Hunga Tonga-Hunga Ha’Apai, Major Eruption and Tsunami, 15th January 2022

Good Morning

A major eruption occurred on the island of Hunga Tonga-Hunga Ha’Apai on 15th January 2022 at 04:14:45 am (UTC).   As with Krakatau, news of the eruption arrived before the pressure wave from the blast due to modern technology (now the internet, then the telegraph).  The eruption was preceded by a smaller one at the end of 2021 which ended 11th January 2022.  Activity picked up again on 14th January 2022.  Our thoughts are with all those affected.

2021 Eruption

Hunga Tonga-Hunga Ha’Apai has been erupting since 20th December 2021.  The initial eruption produced a large plume (height unknown) and was heard up to 2,000 km away in New Zealand.  Activity died down and the eruption was declared over on 11th January 2022.

This eruption added to the land created during the 2009 and 2014/15 eruptions which links the islands of Hunga Tonga and Hunga Ha’Apai.

Fig 1: Hunga Tonga-Hunga Ha’Apai pre the December 2021 eruption (image from Google Earth) on the left and Hunga Tonga-Hunga Ha’Apai on January 7, 2022 on the right (image from Planet (@planet) / Twitter)

January 2022 Eruption

Activity resumed on 14th January 2022 with a 20 km high ash cloud.  Geologists from Tonga reported large explosions and a 5 km wide ash column.  Their report can be found here Tongan geologists observe stunning eruptions at Hunga | Matangitonga .  At the time of writing this is the last update from the news source in relation to the eruption.

An image from @Planet taken, it is believed, two hours before the 15th January 2022 shows that the 14th January 2022 eruption had removed a lot of the subaerial land bridge between the two islands.

Fig 2: Hunga Tonga-Hunga Ha’Apai 15 January pre-eruption from Planet (@planet) / Twitter

On 15th January 2022, a much larger eruption occurred which was heard as far away as Alaska and Canada. USGS estimate the surface wave magnitude as 5.8. The pressure wave has travelled round the globe: it was measured as 7hPa in New Zealand, 2.5hPa in Switzerland and 2hPa in the UK.

Fig 3: Hunga Tonga eruption early on January 15, 2022, taken from the GOES-17 weather satellite.  Source: https://console.cloud.google.com/marketplace/details/noaa-public/goes-17 ( Public Domain).

 The eruption covered the surrounding islands in ash, blocking out the sun in Tongatapu, the main island in Tonga. Tonga lost its internet connection, probably due to damage to underwater cables so an assessment of the damage has not been possible.  The Australian and New Zealand Governments have offered assistance, including over-flights to assess the damage; the flights are hindered by the ash cloud.

Known Impact

A large amount of material is thought to have been ejected into the stratosphere.  This may cause temporary climate cooling in the region and possibly globally.  New land linked the islands of Hunga Tonga and Hunga Ha’Apai was cut through during the activity on 14th January 2022; how much remains has not been confirmed at the time of writing, but it is expected that more of the subaerial edifice has been lost.

A Pacific-wide  tsunami was generated which reached heights of 0.3m (Mexico), 1.3m (California), 2m (Chile), 2.5m (Vanuatu) and 1.5m (Tonga).  Low lying islands such as Atata Island were submerged by the tsunami.   Tsunami warning systems worked; the known fatalities are low.  Although closer to the volcano where residents had only minutes to flee to higher ground, the toll is not known. 

The cause of the tsunami is not known.  It may have been due to one or more of the following: edifice failure allowing to sea water to reach the magma chamber causing a large explosion; a large volume of pyroclastic material dumped into the ocean; or, a submarine landslip. We will have to wait until the experts have had a chance to assess.

