Tag Archives: volcano-tectonic earthquakes

Update on the eruptions at Fagradalsfjall and La Soufrière St Vincent, and status of Mount Pelée

Good Afternoon!

Fig 1: Image from Civil Protection / Webcam 11.05.2021


At the time of writing the eruption at Fagradalsfjall is not only continuing unabated but getting stronger.  After the opening of five new fissures, eruptive activity has focused on one crater, fissure 5. Lava now covers the Geldingadalur valley floor and threatens to engulf the first cones; lava has been flowing steadily into Meradalir since 24 April 2021.

Eruptive activity changed from continuous fountaining with effusive lava flows to periodic jetting after midnight on 2 May 2021. The change is thought to be due to degassing of the magma in the upper part of the eruption channel where a small chamber may have formed.  Each jet is now accompanied by strong gas emissions.  Lava flow, itself, is mostly being carried in lava channels under the crater rim, rather than ejected in the current jets so periodic jetting has not adversely impacted the output.

The onset of jetting can be seen in the tremor plots from local stations. We have included KRI because, being further away, we can see more of the lower frequency lines.

Fig 2: Tremor plots for KRI and MER showing the onset of jetting on 02 May 2021. Source: IMO
Fig 3: Unrest seen on seismometers near the eruption sites with pulses in volcanic activity from midnight on 2 May 2021.  Source: IMO
Fig 4: This image shows the unrest on days 8-9. May. Source:  IMO

Some stats as at 10 May 2021 (Source: Institute of Earth Sciences (hi.is))

  • Area of the Geldingadalsgos lava field: 1.78 Km2 (1.41Km2, 03 May 2021)
  • Volume of erupted lava: 30.7 million m3 (23.0 million m3, 03 May 2021)
  • Lava discharge rate: 12.9m3/s, (7.5m3/s, 03 May 2021)
  • Mg0: varies from 8.5 to 9.8
  • K20/Ti202 ratio: increasing from 0.1 to 0.3

In the first two weeks of the eruption lava flow decreased steadily from 7-8m3/s to 4-5m3/s.  In the second two weeks, five new fissures opened with lava flow varying between 5 – 8m3/s.  In the two weeks to 3 May 2021, one crater dominated with lava flow increasing.  In the week to 10 May 2021, there has been a large increase in the output of lava to 12.9m3/s; the lava field now covers an area of 1.78km2 with a volume of 30.7 million m3.  It is thought that the increase in output reflects changes in the lava channel from the mantle to the surface; it has widened over time.

Changes in chemical composition may mean that materials are mixing in the upper mantle before ascent or there is less partial mantle melt in the magma.  If the latter, the eruption will end when the mantle source is sufficiently reduced.

Geldingadalsgos is still a toddler compared to Holuhraun; Geldingadalsgos’ eruption rate is 5% – 10% of the average eruption rate at Holuhraun between September 2014 and February 2015. Let’s hope it stays that way as it is a lot closer to residential areas.

La Soufrière St. Vincent

The alert status was lowered to orange after a period of relative quiescence on 6 May 2021; only a few long period events and volcano-tectonic earthquakes are occurring each day.  People are allowed back into the orange zone but the red zone remains an exclusion zone.

The last explosive event was on 22 April 2021.  However, a possible lava spine was spotted on photos on 27 April 2021.  Tephra fills the crater, increasing the risk of pyroclastic flows should eruptive activity pick up again.  In the meantime, lahars are the main hazard.

Mount Pelée

Mount Pelée remains on alert level yellow.  Volcano tectonic events are occurring and seismic activity remains at above baseline level.  An area of brown and dead vegetation was confirmed on 8 February 2021 caused by diffuse CO2 emissions; the vegetation has not recovered.   The volcano is slowly reawakening.

Armchair Volcanologist

© Copyright remains with the author; all rights reserved, 2021.

Sources and Further Reading:

In the text and:


Icelandic Met Office: https://en.vedur.is/ (English site)

Icelandic Met Office: https:// vedur.is/ (Icelandic site)

Reykjavik Grapevine: https://grapevine.is/

Department of Civil Protection and Emergency Management | Almannavarnir

La Soufrière St. Vincent

St Vincent and the Grenadines:  https://news784.com/

Barbados: https://www.nationnews.com/

Mt Pelée

Observatoire volcanologique et sismologique de Martinique (OVSM – IPGP): http://www.ipgp.fr/fr/ovsm/observatoire-volcanologique-sismologique-de-martinique-ovsm-ipgp

Alert Level for La Soufrière St. Vincent Raised to Red: Eruption in progress

Update 10.04.2021

At the time of writing, there have been several explosive eruptions now from La Soufrière St. Vincent.  The island has experienced extensive ashfall.  The emergency evacuation has extended to the orange zone.  Ash has reached 51,000 feet (38,000 feet, latest VAA) according to the volcanic ash alerts and the ash cloud has drifted over Barbados.

