Monday, August 20, 2012

El Hierro Reawakened? [Updated 10/15/2012]

It seems as of this hour that the El Hierro volcano might have sprung a new vent underwater off of the Las Calmas area of the island. Earthquake-report.com has an interesting picture of what appears to be a vent on their El Hierro running forum. They quote blogger Jon Frimann as saying that this could be related to dike intrusion, and that eruptions can and do take place without harmonic tremor. Jon is correct to state this, as many eruptions can and do happen with little warning.


Image from Earthquake-report.com of supposed El Hierro coastal activity.


The current photographs from El Hierro, the continuing seismicity, and the apparently new activity in regards to the above photo point to a renewed activity phase for the island, which had not erupted since the late 18th century. While it is still far too early to tell, it appears that the island is once again erupting.

The fact that the activity has been mostly constrained now to the outer flanks, and submarine depths, suggests that the age of the volcano, and the coolness of the solidified lava above it may be protecting the mainland from any activity so far. Indeed this would seem to correlate with the fact that the island has had much uplift, but little subsidence despite the previous eruption releasing lava underneath the sea on the Southern tip of the island. Think of it like a solid chunk floating on a block of jell-o. The island is uplifting because it is currently too dense to fracture and create above-water vents, but uplifts because the ground beneath is lubricated by water, and is from thinner crust.

As the lava bubble forms to the SW of the island, the island would be uplifted to the NE which is consistent with the current measurements.

It could very well be at this time that continued activity on El Hierro might be exclusively submarine. Hotspot volcanoes, much like Hawaii's Loihi mount, tend to follow the path of least resistance to the surface. It could be that, much like the big island of Hawaii, the activity has moved south, and a new Canary Island may be in the works. We will likely not see the result of this migration of lava columns in our life time, as Loihi will take some 10,000 years to break the surface of the ocean in any significant way. But it is still a very fascinating process to watch, which is why El Hierro gets such a good amount of press among bloggers.

El Hierro's webcams were turned off some time ago, so coverage on the eruption will almost exclusively come from Earthquake-report.com, INVOLCAN, and IGN. I will post more updates as they become available.

*****UPDATE*****

INVOLCAN has released a statement regarding the pictures taken from a helicopter flight over the quake area:

"“El PEVOLCA confirma que no se observan parámetros anómalos en la zona sobrevolada por el helicóptero del GES. Científicos del INVOLCAN, que portaban una cámara térmica, y del Instituto Geográfico Nacional no han observado parámetros anómalos en el vuelo de reconocimiento que han realizado esta mañana en el helicóptero del GES, en la zona en la que ayer se atisbó una mancha blanca en el mar y burbujeo. Con este vuelo queda definitivamente confirmado que no se han producido cambios significativos en el proceso magmático activo en la isla de El Hierro, aunque se mantiene el análisis de datos de forma continua.”"

Translation:

"PEVOLCA confirmed that no abnormal parameters observed in the area flown by helicopter from the GES. INVOLCAN scientists, carrying a thermal camera, and the National Geographic Institute have not observed abnormal parameters in the flight of recognition they have done this morning at the GES helicopter in the area in which peered yesterday a white spot on the sea and bubbling. With this flight has been finally confirmed that there were no significant changes in the active magmatic process in the island of El Hierro, while maintaining the data analysis continuously."

Seismic activity today has produced several quakes since early yesterday, but has since subsided with no new significant swarms. If anything further develops, an update will be posted. For now things have not changed much in the last couple of weeks.



*****UPDATE*****

It seems the hype this time over El Hierro might be a bit premature. While there has been a lot of earthquakes lately, all have been at or below a depth of 19km, which is far, far below the earth's surface. El Hierro may have some turbulence at a great depth, but is by no means near an imminent eruptive phase at this time. Seismicity will most likely continue for some time, but may or may not result in further activity.

The main concern is really, at this point, for the people of El Hierro, and as of now, the are in no danger. The quakes, while numerous, do not amount to much more than a stirring of magma currents deep below El Hierro, which is expected given the displacement of materials caused by the last eruption. This could be merely crustal adjustments, or something foreboding... at this time, nobody really has an answer.

It is clear now, that this is an active island volcano. What cant not possibly be clear is whether or not the recent activity is a precursor to more. My gut instinct says that El Hierro will experience more activity in the near future, but m gut instinct is not beholden to scientific scrutiny, and therefore cannot be relied upon. Only time will tell at this point, and for now, it appears that El Hierro might just be having some indigestion from its last bout of activity.

As of now, I am pretty m uch going to stop posting about El Hierro unless it becomes particularly active. It is useless to speculate on El Hierro, as it has consistently made fools of bloggers and scientists alike with its random behavior.

If anything new develops (of interest), I will cover it. If you happen to want to monitor the volcano yourself, please go to Earthqauke-report.com's continuing coverage page. This page will keep you up to date with the latest on the volcano, as they have a reporter (Joke Volta) on the premise, as well as a great information sharing agreement with INVOLCAN and PEVOLCA.

****UPDATE 7/5/2012****

It seems that PEVOLCA has been chastised by a member of the El Hierro Government, stating that they jumped the gun or made false statements harmful to tourism on the island. The issue was that PEVOLCA issued the above picture prematurely claiming that this was a new vent, when this had not been confirmed by scientists or bathymetry readings whatsoever. It becomes a cautionary tale for scientists not to get too excited when they think they see something that has not yet confirmed, and to instead follow due diligence in proving what you are claiming.

