So what is the definition of “hours” that I should have used in anticipating the Katla eruption in my last post on this subject? I must confess that I had anticipated about 72 hours being the likely envelope within which we would see an eruption following the magnitude 3 quake that happened there on Wednesday. But here we are just into Monday, and there has been no eruption yet. But there has been another magnitude 3.8 quake, in this case:
07-18-2011 63.660 -19.116 3.8 magnitude (1.1 km deep 7.0 km ENE of Godabunga)
There have been a flurry of small quakes, that had both preceded the current larger one, and which have now followed it (at least a dozen).
Katla earthquakes of the last 24-hours. The green star denotes the larger earthquake referred to above (Icelandic Met Office)
In the 24 hours before this last there had been over a dozen other earthquakes within the caldera region. The stress is inducing more and more fractures into the rock (hence the earthquakes) and as these coalesce and the rock becomes fragmented in the region of previous magma flows, this creates the weakened channel along which the magma can force its way. Jón Frímann is not reporting any signs of the harmonics that signal significant magma movement at the moment though he suspects that the location of the quakes, now indicate that magma is making its way to the surface. Looking at the seismograph plot that he has there is no question that activity seems to be rising.
Just as a reminder there are two webcams on the site, one is here and the other is here. Neither is showing much yet.
Katla from second webcam at 12:33 am Eastern US time.
We shall see if this is just another step along the way, or if this is now at the point of erupting. But I suspect that it won't be before I get up in the morning, so goodnight!
Well looking at the cloud patterns this morning, if I wanted to stretch my imagination, they do suggest there may be some steam
But as I continue watching, it is purely an artifact of the light. And the scenes return to normal.
UPDATE 2 At the end of the day the sky is clear and there is nothing visible above the surfaces on eith webcam. And so we can relax for a little. The Icelandic Met Office is also saying that an eruption is not likely. However there continue to be a significant number of small quakes that are not just at the surface. Bear in mind that after fractures are created, if the magma is to get through them they have to be held open by the fluid pressure, and that has to work its way up as the magma migrates upwards, and this all takes time.