Thursday, February 16, 2012

El Hierro Volcano Eruption Winding Down

After 3-4 days of continually weak harmonic tremor at El Hierro volcano, it appears that the eruption is starting to wind down on the underwater cone. This does not mean that the risk of further activity, or other eruptive vents opening is over. Over the last few days, around 20 or so earthquakes a day have been recorded to the West of "Bob" (the tentative name for the underwater cone), gradually rising from 20KM beneath the surface, to 7KM yesterday, indicating a rapid dike intrusion. The GPS data shows a stable (not deflating) surface, which indicates that the magma chamber is still quite loaded.

Currently, the harmonic tremor at El Hierro is at a very weak level, with very minute occasional spikes (most likely those spikes are related to the earthquake activity to the West, and not from the vent itself), with the trend going lower and lower. This of course could indicate that the vent has collapsed and is simply re-pressurizing, and is merely gearing up for more action, but as the tremor has been gradually decreasing to the point it is now, my guess is that the vent is sealing up to the point where it can no longer erupt without some massive pressure from the magma chamber.

If anything further happens at El Hierro, rest assured I will cover it. For now, it may be time to finally say, "Bob has gone to sleep"

*****UPDATE 2/17/2012*****

Last evening, there were some images captured of nighttime smoking lava stones seen on camera, a bit to the East of "Bob", even while harmonic tremor remains nearly flat, proving once again that HT readings often do not correspond to actual lava emissions. HT is flat again today, although there was a 2.5 mag quake in the area which residents probably felt a little bit. There is no visible stain on the oceans surface, however a research boat and her crew reported smelling sulphur directly over the vent. It's really anyone's guess at this point as to what the situation looks like. It could easily be a "pillow lava" flow going on at the ocean's floor with occasional rising lava balloons (gas filled lava blobs that combust on the the ocean surface). Pillow lavas typically do not emit underwater "smoke" nor do they release a large amount of gas (it's more like squeezing toothpaste out of a tube, and is fascinating to watch video's of). At least this is my theory. If anything else happens, I will post another update.

*****UPDATE 2/18/2012*****

Tremor still extremely low, but surviving. It is probable some activity is occurring underwater, however any activity is weak with no visible "jacuzzi" area, and there has been no visual observations of lava balloons, or a stain. Current webcam views show a calm blue sea, with no disturbances.

Earthquakes however continue to pick up, with approximately 20 quakes a day over the last few days, and a 3.3 magnitude tremblor this morning. This definitely says that there is still a large, and active magma chamber underneath the island that probably has more in store. With the final collapse of "Bob" and cessation of eruptive activity, it is entirely possible that the magma must find another way to the surface in another location. With the locations and depths of the current quake swarms, it looks a bit likely that this might end up being off of El Hierro's SW coastline, directly W of the main vent.

This could end up being the last post about El Hierro for a while, as other volcanoes demand attention.

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