quote:Recordaantal aardbevingen op Canarisch eilandNog nooit eerder werden er zoveel aardbevingen achter elkaar geregistreerd op het kleine vulkanische eilandje El Hierro, het kleinste van de Canarische Eilanden. De reeks van maar liefst 720 bevinkjes heeft de overheid van deze eilandengroep voor de kust van West Afrika ertoe doen besluiten om voor het eerst in de geschiedenis een vergadering bijeen te roepen van het Stuurcomité van Vulkanische Monitoring. Dit comité werd opgericht om specifieke plannen te realiseren, die de burgerbevolking dienen te beschermen en noodplannen voor vulkanische risico’s moeten ontwikkelen. Inmiddels wordt gesproken over een ‘significante dreiging van seismische activiteit’.Het Nationaal Geografisch Instituut (IGN) en het Volcanologische Instituut van de Canarische eilanden blijft nauwlettend de aardbevingen in de gaten houden, waarvan de kracht van de bevingen (elke dag!) ligt tussen de 1 en 3 op de Richterschaal. De meerderheid van de bevingen vindt plaats tussen 5 en 15 km diepte.Volgens de autoriteiten betekent deze seismische activiteit nog niet direct dat een grotere, significante aardbeving zal plaatsvinden. Het merendeel van de bevingen die zijn geregistreerd, vonden plaats in het Noord Westen van het 280 vierkante kilometer kleine eilandje, bij het plaatsje El Golfo (zie foto hieronder). Een aardbeving op deze plaats zorgde er zo’n 50.000 jaar geleden voor, dat er een enorme landverschuiving plaatsvond, waarbij de helft van de vulkaan in zee gleed. Hierdoor ontstond een ca. 100 meter hoge tsunami die naar de overzijde van de Atlantische oceaan zou zijn gegleden. Schuin tegenover dit eilandje, in het verlengde van de resterende halve kratermond, ligt het Noord Amerikaanse continent..
quote:El Hierro Earthquake Swarm Enters Third WeekThe intensity of earthquakes recorded on the smallest of the Canary Islands, El Hierro, has increased slightly during the last 24 hours. However, the total number of earthquakes recorded daily has lessened since the earthquake swarm initially began on 17 July.The total number of tremors recorded during the past two weeks has now exceeded 1,050, according to the Instituto Geografico Nacional (IGN).The majority of the earth tremors ranged between 1-2 magnitude, but during the past 24 hours there have been least five tremors measuring in excess of 2.0 magnitude on the Richter Scale. A 2.4 magnitude earthquake was recorded at 4:56 p.m. local time on Sunday (31 July 2011).Approximately 50 earth tremors were recorded on Sunday, according to local earthquake monitoring agency Actualidad Volcánica de Canarias (AVCAN). The number is slightly down on the number of tremors recorded on Saturday and significantly less than the 195 earthquakes recorded on 22 July.
quote:The vast majority of the tremors have been recorded in the northwest of the 278.5-square-kilometre island at El Golfo, the location of a massive landslide that created a 100-metre high tsunami almost 50,000 years ago.The earthquake swarm, prompted the Canary Islands Government to convene the first ever meeting on 22 July of the Steering Committee and Volcanic Monitoring, reflected in the Specific Plan Protection Civil and Emergency for Volcanic Risk, given what it described “the significant increase in seismic activity”. The Committee met again on Friday 29 July to discuss the low magnitude seismic activity. It reported that it had stepped up its seismic monitoring operations to identify the source of the earthquakes.Following an evaluation of seismic and volcanological information gathered by the IGN and volcanological Institute of the Canary Islands, the Committee agreed to activate “monitoring and surveillance mechanisms necessary to coordinate the actions of civilian self-protection and information to people listed in the Plan” (translated from Spanish press release). It remains unclear, however, if the unprecedented seismic activitiy on El Hierro is a precursor to a possible future increase in earthquake or volcanic activity.Earthquake swarms are events where a local area experiences sequences of many earthquakes striking in a relatively short period of time. The length of time used to define the swarm itself varies, but the United States Geological Survey (USGS) points out that an event may last for days, weeks, or months.El Hierro’s Volcanic/Seismic PastEl Hierro is situated in the most southwestern extreme of the Canaries. The island was formed after three successive eruptions, and consequent accumulations, the island emerged from the ocean as an imposing triangular pyramid crowned by a volcano more than 2,000 metres high.The volcanic activity, principally at the convergence of the three ridges, resulted in the continual expansion of the island. A mere 50,000 years ago, as a result of seismic tremors which produced massive landslides, a giant piece of the island cracked off, crashed down into the ocean and scattered along the seabed. This landslide of more than 300km3 gave rise to the impressive amphitheatre of the El Golfo valley and at the same time caused a tsunami that most likely rose over 100 metres high and probably reached as far as the American coast.
