Search

Volcanic activity on Tenerife Island is extremely diverse. Three radial rift zones are characterized by cinder cones from basaltic fissure eruptions. A triple junction in central Tenerife exhibits a complex of merged, predominantly phonolitic, stratovolcanoes. The Las Cañadas caldera and widespread ignimbrite deposits reveal high explosive potential. We investigated the crustal and upper mantle structure beneath Tenerife using local earthquake data recorded by two dense seismic networks on the island. For our tomographic inversion, we selected >130,000 P‐ and S‐wave arrivals from ∼6,300 events that occurred during seismic unrests in 2004–2005 and 2017–2021. Synthetic tests confirmed that we could robustly resolve seismic velocity structures to ∼20 km depth. In the upper crust (down to ∼7 km) beneath central Tenerife, a prominent high‐velocity anomaly represents the rigid core of the volcanic complex; at greater depths, a strong low‐velocity anomaly reveals abrupt crustal thickening. Vp and Vs contour lines of 5.2 and 2.85 km/s, respectively, reveal Moho depth variation; crustal thickness beneath Las Cañadas reaches ∼17 km, whereas that beneath other parts of Tenerife is ∼10 km. An anomaly at ∼5 km beneath the caldera with low Vp, low Vs, and high Vp/Vs might be associated with a major phonolitic magma reservoir. Similar anomalies at ∼ sea level may represent shallow magma sources responsible for recent eruptions. Seismicity occurs in a columnar area of high Vp, high Vs, and low Vp/Vs, and may represent hydrothermal fluid migration through brittle media. Based on our results, we constructed a conceptual model of volcanic activity on Tenerife. Plain Language Summary: Tenerife is the largest and most populated island of the Canary Islands archipelago. Volcanic activity in Tenerife has the potential to seriously threaten the population and infrastructure. Two main types of volcanism are observed: explosive phonolitic eruptions from the central part of the island and basaltic fissure eruptions along three radial ridges. We present a new seismic tomography model based on the inversion of P‐ and S‐wave data from local seismicity. Absolute P‐ and S‐wave velocities reveal abrupt crustal thickening from ∼10 to 17 km within an elliptical area coinciding with Las Cañadas caldera in the central part of Tenerife. We suggest a "push‐button" mechanism that facilitates vertical displacement of central Tenerife part, which has high topography and is of higher density than peripheral parts of the island. Beneath Teide, at a depth of ∼5 km, a low Vp, low Vs, high Vp/Vs anomaly may represent an intermediate phonolitic reservoir. Two similar anomalies at shallower depths may represent the uppermost magma reservoirs directly responsible for phonolitic eruptions. Basaltic eruptions along the three radial ridges appear to be directly fed from mantle sources that appear as high Vp/Vs anomalies. Key Points: We constructed a high‐resolution seismic velocity model extending to ∼20 km depth beneath TenerifeThe velocity model shows a crustal thickness of up to 17 km below the Las Cañadas caldera and ∼10 km below other parts of the islandThe reservoir of phonolitic magma is revealed as an anomaly of low Vp, low Vs, and high Vp/Vs at ∼5 km depth [ABSTRACT FROM AUTHOR]

According to the Canarian government's plans, a complete decarbonization of the Canary Islands economy is foreseen from 2040 onwards, which includes the electrification of land transport in the archipelago. However, due to the current low penetration rate of electric vehicles (EVs) on the islands, the number of EVs in circulation is expected to grow significantly in the coming years. Despite this, the network of charging points in Tenerife is currently totally insufficient, which is why it is essential to carry out a study to design the network of charging points in such a way that it can absorb the entire fleet of EVs that is expected to be in place by 2040. To this end, there are studies on the capacity, in terms of parking space, available for the installation of these charging points, but to date there are no studies on this subject supported by mobility data. For this reason, a simulation of traffic in Tenerife in 2040 has been carried out using MATSim (Multi-Agent Transport Simulation) to determine the ideal places to install these charging points and to find the number of charging points needed for the network. [ABSTRACT FROM AUTHOR]

