Unusual seismic activity in the region of Öræfajökull, a formidable Icelandic volcano, has scientists worried that another eruption may be forthcoming.
Öræfajökull [Photo by Uwe Lexow]
Öræfajökull is known to be the largest active volcano in Iceland. The northwest rim of the volcano’s summit crater has Hvannadalshnjúkur, the highest peak in the country. Öræfajökull has erupted a total of two times in known history: once in 1362, and once again in 1727. Though the volcano has only erupted twice in the 1,100 years since Iceland became populated, those two eruptions were quite significant. The 1362 eruption in particular was the largest eruption in Iceland to date, and ash from this 655-year-old eruption has been recently found in Greenland and western Europe.
Earthquakes are rare in the region where Öræfajökull lies. However, there have been small earthquakes occurring in the region since June of this year. This has prompted scientists, authorities, and locals to review past eruptions and see how bad a future eruption could be.
Hvannadalshnjúkur [Photo by Vilhelm Gunnarsson]
Geologists think that magma may be collecting in Öræfajökull’s magma chambers, which has led the ground to rise over the past two years. Just this October 4, a particularly strong earthquake swarm hit the area, with the strongest tremor registering at magnitude 3.4. Though this may not seem like a powerful earthquake, it is for the area in occurred in. When it comes to Öræfajökull, scientists consider earthquakes with a magnitude higher than 3 to be powerful. The last time an earthquake with a magnitude exceeding 3 hit Öræfajökull occurred in 2005.
These earthquakes may also indicate a coming volcanic eruption. These earthquakes are caused by the movement of magma deep inside the volcano, and the pressure makes it likely that a volcanic eruption will occur.
Meltwater floods from the 1362 and 1727 Öræfajökull eruptions flowed down these valley glaciers. [Photo by Dave McGarvie]
The 1362 eruption in particular was quite destructive, and is currently the second deadliest eruption in Iceland’s known history. It also caused one of the largest tephra eruptions in the world in the past 1,000 years. According to a paper on the volcano’s preserved deposits, the eruption actually began with a deposit of the tephra blanket in a low plume.
The paper also found that Öræfajökull’s eruptions can be quite deadly, and also quite complicated. The most powerful phase of the eruption was short-lived, and the stages before and after that phase had differing levels of explosivity.
The 2010 eruption of the volcano Eyjafjallajokull [Photo by Árni Friðriksson]
In 2010, another Icelandic volcano erupted. It was the volcano Eyjafjallajökull, which is now considered to be dormant after its last eruption. That latest eruption, which occurred in 2010, was also preceded by unusual seismic activity caused by magma flowing into the volcano’s magma chambers. The eruption caused extensive air travel disturbance across Europe due to a particularly large ash cloud.
If Öræfajökull had an eruption similar to the 1362 eruption, would it have the same effect as the 2010 Eyjafjallajökull eruption? Researchers say no, it likely would not. The Eyjafjallajökull eruption lasted for weeks, which was why it belched out so much ash. However, an Öræfajökull eruption likely wouldn’t last as long and its effects would be much more localized.
Of course, no can really tell exactly when Öræfajökull will erupt. It’s possible that it won’t even erupt any time soon, and that it’s just grumbling in its sleep. However, scientists are monitoring the volcano just in case it jolts fully awake.
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