This will be a rather short post. During the last day I have received some information regarding Tanganasoga. Apparently it has been known for some time, but held back from the general population of El Hierro, that Tanganasoga is suffering from rapid inflation due to magma injection.
Even though I had two individual sources stating this, I still wanted to have additional confirmation before I wrote about it. After all, now we are talking about a volcanic feature that possibly can cause fatalities. So to get a bit of confirmation I asked GeoLurking to make a plot of the current uplift. It seems to indicate that there is an ongoing inflation in the Tanganasoga volcano.
Carbon dioxide map
CO2 is one of the premier gasses when you try to judge a volcanoes state. If you have an increased emission from a volcano you have yet another precursor to a possible eruption. As can be seen on the image below the area of Tanganasoga is leaking CO2 quite badly right now. The northwestern red area is related to the Roques de Salmor gas-vent.
The inflation of the Tanganasoga Volcano puts strain on the rock face pointing down towards the village of Los Llanillos. As the rock face is put under strain it will sooner or later start to shear and parts of the rock face will start to come loose and fall down.
There is also a small risk of a lateral collapse of the mountain side if an eruption occurs at Tanganasoga. I am not saying that it would be like Mount Saint Helens, the pressure is just not there. But, between 0.5 and 2 cubic kilometer of rock going down into the bay is not good news. And then on top of that, magma flowing down after the falling rocks. Well, I for one would not like to be in the way of it all.
Let us be clear on one thing, I am not saying that there will be an eruption at Tanganasoga. But the pressure build up on the rock alone requires diligent monitoring. And the political will to evacuate Los Llanillos if there is an increased risk of a larger rock fall due to mountain tension. If the risk increases even more, which I think is likely after seeing the CO2 map. They need to make serious preparations for evacuation of everything from Frontera to Sabinosa. Because if there is an eruption at Tanganasoga there will be rockslides, magma flows, and yes even the small risk of pyroclastic flows. And it will all most likely be going into the town of Frontera, so there is not being any leeway for risking a non-evacuation. It is time for the small boys of IGN, Pevolca, Involca and the rest to grow up, and grow a pair.