Tag Archives: KRÝSUVÍK VOLCANIC SYSTEM

Iceland, Reykjanes Peninsula

New Fissures Open Near Geldingadalur, Fagradalsfjall, Iceland

Updated earthquake density video added (uses satellite image as background). 12.04.2021

Good Morning!

Geldingadalur – Where Are We at Now?

Since we last wrote, the new volcano at Geldingadalur has continued to erupt with a lava output rate between 5 m3 per second and 10 m3 per second, filling the Geldingadalur valley with more lava.  The University of Iceland has confirmed that the early lava erupted has a magnesium content of 8.5%, a low titanium dioxide content and is more depleted in rare earth elements (low HREE to LREE ratio) than earlier historic lavas, indicating that it is a more primitive lava sourced from the lithospheric mantle at a depth of between 17 km and 20 km.

On 5 April 2021 at around midday, a new fissure opened up about 700 m north east of the original eruption site.  The fissure, spotted by a sightseeing helicopter, was quickly confirmed by the RUV.is webcam monitoring Geldingadalur. Fortunately, no-one was in the vicinity at the time due to bad weather and sheer good luck; the site had been open to visitors at the time. The fissure is around 200 m long.  Lava from the fissure is flowing into the Meradalir valley. 

Fig 1: New fissure on 05.04.2021 in the foreground with lava flowing to Meradalir on the left of the image.  The original Geldingadalur eruption is on the right of the image.  Photo IMO.
Fig 2: Lava from the first new fissure entering Meradalir at 15:00 06.04.2021. The fissure itself is on the ridge in the background (Photograph: Public Protection/Björn Oddsson).

At around midnight on 6 April 2021, a second fissure opened up between the earlier fissure and the original eruption site.  This had been preceded by a landslip earlier in the day. Lava from this fissure is now flowing into both the Geldingadalur and Meradalir valleys, linking the eruption sites.  It is believed that the three eruption sites belong to the same fissure.

Fig 3:  Photograph from Public Protection/Björn Oddsson showing the three eruption sites and lava flows.
Fig 4: Map showing the location of the three eruption sites from IMO. The fissures are shown as red lines and dots; and, lava flows are based on photography.

Unfortunately, one of the webcams set up by mbl.is to monitor the Geldingadalur cones was lost; its last image is shown below.  We thank mbl.is for providing the webcam; we viewed its images with a lot of interest.

Fig 5: Screenshot from the mbl.is webcam.is set up to monitor the cones at Geldingadalur.  This may be this webcam’s last image. The lava flow to the lower left of the image is from the newest fissure. 

Like the original eruption site, neither fissure opening was heralded by an increase in seismicity in the immediate vicinity. 

Seismicity Post the Initial Eruption

We have updated our earthquake plots for the period 19.03.2021 to 06.04.2021.  We can confirm that there is very little earthquake activity in the vicinity of Geldingadalur.  The fissures are not giving any seismic warning; seismic activity near Keilir dominates.  It is perhaps surprising that magma has not made its way to the surface north east of Fagradalsfjall; does magma finds it easier to make its way through older fault-ridden Pleistocene rock that has not been covered in tougher historic lavas?

Fig 6: Earthquake density plot of the earthquake swarm post eruption (19.03.2021 20:45 to 06.04.2021) by the author. © Copyright remains with the author; all rights reserved, 2021.
Fig 7: Scatter plot of the earthquake swarm post eruption (19.03.2021 20:45 to 06.04.2021) by the author. © Copyright remains with the author; all rights reserved, 2021.

We have also tried our hand at making a video of the earthquake density plots by month from 2008 to 6 April 2021.  Months are numbered from January 2008 (Month 1) to April 2021 (Month 160, which only has 6 days).   If you make it all the way through, you will see that Fagradalsfjall has had several swarms, albeit much smaller than the current one. Enjoy!

Fig 9: Earthquake density plots by the author from Jan 2008 to April 2021. © Copyright remains with the author; all rights reserved, 2021.

As noted in earlier posts, for up-to-date advice and status, check out IMO or the Department for Civil Protection and Emergency, links below. 

The Armchair Volcanologist

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

Sources: 

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

MBL webcams: Livestream of Fagradalsfjall Eruption  and New Webcam

Iceland, Reykjanes Peninsula

An Introduction to The New Volcano, Geldingadalur, Fagradalsfjall, Iceland

27 March 2021

Good Morning!

The eruption at Geldingalur, Reykjanes, Iceland, which started on 19.03.2021 at 20:25, is continuing unabated as I write.  The volcano is happily bubbling away building somewhat unstable but impressive looking cones and covering the Geldingadalur valley floor with lava.

Fig 1: Cones of Geldingadalur, cropped from an image by Berserkur, published under CC BY-SA 4.0

The eruption is steadily increasing at the time of writing; it has a lava output of 5 -7m3 per second.  IMO have estimated that the valley would fill enough for lava to overflow into the neighbouring valley, Meradalir, in a matter of days at the current eruption rates.