Today, nothing much has changed at El Hierro. The situation is about the same as it has been. There has been no new inflation, and the continuing earthquake swarm is in the same location and same depths as it was in the last few swarms. It is anyone's guess as to how this plays out. If the quakes become much shallower, there is a potential for the magma to reach the lava tube system of the 2011 eruption and possibly re-pressurize the shallower system. For now, the quakes are at a steady 20-18km in depth, on the NE part of El Hierro, and they have been at about the same magnitudes for the greater part of the day. No large quakes were felt today, but seismographs continue to record minimal harmonic tremor, and small, frequent quakes no bigger than 2.0.

*****UPDATE 7/7/2012*****

After a day or so of calm, with very little amounts of earthquake swarms in comparison to last few days, the quake swarms and uplift of El Hierro have resumed.   The below seismograph image details the currently (as of this writing) swarm, which has reached a little over half an hour in duration at this time now been sustained all throughout the end of the day. Many had thought the island would be calming down after some light subsidence of the islands deformation, but this new swarm may change that.



*****UPDATE 7/16/2012*****

The deformation and quake swarms at El Hierro seem to be subsiding. This can be chalked up to probable gas release as a result of decompression from the rising magma reservoir, and should continue gradually as the quake swarms and magma injection subside. This in no way means that the island will not have further swarms or injection in the future, although for now it appears the events are over.

The events of the past few weeks are similar to the events that preceded the eruption of "Bob" the underwater volcanic cone off the coast of La Restinga. Over 2,500 quakes have been recorded since the start of the swarm.

There was a lull in quake activity prior to the initial eruption, however seismic instruments and GPS measurements were not in place at the time, so the volcanologists that now know this is an active volcano are in data collection mode. Currently, here is a synopsis of what has occurred within the last month:

Quake swarms and vertical/NE deformation were observed. There has been no significant fluctuation in C02/S02 emissions from the erupting cone or on the island. Deformation reached a peak of approximately 10cm, and as of three days ago, began to subside with 1-2cm of negative inflation occurring. Injections of magma into the magma chamber are confirmed, however since the last avenue for magma to reach the surface has been blocked by cooling and water, this event has ended.

The end of the event likely indicates that the magma injected has reached a critical point and is rejecting new magma. This is probably because the current reservoir has no outlet, and thus is changing magma currents from the mantle by producing resistance and/or feedback due to the fact that the pressure in the chamber is too weak to breach the surface (crust) and generate an eruption at this time.

What this means is that El Hierro is again primed for eruption, however it may not end up in an eruption, rather it could simply cool into a 'crystal mush' over time and generate heightened microseismicity on the island for a long time, given that no crustal adjustments that allow magma to escape to the surface occur.

The future of El Hierro at this time is uncertain. I will be keeping a close eye on it, however until anything new develops, I will probably stop updating this post. Stay tuned for more volcano news!!

*****UPDATE 7/25/2012*****

After a relatively calm week, El Hierro Island is shaking again, and deformation is resuming (there have been several D/I [Deflation/Inflation] events within the last few days). There have been sketchy reports from residents about discoloration in the sea in the El Golfo bay area, however no scientific evidence yet suggests this is related to seismicity or quakes (algae blooms can have the same effect on water color).

The seismicity is remaining at the West tip of the island, mostly underneath a lighthouse at a depths of about 20km, however the new swarms include some stronger quakes, at depths of 3km or less (very shallow respectively) int he same region which leads to the question "Are these shallow quakes magma dike intrusion, or are they simply structural adjustments to the inflating magma chamber and other quakes?". Only time will tell in this case, as more data becomes available.

In any case, this has been a busy day on the island.

*****UPDATE 8/10/2012*****

Inflation is being confirmed by INVOLCAN and IGN, quoted as 'rapid'. This is normal behavior for an active volcano and does not mean that an eruption is imminent, although it does make it more likely. Currently quakes are ranging from 10km-8km below the surface of the island. Shallower quakes are suspected to be crustal adjustments to stress from below and are not considered to be directly volcanic in nature. However the magma chamber IS re-inflating, so it could be a matter of months or years for the volcano to resume its activity. It could also be that the chamber inflates, but does not erupt. Updates will be posted as they happen!


*****UPDATE 8/23/2012*****

The seismic swarm at El Hierro has calmed down, and numbers are looking more similar to the numbers of quakes that were occurring before the most recent swarm. It is confirmed that the last swarm was magma intrusion, with what consequence, nobody is certain. For now, vertical deformations are stable, with slight subsidence, but the amount of deformation that has occurred has left the island about 10cm taller than it started out as, so the injection was significant.

*****UPDATE 9/10/2012*****

Seismicity has increased according to IGN/INVOLCAN and Volcano-report.com. Quakes are occurring with more frequency and intensity, and the depth of the quakes has risen to approximately 10km. While this could be simple crust adjustments, it definitely looks more like magma is trying to rise again. D/I events continue to occur.

*****UPDATE 10/15/2012*****

Seismicity remains constant at El Hierro, and deformations are going up and down. What this means at this time is uncertain, but around 10-20 events a day are still being recorded at various centers within the volcano, at a depth of around 10-13km, which is a bit shallower than it was about two months ago when the depths were 15-20km. This could indicate that magma is slowly pushing its way to the surface, but as a lot of the government funded instruments and science teams have been shut down due to the Spanish budget crisis, I am relying solely on earthquake data and the folks who are still covering the story at Earthquake-report.com.

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