Tag Archives: Múlakvisl

Iceland, Mýrdalsjökull Region

Katla – Further Unrest; an examination of seismicity from 1st January 1995 to 25th June 2023

Good afternoon,

 Fig 1: Katla: photo 3 of 6. Retrieved from http://icelandicvolcanoes.is/?volcano=KAT. Jökulhlaup from underneath Mýrdalsjökull glacier in 1999. It remains controversial whether it was caused by a subglacial eruption. Photographer: Oddur Sigurðsson. Date: 18 July 1999

In recent weeks Katla has been showing a heightened level of unrest.  Just last month there was an earthquake swarm which led to the temporary raising of the aviation alert level to yellow. Yesterday, the Iceland Met Office reported a risk of ongoing earthquakes at Mýrdalsjökull, gas pollution near Kötlujökull and higher than usual water levels at Múlakvisl; this may be indicative of geothermal activity or magma movement.  The alert level is green at the time of writing.

Fig 2: Earthquakes in the Katla caldera 30th June 2023.  Source: Mýrdalsjökull (vedur.is)

So we took a moment to update our Iceland earthquake database to 25th June 2023 (the earthquake list for week ending 2nd July 2023 is not yet available, although they can be viewed on Skjálfta-Lísa (vedur.is)) and plot the earthquakes at Myrdalsjökull, 63.1°N,18.5°W to 64.2°N,20.00°W, and then the caldera area, 63.45°N,18.98°W to 63.72°N, 19.24°W  from 1st January 1995 to 25th June 2023.

Fig 3: Mýrdalsjökull earthquake statistics from 01/01/1995 to 25/06/2023.  2002 to 2004 are associated with a possible intrusion at the Godabunga cryptodome.  2011 to 2012 and 2016 to 2017are associated with jokulhlaups and possible subglacial activity. © Copyright remains with the author; all rights reserved, 2023.

Our earthquake density plots show that most activity is close to Godabunga, Katla’s cryptodome.

Fig 4: Geodensity plot by the author of earthquakes occurring in Mýrdalsjökull from 01/01/1995 to 25/062023.  © copyright remains with the author; all rights reserved, 2023.

Given that activity near Godabunga has dominated the above plot, we plotted a smaller area for the caldera.

Fig 5:  Geodensity plot of earthquakes in the Katla caldera from 01/01/1995 to 25/06/2023 by the author.  © Copyright remains with the author; all rights reserved, 2023.

This plot shows most seismic activity in the NE of the caldera, near the site of the source of the 1955 jökulhlaup, some in the S of the caldera near the source of the 1918 eruption and 2011 jökulhlaup and another swarm on the volcano’s flank, south of the caldera.  The swarm to the south of the caldera occurred in 2011 at the Gvendarfell Ridge.  Later study of the Gvendarfell Ridge found sources of recent flank eruptions, including rhyolitic domes and Surtseyan craters.

We have also plotted monthly geoscatter plots for Myrdalsjökull from January 1995 to June 2023 (25 June 2023) and created a 3D rotating scatter plot for the same time period and area.

Fig 6: Geoscatter plots by the author for Mýrdalsjökull, January 1995 to June 2023 (25 June 2023).  Key:  Current Month Green dots denote earthquakes <3.0M,  Yellow stars denote earthquakes ≥ 3.0M and <4.0M and Red stars denote earthquakes ≥4.0M; and, Prior Months Grey/aqua dots denote earthquakes <3.0M, Old gold stars denote earthquakes ≥ 3.0M and <4.0M, and, Dull red stars denote earthquakes ≥4.0M. Blue triangles denote GPS stations. © Copyright remains with the author; all rights reserved, 2023.
Fig 7:  Scatter plots by the author for Mýrdalsjökull, January 1995 to June 2023 (25 June 2023).  Key: Red denotes older earthquakes and yellow the most recent.  © Copyright remains with the author; all rights reserved, 2023.

We make no predictions.  For updates, please refer to the Icelandic authorities.  IMO is a good starting point.

Armchair Volcanologist

© Copyright remains with the author; all rights reserved, 2023

Sources:

Raw earthquake data:  Icelandic Meteorological office (vedur.is)

Giulisa Sgattoni, Federico Lucchi, Páll Einarsson, Ólafur Gudmundsson, Gianfilippo De Astis, and Claudio Antonio Tranne, “The 2011 unrest at Katla volcano: seismicity and geological context”, JÖKULL. No 69, 2019. https://jokull.jorfi.is/wp-content/uploads/2021/12/J69-53-70

Also see our earlier article for background information: The Katla Volcanic System, Mýrdalsjökull – the not so cuddly Katla