El Hierro

[pennylane]

Alls we need to do is to keep hitting the return key
and we can get shorter lines of text like this :-)

[TripleH]

oops looks like I am talking to myself now you deleted the post lol

[TripleH]

Shouldnt have to do that though PL the formatting of the board should sort it out automatically

[fifi]

Is yours ok now Glen?

[fifi]

I deleted it again Triple H because the long link was on it.[]

[pennylane]

yes thanks Fi. but I'm so used to hitting the return key,
it's habbit now lol.....I think the large photos
the other week caused it too....

Anno TripleH, but I did it when the photos were on
and I just do it automatically now..

Pl x

[Deso]

Ahh, that's better. Thank you. [][]  []

[jand]

Volcanic seismology

GENERAL CONCEPTS ON THE SISMOLOGIA APPLIED IN THE VOLCANIC ACTIVITY

Seismology has historically had great importance in monitoring volcanic, because thanks to her is has able to predict eruptions, Seismicity in a volcanic area is one of the first manifestations of a volcano enters activity in inactive volcanoes, or in his absence in active volcanoes, change the type of eruptive activity.

Seismic signals originating in volcanic areas, are specific to each volcano and will depend on the activity with which count and that's why many researchers have devoted to studying different seismic signals that can register in a volcano. Some of them like Minakami, Latter, Chouet, McNut, Koyanagi, White among others have contributed according to their experiences in various active volcanoes, and with the advancement in technology in the classification of the earthquakes of volcanic origin.

Initially you can start with a traditional classification with the following categories:

Earthquakes Volcanotectónicos (VT), also classified as high-frequency characteristics of these is very similar to tectonic origin, they have high frequencies, in the trace can differences stages of primary wave (P) and secondary (S), usually occur in swarms. The focus can be located from 1 to 20 km of depths and active crater fences are located in or at distances very. They are earthquakes associated with breakdowns of rocks, crevices openings.

Of long period (LP) or low frequency earthquakes originate near the surface, at depths less than 1 km, parameters tend to be very small and have frequencies below the 3.0 Hz, the honk or of the first wave is emerging and it is difficult to distinguish the phases of P and S waves, is usually mixed with surface waves. They are associated with processes of magma degassin

Earthquakes associated with explosions in them stands out the primary wave input and a maximum amplitude associated with the sound wave.

Earthquakes type hybrid, which are a combination between an LP and a volcanotectónico.

LP deep earthquakes, they are very uncommon and occur at depths between 20 - 40 km near the base of the Earth's crust, associated with subduction and in the case of the volcanoes events once registered have been able to correlate with a further emanation of CO2.

Tremors, there are different types as: monochromatic, polychromatic, espasmòdicos.

Signals caused by cold avalanches or pyroclastic flows.

POSSIBLE CAUSES

There are various causes that causes volcanic earthquakes, we will mention some of them below:

Movement or pumping of magma through new or pre-existing fractures generated by the same injection.

Fracturing of rock under the surface by rapid changes of temperature and stress.

Sound vibrations to broadcast channels.

Vaporization of the water in an aquifer in which plays an important role the transmicidad of the aquifer and the thermal contact, this being the example of a geyser

Processes of desgasificaciòn of magma.

[jand]

http://www.01.ign.es/ign/head/volcaSenalesDiasAnterioresHora.do?nombreFichero=CHIE_2011-11-25_20-21&estacion=CHIE&Anio=2011&Mes=11&Dia=25&tipo=2&hora=20-21

Avcan are discussing this on Fb .

Quote

Jordi, if I see the earthquake, I note perfectly as a vertical line in the spectrogram of CHIE on time (Henry).
25/11/2011 20: 14: 23 27.7793 - 18.0594 17 1.7 mbLg NW frontier.IHI

[kevin2003]

[jand]

Avcan

Translated

Current volcanic of Canarias (AVCAN.

