IGN and Pevolca have given us the final good bye of the volcanic vent affectionately known as Bob. It is the fifth time that they declare that the activity is dead. I also note that they claim that they “have put an end to the eruption”. I for one did not know that humanity could put an end to any eruption.
In the same missive they say that there is still tremoring and inflation going on, and that the earthquakes are ongoing. And I who thought this was signs that you should not state that an eruption had ceased.
On the contrary the volcano seems to have been rather active, and has by now reached a distance of only 88 meters from the surface. This with the above given signs make the Pevolca statement rather iffy in my opinion.
Another thing is that the low level harmonic tremor has steadily increased for a week; it is best seen on the EOSO and EGOM stations. This tremor at 0.59 and 0.3 respectively is a sign that most likely is associated with deep magmatic movement. Due to the wave-length a wave of such a low frequency cannot build in a narrow tube or small magmatic chamber. The increase probably means that new magma is moving upwards.
Either we should see new activity at the old vents around Bob, or a new vent formation will take place in the coming week or so.
After the medium sized earthquake swarm that took place at the MAR 20 km to the SSW of Reykjavik there have been reports of HS2 gas smell in the vicinity. The first one to report that was our own commenter Irpsit, who went trekking in the area of Lake Thingvellir. He reported strong smell on both sides of the lake, and that it numbed his nose within minutes. This tells us that the concentration was higher than is technically good for you. The danger with HS2 is that numbs the nose and then you can get into an area with poisonous levels of gas.
It is interesting that the gas emission rate in that area has increased after the 4.2M earthquake swarm. It probably means that in some way one of the volcanic systems in the area was affected since the area is rather large and requires more than a little gas puffing up to affect the nose in such away on both sides of the lake.
In reality there could only have been two volcanoes responsible for this emission, one of them is of course Hengill. Hengill is the largest of the volcanoes in that part of Iceland. But, I would like to make the culprit into Brennisteinsfjöll.
It erupted at 1000AD, 1200AD and at 1341AD. What makes into a likely culprit is that it is known to stink. The actual meaning of the name of the volcano says it all. Etymology is sometimes a useful science for volcanological purposes. Brennisteinsfjöll quite simply means Burnstone Mountain, or even more precisely, the Mountain of Brimstone.
Brennisteinsfjöll normally erupts in an effusive fissure style yielding between 0.2 to 3 cubic kilometers of lava. Two of the eruptions have VEI-2 numbers, the latest during 950AD. So if it erupts it should not be an ashy affair. At least at long as the lake does not get involved.