Eyjafjallajokull is Quieting Down

According to the Icelandic Meteorological Office, the activity at Eyjafjallajokull has diminished in a number of significant ways, although it is not clear whether this is "the end" or just a lull. The plume is "only" 10,000 feet high and is composed of steam only. There are no reports of ashfall, and no lightning strikes have been detected (lightning strikes indicate significant ash concentration). Meltwater from ice surrounding the volcano is small, temperatures from a heat camera are "almost 100 C". Volcanic tremor is decreasing to levels prior to the eruption, except in the frequency band 1-2 Hz which may be due to rising steam. I published a paper ages ago regarding seismicity of a very similar nature at Old Faithful, see Figure 1, reproduced here. It had been noted by scientists studying Karkar Volcano in Indonesia that there was banded harmonic tremor that suggested underground geyser eruptions, and the similarity of the two seismograms (Karkar and Old Faithful) is amazing.

You can get a higher resolution look at the figure by clicking on it, but it's not a high-quality image to start with! I look fondly at the low-quality reproduction of the seismic record (it isn't much better in the pdf of the original article). 1984--before PDF, WWW, and low-quality scanning to make the PDF. Young(er) geophysicists will be laughing--this seismogram was obtained by the now-lost-art of smoked drum seismographs. The art is to take the drum off the case, wrap it in special white paper, and then hold and rotate it over a smoking kerosene lamp. Since I had to do all of my seismic work in Yellowstone during the winter in 1976 (approximately when this record was obtained), we did all of the smoking in an unheated garage in Yellowstone. Kudos to my colleagues at the time, Rick Hutchinson (now deceased) and Gonzalo Mendoza!