Good according to official sources we are back to normal. It is assumed that the PEVOLCA will have enough data to make this decision. On the opening of the tunnel of the Roquillos hope that they were taken into account the indications requested in the report requested from the IGME, if contrary will be conducting a recklessness by someone. (Felix)

[jand]

Avcan

Questions from a spanish person.

Translated

If the Steering Committee of the Pevolca has agreed to such measures because they say that the recorded evolution of the phenomenon this stable, beg someone explain me why is the warning red in La Restinga? Why this warning yellow throughout the island? Why say expect 4.6 earthquakes? Why is Ramon Margalef still in the area? Why open the tunnel after the report on the terrible state that lies? Why there is an increase of gas? Why...? Why...? I have so many questions but the answer is that it this all is standard! Señor@s, we are in full eruption in Las Calmas. possible pre-erupción in the Gulf, do not rule out eruption on Earth, continues a strong tremor that leaves no see earthquakes that still break ground on the seismograph and excluding detachments. (Translated by Bing)

[jand]

http://www.01.ign.es/ign/resources/volcanologia/EHIG/imagenes_sismica/DIA_SP/EHIG_2011-11-25_sp.jpg

La Palma chart looks unusual?

[jand]

https://picasaweb.google.com/110327184570944806725/ElHierroNovember252011?authuser=0&feat=directlink#

Photos of activity on Mt Colorada Cone (176m) and directly in line with vent and Puerto de Naos cone. I read before I came that they were monitoring former significant volcanoes. Look for man in cone on photo without the helicopter. Click on the images to see some more pictures from Ian Carson from today.

[jand]

https://picasaweb.google.com/lh/photo/2adc29N0d3gMt6rhnE9vE9MTjNZETYmyPJy0liipFm0?feat=directlink

I was sure today that the point of emmision had changed from yesterday. Sitting in the same position with my feet in the same 'ash holes', today's emision point was further to the right. I have tried to demonstrate this in the attached photo, using a line I put down yesterday to mark the point. Joke has kindly put the two photos together. - Image courtesy and copyright Ian Carson

[jand]

http://www.enviroliteracy.org/nsfmod/NaturesFury.pdf

Interesting read on volcanoes and earthquakes.

[jand]

Data Update 26/11 – 08:02
 - NO earthquakes to report since midnight UTC
 - VERY STRONG colored stain can be seen on the webcam, even with poor daylight
 - NO Jacuzzi seen so far
 - Both phenomena are linked with each other. The degassing / eruption is continuing and creates big stains since a couple of days. By taking away the pressure from the reservoir in the El Golfo area the earthquakes are almost halted
 - Harmonic tremor is still going on and accordingly it is far too soon to conclude that the eruption is over like some people are declaring at the moment.

[jand]

http://212.170.244.196/

The stain is showing and is very large.

[jand]

http://www.01.ign.es/ign/layout/sismo.do


http://www.ign.es/ign/layoutIn/sismoDetalleTerremotos.do?evid=1114919&zona=1

ESMC

Magnitude

ML 4.1

Region

SPAIN

Date time

2011-11-26 08:11:56.0 UTC

Location

42.35 N ; 8.50 W

Depth

10 km

Distances

23 km NE Vigo (pop 292,745 ; local time 09:11:56.2 2011-11-26)
11 km NE Redondela (pop 30,000 ; local time 09:11:56.2 2011-11-26)
5 km NW Fornelos de montes (pop 2,063 ; local time 09:11:56.2 2011-11-26)


Source parameters not yet reviewed by a seismologist

[TripleH]

So is that it then? All over?

