Update on Askja, Fagradalsfjall, Mount Merapi, Grímsvötn, La Soufrière St. Vincent, Mount Pelée, Mount Nyiragongo

Good Afternoon!

Time to check out the current status of the volcanoes we have been following, especially as the situation has changed for some.  


Fig 1: Image of Askja caldera by  M Ryan, USGS, public domain.

Inflation, thought to be caused by a magma intrusion at a depth of 2km-3 km, started in early August.  GPS data and satellite images detected uplift of 5cm per month; the uplift centred on the western edge of the Öskjuvatn caldera.

The aviation code was raised to yellow on 9 September 2021, following near vertical uplift of 7cm.

Fig 2: Deformation.  Sources: IMO and GPS tímaraðir (vedur.is)

We will take a quick look at local seismicity.  Raw earthquake data was downloaded from IMO for the period 1995 to 14.09.2021 for our plots.

Fig  3a: Left: Geodensity plot of earthquakes from 1995 to 09.09.2021, overlain with earthquakes from 03.08.2021 to 14.09.2021.  Right: scatter plot of earthquakes from 03.08.2021 to 14.09.2021 (colour denotes day from start).  All plots by the author. © Copyright remains with the author; all rights reserved, 2021

The epicentres of current earthquake swarm are mostly to the east of the Öskjuvatn caldera following a near linear route, starting at, or near, the area of maximum earthquake density for the period 1995 to 09.09.2021, and heading for the Viti explosion crater; seismic activity is on the opposite side from the area of maximum uplift. 

Seismicity for 2021 looks pretty similar; the current swarm follows the pattern of earlier seismicity. 

Fig  3b: Left: Geodensity plot of earthquakes from 01.01.2021 to 09.09.2021, overlain with earthquakes from 01.01.2021 to 14.09.2021.  Right: scatter plot of earthquakes from 01.01.201 to 14.09.2021 (colour denotes month).  All plots by the author. © Copyright remains with the author; all rights reserved, 2021.

More information on earlier seismicity can be found in our earlier article: Askja and Herðubreið, The Start of Our Exploration of the Northern Volcanic Zone, Iceland


Fig 4a: Crater at Fagradalsfjall erupting on 14 September 2021. 

The crater at fissure 5 has grown considerably since we last posted about it; it now dominates the surround hills.  The eruption paused on 2nd September 2021, taking a well-earned break; steam and gas emissions continued.  The eruption resumed a couple of days ago.  The aviation code remains orange.

Fig 4b: Tremor plot, Fagradalsfjall (faf).  Source: IMO

Mount Merapi

Fig 5:  Merapi 2011 with Prambanan in the foreground, cropped from an image of Prambanan by Arabsalam, published under CC BY-SA 4.0.  Source: Prambanan Java243.  Prambanan is an 8th Century Hindu temple compound located approximately 17 kilometres (11 mi) northeast of the city of Yogyakarta and designated a UNECSO World Heritage Site.

Both lava domes situated below the south west caldera rim continue to grow, producing numerous pyroclastic flows and avalanches.

The alert level remains at thee and there is a 3km – 5km exclusion zone.


A jökulhlaup started on 1 September 2021 from the western Skaftlá caldera; the peak flow rate reached 520 m3/s on 2 September 2021.  Warnings were issued of the hazard from H2S from water draining from the caldera lake.  The ice-shelf had subsided 1m by 5 September 2021. 

On 6 September 2021, the peak flow rate increased to 610 m3/s, thought to be due to a second release of water from the caldera lake – this time on the eastern side.

The aviation code remains at yellow.

Fig 6:  Top image shows the water levels reached at Eldvatn and the lower one, flow rate.  Source: IMO

La Soufrière St. Vincent

The last ash emissions were on 22 April 2021.  Seismicity has since remained low.  Gas and steam plumes have been observed rising from the crater.

The alert level remains at orange.

Mount Pelée

Volcano-tectonic earthquakes are still occurring in the edifice at depths between 0.2km to 1.2km.  The area of discoloured, downgraded, burned and dead vegetation remains on the south west flanks. 

At the end of July 2021 underwater gas emissions started between St Pierre and the Prêcheur.  This will be investigated to ascertain how it links with the volcano.

The aviation code remains at yellow.

Mount Nyiragongo

The volcano is still active. A [gravitational] collapse in the crater caused and ash plume; ash reached Goma.  Incandescence was seen on 26th July 2021 and a gas and ash plume emerged on 4th August 2021.

Armchair Volcanologist

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


The Smithsonian Institution’s Global Volcanism Program: GVP

Icelandic Met Office: IMO