Copyright of Cuaternario y Geomorfología is the property of Cuaternario y Geomorfologia and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Mitteilungen der Österreichischen Geographischen Gesellschaft is the property of Oesterreichische Geographische Gesellschaft (Austrian Geographical Society) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Willdenowia is the property of Botanischer Garten & Botanisches Museum Berlin-Dahlem, Freie Universitat Berlin and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Willdenowia is the property of Botanischer Garten & Botanisches Museum Berlin-Dahlem, Freie Universitat Berlin and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Background - Species of Agave and Furcraea (Agavaceae, Asparagaceae s. lat.) are widely cultivated as ornamentals in Mediterranean climates. An increasing number is escaping and naturalising, also in natural habitats in the Canary Islands (Spain). However, a detailed treatment of variously naturalised and invasive species found in the wild in the Canary Islands is not available and, as a result, species identification is often problematic. Methods - The present study is based on many years of fieldwork on the islands of Fuerteventura, Gran Canaria, Lanzarote and Tenerife. Results - Fourteen species and several additional infraspecific taxa of Agave have been identified. In addition to the widely naturalised and invasive Agave americana, A. fourcroydes and A. sisalana (incl. the not previously reported var. armata), the following species of Agave were observed: A. angustifolia (incl. var. marginata), A. attenuata, A. filifera, A. franzosinii, A. lechuguilla, A. macroacantha, A. murpheyi, A. oteroi, A. salmiana (var. ferox and var. salmiana), A. aff. tequilana and A. vivipara. From the genus Furcraea three species were found: F. foetida, F. hexapetala and F. selloana. Several of these newly detected species of Agave and Furcraea are at least locally naturalised. A key for the identification of the representatives of these genera in the study area is presented and all species are illustrated. Additional nomenclatural, taxonomic and ecological notes are also provided. [ABSTRACT FROM AUTHOR]

In Tenerife there are a vast number of sub-horizontal blind water mines, called "galleries". Seven air and soil temperatures and CO2 concentration profiles in air were carried out inside the Río de Guía gallery (hereinafter RdG). An anomalous stable maximum temperature point (hereinafter MTP) was found around 2000 m from the entrance. During the warm period, a clear CO2 stagnation was detected before MTP, showing concentrations up to 14,000 ppm. In order to study gas emission and its dynamics inside the gallery, four stations were deployed around MTP. All stations recorded air and soil temperatures, and CO2 and Rn concentration in air from November 2009 to January 2011. After analyzing this dataset, it was possible to characterize the influence of MTP. This thermal anomaly divided the gallery into two sections. In the cold period, the outer section located outwards from MTP became colder while the inner section warmed up owing to a less heat transfer into the deepest part of the gallery. There were several short periods when variations in barometric pressure created an advection movement that was able to temporally change the gas behavior inside the gallery. Two soil gas samples were taken around MTP and their δ13C (CO2) ratios suggested a magmatic origin. All data were combined to create a model for the gas and thermal dynamics inside the gallery. This model, together with identification of background levels in each parameter, allows to identify any anomalous signal that could be elated with changes in volcanic activity. [ABSTRACT FROM AUTHOR]

Carbon dioxide is one of the first gases to escape the magmatic environment due to its low solubility in basaltic magmas at low pressures. The exsolved CO2 gas migrates towards the surface through rock fractures and high permeability paths. If an aquifer is located between the magmatic environment and the surface, a fraction of the CO2 emitted is dissolved in the aquifer. In this paper, an estimation of the water mass balance and the CO2 budget in Las Cañadas aquifer, Tenerife, Canary Islands, is presented. Magmatic CO2 is transported by groundwater and discharged through man-made sub-horizontal drains or galleries that exist in this island, and by the flow of groundwater discharged laterally towards other aquifers or to the ocean. In addition, the pCO2 at the gallery mouth (or entrance) and at the gallery bottom (internal and deepest discharge point where the gallery starts) are calculated and mapped. The total CO2 advectively transported by groundwater is estimated to range from 143 to 211 t CO2 d−1. Considering that the diffuse soil emission of CO2 for the same area is 437 t d−1, the diffuse/dissolved CO2 flux ratio varies between 2 and 3. The high dissolved inorganic carbon content of groundwater explains the ability of this low temperature hydrothermal water to dissolve and transfer magmatic CO2 at volcanoes, even during quiescence periods. [ABSTRACT FROM AUTHOR]

This paper describes design, observation methodology, results and interpretation of the GPS surveys conducted in the areas of the N-W of Tenerife where deformation was detected using InSAR. To avoid undesirable antenna positioning errors in the stations built using nails, we designed and used calibrated, fixed-length metal poles, allowing us to guarantee that the GPS antenna was stationed with a height repeatability of the order of 1 mm and of less than 3 millimeters on the horizontal plane. The results demonstrate that this system is ideal for field observation, especially to detect small displacements that might be masked by accidental errors in height measurements or centering when observed with a tripod. When observations were processed, we found that using different antenna models in the same session sometimes causes errors that can lead to rather inaccurate results. We also found that it is advisable to observe one or two stations in all the sessions. The results have reconfirmed the displacement in the Chío deformation zone for the period 1995–2000 and indicate a vertical rebound from 2000 to 2002. They also confirm that the subsidence detected by InSAR to the south of the Garachico village has continued since 2000, although the magnitude of the vertical deformation has increased from around 1 cm to more than 3 cm a year. Detected displacements could be due to groundwater level variation throughout the island. A first attempt of modelling has been made using a simple model. The results indicate that the observed deformation and the groundwater level variation are related in some way. The obtained results are very important because they might affect the design of the geodetic monitoring of volcanic reactivation on the island, which will only be actually useful if it is capable of distinguishing between displacements that might be linked to volcanic activity and those produced by other causes. Even though the study was limited to a given area of Tenerife, in the Canary Islands, some conclusions apply to, and are of general interest in similar geodynamic studies. [ABSTRACT FROM AUTHOR]

