El Hierro still going strong and a riddle

Some parts (?) of El Hierro experienced a short power outage last night, This was also viewable on the solitary working webcam at the moment which was noticed by some regulars. Quite some earthquakes Mag. 3+ and even some Mag 4+ have been recorded.

chryphia created a new plot which shows the action going on:

Quote:” Here is another 3D plot, no overlays this time .
It shows the current swarm and the older earthquakes in two separate color scales. I wanted to see where the central El Golfo bay earthquakes are located exactly: they are slap-bang in the middle of the northernmost, deep (magenta) swarm, barely visible in this plot. This is where all the other swarms originated, thus I am worried that there is even more magma arriving now. For a good 2D view look at http://www.01.ign.es/ign/resources/volcanologia/html/eventosHierro.html

“

Earthquake Report has a link to an image of all the spectrograms of this crisis stitched together: http://jdcv.es/Media/Hierro/2013/CHIE_upto2903_B.jpg
from http://earthquake-report.com/2011/09/25/el-hierro-canary-islands-spain-volcanic-risk-alert-increased-to-yellow/
Noted by Jim Ludwell.

Earthquake-report.com also used chryphias plot without giving her credit which I personally find absolutely not OK.

Many can explain the current crisis much better than I ever could. So here there are some comments to good to be lost:

GeoLurking says: March 29, 2013 at 04:37
Quote: “when this whole thing was first bopping along, the gov was reticent about doing anything until it became clear that Mag 4.0 quakes were a possibility. Mag 4.0 was where they flinched and it was clear that something could shake loose and hurt somebody, so that was about when they started taking precautions.

One thing that Carl noted was that the seismic gear was probably not set up for volcano monitoring and that IGN and Pevloca had to undergo a paradigm shift from watching for potential landslides to watching for volcanic activity. Outside experts were consulted and new gear was brought in. (the temporary seismic stations and the additional GPS units.)

Now 4.0s seem to be regular fare. It doesn’t lessen the hazard. A 4.0 still releases considerably more energy than a 3.0.
For now, the most immediate threat is still the same. Something getting shaken loose from the bluffs.

Then there is how it plays in the volcano scheme of things. If the quakes are being caused by magma forcing it’s way through the rock, the best that I can envision is a series of normal mode faults. A 3.0 has a maximum displacement of 0.275cm. A 4.0 has 1.17cm. That’s would be a crack about 4.3 times the size of the 3.0. Keep in mind that this is probably pushing the Wells-Coppersmith equations a bit outside of what they were intended for, but it does illustrate the differences in the two quake sizes.

If it is magma pushing through rock, what has happened is that the hoop stress of the rock around the area of the magma has been exceeded and the magma breaks open the rock with what is probably a mode 1 crack. This realm of math is beyond me, so I rely on the Wells-Coppersmith crutch to provide some level of understanding. Going whole hog, and looking at the rest of the formula… a normal mode fault of Mag 4.0 has a down dip rupture width of 1.82 km. If intruding magma is what is at play, it could conceivably make a path about half of that width higher each time it happens. If that starts to show up in the quakes…“

Read the whole comment by clicking it.

