Update
Posted by JAC on 7/28/2011, 4:05 pm
Last update: July 28, 2011 at 2:48 pm by By Tom Pering




Recently El Hierro volcano of the Canary Islands has been experiencing a seismic swarm beneath it, which as of yesterday reached to over 700 events.

Most of these events have been at Magnitudes of around 2 (+/-0.5) and are clustered beneath El Hierro whilst the depths of these earthquakes have been roughly between 9 and 16 km for the most part, with the exception of a few shallower and deeper quakes, the shallowest of which has been around 4 km (as of 27/04/11 8am GMT for the plotted data below) but as shallow as 1 km following this.

If we look at these earthquakes in two plots here http://www.volcano-blog.com/hierro.html we can see the clustering of these earthquakes is mainly confined to an oval area at 10 km depth.

El Hierro is a broadly basaltic volcano which might have been active in 1793 although this is uncertain.





So the big question is, what's happening here?

It is possible that there is magma on the move at depth, perhaps moving into a magma chamber.
Does this mean that there will be an eruption? Maybe, maybe not.

The majority of magma intrusions do not reach the surface, and as has been seen elsewhere, in the past, activity can cease at anytime.

As of yet (to my knowledge) there have been no other signs of moving magma at the surface such as ground deformation or increased gas emission, although GPS antenna have been set up by officials at the Canary Islands.

For now it is too early to tell what (if anything) will happen, so keep watching.

If you would like to follow these earthquakes in more detail or look at the raw data, visit here .

El Hierro Volcano Information :

The triangular island of Hierro is the SW-most and least studied of the Canary Islands.

The massive Hierro shield volcano is truncated by a large NW-facing escarpment formed as a result of gravitational collapse of El Golfo volcano about 130,000 years ago.

The steep-sided 1500-m-high scarp towers above a low lava platform bordering 12-km-wide El Golfo Bay, and three other large submarine landslide deposits occur to the SW and SE.

Three prominent rifts oriented NW, NE, and south at 120 degree angles form prominent topographic ridges.

The subaerial portion of the volcano consists of flat-lying Quaternary basaltic and trachybasaltic lava flows and tuffs capped by numerous young cinder cones and lava flows. Holocene cones and flows are found both on the outer flanks and in the El Golfo depression.

Hierro contains the greatest concentration of young vents in the Canary Islands.

Uncertainty surrounds the report of an historical eruption in 1793.

El Hierro Information courtesy   volcano.si.edu (Smithsonian Institution)

Twitter user @Teideano has also been giving regular updates on the situation.

I have used some of his info in this report.





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Earthquake swarm continues on the Canary Islands - JAC, 7/26/2011, 12:35 pm
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