What Can Telica And Fagradalsfjall Volcanoes Teach Us About La Soufriere

St Vincent’s La Soufriere volcano last erupted on Apr. 13 1979 and rumbled back into life in December of 2020.

(By Ernesto Cooke) – According to research done by the Carnegie Institution for Science, When dormant volcanoes are about to erupt, they show some predictive characteristics—seismic activity beneath the volcano starts to increase, gas escapes through the vent, or the surrounding ground starts to deform.

The research was published in Earth and Planetary Science Letters.

Carnegie volcanologist Diana Roman and his team monitored various eruptions at the Telica Volcano in Nicaragua in 2011. It is a so-called stratovolcano.

Before the eruption, there was a lack of deep seismicity or deformation, and small changes in sulfur dioxide gas emissions, indicating that the explosion was not driven by fresh magma. 

Activities At La Soufriere 

La Soufriere volcano has been in a state of relative calm until December 2020, when it rumbled back into life.

The volcano has since been in an effusive state with the releasing gases that have so far left large patches of deform vegetation visible to those living on the North-Western flanks of the volcano.

Also, in the North-Western communities, sulphur’s pungent smell is attributed to La Soufrière.

On Wednesday, Mar. 25, Geologist Professor Richard Robertson said the magma is getting to the surface because an eruption is ongoing.

However, there are pockets of magma leftover from the 79 eruptions; in late 2020, something would have triggered that magma’s movement, he said.

Starting at 16:53 local time (20:53 UTC) on Mar. 23 2021, the monitoring network started recording volcano-tectonic (VT) earthquakes.

These earthquakes are typically associated with the rock mass’s underground fractures and are commonly generated by magma pushing through an unyielding rock mass.

The volcano-tectonic earthquakes were located beneath the volcano, at depths down to 10 km below the summit.

The largest of these had a magnitude of 2.6 and felt by people living in communities close to the volcano, such as Fancy Owia and Sandy Bay.

VT earthquakes are not to be taken lightly; There was a swarm in November of 2020, La Soufrière went quiet and began erupting effusively in late December 2020.

 St Vincent’s La Soufriere has been classified as a stratovolcano.

Iceland’s Fagradalsfjall volcano 

According to a New York Times report, in Iceland, 18,000 Earthquakes Over Days Signal Possible Eruption on the Horizon.

Geophysicists and volcanologists say the quakes are the culmination of over a year of intense seismic activity.

However, most of the tremors have lasted a few seconds, with light shaking.

Similar tremors have been observed ahead of volcanic eruptions in the past, and the Icelandic Meteorological Office said that magma movements were a likely cause for the continuing activity.

The eruption capped a hectic spell of seismic activity in southwestern Iceland that began around December 2019.

The earthquake swarm started on Feb. 2, 2020, with a 5.7-magnitude quake, and tens of thousands of quakes have since followed, with up to 3,000 in just one day earlier this month.

Although most of the swarms remained small in magnitude, their frequency led scientists to believe that an eruption could be imminent.

Fagradalsfjall began erupting on Mar. 19 2021.

Lateral Blast

Lead scientist Professor Richard Robertson said most of the activity in the crater is now flowing in the South-West direction and there is a possibility that it could compromise the crater wall.

“You can have things like a lateral blast and preferential movement in that south-west direction”, he said.

Robertson said the reasons they had place reflectors on the South Western wall were to look for potential failure in the structure.

“Now our concern was twofold, yes to look at whether the weight of the dome itself, the size of that mass of rock that is now resting on the crater wall could cause it to fail”.

Robertson said if this happens there is potential for the hot material inside the crater to get outside.

“The other thing was to monitor the stability of the South Western crater wall, both because of that kind of event and the potential for other things”.

The Geologist stated that if there were explosions from the South Western part of the crater, the possibility exists for some collapsing in that direction.

“We would hope by then; we would have alerted people in sufficient time so that no one would be in harm’s way”.

Latest Reports

On Saturday NEMO in its latest release said The new dome continues to grow towards the Leeward and Windward sides of the Volcano with the most active gas emissions being at the top of the new dome, as well as the contact areas between the pre-existing 1979 and 2020/21 dome.

The scientist also stated on Saturday that the period of elevated volcano-tectonic (VT) earthquakes which began on 23 March 2021 stopped on March 26, 2021.

Since then, the only seismic activity being recorded are small low-frequency events associated with the growth of the dome. These kinds of events were dominant before March 23, 2021.

Their rate of occurrence does not appear to have changed as a result of the volcano-tectonic earthquake swarm.

On Monday night NEMO stated that Activity at the La Soufrière Volcano continues to be at a low level dominated by small earthquakes associated with the growth of the lava dome.

The alert level remains at Orange. The National Emergency Management Organisation is reminding the public that no evacuation order or notice has been issued.

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