Monogenetic volcanoes are the most abundant volcanic structures on the Earth's surface. Thousands of them exist in different tectonic contexts (e.g., subduction zones, intraplate areas, and divergent boundaries), appearing in groups forming volcanic fields. Tenerife, the largest and highest island of the Canarian archipelago, started to form about 14 million years ago (Ma), as a result of a complex eruptive history and a varied geomorphological evolution, including shield-building stages, volcanic rifts, stratovolca-noes, and monogenetic cones. Tenerife is an active, volcanic, oceanic island, where the last eruption occurred in 1909. In this paper, we propose a methodology for calculating the size of monogenetic basaltic volcanoes based on morphometric parameters, as well as a classification of the size of the volcanoes through the study of 297 scoria cones of Tenerife. Morphometric techniques, based mainly on height (Hco), volume (Vco), and area (Aco), were used together with correlations between different morphological parameters. The result is a simple quantitative classification, easy to use for estimating the size of monogenetic volcanoes. Of the monogenetic basaltic volcanoes of Tenerife, 98.98% fit into this classification, which distinguishes between large (Hco>200; Vco >0.1; Aco >0.5), medium (Hco >100to<200;Vco>0.01 to <0.1; Aco >0.2 to <0.5), and small (Hco <100; Vco<0.01; Aco<0.2) volcanoes. There is a strong correlation between the size of cinder cones and their age: the more recent scoria cones are smaller in size than the older ones. This relationship supports suggestions by other researchers that eruptions have decreased in magnitude and the volume of available magma has become smaller. The results obtained by calculating the size of the scoria cones of Tenerife make possible the extrapolation of this technique to other insular or continental monogenetic volcanic fields. [ABSTRACT FROM AUTHOR]

Cinder cones were produced by the main basaltic eruptive episodes during the last 1 Ma in Tenerife, Canary Islands. The erosion of cinder cones is a natural process that begins immediately after an eruption. Factors controlling the erosion of monogenetic volcanoes include morphology, age, topographic and emplacement characteristics of the morphoclimatic environment, and local runoff depth. The aim of this paper is to document the evolution of gully erosion on 43 dated cinder cones over time and determine whether age is a critical factor in the degradation level of volcanoes, independent of other factors. The methodology employed is based on geomorphological and morphometric analyses. Only 39.5% of the Tenerife volcanoes have gullies; nevertheless, more than 84.6% of the Pleistocene cones present gullies, compared to only 20% of the Holocene volcanoes. This means that 80% of the Holocene cones have no gullies, whereas only 15.4% of the Pleistocene cones are gully-free. Therefore, the older volcanoes appear to have been more affected by torrential rains. Although the age of a volcano is an essential factor in the degree of erosion, other factors intervene as well. The rate and evolution of these cinder volcanoes depend on a combination of these factors. [ABSTRACT FROM AUTHOR]

The volcanic unit of Montaña Reventada on the island of Tenerife (Canary Islands, Spain) is an example of magma mingling and mixing in which the eruptive process was triggered by an intrusion of basanite into a phonolite magma chamber. The eruption started with emplacement of a basanitic scoria deposit followed by emplacement of a phonolitic lava flow characterized by the presence of mafic enclaves. These enclaves represent approximately 1 % of the outcrop and are basanitic, phono-tephritic and tephri-phonolitic in composition. The morphology of each enclave is different, varying from rounded to complex finger-like structures usually with cuspate terminations. In this study we quantified textural heterogeneity related to the enclaves generated by the mixing process and thus provided a new perspective on the 1100 Ad Montaña Reventada eruption. The textural study was performed by use of fractal geometry methods and the results show that the logarithm of the viscosity ratio between the phonolitic magma and the enclaves ranges between 0.39 and 0.81, with a mode at 0.49. This enables us to infer the water content is 2-2.5 wt% for the phonolitic magma and 1.5-2 wt% for the basanitic magma and the enclaves. [ABSTRACT FROM AUTHOR]