Fig 3: Ash plume from the first explosion.  Photo from NEMO

Most of the new lava dome has been destroyed and the 1979 lava dome has suffered some damage.  Removal of the rock has given magma a more open pathway.  The eruption is expected to be larger than the 1979 eruption and to continue for some time; explosions are expected to be the same or greater magnitude. As far as we know, there have not been any pyroclastic flows but they are expected. 

More than 3,000 people are in emergency accommodation and others are staying with friends or relatives.   Saint Lucia, Grenada, Antigua and Barbados have offered to take refugees.  Carnival Cruise Lines and the Royal Caribbean Group will send cruise ships to transport people to other islands. Venezuela has sent humanitarian aid and risk experts.

The north and west of Barbados have been hard hit by ash; the skies turned dark and ash is falling.  Residents have been advised to stay indoors, except for essentials or a medical emergency.  Beaches, parks and fish markets are closed for the time being. People with respiratory disorders have been advised to have their medication with them at all time.  The airport and airspace is closed at the moment.

Latest VAA forecast:

Fig 4: Volcanic ash forecast from Washington VAAC Volcanic Ash Advisory (noaa.gov). The volcano is coloured in red and Barbados is in the red circle.

Thoughts with everyone affected.


NEMO St. Vincent: ‪#‎lasoufriereeruption2021

Hazard zones, St Vincent: Home (nemo.gov.vc)

Washington VAAC: Volcanic Ash Advisory (noaa.gov),

News 784: NEMO: Explosive Eruptions May Continue Over The Next Few Days And Weeks • News784

Barbados Government Information Service: GIS News | GIS (gisbarbados.gov.bb)

Nation News, Barbados: Volcano ash turns northern skies dark – NationNews Barbados — nationnews.com

Update 16:51, 09.04.2021

An explosive eruption started at La Soufrière St. Vincent around 12:40 pm GMT today, sending an ash column 8 km into the sky. The ash cloud reached 20,000 feet, drifting eastwards. Ashfall has been observed at Argyle International Airport.

Scientists warn that further larger eruptions are possible.

The evacuation from the red zone (northern end of the island) is still in progress at the time of writing.

Source: NEMO St. Vincent and the Grenadines | Facebook

Original Post: 12:46, 09.4.2021

Good Afternoon!

Increasing gas emissions and seismic activity, including long period events, indicate that new magma is ascending at La Soufrière St. Vincent and an eruption could be imminent.  An immediate evacuation order was given earlier today (c.1:00 am GMT) for the red zone in the north of the island, impacting 16,000 people.

Fig 1: La Soufrière St. Vincent, seen here from the south. Photo by Richard Fiske, 1980 (Smithsonian Institution).

The new lava dome has been steadily growing since it emerged in December 2020.  The emission of gas and stream from the centre of the dome and its border with the 1979 dome increased on 8 April 2021.  A preliminary VAA noted that a well-defined hotspot was visible in the SW.   Incandescence from the dome was visible in St Lucia.

A swarm of volcano-tectonic earthquakes started on 6 April 2021 beneath the volcano at a depth of around 6 km.  Long period earthquakes have also been observed, indicating that new magma is ascending.

Fig 2: New lava dome on 19 March 2021 between the 1979 lava dome on the right of the image and the crater wall on the left.  Photo NEMO.


Volcanic activity, here, is driven by the subduction of the South American Plate under the Caribbean Plate.

La Soufrière St. Vincent is a 1,234m high stratovolcano located in the north of St. Vincent Island, which rides on the Caribbean Plate. She is the youngest volcano on the island.  At the summit there is a 1.6 km wide crater with a younger crater formed in the 1812 eruption, located in a 2.2 km wide Somma crater.  Her lavas are typical of a subduction zone setting: andesite / basaltic andesite and basalt / picro-basalt.

GVP records 23 Holocene eruptions, the largest of which were VEI 4s in 1812 and 1902.  The 1902 eruption devastated much of the northern end of the island.  A lava dome was extruded in the eruption of 1971, which was destroyed to be replaced by a new dome in 1979 in a series of explosive eruptions.  The 1902 eruption devastated much of the northern end of the island. Pyroclastic flows from eruptions in 1812, 1902, and 1979 reached the coast.

For advice and the status of La Soufrière St. Vincent, please consult NEMO or follow their Face Book page (links below).

Thoughts with those impacted by the evacuation and eruption.

The Armchair Volcanologist

© Copyright remains with the author; all rights reserved, 2021.

Sources and Further Reading

National Emergency Management Organisation (NEMO): Home (nemo.gov.vc) and https://www.facebook.com/nemosvg/

Washington VAAC: Current Volcanic Ash Advisories

The Smithsonian Institution’s Global Volcanism Program (GVP): https://volcano.si.edu/

“Mt. Pelée, La Soufrière St. Vincent and a Quick Tour of the Plates Surrounding the Caribbean”: https://thearmchairvolcanologist.com/2021/02/01/mt-pelee-soufriere-st-vincent-and-a-quick-tour-round-the-plates-surrounding-the-caribbean-plate/