Background

Tonga is an archipelago of 169 flat low-lying coral limestone islands, some with volcanic bases, of which 36 are inhabited. It is home to 105,000 people, of which 70% live on Tongatapu.  Tongatapu has a wealth of archaeological remains, including traces of Lapita pottery from the earliest known settlers, the Lapita. Tonga was also the seat of the Tongan Empire which emerged in 950 AD and declined after 1500 AD; it is now a kingdom with a constitutional monarchy. Hunga Tonga-Hunga Ha’Apai lies 65 km to the north of Tongatapu.

Hunga Tonga-Hunga Ha’Apai is two volcanic islands joined by a land bridge created during the 2009 eruption.  Hunga Tonga is the island on the right of the images and Hunga Ha’Apai the one on the left.  The islands are the subaerial manifestation of the caldera of a submarine volcano.  Its lavas are andesitic.  Five Holocene eruptions are recorded by GVP: 1912, 1937, 1988, 2009, and 2014; all were VEI 2, except for the VEI 0 1988 eruption.  Other eruptions evidenced by rock and ash deposits, including evidence of pyroclastic flows, occurred in 1040 – 1180 CE and 1108 CE; the latter is believed to have formed the caldera and caused 1°C global cooling.

The volcano is situated 100km above the subducting Pacific Plate on the Tonga Plate in the Tonga Kermadec Volcanic Arc.  The Tonga Plate is a microplate which lies between the Pacific Plate, the Niuafo’ou Plate and the Kermadec Plate. 

Fig 4: Earthquake plots by the author showing the subduction zone underlying Hunga Tonga-Hunga Ha’Apai and Tongatapu.  Green dots denote earthquakes less than 6 magnitude, yellow stars greater than or equal to 6 and less than 7 magnitude and red stars greater than or equal to 7 magnitude. Blue triangles denote active volcanoes and the orange triangle Hunga Tonga-Hunga Ha’Apai.  The orange circle denotes Tongatapu.  ©copyright remains with the author; all rights reserved, 2022

The Tonga Kermadec Volcanic Arc lies on the 3,000 km long 100 Ma old Tonga Kermadec Ridge.  The ridge has two segments: the Tonga Ridge in the north and the Kermadec Ridge in the south.  There are two back arc basins to the west of the ridge: the 6 Ma old Lau Basin and 2Ma old Havre Trough, that began opening at 6 Ma and 2 Ma respectively. The Tonga Kermadec Ridge moves independently of the Indo-Australian and Pacific Plates to its west and east, resp.

Armchair Volcanologist

© Copyright remains with the author; all rights reserved, 2022.

Sources:

Raw earthquake data: USGS Earthquakes | U.S. Geological Survey (usgs.gov)

Hunga Tonga – Wikipedia

Tongatapu – Wikipedia

Tongatapu – WikipediaTonga-Kermadec Ridge – Wikipedia

Fagradalsfjall: Aviation Code Downgraded to Yellow

Good afternoon!

Seismic activity at Fagradalsfjall, Iceland, has remained low. The recent swarm is now considered over. The aviation code has been lowered to yellow as a result.

Armchair Volcanologist

© Copyright remains with the author; all rights reserved, 2022.

Sources:

Aviation colour code map: https://en.vedur.is/earthquakes-and-volcanism/volcanic-eruptions/

Icelandic Met Office: https://en.vedur.is

Fagradalsfjall: Update 02/01/2022

Good afternoon!

Updated Earthquake Plots, 2nd January 2022 13:50

Good afternoon!

We have updated the earthquake plots for Fagradalsfjall, Iceland, for the swarm which started on 21 December 2021. 

The swarm had an intense initial period while magma moved along a lateral dike, followed by a less intense period, accompanied by magma ascent.  The Icelandic Met Office, IMO, say that the swarm is following the same pattern as that which preceded the eruption in March 2021. 

Magma is ascending under Fagradalsfjall, itself.  The outlying earthquakes, e.g., at Svartsengi and Krýsuvík, are what Iceland calls triggered earthquakes.  Triggered earthquakes are tectonic in nature, arising as local faults respond to magma movement. 