Fig 2: Image by IMO.  Expected path of the lava over the next few days at the current eruption rate.

Scientists at the University of Iceland are analysing the lava.  To date, they have reported that the lava is a primitive one (i.e. little magma evolution in the crust), indicative of a mantle source at a depth of 17 km to 20 km.  

Geological Setting

The Reykjanes Peninsula lies on oceanic crust created by the Mid Atlantic Ridge.  The Peninsula, itself, straddles the Ridge.  The crust here is 15 km thick, which is unusual so close to a spreading ridge.  However, Iceland is a basaltic plateau overriding a mantle plume. Both the mantle plume and the Mid Atlantic Ridge influence formation of the crust.  There are no magma chambers / reservoirs in the crust on the Peninsula; magma tends to ascend directly from the mantle. 

The Peninsula is made up of lava shields, móberg hills, table mountains and fissure-fed lava flows and crater rows.  The shield volcanoes on the Peninsula formed at the beginning of the Holocene between 10,000 and 7,000 years ago.  Shield volcanoes form from hot picrite or olivine tholeiitic basaltic lava flows with rates of c . 5m3 per second.  The móberg hills formed from submarine fissure eruptions and consist of pillow lavas, breccias and tuffs.  The table mountains were formed from subglacial activity, which had the activity not been constrained by the ice cap, would have resulted in shields.  Later Holocene activity has comprised effusive tholeiitic fissure eruptions which formed crater rows and produced large lava flows that now cover some of the earlier formations.  Historic activity has been between 940 AD and 1340 AD, including the Reykjanes Fires of 1210 AD to 1240 AD; and, the Krýsuvík Fires of 1151 AD to 1188 AD. 

Geldingadalur, itself, is a small valley to the south east of the summit of Fagradalsfjall, a 385m high hyaloclastite subglacial Pleistocene table mountain formed during the Weichselian glacial period, with a subaerial lava cap on its northwest part.  It is currently classified as part of the Krýsuvík Volcanic System.

The Fagradalsfjall area is seismically very active, with large earthquake swarms, notably in 1998, 2000, and 2004, and again now as part of the new volcano-tectonic episode on the Reykjanes Peninsula that started in December 2019.  Various studies from previous seismic activity have noted extensive faulting under the south west part of Fagradalsfjall; these faults strike N-S and NE -SW. In addition, there are two clusters of faults under the eastern part.

Earlier swarms in the current volcano-tectonic episode have resulted in magma intrusions, such as the one at Mt Þorbjörn which we discussed last year, but no eruption.  The latest earthquake swarm which started on 22 February 2021 is the only one to result in an eruption at the time of writing.

Seismicity in the Current Swarm

We have updated our plots for the Reykjanes Peninsula and dividing them between the run up to the eruption on 19 March 2021 at 20:45 and after the eruption to 26 March 2021 15:55.

The plots preceding the eruption repeat the ones shown earlier  so we are just showing the geodensity plot for comparison.  You will note that the earthquakes do not reach down to 15 km in the current swarm to date.  However, there were one or two deeper earthquake in some of the earlier episodes.

Fig 3: Geodensity plot by the author of earthquakes occurring between 63.83314°N, 22.55148°W and 63.96605°N, 21.85666°W from 22.02.2021 to 19.03.2021 20:45.  © Copyright remains with the author; all rights reserved, 2021.

The plots for the period after the onset of the eruption (19.03.2021 20:45 to 26.03.2021 15.55) show that activity is concentrated on Geldingadalur and two spots north east of Fagradalsjall.  Seismic activity has also extended further south.

Fig 4: Geodensity plot by the author of earthquakes occurring between 63.83314°N, 22.55148°W and 63.96605°N, 21.85666°W from 19.03.2021to 26.03.2021.  © Copyright remains with the author; all rights reserved, 2021.
Fig 5: Scatterplot by the author of earthquakes occurring between 63.83314°N, 22.55148°W and 63.96605°N, 21.85666°W from19.03.2021 to 26.03.2021 20:45. Colour denotes earthquake number since the onset of the eruption (red earliest; yellow latest).  © Copyright remains with the author; all rights reserved, 2021.

Whether the earthquake hotspots will lead to new eruption sites, only time will tell. 

For the current status, please consult IMO (link below).

If you wish to watch the eruption , there are local webcams. The link to one is given below.

The Armchair Volcanologist

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

Sources:

Earthquake raw data: IMO:  https://en.vedur.is/

Status reports: https://en.vedur.is/

Webcam link

RÚV.is : Geldingadalur – Volcano (livefromiceland.is)

Iceland, Reykjanes Peninsula

Alert Level for the Krýsuvík Volcanic System Lowered to Orange; the eruption is contained in Geldingadalur for now

20.03.2021

Good Evening!

Fig 1: The eruption at Geldingalur earlier today, 20.03.2021.  Image from IMO.

For this update, our information comes from IMO and the Department for Civil Defence.  We will update our earthquake plots later on.