Renato Rio says: March 29, 2013 at 13:34
Quote: “The PEVOLCA maintains civil protection measures in El Hierro and follows the evolution of the phenomenon
03/29/2013 … 12:38 – Ministry of Economy, Finance and Security
* The data indicate that the seismicity has migrated to the southwest in the last 24 hours. The direction of the Civil Protection Plan for Volcanic Risk (PEVOLCA) maintains civil protection measures that were taken last Wednesday in El Hierro given the magnitude of the seismicity that is occurring to the west of the island.
As you may recall the steps taken by the management of PEVOLCA are the following:
Disabled the lane closest to the on the output side of Frontera tunnel closing the stretch of road between the HI 50 between Cruce de la Tabla and Sabinosa and the access road to the Playa La Madera, the Pozo de la Salud to the confluence with the HI 503. It is important to avoid transit through these areas because of the risk of landslides.
Accesses are opened to the Ermida de los Reyes and the southern Sabinar area, HI 400
Meanwhile it is maintained the yellow alert of information to the population in the area bounded by the HI 500 and the height of the Pozo de la Salud to the south, at the confluence of the HI HI 500 with 400 in the crossroads known as El Tomillar.
As for the seismo-volcanic phenomena, earthquakes located in the last 24 hours have migrated slightly to the southwest over previous days, reaching the west of Orchilla between 15 and 20 kilometers deep at a distance from the coast between 12 and 15 kilometers. The values ​​of CO2 in the atmosphere have increased but are still within normal parameters.
The direction of PEVOLCA wants to remind you that they are doing continuous monitoring and real-time of thr phenomenon, so any change in the pattern of movements that imply risk will be communicated immediately. It also recommends considering the advice of self-protection in the event of earthquakes, known to all, and can be viewed in http://www.gobiernodecanarias.org/dgse/descargas/sismo_hierro/autop_sismo.pdf“

Bruce Stout did some drawings:
To understand the images one needs to read Bruce’s comment and all the follow up’s by Peter Cobbold and Bruce. Bruce Stout says: March 29, 2013 at 14:23

Richie Lee gave us a link to a TV station in the Canary islands where some news might be broadcasted. Canary TV: They don’t stream everything but most live newscasts are available. The last few days they have had coverage of the El Hierro activity.

http://www.rtvc.es/television/enDirecto.aspx?canal=tv

I personally do not think any eruption is imminent, but it is interesting to watch. And in case you need the links again, just holler.

Spica

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A riddle for tonight, while we are watching what is happening in El Hierro and Iceland!
Same as last week …. so link the each clue to a volcano and spot the red herring ….

1 point for each volcano and 1 point for each red herring (with brief explanation)

All solved … Red herrings in bold … Answers ..

No 1 Big Ben

No 2 Mount Churchill

No 3 Hekla

No 4 Glen Coe

No 1 – 2745; Furious 50s; New York landmark; Augustus Pugin; SOLVED
No 2 – Bobsleigh run; Radiocarbon; Battle of Stepney; Infantry Tank; SOLVED
No 3 – 1750; 1104; 1864; 4892; SOLVED
No 4 – 1692; Easter Island; Cauldron subsidence; Harry Potter; SOLVED

Points .. Well done all

Kelda  4 points

Volcanic 2 points

Stephanie Alice Halford 1 point

Inge B 1 point

Kilgharrah

El Hierro’s western part on “Code Yellow”.

Pevolca reacted on the earthquake series that happened yesterday and set the western part of the island to a “yellow alert zone”. All this happened in agreement with the government of El Hierro.

The dramatic events on CHIE yesterday.

Full report (in spanish) and a short excerpt for your information: Closing the lane of the tunnel closest to the exit in Frontera, closing the length of road HI-50 between ‘Cruce de La Tabla’ and ‘Sabinosa’ and the access road to ‘Playa La Madera’, of ‘Pozo de la Salud’ until the crossing with road HI-503.

Yellow informative alert for the population at the zones limited by HI-500 at ‘Pozo de la Salud’ to the South, en the crossing between HI-500 with HI-400 at the crossing known as ‘El Tomillar’.

The best sites to get the newest information are:

• Earthquake report
• El Hierro blog from Manfred Betzwieser in German.

Those 2 sites are not normal blogs like VolcanoCafe publishing a full post every few days but they report close to the “action”.

dfm created a brilliant plot and explained it:

This is the update till 18h43 today

Today there were a number of strong (for El Hierro) earthquakes with quite a few over mag 4 which is quite rare.

In the list of earthquakes you will notice that for the strongest earthquakes there is only one event of similar magnitude (4.6) and that in all the events with mag >=4 (16 out of more than 17000 !) 5 came to happen today.

(The ful list of quakes dfm used can be found in his comment on “Watching Hekla“: dfm says: March 27, 2013 at 21:15 )

Without wanting to be fear mongering, I find this situation unprecedented. If you add this to an also unprecedented trend in the upward component of the GPS, this situation begins to pose a number of questions. Happily (if one may say) the bulk of the seismicity is located at sea and not on the island emerged part.

