Continuous Seismicity in Katla Volcano

Earthquake swarms this time of year are no stranger to Kalta volcano in Iceland, however the current swarm may be cause for at least a minor amount of apprehension. Since late last month, quakes have been occurring regularly within Katla's summit caldera underneath the famed Mýrdalsjökull glacier. Katla regularly has rumblings of this nature, but the latest tremors have also been accompanied by ice melt, which is a cause for concern-- or at least a cause for residents to begin getting their "eruption kits" ready to go.

Katla has not had a major eruption in centuries in recent memory (Jon Frimann pointed out eruptions in 1860 and 1918 int he comments below, however most people were not alive back then) , however in late 2011, it did produce a minor eruption which resulted in a jökullhlaup, or 'glacier outburst flood', in which a significant amount of the glacier covering the caldera was melted, creating a massive sub-glacial lake, that suddenly burst from the outer walls of the glacier to produce a flood laden with liquefied ash, boulders, and chunks of ice that demolished a bridge and damaged roadways and farms on its rampage to the coast.

Katla's 2011 eruption was considered extremely minor for this volcano, which has been responsible in the past for some of the largest eruptions in modern historical time from the Atlantic island. In addition, some scientists claim that the volcano should have erupted shortly after its neighbor, Eyjafjallajökull, did in 2010, but this so far has not occurred.

As the seismicity has been ongoing for over a month now within the caldera, I would certainly say at this point that the volcano is growing restless. Granted, no harmonic tremor has so far been recorded, at least nothing out of the norm... these could be merely crustal adjustments to the volcano due to the shrinking icecap in the summer, and adjustments due to the small discharge of magma to the surface last year compensating for the gap in the magma chamber... one can definitely not be sure as there is currently no employed technology on Katla capable of imaging the magma chamber. 

The volcano, given the fact that thus far there has been no clear signal of magma injection, is by no means in a phase of imminent eruption however. While seismicity remains high, there are still none of the typical signals that the volcano is gearing up for a show. There have been instances when long dormant volcanoes have suddenly blown with little to no warning, and perhaps Katla might be one of them, but it is impossible to tell. As there were no scientific instruments available hundreds of years ago to give us an indication of the behavior of the volcano, we have no record of any precursors from a Katla eruption.

More Earthquakes at Katla Volcano in Iceland

The rumbling at Katla volcano continues, as a month has passed since the current 'swarm' (if you can really call it that) has continued. As the ice retreats above Katla's caldera, so too does pressure decrease on the volcano, thus making it much easier for gases, and heated water to bubble up and produce small quakes. As far as the Icelandic Meteorological Office is concerned, these quakes do not appear to be entirely volcanically related.

The quakes occurring are most likely (not certainly) related to crustal adjustments, and the reduction of the amount of ice on the summit. While this does actually increase the possibility slightly that an eruption could occur, the only reason for this is the pressure decrease. It would still take a fresh (and large) injection of magma into the volcanoes chamber in order to trigger an eruption, and given that there is thus far very little if any change in the normal harmonic tremor, it does not appear that these quakes have any reason to concern Iceland or Europe... at least not yet.

While Katla is widely believed to be "overdue" for an eruption, it is always important to note that even though sometimes there appear to be patterns in volcanic activity, this is really not the case. Looking only at statistical data, it is impossible to really say when a volcano will erupt. Katla will erupt again in the future, but when is a question that cannot be answered yet. I will continue to monitor Katla and if anything new occurs, I will post on it. But right now, I'm going to assume that the volcano is simply 'stretching out' and enjoying the summer, nothing more, nothing less.

El Hierro Activity Ramping Up Again

El Hierro, the volcano in the Canary Islands, may not be quite done yet (as was suspected by a great many following the behavior of this volcano). Although officially the government had lowered the volcanic threat alert level down to "Green", many volcanologists and volcano enthusiasts (including myself) were skeptical about the government's stance on the volcano. This week nearly 20+ earthquakes occurred at depth and some more shallow, as a science vessel captured images of a submarine ash and gas emission at "Bob", the submarine cone of El Hierro.

Other indications point to renewed or at least intermittent activity of the volcano, and much to the chagrin of the authors at Earthquake-report.com, the Spanish government seems to be covering it up, or at least attempting to obscure observations from the rest of the world and scientific community. For what reasons, nobody knows, but I suspect it is another wrong-headed attempt to get tourists to come back to the island.

While the El Hierro submarine vent has been relatively quiet these past couple of months, it has remained in a state of degassing, and the recent emission points to the possibility that the eruption could easily resume at any time. The amount of magma erupted is still far smaller than the volume of the actual magma chamber, and most likely much smaller than the amount of new magma that was injected into the chamber. Due to these facts, it is likely that the El Hierro island could see a longer period of eruptive activity in the future (this could be a precursor event to a more 'traditional' eruption above land, but so far there have been no records of serious GPS deformation, or increased CO2 emission on land).