The eruption which started yesterday on a ridge in Geldingadalur has been assessed as a minor one, contained in the valley; the eruptive fissure is around 500m to 700m long; and, there is no ash or tephra.  Levels of S02 are low, except near the eruption site; gases can accumulate in the valley or other depressions. The main road to Keflavík from Reykjavík has been opened.  However, the road between Grindavík and Þorlákshöfn is closed.  The aviation code has been lowered to orange. 

The eruption may change without notice.  The Department of Civil Defence warn of the potential for new fissures opening either at the current site or elsewhere from the dyke near Fagradalsfjall.  Large earthquakes are considered unlikely at the eruption site but the risk for a magnitude 6.5 still remains for Brennisteinfjöll.  At the moment seismicity on the Reykjanes Peninsula is much reduced.

Fig 2: Map of earthquakes in the last 48 hours on the Reykjanes Peninsula by IMO.

Hazards for those visiting the site are getting too close to the lava flow and not being able to outrun any lava that breaks off it; the craters are unstable and may break, releasing a lava flow; and explosions where hot lava meets water-logged ground.  The Department of Civil Defence advises observers to keep to the hills surrounding the site.  Not that it is easy to get to without a helicopter!

Local webcams have been set up from which the rest of us can watch; one is:

https://www.livefromiceland.is/webcams/geldingadalur-volcano/

For up-to-date advice, please consult IMO or the Department for Civil Defence.

The Armchair Volcanologist

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

Sources:

IMO: https://en.vedur.is/

Department for Civil Defence: https://www.almannavarnir.is/

Iceland, Reykjanes Peninsula

Krýsuvík Volcanic System, Aviation Code Red; A Volcanic Eruption Has Started Near Fagradalsfjall, Iceland

1 Comment

Good Evening,

19.03.2021

Fig 1: Eruption at at Geldingadalur. Image from IMO: A volcanic eruption has begun | News | Icelandic Meteorological office (vedur.is)

This was going to be a post with an update on the earthquake swarm on the Reykjanes Peninsula, but the magma beat me to it!  IMO has just confirmed that a volcanic eruption is underway near Fagradalsfjall at Geldingadalur.  The eruption started at 20:45 19.03.2021. It has been named as Geldingadalsgos, after the valley.  At the time of writing, the eruption is a small fissure eruption; the fissure is c. 0.5km long.

Fig 2: Hópsnes Lighthouse, Grindavik looking towards the Fagradalsfjall system.  Image cropped from one by Martin Morris, published under CC-BY-SA 2.0

The public have been  advised not under any circumstances go close to the eruption site or on Reykjanesbraut. First responders need to be able to drive freely to assess the situation. Scientists are working on assessing the eruption, the site and possibilities.

People living nearby in Þorlákshöfn have been instructed to stay indoors, close windows and turn up their heating to avoid exposure to any volcanic gases.  The Reykjanesbraut has been closed – the main road from the capital region to Reykjanesbær and the international airport at Keflavík.

Fig 3: Aviation code red; source IMO.
Fig 4: IMO’s confirmation of the eruption (third warning down). This is an extract from a screenshot of the page.

Here are the updated earthquake plots by the author, anyway.  The raw earthquake data has been obtained from IMO; this is confirmed earthquakes to date (19.03.2021 15:00). IMO’s page above gives the more recent earthquakes.

What we see from the plots is that seismic activity has now extended beyond Reykjanes to the west and the swarm is still active.  Activity in the swarm is densest to the NE and SW of Fagradalsfjall.   The depth plot shows that earthquakes in the swarm are tending to be smaller and shallower.

Extension of the swarm to the west is in keeping with the swarms which have occurred since December 2019. 

Fig 5: Geoscatter plot of the earthquake swarm by the author from 22.02.2021 to 19.03.2021 (15:00).  Colour indicates earthquake number from 22.02.2021. © Copyright remains with the author; all rights reserved, 2021.
Fig 6: Geodensity plot of the swarm between Svartsengi and Krýsuvík. by the author from 22.02.2021 to 19.03.2021 (15:00).  © Copyright remains with the author; all rights reserved, 2021.
Fig 7: Scatter plot of the earthquake swarm by the author from 22.02.2021 to 19.03.2021 (15:00).  Colour indicates earthquake number from 22.02.2021. © Copyright remains with the author; all rights reserved, 2021.
Fig 8: Scatter plot of earthquake depth v time (earthquake number in the swarm) by the author from 22.02.2021 to 19.03.2021 (15:00).  © Copyright remains with the author; all rights reserved, 2021.

Let’s hope that this is a “tourist eruption”; our thoughts are with anyone affected by this eruption.

For more up to date information, please consult IMO or the Department for Civil Protection.

The Armchair Volcanologist

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

Sources:

Plots by the author.

Source for raw earthquake data: IMO

Icelandic Meteorological Office – IMO (@Vedurstofan) / Twitter

Department of Civil Protection and Emergency Management | Almannavarnir