El Hierro

[fifi]

So if the area is missing out on earthquakes which occur at certain depths they are obviously trying to show how deep it is filled or plugged.

[fifi]

I know nothing about these things really at all but always presumed that the magma was not coming out of Tanganasoga because there wasnt enough force behind it.

[jand]

This is the blog yesterday by Lurking relating to the map.

Copied.
.
Sort of what I have stated. There may be something to the quakes dropping in elevation and increasing in magnitude as they made their transit south, and the eerily quiet region from the swarm to the actual jacuzzi... no quakes.

The latest "wad" has been located in what is ostensibly the upper mantle, possibly a recharge of the overlying area emptied out by Bob... the lower periphery of which seems to correlate with the upper "wad" of quakes across another... eerily quiet area. The upper group is withing the 68% one SD boundary from the original swarms average depth. (points to them being in the same "family")

Early on, back when this all started... this showed up.

http://i42.tinypic.com/1t66gl.png

Its a hole. Slap dab in the middle of the swarm. At the time I attributed it to "tougher" material, I wouldn't go as far as to call it a "plug." It's pretty much under the dominant cone along the E-W ridge line.

Reply

[jand]

Well this is also showing the circle hole this is the link from the above post.

Its fascinating how other people are picking things up I would not have seen this circle hole but it seems to be  all fitting together now .

If you click on the map and enlarge it you can see the circle very clearly.

[fifi]

They are saying the area around the hole which was emptied out before might be filling up again I think and I dont really understand the bit about the connection between the two. Will have another look later. Interesting to see how they figure these things out though isnt it?[]

[jand]

Fifi

Have a look at the map of the islands earthquakes from 1989 - 2006 and look at El Hierro can you see the white blob at the top left of the island is this not the same position as the circle/hole that is being currently discussed?

[fifi]

It looks like it is in approximately the same place. Here are the other two photos again so we can look at the three together and see.[]

[jand]

Volcanocafe Copied

@Betty and others re Silent Zones, Quiet Zones.

In the overall distribution of quakes under El Hierro, there are regions/depths that have few quakes. It seems that these areas follow the boundaries of the major layers under the island. The most significant one is the transition from mantle to oceanic crust, across the MOHO.

Even IGN has noted that the over all shape of these dead zones seem to follow the outline of the islands mass. This makes sense, but I don't think it is quite as simple as IGN presented in their graphic. My opinion is that the keel (bottom) if the island doesn't go as deep and they included the Jurassic era sediment as part of the keel of the island.

Why are there no quakes? Well, since we know that these areas are where the material changes from one type to another (mantle to crust; crust to Jurassic sediment; Jurassic sediment to volcanic infill and modern sediment) it is highly likely that the transition is not a clean break from one type to another type. It's chaotic and haphazard. Being less uniform, it would be easy for material (magma) to move through the region with little opposition and little stress placed on the rock. This would account for the smaller number of quakes.

I am of the "melt formed in place" camp. One linked paper that I have seen here (or at Jon's) put forth the idea that the El Golfo slide's mass movement initiated melt formation by changing the stress field under the island. Even though it has been several thousand years, it is not out of the question for different minerals to melt out at different rates and times. That is the basis of how fractionation occurs anyway.

Carrying this idea further, I think that the lower quakes represent the change to the stress field allowing deeper melt to start moving up to take the place of the material lost to Bob.

As for the circular "dead zone" that may or may not be a "plug." Over time, quakes eventually showed up inside that area. (it was originally sighted in the original swarm). It's alignment is quite interesting... it may be what is left of El Golfo's main vent from thousands of years ago. Other than that, I don't really think there is much more to note, other than being a potential pathway along the periphery of it should enough pressure develop to push to the surface. I imagine that if that happens, there is also a potential of intersecting an old tube system and coming out in an unexpected place.

Eh, time for coffee.