Meanwhile here is the earthquake update for the period since March 26th 8h18 and 27th @ 18h43. It includes the 4.6 quake.

The color of the quakes is linked to their position on the list (more than 1200 events since March 18th).
I will probably change this next time as the color scale loses its interest.

It is interesting to note in the time-lapse animation that there are first some cluster of quakes in the previous parts, leading to a hypothesis of a “sill” of sorts or at least to an accumulation of rock breaking in the same place. Then most of the “strong” (meaning over Mag 3 ) quakes seem to appear on the border of that cluster (look at 0’20”). Could it be that there was some renewal of magma arrival (a new “bolus”) and that the constraints bring some rock breaking on the limit of the previous cluster. I will only repeat that these new events happen in a zone previously devoid of earthquakes.

The 4.6 event can be well see at 00’49″ on the center-left part of the plot, over the 27,6 mark on the abscesses.

Do look at the end of the video in the zoom sequence (1’22″ and 1’28″)

On the right side of the colorbar the terrain elevation scale is shown. Magnitude of the events (sorry I stopped at 4 !) is shown on the lower part of the plot.

Data from IGN and NOAA, made on Gnu Octave.

Peter Cobbold noted: Bearing in mind the GPS stations are ~15km away from the swarm centre the 100mm uplift in ten days is unusually high for Hierro. Previous swarms have been co-located with the GPS stations and resulted in smaller uplifts over longer periods,IIRC.

Yesterdays trend. El Nathan did not really see a tendency of the earthquakes coming closer to the island.

In case more earthquake swarms happen, there is the possibility of rockfall (or maybe even landslides). At the very moment an eruption on the island is unlikely in my eyes. (Personal layman opinion.)

Links to watch El Hierro (besides the cams) are to be found on Wonder what Bob is up to.

HEKLA
Lets not forget some here like Jamie and Islander are still on a 24hr Hekla watch.
Hekla is still on alert level yellow but not all too much happened close to it yesterday.
Islander also informed us:
Hekla “news service” latest scoop : IMO has brought back online the fourth (4) SIL for monitoring the greater Hekla area. These are HAU from the west, fedgar. (http://hraun.vedur.is/ja/oroi/fed.gif) from the north, VAT from the east and MJO from the south. Nothing EQ wise then can escape the sharp eyes of the IMO staff. http://hraun.vedur.is/ja/oroi/index.html
Fedgar is not on this overall map.

Again the Hekla links:

• Hekluvöktun Hekla Data
• Hekla GPS
• Borehole Strain and Hekla seismicity
• Website on Hekla ( Swedish)
• Jarðskjálftar
• Seismic stations close to Hekla

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Other sites have the information about the earthquakes too but dfm’s plot is only on VC.

Spica

Continued activity at El Hierro

Since the last post has grown somewhat ‘large’, I thought I could better create a new post with some updated information, and less than about 600 (!) comments to scroll by. Because the last post (and the comments section) was really full with excellent links, I will start off by providing the link to the previous post:

http://volcanocafe.wordpress.com/2013/03/22/keeping-a-close-eye-on-el-hierro-and-ntv-riddle/

Several commenters have mentioned that the period between the flare-ups of earthquake activity has been steadily increasing, and that the intensity of the earthquakes has been increasing as well. Below is the tremor graph of today, which shows a phase of intense quaking/shaking just after midnight and another phase this afternoon, which produced the largest EQ of this renewed activity yet at M4.1

Tremor graph published by the IGN.

harrie has mentioned that over the last few days a clear trend in EQ’s could be seen, translating to a general westward and upward movement of the ‘active front’ where the quakes were generated. However, this afternoon he mentioned that this upward trend of EQ’s has stopped since about 100 listed EQ’s ago, while the trend of more intense EQ’s with time has not. This might mean that the mechanism that has been seen by many as being the growth of a sill, has come to a stop, while the magma flow has not. This could mean a hard stop has been reached, while pressure is now slowly rising in the system, looking for a way out in another direction, which might be directly upward through one of the many pre-existing-but-inactive dikes/conduits below El Hierro.

