Saturday, August 23, 2014

A small eruption, so far (but the threat is getting bigger)

Jón Frímann is reporting that the eruption has started, but as yet is small. There are some web cameras and in the comments on his post there is some discussion of what they show, with the picture below showing what appears to be the start of a fissure eruption. This is consistent with an intrusion of the magma in the form of a dyke which is traceable from the earthquake patterns.


Figure 1. Webcam view of the start of the Bárðarbunga volcanic eruption.

The activity seems to be occurring in several places, with that part that is under the ice not being visible, were it be occurring, though if it breaks through the ice then this is where the larger plumes might be generated.

Figure 2.Earthquakes around the site (Icelandic Met Office)

The condition has been changed to RED, with the Met Office reporting that there are 150 to 400 m of ice above the surface in the region of maximum activity, and it will take some time for the magma to burn through this to the point where it ruptures, if it is big enough to do so. However the latest earthquakes include one of over 4.5 which is quite a bit bigger than earlier ones.

This has been UPDATED on 24 August

And on August 25th.

And on August 27th, as the quakes continue and approach the surface

.

The activity is continuing to grow.


Figure 3. Later on the 23rd. (Icelandic Met Office via Jón Frímann)

The eruption is definitely occurring along a rift in the rock. The development can be seen from a picture of the developing earthquakes from the 16th August, as Jón Frímann shows.


Figure 4. Development of the eruption as the magma moves along a rift to form a new dyke which is rising to the surface, prior to the eruption on the 16th August (Icelandic Met Office via Jón Frímann)

The growing size of the potential eruption can be seen from the latest picture of the earthquake activity, with it spreading away from the caldera.


Figure 5. Overview of Iceland showing the increasing scope of the activity on 24 Aug. (Icelandic Met Office)

The dyke is reported to be 40 km long already, and the magma, outside the ice cap may likely flow without much of it generating the high clouds of ash that are a threat to aircraft, and future weather patterns in Europe. (These eruptions can last some time). However if the bit under the icecap breaks through then the combination of water turning to steam and thermal shock on the rock can generate the very small particles which become a threat to both.

25th August Most of the activity is still occurring about 5 km below the surface, and the question becomes where, if anywhere, will the eruption reach the surface.


Figure 6. Earthquake activity 25th August 2014 (Icelandic Met Office).

The latest quake above magnitude 3.0 is at the northern end of the activity, suggesting that perhaps the magma is flowing in that direction, so that if it were to migrate to the surface then it would not come out under the ice cap. Which would be good news from the viewpoint that it is less likely that this will generate the high clouds of micro particles that might have occurred, as they did with the Eyjafyallajokul eruption in 2010.



There is, however, another concern that comes from the basaltic flows of lava, and was at its likely worst in 1783 when the nearby rift at Laki opened. The gases produced are toxic and were of sufficient volume that a large portion of the livestock and crops died, leading to the death of a quarter of the population from famine. The impact on Europe was also severe, with some suggesting it as a partial cause of the French Revolution. In part this was because of the resulting haze (which spread globally)which dropped temperatures around the world.

It also lasted eight months.

August 27th - The activity continues with quakes above 3.0 along the dyke, and with the earthquakes seeming to be approaching the surface.


Figure 7. Earthquke activity 27th August 2014 (Icelandic Met Office)

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