[jand]

volcanocafe Copied

GeoLurking.
 I suppose you have looked at the result from microseism and gravity surveys on El Hierro ?
 How does it compare with your velocity analyses ?

http://www.gradient-geo.com/library/storing.php?doing=T91oVy5lr

http://www.heliophagia.org/other/tru10b/gorbatikov3.pdf

Reply

GeoLurking says:

 December 9, 2011 at 21:48

Actually, no I haven't. This is the first I've seen of these two papers... which on initial peeking seem to be a Godsend in what the underlying structure is.

Many thanks for the links. Time to read.

Reply

Carl le Strange says:

 December 9, 2011 at 22:01

The first paper pointed to an odd thing.
 The Lomo Negro 1783 eruptions has a separate chamber than the one that seem to be active now. Because every data I have seen so far is that it is the El Golfo magma chamber that is active now, not Lomo Negro.
 Lomo Negro chamber has been totally without quakes (at least almost), but there has been heavy quaking where they found that the El Golfo volcano had solidified it's magma body. No wonder Bob sprang into life, the entire system upwards of El Golfo is like a huge slab stopping all the action.
 Hopefully Bob will relieve the pressure buildup untill the eruption finnishes, otherwise this could get messy.

Reply

[jand]

Bob is giving burst almost every 5 minutes for a hour now.
 What is he doing?

Reply

Carl le Strange says:

 December 10, 2011 at 06:51

Read the article about Drumbeaths...

Reply

Betty says:

 December 10, 2011 at 07:46

Yeah, but now are we saying that these are drumbeats? Are they regular enough for that?

We DON'T want drumbeats.

Reply

Carl le Strange says:

 December 10, 2011 at 06:53

Drumbeats where back in full swing during the night, and this time it was obviously not a ship. http://www.02.ign.es/ign/head/volcaSenalesDiasAnterioresHora.do?nombreFichero=CHIE_2011-12-10_05-06&estacion=CHIE&Anio=2011&Mes=12&Dia=10&tipo=2&hora=05-06

Reply



GeoLurking says:

 December 10, 2011 at 07:38


Yay!! Kiyoo Mogi's paper!

"Relations Between the Eruptions of Various Volcanoes and Deformations of the Ground Surfaces Around Them."

http://repository.dl.itc.u-tokyo.ac.jp/dspace/bitstream/2261/11909/1/ji0362002.pdf

This work is the basis of a lot of later InSar and gravity field theory. It's what ya call, a "foundation piece." It treats the area around the volcano as an elastic half space and uses some simplifications to determine what sort of ground movement would be seen with an inflating volcano. (or deflating)

I managed to get the geophys package loaded into R, and have muddled through a couple of example runs... though I am still having trouble understanding what the program writers are getting at... seems they neglected to document what units they are using, and they normalize the output. Normalized to what I don't know. They didn't state the units.

However, their documentation was enough for me to replicate it in Excel, and spurred me to look for the original Mogi paper again.

Anyway, I thought I would share. Enjoy.

[jand]

earthquake-report.com

Update  09 – 10/12
 Diario de Avisos had an interview with Alpidio Armas, the president of El Hierro. One of the most important quotes Mr. Armas said, was that the volcano grew 80 meters the last couple of weeks.  The change in depth was measured by the oceanographic ship Ramon Margalef. The first bathymetry took place on October 24 (2 weeks after the start of the eruption) and the last one last week. Mr. Armas also said that according to the data of the Ramon Margelef 3 vents are active now and then.


What to expect next ?
 Based on Mr. Armas interview and taking into account a number of uncertainties, Earthquake-Report.com expects that :
- if the eruption continues at the present rate and in the same vent, it will take max. 2 weeks to arrive at a depth less than 100 meter. We than expect very strong Jacuzzis during the hydromagmatic bursts.
- if the same process continues for about 3 to 4 weeks and in the same vent we expect regular hydrovolcanic explosions  during the bursts.
- if the same process goes on 5 to 6 weeks the eruption may become Surtseyan. This is the most spectacular phase of the eruption. During this phase of the  eruption ash and steam clouds can reach hundreds of meters to several km in height.  Particular to Surtseyan eruptions are the thick,dark-pointed jets of fragments, often headed by bombs, shot out of the vent.
 - if the same process goes on 7 to 8 weeks and in the same vent, the eruption will have created at least a new island
 - the main vent is at a safe distance from La Restinga, so we do not see immediate danger for the population. 90% of the time the wind blows from the north or north east at this time of the year and accordingly the eventual ash will be blown further in the Las Calmas sea, avoiding damage at La Restinga..
- If a new island forms, it may indicate several months of uncertainty for the La Restinga population as nobody knows how long the eruption will last and when it will finally stop for a longer time as there may be several new eruptive periods.
 Our expectation is based on medium harmonic tremor like we had the last couple of days. In case of strong or very strong harmonic tremor the time to get to these different phases may well be a lot shorter.

