Eruption - continued.

Day 5 of the explosive activity at Eyjafjallajökull Volcano, and many european airports remain closed. The eruption is still sending ashes 8km into the atmosphere, and doesn't show any signs of weakening - for more details on the ongoing eruption, check the webpage of the nordic volcanological institute at the university of Iceland, or this site showing various satellite images and animations of the evolution of the plume. And just in case you wanted to see a little photographic summary of the eruption that started on March 20th, here a very nice collection of 18 pictures.

Some of the most impressive images of the current explosive eruption can be found on Stromboli Online - where I found the image at the beginning of this post. I have been wondering what causes lightning in eruption clouds, so I did a little research on this topic. It seems that the mechanisms are quite different to those leading to thunderstorms, and obviously the processes occuring in the eruption plume are rather complex and not fully understood - and only few studies have been published on the topic. I found a lot of useful information in a recent journal article talking about it (James, M.R. et al., 2008, Electric Charging of Volcanic Plumes, Space Science Reviews, Vol, 137, pp. 399-418). I don't understand at all the details of the article, but my understanding of it is, in a nutshell: There is a difference in electric charge between the bottom and the top of the eruption plume. The charging itself happens primarily due to two processes: Electromagnetic emissions due particles interacting with each other, or when particles break; and the very rapid disruption of water surfaces (by boiling of water, for instance when water (or ice!) hits molten rocks at about 1200C. I did not know that boiling water causes charging! But it is somehow linked to the fact that water molecules are strongly polar, i.e. there is a difference in electrical charge between the oxygen atom and the two hydrogen atoms). When the difference in charge reaches some threshold, lighning occurs. (If anyone who reads this thinks I am totally off the mark, please do let me know!!). Confusing, but beautiful!

Oh, and in case you were wondering how the CO2 put out to the atmosphere by Eyjafjallajokull compared to that "saved" by canceling 60% of flights in Europe: On average in one normal day, close to 350'000 tons of CO2 are released by commercial flights in Europe. The current situation saves about 206'000 tons of CO2 - compare it to a mere 15'000t produced by Eyjafjallajokull... (Here the website where I got that from).