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>>> El Hierro and Cumbre Vieja Wiki for noobs to understand the real threat!!!

 
Southgaia
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10/11/2011 12:36 PM
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>>> El Hierro and Cumbre Vieja Wiki for noobs to understand the real threat!!!
The real problem is CUMBRE VIEJA em LA PALMA

La Palma is a volcanic ocean island. It is currently the most volcanically active of the Canary Isles. Historical eruptions on the Cumbre Vieja occurred in 1470, 1585, 1646, 1677, 1712, 1949, and 1971.

1949 eruption

During the 1949 eruption, three vents - Duraznero, San Juan and Hoyo Negro opened and lava was erupted. Also during the eruption two earthquakes occurred with epicentres near Jedey. Following the earthquakes a fracture approximately two and half kilometres long - about 1/10 of the exposed length of the Cumbre Vieja, opened and parts of the western half of the Cumbre Vieja ridge moved about 1m sideways and 2m downwards towards the Atlantic Ocean.[3][4] The fracture is still visible (2008) and still has the same dimensions recorded in 1949.

It is considered that this process was driven by the pressure caused by the rising magma super-heating water trapped within the edifice of the volcano. It is unlikely that the trapped waters could vapourise due to being under considerable pressure. What is postulated is that the waters were heated to a point where they could not absorb further thermal energy in the available space. Continuing heating required the water to expand further and the only way it could do so was to move the flank of the volcano. This resulted in the two earthquakes that were reported as occurring during the eruption.
Proof that the water did not vaporize are the absence of phreatomagmatic explosions - steam escaping explosively from the ground is often a precursor of volcanic activity. Further evidence that vapourisation did not occur is that when the rift was visited the following day by Rubio Bonelli,[3] he reported that the newly opened fissure "... Was not issuing fumes, vapor, steam, ashes, lava or other materials ..." In fact at no time during or after was steam or phreatomagmatic activity reported. This reinforces the claim that the waters trapped within the edifice never vaporized which they would do if the pressure had fallen sufficiently to allow the super-heated water to flash into steam.

1971 eruption

The 1971 eruption occurred at the southern end of the Cumbre Vieja at the Teneguia vent. The eruption was mainly strombolian in style. Lava was also erupted. Such seismic activity did not occur during the 1949 eruption. Residual thermal activity continues.

Future threat

The British Broadcasting Corporation (BBC 2 Channel) transmitted “Mega-tsunami; Wave of Destruction”,[5] which suggested that a future failure of the western flank of the Cumbre Vieja would cause a "mega-tsunami."

Day et al. (1999)[6] and Ward and Day (2001)[7] hypothesize that during a future unascertained eruption, the western half of the Cumbre Vieja – approximately 500 km3 (5 x 1011 m3) with an estimated mass 1.5 x 1015 kg – will catastrophically fail in a massive gravitational landslide and enter the Atlantic Ocean generating a so called "mega-tsunami." The debris will continue to travel, as a debris flow, along the ocean floor. Computer modelling indicates that the resulting initial wave may attain a local amplitude (height) in excess of 600 metres (1,969 ft) and an initial peak to peak height that approximates to 2 kilometres (1 mi), and travel at about 1,000 kilometres per hour (621 mph) (approximately the speed of a jet aircraft), inundating the African coast in about 1 hour, the southern coast of England in about 3.5 hours, and the eastern seaboard of North America in about 6 hours, by which time the initial wave would have subsided into a succession of smaller ones each about 30 metres (98 ft) to 60 metres (197 ft) high. These may surge to several hundred metres in height and be several kilometres apart but retaining their original speed. The models of Day et al.[6] and Ward and Day[7] suggest that it could inundate up to 25 kilometres (16 mi) inland. This would greatly damage or destroy cities along the entire North American eastern seaboard, and tens of millions would be killed as Boston, New York City, Miami, and many other cities that are located near the Atlantic coast are leveled.

Detailed geological mapping shows that the distribution and orientation of vents and feeder dykes within the volcano have shifted from a triple rift system (typical of most oceanic island volcanoes) to one consisting of a single north-south rift.[8][9][10] It is claimed that this structural reorganization is a response to evolving stress patterns associated with the development of a possible detachment fault under the volcano's west flank.[6][7] Siebert (1984)[11] showed that such failures are due to the intrusion of parallel and sub-parallel dykes into a rift. Eventually the structure becomes unstable and catastrophic failure occurs. There is no evidence that the 1949 section of the rift extends in a north south direction or that there is a developing detachment plane. Research is ongoing.



[link to en.wikipedia.org]

Last Edited by Phennommennonn on 10/11/2011 05:47 PM
Southgaia  (OP)

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10/11/2011 12:40 PM
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Re: >>> El Hierro and Cumbre Vieja Wiki for noobs to understand the real threat!!!
[link to drpinna.com]
Southgaia  (OP)

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10/11/2011 01:16 PM
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Re: >>> El Hierro and Cumbre Vieja Wiki for noobs to understand the real threat!!!
[link to www.rtvc.es]





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