[jand]

Update 26/11 – 08:51
 - Joke reports that she sees a stain from El Pinar (El Pinar is approx. 10 km from La Restinga) and is located on the mountain itself.  She also reports that she cannot find any turbulence in the sea
 - Ian reports more or less the same

Update 26/11 – 09:05
 - the beautiful calm Las Calmas sea enables us this morning to trace the eruption vent. The arrow on the picture below is the location were we expect that the vent is (probably) degassing. About 15 to 30 minutes ago, we have spotted here the source of a white stain.  Unfortunetely the Telefonica operators have since zoomed more to the left .  The Telefonica operators have since zoomed the image and probable stirring action has to be located at the upper right corner.

[jand]

TripleH

There are so many conflicting stories at the moment.

As stated before the harmonic tremors are still ongoing see link below

http://www.ign.es/ign/head/volcaSenalesAnterioresDia.do?nombreFichero=CHIE_2011-11-26&estacion=CHIE&Anio=2011&Mes=11&Dia=26

Therefore magma is still moving somewhere?

[jand]

Experimental and model constraints on degassing of magma during ascent and eruption

James E. Gardner†1,
Alain Burgisser2,
Matthias Hort3 and
Malcolm Rutherford4

+ Author Affiliations

1Department of Geological Sciences, Jackson School of Geosciences, The University of Texas at Austin, Austin, Texas 78712, USA


2Institut des Sciences de la Terre d'Orleans, 45071 Orleans, France


3Institut für Geophysik, Universität Hamburg, 20146 Hamburg, Germany


4Department of Geological Sciences, Brown University, Providence, Rhode Island 02912, USA



Abstract

Surface volcanic gases may reflect volatile budgets in magma and forecast impending eruptions, and their release to the atmosphere may affect climate. The dynamics of magma degassing is complicated, however, by differences in the solubility, partitioning, and diffusion of the various volatiles, all of which can vary with pressure, temperature, and melt composition. To constrain possible gas outputs, we carried out experiments to determine how Cl partitions between water bubbles and silicate melt, and decompression experiments to examine how Cl behaves during closed- and open-system degassing. We incorporated our findings and those from the literature for CO2 and S into a steady, isothermal, and homogeneous flow model to estimate fluxes of gases at the vent from ascending water-rich magma, assuming different scenarios for the onset and development of permeability in bubbly magma. We find that, for given permeability scenarios, total gas fluxes vary with magma flux, but ratios of gas species do not change. The S/Cl and SO2/CO2 ratios do change, however, depending on whether the magma is oxidized or reduced. After magma fragments into a Plinian eruption column, gases continue to escape from cooling pumice in the plume, but here the rate of gas release is controlled by diffusion, which varies with temperature. Degassing of pumice and ash was modeled by linking a steady-state plume model, which gives the vertical variation of mean temperature and velocity of particles inside the plume, to a conductive cooling model of pumices, which controls diffusion of Cl, CO2, and S in pumice. We find that gas loss increases with column height (mass flux) and initial temperature, because in both cases pumices cool over a longer time period, allowing more gas to diffuse out of the matrix glass. The amount of gas released also depends on the size distribution of particles in the erupting mixture, with less being released for a finely skewed distribution.

[jand]

http://www.geo.mtu.edu/rs4hazards/Project%20resources/Publications/Nadeau_etal_2011.pdf

Copied part of the above link.