Fig 4: Geodensity plot by the author of earthquakes at Fagradalsfjall the period 21.12.2021 to 02.01.2022.  © Copyright remains with the author; all rights reserved, 2021.
Fig 5: Geoscatter plot by the author of earthquakes at Fagradalsfjall the period 21.12.2021 to 02.01.2022.  Colour denotes age: red is the oldest and yellow the youngest. © Copyright remains with the author; all rights reserved, 2021.
Fig 6: Scatter plot by the author of earthquakes at Fagradalsfjall the period 21.12.2021 to 02.01.2022.  Colour denotes age: red is the oldest and yellow the youngest. © Copyright remains with the author; all rights reserved, 2021.
Fig 7: 2D Depth v Earthquake scatter plot by the author of earthquakes at Fagradalsfjall the period 21.12.2021 to 02.01.2022.  Colour denotes age: red is the oldest and yellow the youngest. © Copyright remains with the author; all rights reserved, 2021.

Armchair Volcanologist

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

Source

Raw earthquake data: https://skjalftalisa.vedur.is/#/page/map

Update 31/12/2021

Following a drop in seismicity over the past couple of days, visitors are now advised to avoid the area.

A similar drop in seismicity was observed immediately before the March 2021 eruption.

If the volcano does erupt again, this would be considered a new eruption in the same place; the earlier eruption was declared over three months after the cessation of activity on 19 September 2021.

Update 28/12/2021

The earthquake swarm at Fagradalsfjall, Iceland, is continuing.  While the swarm has slowed down a bit, 19,000 earthquakes have been recorded by the automatic SIL system since the swarm started.  14 earthquakes over 4.0 magnitude have occurred.  An alert for the risk of rockfall and landslides in the area has been raised; visitors are advised to stay away from the area.

We have plotted the confirmed earthquakes from 20 December 2021 to 28 December 12:50.  This shows the dike propagation south west of Geldingadalur, with additional activity near Kýsuvík and Svartsengi.

Fig 1: Geoscatter plot of the earthquake swarm between 20.12.2021 and 28.12.2021 12:50 by the author.  Red denotes oldest quakes and yellow the newest.  © Copyright remains with the author; all rights reserved, 2021
Fig 2: Scatter plot of the earthquake swarm between 20.12.2021 and 28.12.2021 12:50 by the author.  Red denotes oldest quakes and yellow the newest.  © Copyright remains with the author; all rights reserved, 2021
Fig 3: Geodensity plot of the earthquake swarm between 20.12.2021 and 28.12.2021 12:50 by the author.  © Copyright remains with the author; all rights reserved, 2021.

Only time will tell where and when lava will emerge.  In the meantime, if you are lucky enough to be in the area, be aware of the risk of rock fall and landslip.

Armchair Volcanologist

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

Sources:

Raw earthquake data: https://skjalftalisa.vedur.is/#/page/map

Icelandic Met Office: en.vedur.is

A Christmas Present for La Palma; Eruption Declared Over 25th  December 2021

Good evening!

There was some good news for La Palma over the week end; the eruption was declared over on 25 December 2021.  The eruption, itself, ended on 13 December 2021 at 22:21.  There was a precautionary period of waiting before announcing the end of the eruption.

This is an important milestone in the process to recover and rebuild.

Fig 1:  Seismic signal showing the end of the eruption. Source: IGN

Statistics

Eruption

The eruption started on 19 September 2021 as a flank eruption on the Cumbre Vieja volcano and ended on 13 December 2021.  The duration of the eruption was 85 days and 8 hours – the longest for which there are historic records.

The eruptive style is described as Strombolian fissural with phreatomagmatic pulses.

The average height of the plume was 3.5km and its the maximum height was 8.5 km on 13 December 2021.

Edifice

The cone’s height is now 1,121m.

There are six craters, with diameters ranging between 106m and 172m.

