El Hierro – What did Elvis have to do with the Island?

Photograph by unknown. Orchilla Lighthouse, famous for being “The end of the World”.

During the night life got fairly interesting in El Hierro as the residents woke up from no less than two earthquakes above 4M. The larger of these two reached 4.4M.

Otherwise it seems like the magma continues to move in a general southwesterly direction. This has had as an effect that many of the GPS stations on the island is registering a downfall. It is at the moment uncertain where the magma is going.

The activity that we have seen during the last weak and a half is a sill intrusion, or a horizontal oblong shaped flat intrusion between different layers of rock. The intrusion has happened at great depth, around 20 kilometers deep. The activity started roughly under the old volcano of Tanganasoga, and then progressed towards the south east, passing the famous lighthouse of Las Orchillas on the way. The lighthouse is famous for being called “The End of the World”, a strangely fitting denominator when taking the current activity into account.

If we look closer at the 4.4M earthquake it had some rather intriguing features. It had a very weak transient in the beginning. The transient is the initial earthquake that is starting the rift of the fault plane, it was around 1.9M in this initial phase. After that a heavy magmatic component started as magma gushed in to fill the void left by the earthquake, and as the magma entered it further delaminated the layers in the rock, and more magma flooded in and so on and so forth. Let us just say that it was a lot of magma moving very rapidly.

Image by IGN. The earthquake starts at roughly 41 minutes, and it continued for 6 minutes before ending.

The angle was also rather interesting. The fault plane was tilted at 134 degrees, so the propagation of the earthquakes fault plane was going upwards at an angle. This gave the earthquake a fairly hard profile to plot, and both location and depth was changed due to this. Initial depth was set at 12 kilometers, as that was the end point of the faulting, but the beginning of the faulting was at 21 kilometers. And at an angle of 134 degrees this makes the start and finish line of the earthquake being somewhat different in location.

The earthquake was both Long Period, and a of the Broadband type. What I like to call a wet earthquake as oposing the dry earthquake that is associated with tectonic movement. It also look quite a bit like the sonic signature of water moving unexpectedly in a tube.

Worried in El Hierro?

The activity is right now inconclusive. The activity has started to show higher up, but the bulk of the earthquakes is still deep down. So it is fairly impossible to say where an eruption might occur. Some believe that it will happen in the western part of the island, or out at sea south to southwest of the lighthouse. Some believe it will in the end be an eruption closer to land from the vent called Bob, or even on land close to La Restinga.

In the end it is more likely that we will have another Effusive Lava Vent In the Sea, or to put it in short, another ELVIS.

If you are feeling really worried, or things get worse you should read the splendid article on volcano preparedness written by our resident Icelander. More volcano wisdom in that article than anywhere else, a wisdom coming out of extended experience of volcanic eruptions.

https://volcanocafe.wordpress.com/2012/06/29/icelanders-do-prepare-for-eruptions-a-personal-observation/

I would also recommend that if you feel the need to relocate yourself quickly, go to the eastern part of the Island. It should be fairly safe since there has been no activity there. In the light of things, if you are really worried, or things heat up even more, do not wait for an official call for evacuation. Just go if you can or feel the need. Remember that in the end it is you who are responsible for your decisions regarding you and your loved ones.

CARL