quote: Op woensdag 19 oktober 2011 14:40 schreef Scrummie het volgende:Kan deze gekoppeld worden aan de vorige in de reeks?
quote: Op woensdag 19 oktober 2011 14:53 schreef bwt het volgende:Dan zal ik gelijk een paar handige links er neer zetten die veel info bieden over de uitbarsting.
quote: Op woensdag 19 oktober 2011 14:58 schreef Frutsel het volgende:[..]is ie toch al?
quote: Op woensdag 19 oktober 2011 15:14 schreef Scrummie het volgende:Raar, hij stond niet in mijn AT lijst, vandaar de vraag. Nu wel uiteraard omdat ik erin gereageerd heb.
quote:20/10/2011 @ 08:40 According to the IGN, the El Hierro underwater eruption is slowing down. The tremors have decreased in intensity as have the number of earthquakes which would indicate that the current process is coming to its final stage.
quote:the geological evolution of the Canary Islands. Today at 20:00The PhD in Geological Sciences and Research Professor Juan Carlos Carracedo CSIC also director of the volcanological station of the Canaries, presented this Thursday, October 20, the book I Geology of the Canary Islands in the Museum of Science Elder and Technology of The Palmas de Gran Canaria. Professor of Geology at the University of Las Palmas de Gran Canaria Francisco Pérez Torrado will be responsible for performing the initial presentation of the act. Juan Carlos Carracedo perform a review of the geological evolution of the Canary Islands. Will refer to the beginning of the old Canary by the action of a hot spot for more than 55 million years ago until now represented by the last eruption in the Canary Islands and the first underwater documentary, recently occurred in El Hierro, the youngest island of the archipelago . The book launch will take place this Thursday, October 20th at 20.00 pm in the Elder Museum of Science and Technology of Las Palmas de Gran Canaria.
quote:Scientists confirm that the seismic process is losing momentumThe researcher of the Higher Council for Scientific Research (CSIC), Joan Martí, and responsible for Monitoring Volcanic National Geographic Institute (IGN), Carmen Lopez, have confirmed that the submarine eruption of El Hierro has expelled magma, which is still going abroad because samples of basalt "typical" in the Canary Islands that have been collected.But noted that the magma "is coming out," Lopez said the tremor signal has been reduced progressively and that the deformations are stable, so it noted that the seismic process is losing strength.Marti said that the eruption was not "too large" and dismissed the idea that an explosion soon, because the first phase tends to end, so that "we are returning to normal." In a second phase, said it was not until within weeks or months.For this reason they will stay ahead of the equipment and scientific instrumentation on the island, which is higher than it had at the beginning of the volcanic crisis, "he said." Although the researcher found that the risk to the population has not been great so far, acknowledged that "caution is always short."He recalled that from July to October were recorded on the island more than 10,000 earthquakes due to magma movement at first, adds, had a horizontal path, only to be vertical, reaching the surface. For scientists the peak was the bubbling was observed recently in the sea surface.For Martí "things have been done right the first time" because it detected the "minimal changes" of the situation and "has occurred that was predicted."
