Most news outlets have gone quiet on the eruption at El Hierro over the last couple of weeks. Indeed, signs were that the eruption was slowing down, which indeed it has done. That is not to say that the activity has stopped.
In actual fact, the last few days have been some of the most interesting – largely because it took some time for oceanographic vessels to get into place. A number of tools and vessels have been deployed to better image what’s been going on and some spectacular imagery has been put together which I thought I might share.
First up, we have the current seismic situation. As you can see, the harmonic tremor is ongoing (and has been constant since the 10th October). You can see a peak in activity in the last hour – these kinds of events are probably related to individual ruptures as the magma breaks a new fracture path.
El Hierro seismic activity, 27th October 9.15 BST
Next up, we have the sediment plume in the water, as seen on the 23rd October (4 days ago) from the MODIS instrument on NASA’s Terra satellite. You can find more info here.
MODIS capture of the sediment plume south of El Hierro.
On Sunday the Ramon Margalef research vessel got within spitting distance of the vent, and conducted a series of echosounder sweeps to look at the new bathymetry. The spectacular imagery returned allows us to isolate the location of the main submarine vent (I should highlight here that since posting some question has been raised as to whether this is the right vent or not).
Echosounder bathymetry of the new vent
There’s more info here.
As far as where this eruption is heading, while the amplitude of the harmonic tremor has certainly reduced, the focus of the seismic activity appears to be shifting slightly; activity int he last 4 days seems to have been concentrated deeper and further North than the earlier activity, which might suggest either that the more accessible high-level magma is mostly exhausted, or that recharge of the chamber is occurring from depth. I don’t know enough about the El Hierro system to give you a steer either way on that one. Here’s the seismic location plot (earthquakes in the last 2 days in red, 2-4 days in dark blue, the rest in light blue):
Seismic event locations. Up to date data available here: http://www.01.ign.es/ign/resources/volcanologia/HIERRO.html
The movement of this much magma has had impacts on the island of El Hierro itself, even if the eruption itself hasn’t broken the surface; GPS networks have demonstrated some significant land movement, with the southern arm of the island rising by a couple of centimeters, while the western arm has subsided by as much as 5 cm in places. An interesting video showing the changes is below:
I’ll update if anything significant or pretty turns up – expect some nice stuff soon, as the Ramon Margalef is due to put its ROV in the water later today. I’ll link here again to the video I mentioned in my Brent Tor post the other day (talking about the remnants of a Carboniferous submarine volcano). This video shows an underwater eruption from Tonga last year, and it’s a beautiful example of this kind of activity.
http://www.newscientist.com/blogs/nstv/2011/10/underwater-volcano-spews-exotic-lava.html
Previous El Hierro updates here and here. All seismic plots are courtesy of IGN.
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