Lava

200 million cubic meters erupted, covering an area of 1,219 hectares with an average thickness of 12m and maximum width of 3,350m.

The maximum temperature was 1,140°C.

Two lava deltas were created covering c. 48 hectares (one c. 43 hectares and the other 5 hectares).

Damage

2,988 buildings were destroyed and 138 damaged, according to satellite data. This is initially analysed by the local authorities as 1,345 residential properties, 180 agricultural, 75 industrial, 44 leisure, 16 public and 16 other; the shortfall is attributed to properties having more than one building within their boundaries.

Infrastructural damage includes: 73.8 km of road have been damaged along with streets and crossings; and, 130km power lines, 85 medium voltage towers, 1500 low voltage poles and 19 distribution centres.

We do not have an up to date analysis of the extent of the damage to crops and livestock.

Around 7,000 people were evacuated.

There was sadly one fatality which is under investigation.

Seismic Activity

9,135 earthquakes were recorded in the period from 11 September (the onset of the swarm) and today, 27 December 2021.  Due to the severity of the volcanic tremor, many smaller quakes were not recorded.

We have plotted the sequence.  The results are shown in the video below.

Fig 2: Earthquake plots by the author of the swarm from 11/09/2021 to 27/12/2021. © Copyright remains with the author; all rights reserved, 2021.

 Earthquake activity is continuing at the time of writing.

Armchair Volcanologist

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

Sources:

El Time: ElTime.es

Raw earthquake data: Instituto Geográfico Nacional (IGN)

Fagradalsfjall, Iceland, Aviation Code Raised to Orange

Good afternoon!

A large earthquake swarm started at Fagradalsfjall late on 21 December 2021, 2-4 km NE of Geldingadalir, thought to be caused by a lateral dike intrusion.  Due to the increased seismic activity, the aviation code was raised to Orange yesterday, 22 December 2021.

Fig 1: Icelandic Met Office, IMO’s map of the swarm.  Source: IMO

The eruption at Fagradalsfjall had stalled on 18 September 2021, with no new lava flows to the time of writing.  Ground deformation indicated that magma was still flowing into the crust.

Fig 2: Ground deformation at Krýsuvík.  The red line denotes the start of the March 2021 eruption. Source: IMO

We have downloaded and plotted the earthquakes from 1 September 2021 to 23 September 2021 (source for raw data: IMO ). This includes the swarm which started near Mount Kelir in late September 2021, which may or may not have heralded the current reactivation of the dike.

Fig 3: Geoscatter plot of the swarms from 1 September 2021 to 23 December 2021 by the author.  Colour denotes age: red being the earliest and yellow the most recent. © Copyright remains with the author; all rights reserved, 2021.
Fig 4: Scatter plot of the swarms from 1 September 2021 to 23 December 2021 by the author.  Colour denotes age: red being the earliest, and yellow the most recent. © Copyright remains with the author; all rights reserved, 2021.

While it is considered likely that the activity will result in a renewed eruption, when and where is not certain.

Armchair Volcanologist

23 December 2021

© Copyright remains with the author; all rights reserved.

Sources included in the text.

Grímsvötn, Aviation Code Raised to Orange 6th December 2021 (Since Lowered to Yellow)

Good morning!

Update 8 December 2021

The alert level has been lowered to Yellow. To date no eruption has followed the jökulhlaup or increased seismicity. As Grímsvötn may erupt with little warning, the situation remains closely monitored.

Original Post 6 December 2021

Fig 1: Líndal. A. (1 June 2011). Grímsvötn: photo 3 of 14. Retrieved from http://icelandicvolcanoes.is/?volcano=GRV

The alert level for Grímsvötn  has been raised to orange following the draining of the caldera lake over the past few days, the resulting jökulhlaup, and increased seismicity today.

Fig 2: Aviation codes for Icelandic Volcanoes.  Grímsvötn is orange.  Source: IMO

The ice-cap has subsided by c. 77 metres.  The water drained via the Gígjukvísl river; the discharge in Gígjukvísl river yesterday around noon was 2800 m3/s, reducing later in the day.

