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- Carracedo, J. C., et al.
(författare)
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Evolution of ocean-island rifts : The northeast rift zone of Tenerife, Canary Islands
- 2011
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Ingår i: Geological Society of America Bulletin. - 0016-7606 .- 1943-2674. ; 123:3-4, s. 562-584
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Tidskriftsartikel (refereegranskat)abstract
- The northeast rift zone of Tenerife presents a superb opportunity to study the entire cycle of activity of an oceanic rift zone. Field geology, isotopic dating, and magnetic stratigraphy provide a reliable temporal and spatial framework for the evolution of the NE rift zone, which includes a period of very fast growth toward instability (between ca. 1.1 and 0.83 Ma) followed by three successive large landslides: the Micheque and Guimar collapses, which occurred approximately contemporaneously at ca. 830 ka and on either side of the rift, and the La Orotava landslide (between 690 +/- 10 and 566 +/- 13 ka). Our observations suggest that Canarian rift zones show similar patterns of development, which often includes overgrowth, instability, and lateral collapses. Collapses of the rift flanks disrupt established fissural feeding systems, favoring magma ascent and shallow emplacement, which in turn leads to magma differentiation and intermediate to felsic nested eruptions. Rifts and their collapses may therefore act as an important factor in providing architectural and petrological variability to oceanic volcanoes. Conversely, the presence of substantial felsic volcanism in rift settings may indicate the presence of earlier landslide scars, even if concealed by postcollapse volcanism. Comparative analysis of the main rifts in the Canary Islands outlines this general evolutionary pattern: (1) growth of an increasingly high and steep ridge by concentrated basaltic fissure eruptions; (2) flank collapse and catastrophic disruption of the established feeder system of the rift; (3) postcollapse centralized nested volcanism, commonly evolving from initially ultramafic-mafic to terminal felsic compositions (trachytes, phonolites); and (4) progressive decline of nested eruptive activity.
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- Carracedo, Juan Carlos, et al.
(författare)
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Geological Hazards in the Teide Volcanic Complex
- 2013
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Ingår i: Teide Volcano. - Berlin, Heidelberg : Springer Berlin/Heidelberg. - 9783642258923 - 9783642258930 ; , s. 249-272
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Bokkapitel (refereegranskat)abstract
- The island of Tenerife displays contrasted densities of population, from the densely occupied coastal zones (including tourist resorts, airport, energy facilities, etc.) to the sparsely populated forests and mountainous highlands, where most of the recent volcanic events are located. Considering the low frequency of historical eruptions (compared to Hawaii or Reunion Island for example), the assessment of geological hazards must also rely on the analysis and interpretation of prehistorical events, going back to at least the Late Quaternary. In this chapter, we review the hazards related to Teide’s volcanism, but also those from increased seismicity and from slope instability. We discuss the origin of low magnitude earthquakes, and particularly the 2004 episode of unrest. New estimates on cumulative volumes for resurfacing by lava flows during the last few thousand years are provided to serve as a tool for building a lava flow hazard map of Tenerife. Hazards related to explosive activity are also considered and although possible, with phreatomagmatic eruptions being the most likely style anticipated, explosive events are of relatively low probability at Teide in the near future.
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| 5. |
- Carracedo, J.C., et al.
(författare)
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The NE Rift of Tenerife: towards a model on the origin and evolution of ocean island rifts
- 2009
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Ingår i: Estudios Geologicos. - : Editorial CSIC. - 1988-3250 .- 0367-0449. ; 65:1, s. 5-47
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Tidskriftsartikel (refereegranskat)abstract
- The NE Rift of Tenerife is an excellent example of a persistent, recurrent rift, providing important evidence of the origin and dynamics of these major volcanic features. The rift developed in three successive, intense and relatively short eruptive stages (a few hundred ka), separated by longer periods of quiescence or reduced activity: A Miocene stage (7266 +/- 156 ka), apparently extending the central Miocene shield of Tenerife towards the Anaga massif; an Upper Pliocene stage (2710 +/- 58 ka) and the latest stage, with the main eruptive phase in the Pleistocene. Detailed geological (GIS) mapping, geomagnetic reversal mapping and stratigraphic correlation, and radioisotopic (K/Ar) dating of volcanic formations allowed the reconstruction of the latest period of rift activity. In the early phases of this stage the majority of the eruptions grouped tightly along the axis of the rift and show reverse polarity (corresponding to the Matuyama chron). Dykes are of normal and reverse polarities. In the final phase of activity, eruptions are more disperse and lavas and dykes are consistently of normal polarity (Brunhes chron). Volcanic units of normal polarity crossed by dykes of normal and reverse polarities yield ages apparently compatible with normal subchrons (M-B Precursor and Jaramillo) in the Upper Matuyama chron. Three lateral collapses successively mass-wasted the rift: The Micheque collapse, completely concealed by subsequent nested volcanism, and the Guimar and La Orotava collapses, that are only partially filled. Time occurrence of collapses in the NE rift apparently coincides with glacial stages, suggesting that giant landslides may be finally triggered by sea level changes during glaciations. Pre-collapse and nested volcanism is predominantly basaltic, except in the Micheque collapse, where magmas evolved towards intermediate and felsic (trachytic) compositions. Rifts in the Canary Islands are long-lasting, recurrent features, probably related to primordial, plume-related fractures acting throughout the entire growth of the islands. Basaltic volcanism forms the bulk of the islands and rift zones. However, collapses of the flanks of the rifts disrupt their established fissural feeding system, frequently favouring magma accumulation and residence at shallow emplacements, leading to differentiation of magmas, and intermediate to felsic nested eruptions. Rifts and their collapse may therefore act as an important factor in providing petrological variability to oceanic volcanoes. Conversely, the possibility exists that the presence of important felsic volcanism may indicate lateral collapses in oceanic shields and ridge-like volcanoes, even if they are concealed by post-collapse volcanism or partially mass-wasted by erosion.
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- Pérez-Torrado, Francisco José, et al.
(författare)
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Eruptive Styles at the Teide Volcanic Complex
- 2013
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Ingår i: Teide Volcano. - : Springer Berlin/Heidelberg. ; , s. 213-231
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- The wide variety of volcanic products composing the Teide VolcanicComplex (TVC) reflects an unusual assemblage of eruptive styles, with awide range of phenomena represented and only plinian and phreato-plinian styles truly lacking. This diversity is due to spatial and temporalvariations in magma composition (mafic magmas of the rift zones andfelsic magmas of the central edifice), variable magmatic volatile contentsand the interaction of magma with external water (snow, groundwater,etc.). Overall, strombolian eruptions are the most frequent eruptive styleat the TVC. Explosive eruptions of felsic material tend to be of lowvolume, for example, the largest explosive event during the Holocene, Montaña Blanca (ca. 2 ka), produced*0.2 km3DRE of phonoliticpumice during an eruptive sequence that reached explosivity of sub-plinian magnitude. Examples of phreatomagmatic activity (surge depos-its) have been described both on the northern flanks of Teide volcano aswell as from the summit area of Pico Viejo volcano. Until now moststudies on volcanic hazard assessment have focussed on ash fall and lavaflow hazards in the Canary Islands, but phreatomagmatic eruptions andtheir potential effects may have to be seriously considered as well.
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