As the smoke starts to clear at El Hierro we get a much more detailed picture of what is happening. As data has poured in we can now deduce a few things.
First of all GPS figures today confirmed that this is indeed a fourth bolus of magma coming up from the depth. The first one in July 2011 started the entire hubbub and in the end caused the sub-aquatic eruption south of La Restinga. A second bolus in January that followed the same path revigorated the ongoing eruption briefly, but was too small to keep up the pressure in the volcanic system and the eruption dwindled to a halt. The third bolus is so far the most interesting, during a few days more magma arrived than during the first one that caused the eruption. The magma arrived at the same place as for the first two (around the Tanganasoga volcano), but then it took an entirely new path and created quite a few earthquakes as it moved towards the western point of the Island. The fourth bolus also arrived at Tanganasoga, and immediately started to move south and slightly downwards.
We still have only one set of data points for the GPS, but since it is visible on many of them it is still credible. What is a good test for if there is actual inflation or not is to check for motion in EW and NS directions. A false read normally does not show that.
The earthquake swarm is very vigorous with more then 100 earthquakes per day. The pattern is still continuing with a south and slightly down dipping motion. We will see if the hard tested village of La Restinga will have to suffer both the knowledge and the feeling of magma moving straight down under their feets.
We can also rule out any degassing or actual small eruption, what initially looked like harmonic tremor are most likely small earthquakes, there is no clear signal showing harmonic tremor to this date.
There is no way to know if this bolus will cause an eruption or not. The lack of harmonic tremor says that it will at least not happen within the next 24 hours or so. But, for the residents on El Hierro the same advice is always valid, stay on top of the news.