Fig 3:  Measurements of the jökulhlaup as it impacted the Gígjukvísl river.  Source: Línurit (vedur.is)

At the time of writing, there have been 25 earthquakes in the last 48 hours in the vicinity of Grímsfjall.  A magnitude 2.3 occurred at 06:15, followed shortly afterwards at 06:16 by a magnitude 3.6.  There have been a few aftershocks.  No volcanic tremor has been detected.

Fig 4: Map of earthquakes at Vatnajökull.  Grímsfjall is roughly where the green star is; the green star is the location of the 3.6M earthquake.  Source: Vatnajökull (vedur.is)

Volcanic eruptions have occurred after draining of the caldera lake in the past, attributed to the sudden decrease in pressure destabilising the system; IMO cite the 2004, 1934 and 1922 eruptions.

Armchair Volcanologist

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

Sources

Icelandic Met Office: IMO

Icelandic Volcanoes: Icelandic Volcanoes (icelandicvolcanos.is)

Mount Semeru, Eruption 4th December 2021

Update 9/12/2021

Sadly the death toll from Mount Semeru now stands at c.40 as of noon today (local time). Over 100 have been injured.

The lava dome collapsed from 1st to 6th December 2021 generating both lava and pyroclastic flows. The largest dome collapse occurred around 14:47 on 4th December 2021 to be followed by pyroclastic flows from 15:10, causing the fatalities. Rescue efforts have been hampered by later eruptive activity.

Sources: https://www.msn.com/id-id/berita/other/semeru-eruption-death-toll-rises-to-43/ and https://volcano.si.edu/volcano.cfm?vn=263300

Original Post, 5/12/2021

Fig 1: Image from 1985 eruption of Semeru, cropped from a photo by Tom Casadevall, 1985 (U.S. Geological Survey).  Source:  GVP

Sadly, 13 people have been killed, 7 missing and c. 100 injured, at the time of writing, following the collapse of the lava dome on Mount Semeru on 4 December 2021. Ash rose to a height of 50,000 feet, covering 11 villages.  Flows of hot gas and lava travelled 800m at least twice on Saturday, reaching a nearby river.  Two bridges were destroyed, including one connecting Lumajang to Malang. 900 people have been evacuated.  10 trapped in mines were rescued. Heavy rain and a thunderstorm had led to destabilisation of the lava dome. The volcano had been on alert level II (Waspada).

Mount Semeru is 3,657m high a stratovolcano with pyroclastic cones and fissure vents. Lake-filled maars follow a N-S trend cutting through the summit. She is located in the Lumajang district, East Java.  Java lies above the subduction zone where the Indo-Australian Plate subducts under Sunda Plate .  Her lavas are Andesite / Basaltic Andesite and Basalt / Picro-Basalt.  Over 1m people live within 30km of the volcano.

GVP records 65 Holocene eruptions since 1818, which range from VEI 1 to VEI 3.

Our thoughts are with those affected.

Armchair Volcanologist

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

Source& Further Reading

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

Indonesia: Mount Semeru volcano eruption kills 13 as thousands flee | The IndependentMount Semeru volcano eruption death toll at 13 as ash covers vehicles up to their roofs – World News – Mirror Online

Cumbre Vieja Eruption, Update 19 November 2021

Good evening!

The eruption of Cumbre Vieja continues unabated with Strombolian activity, lava fountains from many vents, lava flows, and ash emissions. .  As of 16 November 2021, Copernicus reported that 1,042.1 hectares of land have been covered by lava.  Rainfall now adds to the hazards created by volcanic ash.  The cone reached a height of 1,130m by 10 November 2021. Sadly, one fatality has occurred; one person who had gone to assist with ash clearance was found dead in his home.