2000]. In most such tremor models, higher bubble concentrations
or more rapid flow of bubbles and bubble#8208;rich
fluid generate stronger tremor. It follows that more numerous
or larger volumes of bubbles producing larger amplitude
tremor signals would, after rising through the conduit, result
in a greater SO2 emission rate (Figure 2c). These processes
are non#8208;destructive and may be continuous, in agreement
with the persistence of tremor both prior to and immediately
following explosions at Fuego.
[12] In addition to correlation with tremor, both long#8208; and
short#8208;term decreases in SO2 emissions were observed prior
to explosions (Figures 2a and S2): from 6.4 kg/s to 0.31 kg/s
over #8764;1.5 hrs (explosion 14), and from 2.6 to 0.36 kg/s in
#8764;4 min (explosion 16). One way to explain this is by variable
gas supply, which could result from variable magma
and/or bubble ascent rates, variable spatial distribution of
gas in the conduit, or both. Non#8208;uniform distribution of gas
in magma is not unreasonable; bubbles in basaltic melts may
concentrate into layers or clusters with instabilities causing
further variability in bubble distribution [Manga, 1996]. If
bubble layers collapse into large gas slugs, the slugs could
burst through crater backfill, causing ash#8208;rich explosions
[Patrick et al., 2007]. However, when time#8208;series from
separate vents are examined, similarity between degassing
patterns at the two vents, which indicates some degree of
coupling, disappears prior to explosion 11 (Figure 2b); the
only anticorrelation between emissions from the vents
occurred immediately prior to explosion 11 (r = #8722;0.51 for 179
samples over #8764;8 minutes), when flank vent emissions were
relatively high. In contrast, the highest correlation occurred
immediately following explosion 12 (r = 0.76 for 100 samples
over #8764;6 minutes). If short#8208;term variations in SO2 emission
rate are the surface expression of variable bubble concentrations
within the magma column, instances when highly
correlated SO2 emission rates dominate may be indicative
of uninhibited gas release from both vents, while periods
of dissimilar SO2 time#8208;series may represent inhibition of
gas release from the summit.
[13] Based on our observations of Fuego's activity, we
have developed a model for small, ash#8208;rich explosions
(Figure 3). We consider background activity to be free
degassing from both vents (Figure 3a). Given the absence of
effusive activity, we assume magma supply was low during
our field campaign, and such conditions may lead to
enhanced cooling, degassing, crystallizing, or 'stiffening' of
magma in the conduit.

[kevin2003]

[fifi]

Article  (La Gran Epoca)

The inhabitants of the island of El Hierro who were evacuated  from their homes in October because of  landslide hazards due  to the increase in seismicity caused by the eruption process could return to their homes yesterday as reported by the Cabildo El Hierro.

They do not predict earthquakes greater than 4.6 degrees, which could cause some landslides, so the island's authorities authorized the return of the evacuees of Las Puntas and Pozo de las Calcosas.

Today the island woke up with no record of earthquakes and yesterday there were  only 9 earthquakes reported.

They also allowed the opening of the Eco-museum, which hosts a deserted village built in the past and the reopening of the Lagartario with indigenous species over 60 inches. ( Lizard museum I think)

The Roquille tunnel was reopened for daytime and night time. Three accelerometers were installed to control potential landslides by earthquakes.

The red alert level in  La Restinga, the ongoing submarine eruption in the Sea of Calm, and the yellow alert on the island continue.  The situation is calm and the magnitudes  recorded are under 3.7 degrees.

The area closest to the underwater eruption access to Tacorón coves and beaches of Puerto Naos are still closed.

The underwater eruption off the coast of La Restinga, according to the scientific committee, continues with amplitude tremors and  the volcano is still emitting material from the inside which is coloring the sea.

Bathymetry by the Scientific Committee on Ship Ramon Margalef, said the submarine volcano recorded a decrease in the height of the cone "which means they are producing sector collapses of frequent submarine eruptions themselves," added the scientists in their report published yesterday.

It also announced that the vertical deformation is declining in the west, in Sabinosa and Pozo de la salud, and remains in the Gulf.

Scientists say that finally, the scene of a possible eruption in the northern sector in the Gulf is still there but stated that "the situation is unclear and  it is not imminent at this time."

[fifi]

Erupting on webcam at the moment



http://earthquake-report.com/2011/11/12/32535/

Weebcam link above

[kevin2003]

quote:Originally posted by fifi

Erupting on webcam at the moment



http://earthquake-report.com/2011/11/12/32535/

Weebcam link above

[fifi]

[][][]

[fifi]

....and just as its happily smoking away they cut the camera and put this image on camera two instead.[}:)]




Camera 2 is on the stain now I think and not the erupting area