KarenZ mentioned that AVCAN has posted a warning on their Facebook page, stating that El Hierro inhabitants should keep an eye on the TV and an ear to the radio to be sure not to miss anything if official sources issue a warning, or other critical information.

Vulcanoelhierro.es (in Spanish) has published an article stating that so far nothing abnormal has been sighted while performing acoustic depth measurements to detect anomalies at the seafloor which might indicate the activity has reached the ocean floor. Sissel, an earthquake-report reader is being mentioned by earthquake-report.com for providing an image of the cruising traject of the ship. There it is also mentioned that INVOLCAN has sent in a team to reinforce measuring systems, and to measure CO2 as well.

Image by earthquake-report.com

On the other hand, the deformation is still ongoing. In fact, the scale had to be adjusted to still be able to see the deformation at the Sabinosa station. Below is the deformation image, for all to draw their own conclusion…

Sabinosa up-down GPS deformation. Image by IGN.

Sabinosa east-west GPS deformation. Image by IGN.

Let’s also not forget dfm‘s rotating 3D plots which show the earthquakes in time-lapse mode, projected with the El Hierro geography, with an explanation in his comment. I will try to keep this one updated if he decides to post a new one with updated data as time progresses.

And last but not least….

I would also like to point to some of Kilgharrah‘s ’Name those Volcano’ riddles. Only one has been solved so far, so lots of opportunities for a volcanophile to rise on the volcanophile-list-of-fame (currently dominated by Alison and several other women) remain for all!.

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Name those Volcanoes Riddle

Note – this weeks riddle is a little different …. In order to identify each volcano you have to establish a link (some are more tenuous than others) between the volcano and various classifications, dates, places, events, people etc …. each clue has three genuine links and one ‘red herring’ included!

1 point for each correct volcano and 1 point for each ‘red herring’ (which must be identified with an explanation) guesses wont count ….. good luck!

No 1 - Lord Byron’s wife ; November 5th 2013 – Australian sporting event; Lethal mud slides; Pacific Ring of Fire; SOLVED

No 2 - Stratovolcano; Canada; Formula 1 Team; Angels – song; SOLVED

No 3 - Stromatolites; 40,000; Rain forest; UNESCO; SOLVED

No 4 – UK; Dormant; Summer Rain – song; Vintage Car Museum owner; SOLVED

Hints: ‘red herrings’ are now marked in bold! I have added to the clues as well to help get them solved!

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El Nathan

Renewed activity at El Hierro

VC-commenters arjanmm and Alison noted at 14:54 and 14:59 UTC today that some tremor was going on at our famous Canarian friend El Hierro. A clear rise in tremor, combined with several earthquakes were seen at the seismic stations on El Hierro, most notably on the CHIE-station.

The tremor and EQ’s seen at the CHIE-station. Image by IGN.

Another view of the onset of the tremor and quakes. Image by IGN.

Diario El Hierro (the local newspaper) has already posted a news item about the renewed activity on their island, stating that “an important seismic reactivation” has occurred at their volcano. They state that up to now, 30 earthquakes between M1.9 and M2.6 have been measured, making this a significant reactivation event indeed. A quick look on the list of EQ’s published by the IGN tells that so far (19:00 UTC) 55-60 EQ’s between M1.7 and M2.7 have been detected.

The locations of the earthquakes. Image by IGN.

dfm has been very quick in 3D-plotting the renewed activity as well, as can be seen below. Thanks for that dfm and others!

Image by VC-commenter dfm

Whether this new activity will lead to a baby brother or sister of Bob will remain to be seen, but it is sure that something is on the move again deep below El Hierro. As we have seen with the birth of Bob, there don’t need to be many shallow quakes in an area for a new fissure to open and allow the lava to erupt, whether this is on the seabed or not.

