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Katla volcano, located near the southern end of Iceland's eastern volcanic zone, is hidden beneath the Myrdalsjökull icecap. Katla is one of Iceland's most active and most dangerous volcanoes, infamous for its large eruptions happening on average every 50-100 year, causing devastating glacial floods (jökullhlaups).
In recent year, increased seismicity and inflation of Katla has been being measured. Katla, statistically due for a new eruption, is being very closely monitored and an eruption in a not too distant future would not come as a big surprise.
Recent earthquakes under Katla volcano as of 22 June 2017, showing two small swarms (image: Icelandic Met Office)
Over the past days, seismic activity under the large ice-covered volcano has increased. It seems likely that at least some of this activity is caused by injections of new magma into the volcano's system, as some earthquakes were detected at depths between 10 and up to 25 km where no normal tectonic activity that could be triggering the earthquakes is expected. ...more
Most earthquakes in the recent swarms were tiny, with only 5 quakes during the past week above magnitude 3 (the largest being a 3.6 event on Tuesday). For the time being, the observed activity seems small and probably does not mean that a new eruption of Katla is imminent. [less]
Recent earthquakes under Katla volcano as of 26 Jan 2017 (image: Icelandic Met Office)
Seismic activity has increased at the volcano. A magnitude 4.3 earthquake occurred under the volcano on 26 Jan at shallow depth beneath the summit caldera covered by the Mýrdalsjökull glacier. ...more
Scientists now believe that the increased seismic activity indicates that the volcano is more likely to erupt in the near to medium term future compared to some years ago, but it is impossible to make any precise predictions. Icelandic authorities are increasing their surveillance of the volcano, which is one of the country's largest and most active, with potentially devastating eruptions due to the hazard of catastrophic glacial floods. [less]
Recent quakes under Katla volcano in Iceland (image: IMO)
An increased number of earthquakes has been occurred at shallow depths (few km) under the SW part of the ice-covered volcano's caldera. ...more
The largest event was a near-surface magnitude 3.5 event 3.9 km ESE of Goðabunga at 07:09 local time this morning. Whether the quakes are volcanic in origin (a swarm caused by magma intrusion) or caused by adjustments of the glacier's weight (or likely both) is unknown.
Magnitude vs time distribution of recent quakes at Katla (IMO)
Following Monday's large earthquakes, the volcano remains relatively calm seismically, with only small swarms of deep to shallow earthquakes occurring under the northern flank. According to experts, there is currently no sign of an eruption being imminent. ...more
Icelandic authorities are aware of the potential danger the next eruption of Katla represents (whether it occurs in the next months or only decades from now). A delegation of the volcanologists from the Icelandic Met Office was invited to discuss with a committee of the Icelandic Parliament about how to respond in case of an eruption. The biggest hazard are large-scale, potentially catastrophic glacial floods when an eruption occurs, which is likely going to be subglacial, as a result of rapid melting of ice by magma. A fast and wide-spread evacuation of all river beds draining from the Katla massif and alternative routes are likely a major topic in such plans. [less]
Earthquakes under Katla volcano during the past 48 hours (image: IMO)
At least one earthquake of magnitude 4.5 occurred this morning under the volcano, the strongest recorded for Katla in recent decades. It was felt in nearby areas. ...more
The Icelandic Met Office (IMO) reported two quakes, one at 01:47:02 local time at 3.8 km depth 8.1 km east of the summit (Goðabunga) followed 20 seconds later by another magnitude 4.5 quake at 0.1 km depth. Caution is required as these data are from automatic calculations which could actually in fact describe only one quake. During the past 48 hours, IMO has detected 48 earthquakes - most of them tiny, but including 4 of magnitudes of 3 or higher - at shallow depths under Katla. [less]
Location and time vs depth of recent earthquakes under Katla volcano
An increased number of small earthquakes, up to magnitude 2.7, has been occurring near the surface or at very shallow depths under Katla's ice cap since yesterday. ...more
These quakes are most likely related to weight adjustments of the thick ice cap during the ongoing seasonal melting and unlikely to represent a true seismic swarm caused by (internal) volcanic activity. In the meanwhile, the alert (uncertainty level) for the areas around rivers from the Mýrdalsjökull glacier has been cancelled by Iceland authorities. [less]
Epicenters of earthquakes at Katla during the past 7 days
Earthquakes have been more frequent recently under the volcano recently. Most of them were small (below mag. 3) and shallow events. It is unknown whether these relate to magmatic movements inside the volcano, increased hydrothermal activity or are adjustments of the ice cap due to increased melting. ...more
The government has declared "Uncertainty level" for Katla volcano yesterday. The largest hazard comes in the form of melt-water floods and sulfurous volcanic gasses dissolved in and released from glacial rivers. People are advised not to stop at Múlakvísl and Jökulsá and other glacier river valleys and keep cell phones turned on in order to be able to receive potential SMS alerts.
