[breaking] Vulkaanuitbarsting bij Canarische Eilanden

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Op maandag 3 oktober 2011 11:19 schreef Jumparound het volgende:

[..]

En waarop baseren ze dat dan?

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2011-10-03 10:54:15.31hr 32min ago 27.64 N 18.07 W 17 2.8 CANARY ISLANDS, SPAIN REGION

2011-10-03 10:27:49.61hr 58min ago 27.63 N 18.07 W 14 2.7 CANARY ISLANDS, SPAIN REGION

2011-10-03 10:14:43.42hr 12min ago 27.63 N 18.08 W 15 3.4 CANARY ISLANDS, SPAIN REGION

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Magma on the move in El Hierro, Canary Islands

This is happening faster then I expected. But it seems that magma is now on the move upwards in El Hierro volcano in Canary Islands. This is evident by the earthquake patterns that are emerging from the volcano. Given the earthquake locations, most likely place for a eruption to take place is out on the ocean based on that. But sometimes magma can find different pathways up the surface without a lot of warning.



Latest earthquake map from Instituto Geográfico Nacional that shows clearly the earthquake pattern since the dike intrusion did start in El Hierro. Copyright of this picture belongs to Instituto Geográfico Nacional.

At the moment it is impossible to know when and where a eruption might start. It depends on many factors. But it is now clear that magma is on the move upwards. So far the magma seems to be around 10 km up in the earth crust under El Hierro. So it is clear that the magma is on the way up and most likely preparing for a eruption.

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35mm deformation at El Hierro
The Instituto Geografico Nacional (IGN) has reported surface deformations exceeding 35mm on the Spanish island of El Hierro, where residents have been alert for a possible volcanic eruption. The number of earthquakes recorded since July 17 on the smallest of The Canary Islands exceeded 9250 on Tuesday morning. IGN confirmed on Monday that 1172 earthquakes were recorded last week, the majority of which were located in the sea to the SW of the 280-sqkm island. 52 of the earthquakes were felt by the local population, estimated to be approximately 10,000. A further 10 earthquakes, exceeding 3.0 magnitude on the Richter Scale, were felt during Monday and early on Tuesday. Hierro, a shield volcano, has had a single historic eruption from the Volcan de Lomo Negro vent in 1793. The eruption lasted approximately one month and produced lava flows. The recent surge in the number and intensity of earthquakes prompted officials from the IGN and The Canary Islands Government to raise the alert level for the Hierro volcano to ‘Yellow’ late last month.

Seismologists say the majority of the earthquake activity has shifted from El Golfo in the island’s northwest to beneath the Las Calmas Sea in the south. However, magma is now on the move upwards while the depth of earthquakes has become increasingly shallow in recent days with most being recorded at a depth of 10 to 14 kilometres. Movement of magma towards the surface signifies that a volcanic eruption is likely to happen, but the timing of such remains unclear. Volcanologist Juan Carlos Carracedo last week suggested that an eruption on El Hierro would “not be a major surprise”. He explained: “It is the youngest of the Canary Islands. There is a ball of magma which is rising to the surface and it is stationed at the limit of the earth’s crust. At the moment we do not know if that ball of magna will break the crust and cause an eruption.” IGN Director, María José Blanco said that any eruption on El Hierro would most likely have a “low explosion value”.

A dramatic rise in recorded earthquakes on El Hierro last Tuesday prompted officials to evacuate some local residents, shut El Hierro’s main tunnel, and close local schools. The Spanish Civil Guard (Guardia Civil) advised almost 50 residents of the municipality of La Frontera to leave their homes because of landslide fears. Two units of the Spanish military’s emergency intervention unit (EMU) were also placed on standby to depart the nearby island of Tenerife to assist in the possible evacuation of hundreds of other El Hierro residents. Meanwhile, the island’s main tunnel (Tunel del Golfo), which links Frontera to Valverde, was shut forcing motorists to travel across the 280-sq-km island via a mountain road. The Cabildo de El Hierro also ordered the closure of schools on Wednesday.

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El Hierro scientist:'More worried about earthquakes'
The Scientist in charge of the team studying the seismic activity on the Canary Island of El Hierro, Nemesio Pérez, has told the press how is is more concerned about earthquakes on the tiny island than he is of any Volcano eruption "Usually in the Canaries, they have not been that explosive, just trickles of lava. There are victims when there are earthquakes, which is why I am more concerned about the earthquakes rather than the eventual eruption."