Fig 1: Screenshot on 19/11/2021 from RTVC’s webcam monitoring the eruption.  Source: DIRECTO | Erupción del volcán en La Palma – YouTube

Seismicity picked up again in the last few days along with a ground uplift detected at GPS stations LP03 and LP06.

Fig 2: Earthquake count by day by the author for earthquakes from 11/09/2021 to 19/11/2021 (part day), created from publicly available earthquake data provided by IGN.  © Copyright remains with the author; all rights reserved, 2021.
Fig 3: Ground deformation at GPS stations LP03 and LP06.  Source: IGN

 To date there have been 5 earthquakes of 5 Mag. or more.

Fig 4: List of earthquakes greater than or equal to 5 Mag. for earthquakes from 11/09/2021 to 19/11/2021 (part day), extracted from publicly available earthquake data provided by IGN.  © Copyright remains with the author; all rights reserved, 2021.

Here are updated earthquake plots.  All of the action is centred around two depths: 7 -16 km and 30 -39 km, with a very few earthquakes in between; there are a few earthquakes with depths of more than 39 km.

Fig 5: Earthquake count by depth by the author for earthquakes from 11/09/2021 to 19/11/2021 (part day), extracted from publicly available earthquake data provided by IGN.  © Copyright remains with the author; all rights reserved, 2021.

For the updated video, we have provided the scatter plots for only earthquakes greater than  or equal to 3.0 Mag. because the smaller earthquakes obscure the action; all earthquakes are included in the geoscatter plots.

Fig 6: Video by the author of geoscatter plots for earthquakes from 11/09/2021 to 19/11/2021 (part day) and scatter plots of earthquakes greater than or equal to 3.0 Mag. for the same period.  © Copyright remains with the author; all rights reserved, 2021.

Magma still appears to be stalling at the two depths: 7 -16 km and 30 -39 km prior to ascent (refer to La Palma: Earthquakes and Magma Plumbing for more information).  How much of it reaches the surface remains to be seen.

Armchair Volcanologist

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

Sources:

Raw earthquake data: Instituto Geográfico Nacional (IGN)

Other links are provided in the text.

La Palma, Update 26.10.2021

Good evening! 

New Earthquake Plots

It has been a week since we updated our last earthquake plots for La Palma so time to take another look.  The eruption has continued in the meantime, with seismicity and seismic signals increasing.  Earthquake activity continues mainly within the two levels 7 -16km and 30 to 42km identified in our previous plots.

Fig 1: screenshots of the eruption 26.10.2021 from local webcams: left, TV Canarias live stream (source: https://www.youtube.com/watch?v=INvrtMg5tSQ); and, right, Hotel Galeon (source: https://eruption.acme.to/slideshow.php?getcam=hotelelgaleon)  (still photos).

Several partial collapses of the main cone have occurred.  The latest was yesterday, releasing a large amount of the lava to the west, which went over existing lava flows.

The latest statistics reported on 26th October 2021 are:

  • 908.2 hectares of land have been affected by lava. 
  • 2,162 buildings haven been destroyed by lava, with a further 124 suffering damage.
  • 66.2km of roads have been lost, with  a further 3.4km damaged.
  • 6,800 hectares of land have been covered by ashfall (reported 22nd October 2021).
  • Cost of lost banana plantations c.100m Euros, 150 hectares are under lava and others are in the exclusion zones; other crops, vineyards and livestock farming are also impacted.
  • SO2 emissions 40,800 tons per day. CO2 emissions up.

In the last 24 hours ground uplift of 10cm has been recorded at the station on the south of the volcano near the eruption site, which the volcanologists monitoring the eruption think may signal an increase in lava flow or the opening of a new vent.

