A magmatectonic phenomenon called Drumbeats was originally discovered by the USGS at Mount Saint Helens Back in 2006. At 16.15 a similar phenomenon started at El Hierro in the Canary Islands, Spain.
First of all, let me say once and for all, El Hierro will not erupt like Mount Saint Helens. They are two totally different types of volcanoes.
At Mount Saint Helens it was caused by pressure build up pushing a magmatic plug that had formed in the vent after the explosive eruption. That pressure than pushed the plug up 5 millimeters at every other minute. Seeing a small mountain jumping up half a centimeter every 120 seconds would be, I presume, a rather impressive thing to actually watch.
In all likelihood it is a similar process that is ongoing at El Hierro as I write this. But, it is very unlikely that there will be a plug pressed out, it is more likely that this is a widening of a fissure leading up to a new eruptions spot, or a widening process of the tube leading to Bob south of La Restinga. It could also be pulsations in the magma flow.
I guess that before the evening is over we will have a plot showing exactly from where the Drumbeats are originating from.
A short lesson of physics seems to be in order here. The reason for this is that Avcan has stated something that is plain wrong regarding a ship putting out “pulses” that creates the Drumbeats.
The energy in each pulse (drumbeat) is a function of amplitude times duration. In this case the required energy needed in each pulse varies between 60MJ and 360 MJ. What is that then? Well, that would be the same as 60 to 360 mega-Watts of electricity. Or 60 to 360 cars hitting the same spot at 100 km/h each. Or 15 to 83kg of C4 explosive. To put it mildly, there is no ship and no equipment on El Hierro capable of producing that every other minute for hours. Pure, and simple physics. Remember that we can see the signal on other stations, on other islands.
Logic is good, but physics is better when dealing with nature!
http://www.isla.hawaii.edu/volcano/IWARS06/pdf_presentations/matoza_iwars06_sthelens.pdf Realy good Power-point, a bit big.
http://pubs.usgs.gov/pp/1769/chapters/p1769_chapter01.pdf This paper is explaining what I think is happening here.