volcano’s unrest and as a result, know if the unrest will escalate into full fledged eruptions. 

This was evident as volcanologist Professor Dr Richard Robertson was able to predict the eruption of the volcano hours before it blew on April 9, 2021. 

Lynch said the multi-prong approach also includes land risk planning which allows for the better use of land to not have people in flood and lahar prone areas.  

 He said land risk planning also means having better roads, bridges and other types of infrastructure that are more resilient and robust to volcanic hazards like lahars and ash.  

 Lynch said also it is also important to have proper policies that can incentivise certain activities and actions, and impose penalties for persons in breach of certain regulations; and that with education and outreach the population will become more educated and will respond better to warnings.