If our expectations are coming true, the eruption will make El Hierro appearing in every news show in the world. The island will start to attract visitors from all over the world.

--------------------------------------------------------------------------------
Carl le Strange says:

 December 10, 2011 at 08:09


Of course Armas had to say that last sentence...
 Volcano tourism indeed!

Otherwise he actually was pretty much on the money regarding what will probably happen as long as the Eruption stays with Bob.
 I am still fearing that Tanganasoga will put in an appearance.
  Reply

[jand]

This shows movements up to 0730 this morning.

[jand]

Carl le Strange says:

 December 10, 2011 at 08:11

That is a sort of Drumbeats. Regular or not it is pulsing, and that usually mean that a horkload of magma is going somewhere.

As long as the drumbeats goes into Bob there is not much to worry about.
 But if these are drumbeats due to something being pushed up at Tanganasoga, then we do not want them.
My guess right now, pulses of magma moving to Bob...

[jand]

GeoLurking says:

 December 10, 2011 at 08:12

And another thing to think about.... that background image is from tomographic work from pre-2009. The left right alignment may be a smidgen off, but it seems that the focus of the quakes (the ones that show up here are mostly in the pre-bob group) is over top of what was supposed to be colder material... if I read the background correctly.

On the left diagonal "no quake" line, there is a grouping of quakes that snake up towards shallower depths. I wonder if that was a feeder that never made it to the surface, stopping about 6km down with a second offshoot that got to about 3 km in cracking the rock.

Again... I ain't no geophysicist. I just plot stuff.

Carl le Strange says:

 December 10, 2011 at 08:13

And that wedge could be what is pushed up under Tanganasoga, and that would be rather worrysome.
 Time to go for a long walk and ruminate on wedges, pressure and the meening of it all...

[jand]

GeoLurking says:

 December 10, 2011 at 08:06

Well, the really odd part is that "wedge" where there are two diagonal lines of "no quakes" that I have circled. I didn't expect that. It took be by surprise. The last thing I expected was to see a possible outline of a possible old vent structure.

[fifi]

"If the same process goes on 5 to 6 weeks the eruption may become Surtseyan" (Quote)

I hope so [] It would be the safest outcome too.

Interesting to see the drum beats back again and this time definitely not caused by sonar from the ship. It could mean that it is pushing the plug up and maybe something will happen after all in Tanganasoga though which would not be good. http://volcanocafe.wordpress.com/2011/11/29/drumbeats-of-el-hierro/

[jand]

Well whatever has been happening since early this morning is still going strong .

[jand]

Copied below parts of the text relating to a volcano that errupted .

Its interesting to see that just before the explosive fase seismic movements similar to what is shown in the above graph started.

Maybe its nothing or just coincidence I just thought reading it could it mean something for El Hierro.?

Copied from

http://pubs.usgs.gov/pp/1769/chapters/p1769_chapter01.pdf

Late on March 24, a number of spasmodic bursts occurred that raised the rate of earthquake occurrence even higher (fig. 16). The largest events recorded during the 1986 eruption of Augustine Volcano occurred on March 26 and 27 and ranged in magnitude from 1.3 to 2.1 (fig. 4). Seismic signals with waveforms that resemble explosion events began to appear at 0957 AKST on March 26 (Power, 1988) (fig. 16). Power (1988) reported an upward migration of average hypocentral depth from 0.21 to 0.82 km a.m.s.l. during the precursory phase.
Explosive Phase—March 26 to April 8, 1986

[jand]

Volcanocafe Copied.

