Tirelessly updating Avalon on the El Hierro eruption.

[randles]

Source: https://youtube.com/watch?v=p1UWdAPPKxE

The research vessel "Sarmiento de Gamboa" close to the eruption vent El Hierro

[Hervé]

Some of the main special equipments Sarmiento de Gamboa was built for:

Main page: http://www.utm.csic.es/sarmiento.asp?switchlang=2

Animations:

http://www.utm.csic.es/doc/bo_sarmie.../Man_rov_1.swf

http://www.utm.csic.es/doc/bo_sarmie...s/multihaz.swf

Sarmiento de Gamboa just came back sailing over Polly...

[Hervé]

Strongest so far (2.6 at 09:00:13):

For the day:

Frequencies spectrogram, the vertical streaks indicate “events” (tremors/EQs) whereas the horizontal ones reflect volcanic/magmatic activity:

From Wikipedia: A Harmonic tremor is a sustained release of seismic and/or infrasonic energy typically associated with the underground movement of magma and/or venting of volcanic gases from magma. Being a long-duration continuous signal from a temporally extended source, a volcanic tremor contrasts distinctly with transient sources of seismic radiation, such as tremors that are typically associated with earthquake and explosion.

How it's looking like now from Las Puntas de La Frontera:

Refresh your browser to get the latest traces

For the last 10 days, following the count of EQs as shown by the orange bars (≥ 2.0), it now shows whatever Polly is up to as far as seismic activity is concerned:

Since the beginning

New cumulative graph starting October 10, 2011. The continuously changing scales keeps compressing the earlier graphs to the bottom and to the left!

Location of the EQs for the last 10 days:

Since the beginning

Refresh your browser page to get the latest numbers and positions.

[Hervé]

Ramon Margalef is back from Los Christianos straight into the GPS dead zone... to perform additional geophysical surveys.

[Hervé]

As for Sarmiento de Gamboa, continuing sismic and gravimetric profiles in the El Golfo area:

In this diagram, the "Reflected wave" associated with the white-line paths should instead say: "Refracted wave."

This will give the profile of the crust under and in and around El Hierro so that we know more precisely what we are dealing with below the seafloor and how the different layers are arranged.

[Hervé]

Polly's has had a good snooze: not one EQ logged by IGN between 5 pm yesterday and 9 am this morning...

The only activity registered on the seismograms are the sismic campaign airgun shots:

[Hervé]

While yesterday the Sarmiento de Gamboa was surveying the Sea of Calm:

Trawling its net of hydrophones to catch those elusive airgun shots compression waves...




This guy was busy flying around...



To catch these:

... and I thought Polly was having a snooze... ' been busy too!

[Hervé]

Today... still only one EQ logged by IGN... and some tourists on the Sea of Calm...

While Ramon Margalef was busy criss-crossing in front of La Restinga:

... it's been standing still on that spot for over an hour! As if moored.

******************
The second EQ of the day came while posting the above... a 2.1

[Hervé]

40 minutes later... still on the same spot...

Waiting for this guy to come back from running errands...

... and it's almost night time...

... back to work...

[Daughter of Time]

Stunning! Thank you Amzer! It's great to be informed.
And thank you Randles.

[Hervé]

Strongest so far (2.6 at 23:29):

For the day:

Frequencies spectrogram, the vertical streaks indicate “events” (tremors/EQs) whereas the horizontal ones reflect volcanic/magmatic activity:

From Wikipedia: A Harmonic tremor is a sustained release of seismic and/or infrasonic energy typically associated with the underground movement of magma and/or venting of volcanic gases from magma. Being a long-duration continuous signal from a temporally extended source, a volcanic tremor contrasts distinctly with transient sources of seismic radiation, such as tremors that are typically associated with earthquake and explosion.

How it's looking like now from Las Puntas de La Frontera:

Refresh your browser to get the latest traces

For the last 10 days, following the count of EQs as shown by the orange bars (≥ 2.0), it now shows whatever Polly is up to as far as seismic activity is concerned:

Since the beginning

New cumulative graph starting October 10, 2011. The continuously changing scales keeps compressing the earlier graphs to the bottom and to the left!

Location of the EQs for the last 10 days:

Since the beginning

Refresh your browser page to get the latest numbers and positions.

[Hervé]

INVOLCAN / Guardia Civil have open their own YouTube channel where they are uploading their videos from their flights over the La Restinga plume.

Here is one from November 29 in which Sarmiento de Gamboa is seen at the edge of the plume:

Source: https://youtube.com/watch?v=OhYqCxpoJbM

Today, December 1st, 3 vessels are cruising in the La Restinga area:

Ramon Margalef

Salvamar Adhara

Sarmiento de Gamboa

[Hervé]

Margalef's threadings overnight:

Gamboa's flight over El Hierro... (GPS connects the last known positions):

Salvamar Adhara check out:

Concert Margalef-Guardia Civil:

Camera oddities...

All keeping an eye on that ever growing multicolored plume...

[Hervé]

Ever changing color and shape of the plume:

Time to report back...

New camera view of La Frontera:

[Hervé]

From space yesterday:

[Hervé]

New release of INVOLCAN/Guardia Civil pictures from the 14th of November:

[Hervé]

Pyroclastics ejected by the volcano this morning


Research continues in the waters of El Hierro


Earlier today, at sea, steaming pyroclastics came up which disappeared leaving a large brown stain .