Depth & magnitude vs time of earthquakes under Katla
Depth and magnitude of quakes near Katla during August
As can be seen from our new plots of recent nearby quakes, the number of earthquakes near Katla appears to have been gradually increasing during August. However, most quakes are very shallow and probably NOT caused by magmatic movements, but adjustments of the shallow hydrothermal system. A possibility is that this is a seasonal pattern caused by the warming and increased melting of ice during summer. ...more
To watch out for, when trying to anticipate a new eruption, would be earthquake swarms at some depth (5-20 km) that become shallower. [less]
Another seismic swarm has occurred at Katla volcano yesterday. About 30 small quakes at shallow depths mostly between 1 and 6 km in the central part of the caldera were recorded and could indicate another intrusion or changes in the hydrothermal system.
Earthquake swarm at Katla volcano on 5-7 June 2012 (Icelandic Met Office)
A new swarm of earthquakes has started Tuesday (5 June) evening at Katla volcano. Until now, 34 quakes up to magnitude 2 have been recorded beneath the volcano, at mostly shallow depths around 3-7 km. The quakes are clustered in the SE part of the caldera, and could indicate that a magmatic intrusion is taking place in this area. Whether this is a precursor to a possible eruption of the volcano remains speculation.
Small earthquake swarm at Katla volcano during 28-29 May 2012 (Icelandic Met Office)
A swarm of 14 small to very small mostly very shallow quakes occurred at Katla volcano yesterday and today. Epicenter depths were reported between 0.1 and 12.2 km. Judging from the depth and magnitude of the quakes, the most likely cause for the seismic swarm are adjustments of the hydrothermal system under the icecap, and probably not magmatic intrusions (which would be possible indicators of a future new eruption). ...more
Earthquake swarm at Katla volcano on 15 May 2012 (Icelandic Met Office)
Katla volcano continues to show signs of increased unrest. A small glacial flood occurred from under the volcano's icecap Katla around 28 April 2012 and possibly again around 7-8 May, both times accompanied by increased levels of harmonic tremor. This suggests that magma movements inside the volcano might be heating up the ground, causing increased melting. ...more
A small seismic swarm at depths of 1-2 kim occurred yesterday 15 May. [less]
Jón Frímann on his dedicated blog about Icelandic (and not only) volcanoes closely follows what is happening there: a cluster of minor earthquakes has been showing up under the Katla volcano caldera. This has been following a gradual increase in seismic activity under Katla during the past few weeks. It could be a signal of new volcanic activity to be expected on a timescale of few weeks to months. A new eruption would probably be heralded by a strong seismic swarm, and could start and build up rapidly. It did so in July 2011 when a sudden increase in earthquake activity occurred and there was an small eruption without warning.
Volcanic tremor (a low frequency vibration often caused by magma rising to the surface) has been observed under Katla volcano in southern Iceland, Jón Frímann reports on his Iceland volcanoes blog (see below), closely following seismic activity in Iceland recorded both by national instruments and his own private geophone network. ...more
According to Jón, there are 2 possible explanations: one could simply be an increase in hydrothermal activity in the northern part of Katla volcano. The second could be magma movements at depth although there have been no significant earthquakes that usually would accompany an intrusion or small (sub-glacial) eruption, although this still could occur in the near future as often observed in the past during similar episodes of tremor followed by earthquakes. [less]
Recent earthquakes beneath Katla and Hekla volcanoes (Icelandic Met Office)
Two of Iceland's most known and active volcanoes are showing signs of unrest. Another seismic swarm (after the last one around 3 Feb) occurred at Katla volcano yesterday, although it was weaker than the previous ones. Most likely, the swarm was caused by another shallow dike injection (magma intrusion) beneath the crater, confirming the ongoing unrest at the volcano. ...more
A small, but very shallow 1.2 magnitude quake happened beneath the summit of Hekla volcano at just 100 m. [less]
Seismicity in Iceland during the past 2 days (Icelandic Met Office)
Small seismic swarms have occurred near Katla volcano (S Iceland), Henggil volcano (SW Iceland) and a weaker swarm near Askja (N-Central Iceland) during the past 48 hours. The cause of the swarms is unclear and their intensity is not alarming. They are not necessarily volcanic, but could related to tectonic stress release around the main Icelandic rift zones.
Signs of unrest beneath Katla, one of Iceland's most active volcanoes continue. A seismic swarm was recorded under the northern part of Katla volcano's caldera beneath the Mýrdalsjökull glacier in southern Iceland over the past 48 hours. 35 quakes of up to 3.2 magnitude, many at shallow depths, occrred mostly in the afternoon of 27 Oct.
A mew seismic swarm is occurring at Katla volcano, with over 60 small earthquakes of magnitudes of up to 2.6 at 1-8 km depth beneath the caldera since Sunday. It could be a possibility that this swarm is caused by the injection of magma at depth, but could also be due to structural displacements. It is unclear whether the recent signs of unrest at Katla are the precursors of a new eruption in a near to medium future.
Katla volcano, hidden under the large Mýrdalsjökull glacier in Southern Iceland, located just east of Eyafjallajökull volcano, is showing signs of unrest. In the past 48 hours, 8 earthquakes have occured under the ice cap, which could be a a sign towards a reawakening of the volcano which last erupted in 1918 and is considered overdue. Katla's eruptions are normally accompanied by large and extremely destructive glacier floods, so-called jökulhlaups. ...more
Although too early to send an eruption warning, the Icelandic authorities are monitoring the activity under Katla carefully. [less]
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