This "chugging" could indicate that Bob is having a bit of difficulty in maintaining the vent/feed. As water rushes in and blocks the pipe, it gets vaporized and pushed back out. Rinse-repeat. Eventually it won't be able to push it out and the "chugs" will slow. (if I'm correct) When it stops then the deeper system will either cool in place and go to sleep, or pressure will build. (cool, I'm right either way) What happens down deep... that's anybodies guess. It may not like being unable to vent the pressure.

One thing is for certain... IGN should be in possession of or very soon to be in possession of, the most detailed picture of what it's like down there. Here's to hoping they don't play the idiot politics game and just makes whatever call based on what the data actually says. Screw the wishful and career minded politicians. THEY don't matter. Peoples lives do. If the politician doesn't like it, tell them (who ever it may be) to take a nice long swim out at Bob's Jacuzzi™. I'm sure the low pH water will heighten their awareness to the situation

[jand]

Here is my translation of the latest Barrera post, "The magma is concentrated in the south and rising to the surface". It seems to underscore a lot of what is being discussed here. (Señor Barrera is a Spanish volcanogist who has extensively mapped the Canary Islands.)

December 8, 2011 by José Luis Barrera Morate

"For several days, the earthquakes in the El Golfo region have been decreasing in magnitude and quantity. The pressure of the magma has decreased and it has not been transferred to the Las Calmas Sea as it was with the first seismic crisis that occurred from 19 July to 10 October. In the second crisis, since 14 October, the magma has been putting pressure on two different depth levels that correspond to areas of the upper mantle. It was not able to find an exit while it was still going strong, and with the decrease in new material coming from the mantle its momentum has run out. The earthquakes clearly marked a fissure where the southern extension reached the point of the submarine eruption. The magma attempted to open two vents: the submarine one that opened in La Restinga, and a new one in El Golfo. Such fissure behavior with several exit points has been very common in many eruptions in the Canaries.

The new data obtained by the two oceanographic ships: the Ramon Margalef and Sarmiento de Gamboa, indicates that the eruption, which they say has three vents, is emitting blocks of lava to the surface from about 150 m depth. From the 200 meter depth of October 28th, the volcano has risen about 50 meters. This explains the frequency with which the smoking lava stones occur in the Las Calmas Sea.

The best submarine lavas of the Canary Islands surface in the Caldera of Taburiente on La Palma island. There you can see concentrations of pillow lava with very vesicular nuclei, like the vesicular blocks that have been collected in the Las Calmas Sea.

The red alert in La Restinga has gone to yellow. It only remains red in the marine area of the eruption. It would be interesting to collect samples of all the emissions that have appeared, in order to establish a sequential tracking of the eruption."

http://blogs.elcorreogallego.es/elhierro/2011/12/08/el-magma-se-concentra-en-el-sur-y-asciende-hacia-la-superficie/

[jand]

Denise says:

 December 10, 2011 at 19:33
A picture of the "vesicular" lava is on the website linked above. And for those of you who read Spanish, the comments are also interesting. Señor Barrera responds personally to every comment. One reader asked if the danger of an eruption in the north had passed, given the lower seismic activity. Barrera responded that that danger has not passed, only diminished, and that as long as the eruption remains active at La Restinga, anything can happen.

Reply

[jand]

No Change in the chugging/dreambeats since midnight .

[jand]

http://www.unc.edu/~leesj/FETCH/Papers/Lees_etal_GJI_2004.pdf

This is very interesting it describes in the Summary the chugging in another volcano from 2003.