Perez, who is the scientific coordinator of the Canaries Institute of Volcanology (Involcan) continued : "Spain has a seismic alert system comparable to that of a third-world country," he says. "Predicting volcanic activity has three components: tremors, gas emissions and deformations. But in Spain, attention is only paid to the first stage."

He told reporters how any volcanic eruption would not be rare, but the uncertainty stems from the fact that in El Hierro there isn't just one major volcano but around 500 vents on the island. As such, no one can be sure where the lava will flow if there does end up being an eruption.

The problem that this causes is that it is impossible to monitor and cordon off each and evert vent, but each one could still produce potentially fatal toxic fumes.

The Island residents have actually felt around 60 of the 9'000 recorded earthquakes over the past two months, however the frequency and strength has increased over the past two weeks.

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Vulkaanuitbarsting Tenerife helpt aardverschuivingen te begrijpen

AMSTERDAM - De ontdekking van een grote vulkaanuitbarsting op Tenerife van 733.000 jaar geleden werpt nieuw licht op aardverschuivingen. Zo is men in de toekomst mogelijk beter voorbereid op de gevolgen van dit soort grote catastrofes.

Vulkanologen van de Universiteit van Leicester ontdekten op het Canarische eiland Tenerife een aardverschuiving ten gevolge van een grote vulkaanuitbarsting waarbij een deel van de zijkant van de vulkaan de zee in verdween.

Ze publiceerden hun bevindingen in de oktober-editie van het tijdschrift Geology.

Bijzonder

Het is bijzonder dat niet vrijwel de hele aardverschuiving door de uitbarsting de zee in verdwenen is. "Het is een van de best bewaarde en toegankelijke voorbeelden van zo’n ontzagwekkend fenomeen, omdat het puin van zulke aardverschuivingen zich meestal over de oceaanbodem verspreid en daardoor ontoegankelijk voor verdere studie", verklaart Dr. Branney, een van de onderzoekers.

Het achtergebleven puin en gruis op Tenerife bevat onder andere blokken van snel afgekoeld stollingsgesteente. Radioactieve mineralen in de gestolde lava maakten het voor de onderzoekers makkelijk om zeer precies de datum van de uitbarsting te bepalen.

Klimaatverandering

Klimaatverandering wordt vaak aangewezen als reden voor aardverschuivingen op eilanden in de oceaan. Dat was nu niet het geval. Een groeiende koepel van hete lava duwde van binnenuit de zijkant van de vulkaan naar buiten toe.

Zulke gebeurtenissen zijn niet ongewoon, maar komen zeer onregelmatig voor. Ze begrijpen is daarom van belang omdat de effecten duizenden kilometers verderop grote problemen kunnen veroorzaken.

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2011-10-06 12:27:35.131min ago 27.67 N 18.04 W 13 3.1 CANARY ISLANDS, SPAIN REGION
2011-10-06 10:47:31.92hr 11min ago 27.69 N 18.04 W 14 2.8 CANARY ISLANDS, SPAIN REGION
2011-10-06 10:38:24.52hr 21min ago 27.67 N 18.04 W 12 2.5 CANARY ISLANDS, SPAIN REGION
2011-10-06 10:35:53.02hr 23min ago 27.66 N 18.02 W 14 2.7 CANARY ISLANDS, SPAIN REGION
2011-10-06 10:30:10.72hr 29min ago 27.68 N 18.03 W 16 2.5 CANARY ISLANDS, SPAIN REGION
2011-10-06 10:28:05.02hr 31min ago 27.67 N 18.03 W 12 2.6 CANARY ISLANDS, SPAIN REGION
2011-10-06 10:24:34.72hr 34min ago 27.69 N 18.03 W 16 2.5 CANARY ISLANDS, SPAIN REGION
2011-10-06 10:21:02.02hr 38min ago 27.69 N 18.02 W 16 2.5 CANARY ISLANDS, SPAIN REGION
2011-10-06 10:16:11.02hr 43min ago 27.68 N 18.03 W 16 2.6 CANARY ISLANDS, SPAIN REGION
2011-10-06 06:34:04.36hr 25min ago 27.69 N 18.05 W 13 2.6 CANARY ISLANDS, SPAIN REGION
2011-10-06 05:43:12.37hr 16min ago 27.69 N 18.04 W 12 2.8 CANARY ISLANDS, SPAIN REGION
2011-10-06 05:03:17.07hr 56min ago 27.67 N 18.04 W 12 3.2 CANARY ISLANDS, SPAIN REGION

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Op donderdag 6 oktober 2011 15:45 schreef bwt het volgende:
is ook erg goed te zien op de seismogr. data van mijn vorige post.