The volcano caused quite a stir in the scientific community when the eruption was preceded by many thousands of small quakes. The island itself had not had an eruption since the 1700's, which was poorly documented internationally (locally, there is a wealth of knowledge and history), and most people had thought the Island to be dormant. That changed when a presumed eruption started taking place off the coast of the fishing village of La Restinga. The eruption was spotted when dead fish started washing ashore, and a large 'stain' on the oceans surface manifested. This was followed by what is known as a Serretyan eruption, which produced 'lava balloons' - bubbles of gas filled lava that would float to the oceans surface, and produce a fiery burst when the lava cracked and exposed superheated gas to oxygen. The lava rocks would then fall back to the ocean floor, building the underwater cinder cone further.

This continued for some months, and eventually dwindled down to a degassing phase. Many people had hoped/thought that the volcano would eventually create a brand new mini Canary Island, in what is called a Surtseyan eruption (where a submarine volcano breaks the water's surface to crate either an ephemeral island, much like what occurs regularly in the Marianas island/volcano chain, or a more permanent island like the recent eruption of Jebel Zubair in Yemen). It would have been a spectacular site for those on the island, and those that were watching the eruption webcam before the Spanish government shut it down (apparently running a webcam is really expensive! Yeah right...).

So I will again follow the goings on at La Restinga like I did before the eruption ended to bring you updates as they happen. This is a fun and suspenseful volcano for me to write about because it is such an unusual eruption, and it's occurring on an Island that didn't have much historical eruptive history. I always enjoy a good surprise. I'm not so sure the residents at La Restinga do however, as apparently they are beginning to loathe the attention that their volcano is getting, both from the reporters at El Hierro, and their own government.

Large Quake Swarm At Katla Volcano

Katla volcano is again showing increased seismicity and unrest, as the Icelandic cold season comes to a close. Today there were over 25 small quakes within the caldera, with most of the quakes in the range of 1.0-2.0 in magnitude. Katla volcano has long been thought to be overdue for an eruption. As the train of thought goes, as goes Eyjafjallajökull, so goes Katla shortly thereafter. This has proven to be somewhat of a guesstimate,  as Katla has refused to blow even after the 2010 eruption of Eyjafjallajökull which caused massive disruption to transportation in Europe.

Katla has been having near continuous quakes under its caldera for decades. While lately it may seem that Katla is preparing to blow, it should be noted that many quake swarms occur in the area regularly. These quakes are probably (almost definitely) related to magma intrusion into the caldera, it remains a phenomena that is unlikely to produce a massive eruption.

Katla volcano is covered in a thick glacier, and as such has somewhat of a natural eruption suppression system in place, given that the ice sheets are so thick. The volcano does frequently have magma intrusion, but most of the time, the ice mitigates this and simply causes glacier outburst floods (jökullhlaups) to occur, typically not resulting in explosions. However when Katla builds enough pressure, the result can be disastrous.

The current activity at Katla volcano is not a surprise, nor unexpected, and probably will not result in a whole lot of action. The media such as the BBC, or the Telegraph, will most likely blow this out of proportion. It is important to note that Katla frequently has quake swarms, dike intrusions, etc, that do not immediately manifest themselves as volcanic activity. However there is always a risk that an eruption could occur as a result of these magmatic intrusions into the volcanic system.

As always, time will tell if this will result in anything. A good 90% of the time, quake swarms are merely a distant precursor to a future eruption and nothing more. Sustained swarms are the ones to watch for, and given the past few weeks, I'm fairly certain that this is simply normal behavior for the volcano. Nonetheless, it is a noteworthy swarm, and you can watch the near real-time activity at http://en.vedur.is.

Quiet month

There isn't a whole lot going on in the volcano world this month. The usual suspects are still erupting (you can see them at http://volcano.si.edu), and the rest of the world for now is pretty quiet. I have not been posting blogs lately as I am still in the midst of setting up my new computer system and importing my volcano databases, earthquake monitoring programs, and other neat plugins that show what the Earth is up to.

Rest assured as anything of particular interest occurs, I will certainly post about it.

I would however like to take an opportunity to say thank you to my readers, and those who are supporting this blog. It takes a lot of energy, and contemplation to write a blog that is worthy of your time, so to those that take the time to read when I post an article, I would like to say thank you.

The lull in volcanic activity this month is always a good thing for those that live around volcanoes, except of course for communities that depend on volcano tourism. Most of the volcanoes erupting currently are volcanoes that are either in a continuous state of eruption, or are frequently in a state of unrest. There have not been many reports lately of any volcanoes that have erupted with any amount of surprise.

Cheers to that!