Iceland’s Katla volcano has been showing increasing signs of unrest over the last weeks, to include swarms of small earthquakes occurring every ten minutes or so, and it may be that the volcano is working up to an eruption. Katla is perhaps the most dangerous volcano in Iceland and so is being watched very closely. The danger Katla poses is not so much from pyroclastic flows and ash as from flooding and lahars.
The largest earthquakes have been magnitude 3.2, one of these last Thursday. It is hoped that the increased seismic activity at Katla will gradually subside, but of course it might not. Scientists are uncertain whether the recent quakes are being caused by magma intrusion, but it does seem likely given the recently observed harmonic tremor there, a prime indicator of magma movement. Earthquakes are not unusual at Katla, but the recent swarms of them are.
Katla is situated in the south of Iceland beneath the Mýrdalsjökull glacier (no, I can’t pronounce that either) which of course tends to melt from Katla’s heat and flood surrounding areas prompting rapid evacuations. Katla last erupted in 1918.
Last year’s eruption of the Eyjafjallajokull volcano forced hundreds of people to be evacuated and paralyzed international air travel for weeks because of a hovering ash cloud. And history has shown that when the Eyjafjallajokull volcano erupts Katla isn’t far behind. In the past 1,000 years, all three known eruptions of Eyjafjallajökull have triggered subsequent Katla eruptions.
Katla produced VEI 5 eruptions in 1721 and 1755, those being the size of the Mt. St. Helens eruption of 1980. Should this happen again Iceland could be in for some quite serious trouble and air traffic would be seriously impacted in the north Atlantic.
In other news another quake in the Banda Sea struck this morning, the 5th since the end of August, this one being a magnitude 4.3. The Banda Sea is a geologically complex zone around which are several volcanoes which I will be watching for activity. Moving right along the Ranakah volcano on the Indonesian island of Flores is showing increased activity and the alert level has been raised for the volcano. Ranakah has several vents the newest of which, dubbed Anak Ranakah, has a lava dome in it (never a good sign) and authorities are concerned that a partial collapse of the dome could generate pyroclastic flows, which would be a bad thing.
Raised alert levels at Rahakah pose the risk of inducing an influx of the curious unclear on the concept of an “attractive nuisance.”