Friday, March 22, 2013

El Hierro Springs Back to Life [updated 4/11]

The now famous island of El Hierro in the Canaries is rumbling back to life. Tremor has increased over the last couple of days with strong volcanic quakes, coupled with even more tectonic quakes. IGN is reporting on the new activity frequently on their social media, and Earthquake-report.com is picking up the story as well with frequent updates to their main El Hierro report blog.

Tremor levels are currently at their strongest since activity slowed down and nearly ceased. The signals indicate that there is magma intrusion very deep within the chamber, at a depth of around 20km (+/- 5km), and inflation of the island is picking up again.

Recent news also determined that aside from the main cone from the last eruption, there was actually a second vent, which some of us including myself had suspected. This vent was far deeper, and not nearly as proiminent as the main vent.

El Hierro could very well be becoming 'active' again, and time will tell in the next few weeks/months if the magma intrusion will continue. I will update this post should anything further develop.

The volcano had caused some headaches for residents, who were hoping for a tourism boom, but the actions of the Spanish media and government had the opposite effect, which ended up scaring away many European tourists, and causing economic woe for La Restinga, a small town on the southern tip of the iron shaped island (El Hierro literally translates to "The Iron"). The town of La Restinga was evacuated for days/weeks otu of concern for gas emissions, and the potential for the submarine cone to enter a Surtseyan type eruption (we now know that it was a Surretyan eruption, forming 'lava balloons' with fluid lava and gas bubbles).

The next phase of the island remains unclear. The island has many cones, and no clear central vent, so it is likely that his pattern would continue. If El Hierro has another eruptive episode, it would likely be another submarine cone building event, or a cone building event on the main island itself, however the seismicity points to a probable submarine event in all likelihood. Still far too soon to tell, and the quakes are still very deep.

****UPDATE 3/22*****

Tremor is consistent and increasing. Deformation is occurring on the West end of the island and pushing it to the East. Hundreds of volcanic tremors are being recorded at depth each day. Sustained tremor will most likely result in rock fracturing, leading to further shallow dike intrusion. Keep an eye on El Hierro (again!).

*****UPDATE 3/28*****

Earthquake activity has been consistently picking up now. Vertical and Eastward deformation is continuous. Quakes are not shallower at depths of 12-9km. magnitude of the quakes is increasing (average from 3.0-4.1) and they are numerous. The epicenters of the quakes are still out to the NW in the ocean, but migrating back and forth farther out, and closer to the island. Residents claim they are feeling constant vibrations on the island, and rockfalls are occurring in the El Golfo area. Tremors now exceed the amount of seismicity that preceded the 2011 eruption, however no eruption is yet imminent, and INVOLCAN and the Spanish government are keeping the island at alert level "Green" for now.

This will most likely change if the quakes get a lot shallower, and magma intrusion continues. For now it appears that this is a massive inflation event, although at depths that would make an eruption impossible for now. If the intrusions reach the 3-1km depths, it would be wise to start worrying. CO2 and other gas emissions continue to be measured on the island and near the previous vent, but so far are stable and show no signs of an imminent eruption. The threat right now is from rockfalls in the unstable cliffs of El Golfo, and damage to lava caves (visitors have been asked not to go exploring due to the possibility of collapses).

*****UPDATE 4/1*****

The rumblings on the island anf deformation are causing rockfalls int he El Golfo area (Northern section of the island, in the 'crater' area, which is technically the area of an ancient landslide event). The unstable cliffs are being disturbed by the deformation and constant rumbles from offshore. People are advised to keep their distance from the cliffs.

PEVOLCA and INVOLCAN (also the Spanish government) are not raising the alert level of the volcano at this time. The earthquakes and magma intrusions are well off shore (abotu 3KM to the West of the island) at depth, so there is no danger to anyone on the mainland unless the intrusions become shallower and closer to the island. So far it looks like the swarm will remain offshore and not bother anyone too badly.

The quakes, aside from the deformation and rock slides, are not causing any damage, although there was a magnitude 4.9 quake the other day that was clearly felt on the island. The seismic crisis is ongoing at this time, and updates are being posted regularly on Earthquake-report.com's website. 

*****UPDATE 4/5*****

The seismicity at El Hierro is calming down at the moment. For the last two days, the earthquakes have decreased in number and magnitude. It is possible that the current magma injection has ceased for now. Deformation remains high, with slight deflation now occurring (things may be settling down). This probably means there will be some follow up quakes as the island 'readjusts' to the inflation and Eastward deformation, but at least for now things are calming down.

*****UPDATE 4/9*****

The seismic crisis seems to have ended as of yesterday (or even the day before, hard to tell). Tremor is back to background levels while a few small aftershock type quakes are happening sporadically. For now, injection of magma into the chamber seems to have ceased, and slight deflation is occurring. Updates have stopped for the most part from INVOLCAN, PEVOLCA, and Earthquake-report.com. The CHIE seismograph on www.ign.es is showing almost flat lines now.

*****UPDATE 4/11*****

As is ever the case with El Hierro, the island's earthquake troubles returned again today with a mag 4.1 quake off the West Coast. Rockfalls were reported in the El Golfo region, and pictures/videos are posted on Earthquake-report.com's El Hierro article.

The Government had lowered the alert from yellow to Green (pre-alert) level, but it remains to be seen whether they keep it there, or if quake swarming will now resume. El Hierro has the habit of start-stop-start when it comes to its activity.

No comments:

Post a Comment

Comments are moderated. See the comment policy for details.