[jand]

Plugs and chugs—seismic and acoustic observations of degassing
explosions at Karymsky, Russia and Sangay, Ecuador

Abstract
Frequent degassing explosions, occurring at intervals of minutes to tens of minutes, are common at many active basaltic and
andesitic volcanoes worldwide. In August 1997, April 1998, and September 1998 we recorded seismic and acoustic signals
generated at two andesitic volcanoes with 'Strombolian-type' activity. Despite variations in explosion frequency (5–15 h21 at
Karymsky as opposed to 1–3 h21 at Sangay), the signatures of the explosions are remarkably similar at these two, diverse field
sites. In all explosions, gas emission begins rapidly and is correlated with an impulsive acoustic pressure pulse. Seismic
waveforms are emergent and begin 1–2 s before the explosion. We classify explosion events at the two volcanoes as either
short-duration (less than 1 min) simple impulses or long-duration (up to 5 min) tremor events. Many tremor events have
harmonic frequency spectra and correspond to regular 1 s acoustic pulses, often audible, that sound like chugging from a
locomotive. Chugging events are intermittent, suggesting that the geometry or geochemistry of the process is variable over short
time scales. We attribute the 1 Hz periodic chugs to a resonant phenomenon in the upper section of the conduit. q2000 Elsevier
Science B.V. All rights reserved.
Keywords: degassing explosions; Strombolian-type activity; seismo-acoustic signals

ftp://ftp.ingv.it/pub/jacopo.taddeucci/PAPERS/Johnson-LeesJVGR00degassingexplos.pdf

[jand]

http://www.youtube.com/watch?v=kSTTkq4_0Hk&feature=player_embedded

New Video from the Guardia Civil helicopter yesterday of the stain.

[jand]

Volcanocafe

Copied.

Using a generic shear modulus of 30 Gpa, and the calculated displacement of station FRON using FRON-LPAL and FRON-ALAJ to determine a total of 34.8 mm displacement from 21 July to 9 October (about when the tremor started and Bob was born), and using a distance of 4.1 km from FRON to directly over the assumed point source, I get the following estimates for the size of the "chamber"

http://i42.tinypic.com/1zxutzc.png

Keep in mind that there is a bit of assumption in that. First, the model assumes a point source for the chamber, we know from the initial quake swarm that it is likely cylindrical in shape. Before the tremor started, the quakes migrated south and deeper, then Bob popped the cork.

In all likelihood, the "chamber" volume is going to be closer to the green line. This doesn't mean all that is gonna come out, we have no clue how much of that is eruptable material.

Considering that the period of inflation was about 80 days, you can make a rough fill rate estimate off of this. Notable from the GPS at IGN, the displacement seems to hover around where it was at when the eruption started.

It would not be too far of a reach to assume that the fill mechanism is maintaining this rate and that Bob is bleeding it off at about a constant rate in order to keep the displacement relatively constant since 9 October.

GeoLurking says:

 December 11, 2011 at 06:43

Oh, almost forgot, the red line assumes a 10 km "chamber" depth (center), the blue line – 15 km, and the green – 20 km.

GeoLurking says:

 December 11, 2011 at 06:48

Averaged over the 80 day period... that works out to 562,500 m³/day, 1,687,500 m³/day or 3,800,000 m³/day of "stuff."

[jand]

Volcanocafe copied.

http://physicsworld.com/cws/article/news/2654

This is an interesting article. It is the most simple and clearest explanation of chugging I have found. I wonder if somewhere there is a plug which is stopping a more violent eruption. Could it be Tanganasoga.? It would explain the dead area where there have been virtually no Earthquakes which seems to be located beneath the area of the Tanganasoga.ash cone.

[jand]

Avcan FB Copied

New post for comments on WEBCAMS, the telephone is the sea and the English Channel perfectly with the bubbling, and in the panorama we have an idea of its extent.
http://hierroendirecto.movistar.es/


DURING, the stain can be seen perfectly and has a dark as Brown in the Center and something bubbling...
http://www.rtvc.es/volcanelhierro/volcanendirecto.aspx

and in the pinewood where also looks spot stands the bubbling and seen something its extension from another point when get the panoramic view and is very important if there are explosions, heard then is you can hear...
http://www.ustream.tv/channel/ACN-media

Explosions are more numerous and more close, today in the light of that tremor may have some burbujeo of those show. (Henry)

[TripleH]

CONGRATULATIONS jand on reaching 1000 posts Yahoooooooooooooooo

[jand]

Volcanacafe Copied

stoneyard says:

 December 11, 2011 at 10:32

If it is a lavaplug on tangasoga, and it starts to push up, will we be seeing something like pablo and pedro on la gomera?