Fig 2: Ground deformation at the station nearest the eruption site.  We have circled the latest data point to make it easier to spot.  Green line marks the onset of the eruption (added by IGN). Source: IGN
Fig 3: Seismic signal today.  Source: IGN

Recent Seismicity

Fig 4:  Plot by the author of earthquake number by day; Day 1 is 1 October 2021, Day 26 is 26 October 2021.  © Copyright remains with the author; all rights reserved, 2021.
Fig 5:  Plot by the author of earthquake depth and magnitude by day; Day 1 is 1 October 2021, Day 26 is 26 October 2021.  © Copyright remains with the author; all rights reserved, 2021.

We have made geoscatter and scatter plots of the swarm from day 21, the onset of the deeper earthquakes.  We have also made plots of the earthquakes over 3.0M, as these tend to get lost in the in the middle level swarm (7-16km). 

Fig 6: Geoscatter and scatter plots of the earthquakes between 1st October 2021 and 26th October 2021 (08:06:14) by the author.  © Copyright remains with the author; all rights reserved, 2021.
Fig 7: Geoscatter and scatter plots of the earthquakes greater than 3.0M between 1st October 2021 and 26th October 2021 (08:06:14) by the author.  © Copyright remains with the author; all rights reserved, 2021.

There are now a few earthquakes between the two swarms but little in the way of reported earthquakes heading for the surface; the latter may mean that lava is flowing freely through the existing conduit, or that a new conduit may be in the offing.  The hike in ground deformation reported above near the eruption site may indicate that whatever ensues, it is likely to be near the current eruption site – speculation on our part.

The eruption is now in its sixth week, lasting longer than recent previous eruptions, with no sign of waning. Has the initial eruption of magma created the right conditions for new magma to erupt from a greater depth, e.g. by creating a pathway for it and/or removing some of the constraining pressure? Only time, and a lot of research by the experts, will tell.

Armchair Volcanologist

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

Sources

News reports: El Mundo,  https://www.elmundo.es  and El Time, https://www.eltime.es/

Raw earthquake data: Instituto Geográfico Nacional (ign.es)

Aviation Code for Fagradalsfjall Lowered to Yellow, 18 October 2021

Good Afternoon!

The eruption at Fagradalsfjall has halted.  No lava has been erupted in the period 18 September to 18 October 2021 (or to the time of writing).  The seismic swarm at Kelir has lessened.  Gas emissions have decreased. The aviation code has therefore been lowered.

Fig 1: Image of Kelir cropped from Keilir (mountain) – Wikipedia, published under CC BY 2.0

The eruption will not be declared over for some time.  It is not possible to tell if this is a temporary lull or the eruption has ended; the eruption may resume at the same location in Fagradalsfjall or at a new fissure.   As the authorities have pointed out, this can only be determined in retrospect. 

The volcanic hazards are currently: gas, high temperatures both in the area and the lava field, earthquakes and rockfalls.

It’s been a few days since we looked at the latest earthquake swarm at Kelir, which is on-going.  Here are the updated plots.

Fig 2:  Count by day in the confirmed earthquakes reported by IMO; plot by the author.  © Copyright remains with the author; all rights reserved, 2021.
Fig 3:  Depths and magnitudes by day  of  the confirmed earthquakes reported by IMO; plot by the author. Blue columns are minimum depth (deepest); orange columns are average depth; grey columns are maximum depth (shallowest); yellow columns are average magnitude; and, light blue columns are maximum magnitude.  © Copyright remains with the author; all rights reserved, 2021.

From the plots we see a slow decrease in average depth.  This is borne out by the scatter plots. Let’s look at them.

Fig 4: Video by the author of geoscatter plots and scatter plots by day of the earthquake swarm at Kelir  from day 1 (27.09.2021) to day 25 (21.10.2021).  Note: day 25 is not a complete day.  © Copyright remains with the author; all rights reserved, 2021.,

Whether or not the eruption will resume and where, only time will tell.

Armchair Volcanologist

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

Sources

Raw earthquake data:  IMO

IMO: The Civil protection crisis level lowered from alert to uncertainty phase | News | Icelandic Meteorological office (vedur.is)

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