Wednesday, August 15, 2012

Seismicity Picks Up At El Hierro

El Hierro Island in the Canaires made headlines last year when a submarine eruption occurred less than a mile off the coast of the fishing village of La Restinga, creating an underwater cinder cone, and providing a demonstration of a Serretyan eruption (An eruption consisting on gas filled lava 'balloons' that burst at the ocean surface in a puff of flame, only to sink to the ocean floor and pile up) that thrilled scientists and other volcano enthusiasts. The eruption technically ended some time after the government said it did, but lately seismicity has been picking up and the epicenters of the quakes appear to be getting shallower.

As far as the folks over there at Earthquake-report.com are concerned, they have been on top of things from the get-go with a 'reporter', Joke Volta, on the ground, taking daily pictures and reporting on any earthquakes or changes.

The last few days have seen on average 5-10 smallish quakes, with some larger (mag 4.0 and up) earthquakes. When the seismic swarms resumed, the depths and locations of the quakes were fairly consistent, with most being at the Western tip of the island, 20km below a lighthouse. These quake swarms have now migrated to the center of the island in the area known as El Golfo (the area that resembles a crater, but is actually the result of an avalanche thousands of years ago), and are now occurring at shallower depths (the latest swarm is taking place at a depth of around 12km).

INVOLCAN and PEVOLCA, in conjunction with ER seem to believe this is indeed related to magma dike intrusion at this time, and preparations are underway to possibly raise the alert level of the volcano again from "Green" back to "Yellow", but this is only preparation and precaution, and as of now there is no cause to actually raise the alert level, although I suspect if the quake swarms continue for a lot longer, we will probably see the alert level raised, and maybe even another eruption from the island.

Deformation on the island lately has been stable, although since the end of the last eruption, the island has been uplifted some 10cm! This clearly indicates magma rising in the chamber. Some subsidence has occurred, but for the most part the island right now is stable. Time will tell what the results will be.

*****UPDATE 8/17/2012*****

Earthquake-report.com is reporting over 58 quakes have occurred in the last day in the El Golfo region of El Hierro.

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