We should definitely keep an eye on what is happening, since the combined knowledge of all commenters and the powers of data processing by some of them, can surely help in painting a picture of what is actually going on, even though official sources might sometimes disagree. In Bobs case, several commenters have had a better grip of the reality at times than official sources, so don’t be afraid to speak out if you think you have found something important.

And finally, a short note to all readers and commenters; try not to swamp the IGN website or any other site that locals might need to get the information they need. If possible, quote text and provide the source, and upload images and post the link to the uploaded image instead of linking directly to the source to prevent overloading of those websites. With that in mind, please don’t forget VC’s special section about Bob/El Hierro: 

http://volcanocafe.wordpress.com/volcano-monitoring/

El Nathan

Tenerife – Journey inside a lava tube

Post by dfm:

Tenerife is part of the Canarian archipelago. These islands are located in the Atlantic Ocean, not very far from the coast of Morocco. There are 7 islands, which are Lanzarote, Fuerteventura, Gran Canaria, Tenerife, La Gomera, La Palma and finally El Hierro. All islands are of volcanic origin and the main hypothesis of formation refers to a magma hot spot leading to the formation of the islands. I have had the chance over time to visit several islands (Lanzarote, Gran Canaria and lastly Tenerife). Of course each island has its own charm and interest, but I must admit that Tenerife has left me with a stronger impression. 

The variety of landscapes, type of lavas, volcanic cones, lava fields is really impressive. Also the fact that, even in the national park, one can go roughly as he pleases is to be taken into account (In Lanzarote, for instance, you cannot take a walk on the lava fields in the national park).

So here is my account of a visit made to the Cueva de los Vientos.

Context:

The Cueva de los Vientos is located in the village of Icod de los Vinos, on the west side of the island. It has been proposed as a touristic attraction since only a few years (I think 2009). First there is a quick presentation by the guide of the volcanic origin of the island, and some explanations on how lava tubes form and of the different type of lavas produced by the Teide (A’a and Pahoehoe in this location). Then the tour continues with the visit itself and begins with a short trip by minibus to the cave area.

The guide shows different types of lava on the site and then we proceed with the visit of the cave using an old bridle path to get access to the cave.

Example of Pahoehoe lava – photo by author

The Cueva del Viento itself is a very large structure (the largest of its type in Europe) with a cumulative length of about 17 kilometers. Only 200 meters are open to visit.

Source : Information brochure from the website http://www.cuevadelviento.net/

The formation of the cave (or caves) dates back to a Pico Viejo eruptive episode about 27.000 years ago.

The visit allows to see many volcanic features related to lava tubes.

photo by author

Hard hats and spelunking type lights are supplied, there is no artificial lighting in the cave.

photo by author

Details from the tube’s ceiling with solidified drops of lava.

photo by author

Inside the tube – note the different heights of the floor showing different periods of the eruption with diminishing lava flowrates. The width of the canal is about 2,5 meters.

photo by author

A side tunnel – there are several lava tubes in this network. Note the texture of the floor, which is quite irregular and shows the lava flow when it cooled down and solidified.

photo by author

Two tubes converge.

photo by author

Here one can very clearly see different phases of the eruption with diminishing lava height.

photo by author

This is a fallen section of ceiling showing a Pahoehoe pattern. This shows the tunnel formation mechanism in which lava cools in surface and continues flowing underneath in the newly formed tunnel. Sometimes the ceiling falls after a time. In that case the event happened after the lava flow stopped in the tunnel. In the area there can be several layers of lava tubes all piled up a bit like tunnels for subway systems.

The visit finishes off with some time in the dark to feel the atmosphere of the cave (in which some specific fauna can be found). The visit finishes by a return to the visitor center by minibus looking at A’a type lava flows.

You can find all the information needed on the website. Some visits are in English, German, French or Spanish, depending on the day of the week.

dfm

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As Inge B. mentioned, please note these posts about the Lanzarote lava tubes by ukviggen:

A Tube’s Tale: Part 1 – formation
A Tube’s Tale: Part 2 – strange creatures and the human touch