DIARIOELHIERRO.ES, writing (12.01.2011. 15:52 pm)
Oceanographic vessels Ramon Margalef and Sarmiento de Gamboa continue their research in the waters of El Hierro at the request of Civil Protection Plan for Volcanic Risk (Pevolca) with the aim of providing advice to the scientific committee integrated in that plan.

In this matter, the ship "Sarmiento de Gamboa" finishes its work today with the conducting of bathymetric, gravimetric and seismic profiles which began last Tuesday. To begin with, the campaign was originally planned as a research on the continental shelf of the Canaries.

It is reminded that the issuance of this ship involves the Geological Survey, Marine Technology Unit of the CSIC, the Spanish Institute of Oceanography and the Navy Hydrographic Institute.

For his part, Spanish Institute of Oceanography (IEO)'s Ramon Margalef's part six of its Campaign Bimbache 2011 runs until December 3, focused on multibeam bathymetric survey with sediment samplings and acquisition of echograms of the water column.

This research will provide important information for monitoring the eruptive episode and will be soon joined in this task with a second ship of the IEO, the Cornide de Saavedra, which will continue the data acquisition initiated by the Canary Islands Oceanic Platform (PLOCAN) and Ramon Margalef on the study of physical and chemical evolution of the slick from the volcano.

Eruptive processes

Scientists at the National Geographic Institute, on board a Search & Rescue vessel, ascertained that the pyroclastic appeared early in the morning today then disappeared and gave way to a brown stain, composed of fine material, which spread very rapidly on the sea ​​surface. Maritime Rescue Cooperation is being helpful for nighttime inspections, recognition of the area and collection of water samples, necessary to determine their physicochemical properties.

Regarding the seismicity, it should be noted that IGN has confirmed that only 3 earthquakes occurred during yesterday; at 9:00 am, 16:17 hours and 23:25 hours, none of them felt by the population . According to the provisional data from the Institute, until 13 pm today, there had only been two earthquakes with magnitudes less than 2 on the Richter scale.

The tremor signal has remained constant throughout the day, showing a slight decrease over 15 hours and mid afternoon. Notably, there have been few pulses, and of low amplitude, and the analysis of the data yields no evidence of any second source of tremor.

Finally, it is noted that the stations monitoring ground deformation show that the deformation maintained the pattern of recent days, following the same trend of deflation in the vertical component of the stations south of the island and east of the Gulf and stability in the horizontal components .

[Hervé]

From this morning Guardia Civil flight:

Reaching La Estaca...

Wrapping around La Restinga...

Far cry from what we can see on the webcams...

Ramon Margalef daily mud bath...

... complete with fresh-out-of-the-oven beauty pumices...

[Hervé]

Interesting data offered at Volcanocafe. com by Geolurking from a preliminary study of S-waves and the speed at which they seem to travel under El Hierro.

To understand Geolurking's graph, one has to know that seismic S-wave cannot travel or be propagated through liquids or gases. Another property of S-waves is that the denser the propagating medium, the faster the wave travels. Density of the propagating medium being also an index of the porosity of that medium, it therefore can be correlated to the amount of liquid/gas it's hosting.

Using both P and S waves travel times and the difference in time it took them to arrive at a particular station, knowing that P-waves are not hindered by the state of the propagating medium; the arrival time difference can be correlated to the density and therefore the porosity of the material the S waves travelled through.

Combining the above, when a medium is somewhat porous and therefore hosts gases or liquids, whether water, hydrothermal fluids or melted rocks, the S -waves slow down in their propagation speed, lengthening their travel time.

Accordingly, the slower the speed of travel/propagation, the higher the liquid/gas content inferred from the geater differences of travel time between P and S waves.

Here is his graph (note the graph's top starts at a depth of 10 kilometers) and some of his comments:

Image: GeoLurking, rights reserved. The original image that started the discussion. Here we can see what might be a magma chamber, and the feeder tube that goes down into the deep. Location of the inferred magma chamber is below Tanganasoga volcano.

When an earthquake appears in a seismic catalogue, you are given the latitude and longitude of the epicenter, and the depth. The addition of depth turns that position report into a hypocenter, because it locates the quake in three dimensions. In the more detailed phase portion of the reports, you can obtain the arrival times of the quakes. Take the difference in arrival times for each station with respect to the event time, and you have how long it took for the quake’s energy to reach the station. Knowing the distance from the station to the quake, and you can work out the speed of that seismic wave.

P-waves are compression waves, much like sounds are a compression waves. The molecules move toward and away from the direction of travel. S-waves are transverse waves, they move side to side with respect to the direction of travel. The density of the medium that the waves travel through affects the speed of propagation, or how fast the waves moves. S-waves cannot travel through a pure liquid as S-waves.

When the rock density goes up, the difference in the speed betweed P and S waves grows smaller. With lower rock density, the speed difference grows larger.

Again, my standard caveat: I am not a geologist and am not trained in that field. I could be very wrong in my methods. Take it with questioning view, which is sane way to look at it.

One could say that the ground under Tanganasoga is made of Swiss cheese with it's cohorts of ancient lava tubes, etc...

However, the additional data of ground deformations and CO2 releases in that area do suggest that, although Swiss cheese, the holes may be indeed filled with hydrothermal fluids if not magmatic melts... consideredring that Polly is not that far away and spewing smoking Restingolitas once in a while.

What's certain is that the magmatic melts didn't follow the old Tanganasoga Swiss cheese path but ended up in front of La Restinga; meaning it was the free-est and easiest path to surface.

Hopefully, the gravimetric and sismic campaign of Sarmiento de Gamboa will soon shed better light on the underlying structure of El Hierro.

[Hervé]

El Hierro from space yesterday, December 1st: