Sunday, December 4, 2011

New Activity in Grímsvötn Volcano, Iceland

Several sources are reporting harmonic tremor at Grímsvötn volcano in Iceland. Grímsvötn volcano had its largest eruption in 140 years just months ago in May of 2011, which was approximately 10 times the size of the eruption at Eyjafjallajökull in 2010. The eruption at Grímsvötn however fell upon favorable winds for Europe, and did not cause the same amount of airway chaos as the 2010 eruption.

Reports thus far are that the tremor in Grímsvötn is much higher and stronger than the tremor that led up to its last eruption. This however does not mean that an eruption is imminent, or going to occur for sure. Harmonic tremor does typically indicate magma movement, but it could also be hydrothermal. In any case, the tremor could merely mean that the magma chamber is beginning to inflate again, and this could stop at any time if the pressure is right.

Grímsvötn is one of Iceland's most active volcanoes, and also one of the largest. Its remote location in the middle of the Grimsfjall glacier, the largest in Iceland, makes it a relatively safe volcano, all things considered. It has however had massive eruptions that in the past have discharged incredible amounts of glacial melt water into the ocean. The last eruption, though powerful, did not last long enough to melt a significant portion of the glacier, though floods did occur.


  1. A few comments to Grímsfjall (thats actually the real name of the volcano, Grímsvötn is the name of the lake below the glacier, icelandic vötn mean water or lake).
    High tremor in the area can also be caused by water fowing under the glacier. This is called jökulhlaup (glacier run, glacial flood) and happens from time to time when the lake is filled up with melt water from the glacier above. Since the last glacier run happened almost exactly one year ago, this is quite unlikely.
    The glacier above is called Vatnajökull.
    And the last eruption actually doesn't melt much of the glacier, because the eruption took place at the same spot of the last two eruptions (1996 and 2004). So there was not much ice in this area.

  2. Very true, tremor can be caused by many different factors, however harmonic tremor at depth is typically associated with magma movement as it indicates dike intrusion or inflation of a magma chamber.

    As for the naming convention, it seems that with Icelandic volcanoes there are many different names for many different volcanoes. When I reference volcano names, I do so by referencing the Smithsonian Global Volcanism Program (GVP) and their information, (on their site they refer to Grímsfjall volcano as Grímsvötn). Eyjafjallajökull for example is (shortly) referred to as Eyjafjöll on some sites, and occasionally simply "Eyja"... so apologies for the Grímsfjall hiccup as these things get confusing if you're not a local. Thank you for adding to the info however, always appreciated.

    The eruption in 2011 most likely melted a lot of glacial ice off of the top, and blogger Jon Frimann has posted (what I believe to be ) a more updated picture of the Grímsvötn lake on his blog banner. It shows very little ice within the caldera, and the rims are still black with ash from the previous eruption, so if an eruption does start, it will likely be fa bit less explosive than last time. Time will tell!


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