quote:El Hierro Volcano about to end 'eruptive phase'CSIC Scientists monitoring the volcanic eruptions on El Hierro, together with the National Geographic Institute (IGN), confirmed earlier this morning that the 'eruptive phase' of the volcano is now decreasing. However, this is not to say that the activity as a whole has come to an end as it is likely that the volcanic activity may move towards a further phase.Scientists also confirmed that tremors on land associated with the volcanic activity had also subsided considerablly over the past few days.Ground deformations, drinking water samples and lava samples are still being analyzed.Carmen Lopez, for the IGN confirmed "What had been assumed from the outset is that it was an eruption of basaltic magma which reached a depth of 11 or 12 miles and has been moving for more than three months until it found a place to rise to surface, which is what it has now done."The Volcanologist said how the submarine eruption began at 1,000 meters below sea level and had been moving north at a depth of just 200 meters, which is why the effects were seen on the surface.Lopez stressed the importance of waiting for all current activity to cease before declaring that the eruptive process was about to enter a new phase as it wasn't unheard of for the same activity to re-start after a short break.The scientists on the island are continuing to monitor the volcano, but believe that any threat to the population is "low".VOLCANO EARTHQUAKES AND FISHES EL HIERRO
quote:20/10/2011 @ 16:25 – The tremors on El Hierro continue but have decreased in intensity.20/10/2011 @ 16:22 So far today there have been 8 earthquakes around the island of El Hierro, as follows:Date Time(GMT) Latitude Longitude Depth(km) Richter 20/10/2011 14:16:32 27.6537 -18.1143 22 1.6 20/10/2011 13:37:10 27.6643 -18.0698 18 2.0 20/10/2011 11:49:10 27.7696 -18.0474 23 1.8 20/10/2011 11:46:34 27.7806 -18.0809 23 1.7 20/10/2011 11:40:15 27.7986 -18.0671 22 1.6 20/10/2011 11:08:29 27.6772 -18.0406 18 1.5 20/10/2011 09:19:33 27.9209 -18.1141 11 1.7 20/10/2011 00:13:27 27.6580 -18.0820 16 1.5
quote:El Hierro : Tunnel reopens but red alert remainsThe evacuated residents of La Restinga on the island of El Hierro will be allowed to return to their properties as from from 08:00 on Friday due to the decrease of seismic activity. However, the authorities will maintain surveillance 24 hours a day in the likelihood of activity returning and a further evacuation being necessarry. The Los Roquille tunnel will open between the hours of 08.00 ro 20.00.For the time being schoolchildren have been moved from the village to study at the town of El Pinar closeby.The Los Roquille tunnel will only be open during daylight hours to begin with, however it may be permitted to open throughout the night depending upon the developments over the coming days.With regards to the evacuations at La Frontera, a technical committee comprising of teh El Hierro local council, The Canary Islands Regional Government and the Geological and Mining Institute of Spain (IGME) have assessed the situation and are due to inform the owners if they may return to their homes.PEVOLCA also confirmed that the state of alert remains as 'red', and that this is likely to remain the case until data suggests that the eruptions are over.
quote:El Hierro - update 6Little seems to have changed in the eruption of El Hierro since my last update on it. That was on 19 October, 2011. Harmonic tremor is constant, but appears to have dropped a little in the past few days. But with the fluctuation that is often increases again before it drops down again. This means that the eruption is ongoing, but is loosing power to continue at current eruption vent. This was not unexpected. This has however not slowed down inflation in El Hierro from what I can gather on GPS data on El Hierro.As the current eruption vents close down it seems that earthquakes have started again under El Hierro. But the earthquakes have the depth from 28 km and up to around 5 km. This strongly suggests that new magma is entering under El Hierro and is again increasing the pressure inside the El Hierro magma sill (or chamber, but note that El Hierro does not have a stable magma chamber it seems). This increases earthquakes while the magma does not have any good path up to the surface. When a new path for the magma starts to form again, a large earthquake swarm is going to take place in El Hierro. It is not going to be anything bigger then already has taken place in El Hierro already. With the largest earthquakes going up to Mb5.0 in size. That is at least my opinion.The major risk in the current eruption cycle of El Hierro is the risk that new eruption vent is going to open up nearby a human population without warning. But El Hierro has a lot of cinder cones from earlier eruption cycles. That creates the risk that a new eruption vent is going to open up on dry land without warning. But it is impossible to know when and where that might happen.Claims that this eruption in El Hierro is going to create tsunami due to landslides are false and have no basic in fact or reality. As landslides are unlikely to happen in this eruption episode or if a eruption happens on dry land.
quote:El planeador submarino Altair y la erupciÃ³n en El HierroThe Seaglider unmanned underwater glider 'Altair' in the Canary Islands Oceanic Platform (Plocan) began work on Wednesday (October 19) in waters of the Calm Sea, across from El Tacorón on the island of El Hierro. Its implementation is the main novelty in the research conducted by Professor Ignacio Lozano ship in the eruptive process occurred off the coast of El Hierro.