Phase equilibrium experiments were performed to determine the pre-eruptive conditions of the explosive eruption of Montaña Blanca (2020 bp) that occurred from a satellite vent located on the east flank of Teide volcano (Tenerife). Crystallization experiments used a phonolitic obsidian from the fall-out deposit as the starting material; this contains 5 wt % anorthoclase, diopside and magnetite with minor amounts of biotite and ilmenite, set in a glassy matrix that contains microlites of Ca-rich alkali feldspar. Temperature was varied between 850 and 800°C, and pressure between 200 and 50 MPa. The oxygen fugacity (fO2) was varied between NNO + 0·2 (0·2 log units above the Ni–NiO solid buffer) and NNO − 2, and dissolved water contents varied from 7 to 1·5 wt %. Comparison between natural and experimental phase proportions and compositions indicates that the main body of phonolitic magma was stored at 850 ± 15°C, 50 ± 20 MPa, 2·5 ± 0·5 wt % H2O at an fO2 around NNO − 0·5 prior to eruption, equivalent to depths of between 1 and 2 km below the surface. Some clinopyroxene crystals hosting H2O-rich melt inclusions possibly originate from an intermittent supply of phonolitic magma stored at somewhat deeper levels (100 MPa). The Ca- and Fe-rich composition of alkali feldspar phenocryst rims and microlites attests to the intrusion of a more mafic magma into the reservoir just prior to eruption; this is evidenced by the appearance of banded pumices in the later products of the eruptive sequence. The comparison with other phonolitic magmas from Tenerife and elsewhere (e.g. Vesuvius, Laacher See) shows that differences in the eruption dynamics of phonolitic magmas can be correlated with differences in magma storage depths, along with variations in pre-eruptive volatile contents. [ABSTRACT FROM AUTHOR]

Trapeliopsis gymnidiata, a terricolous species from the Canary Islands, is described as new to science. It has previously been confused with T. wallrothii, but differs by the soft, partly decorticate isidia, or rather gymnidia, that leave inconspicuous scars after falling off. Trapeliopsis wallrothii is known only from high mountains in Macaronesia, while T. gymnidiata is a lowland species. Trapelia rubra from Madeira is also described as new to science. It grows in similar places and resembles some morphs of Trapelia coarctata, but differs by the nearly squamulose areoles, the crenulate, seemingly sorediate, apothecium margin that does not become excluded, and especially by the patchy red colour (skyrin) in the medulla. [ABSTRACT FROM AUTHOR]

Many oceanic island rift zones are associated with lateral sector collapses, and several models have been proposed to explain this link. The North-East Rift Zone (NERZ) of Tenerife Island, Spain offers an opportunity to explore this relationship, as three successive collapses are located on both sides of the rift. We have carried out a systematic and detailed mapping campaign on the rift zone, including analysis of about 400 dykes. We recorded dyke morphology, thickness, composition, internal textural features and orientation to provide a catalogue of the characteristics of rift zone dykes. Dykes were intruded along the rift, but also radiate from several nodes along the rift and form en échelon sets along the walls of collapse scars. A striking characteristic of the dykes along the collapse scars is that they dip away from rift or embayment axes and are oblique to the collapse walls. This dyke pattern is consistent with the lateral spreading of the sectors long before the collapse events. The slump sides would create the necessary strike-slip movement to promote en échelon dyke patterns. The spreading flank would probably involve a basal decollement. Lateral flank spreading could have been generated by the intense intrusive activity along the rift but sectorial spreading in turn focused intrusive activity and allowed the development of deep intra-volcanic intrusive complexes. With continued magma supply, spreading caused temporary stabilisation of the rift by reducing slopes and relaxing stress. However, as magmatic intrusion persisted, a critical point was reached, beyond which further intrusion led to large-scale flank failure and sector collapse. During the early stages of growth, the rift could have been influenced by regional stress/strain fields and by pre-existing oceanic structures, but its later and mature development probably depended largely on the local volcanic and magmatic stress/strain fields that are effectively controlled by the rift zone growth, the intrusive complex development, the flank creep, the speed of flank deformation and the associated changes in topography. Using different approaches, a similar rift evolution has been proposed in volcanic oceanic islands elsewhere, showing that this model likely reflects a general and widespread process. This study, however, shows that the idea that dykes orient simply parallel to the rift or to the collapse scar walls is too simple; instead, a dynamic interplay between external factors (e.g. collapse, erosion) and internal forces (e.g. intrusions) is envisaged. This model thus provides a geological framework to understand the evolution of the NERZ and may help to predict developments in similar oceanic volcanoes elsewhere. [ABSTRACT FROM AUTHOR]

Recent studies on Teide-Pico Viejo (TPV) complex have revealed that explosive activity of phonolitic and basaltic magmas, including plinian and subplinian eruptions, and the generation of a wide range of pyroclastic density currents (PDCs) have also been significant. We perform a statistical analysis of the time series of past eruptions and the spatial extent of their erupted products, including lava flows, fallout and PDCs. We use an extreme value theory statistical method to calculate eruption recurrence. The analysis of past activity and extent of some well-identified deposits is used to calculate the eruption recurrence probabilities of various sizes and for different time periods. With this information, we compute several significant scenarios using the GIS-based VORIS 2 software (Felpeto et al., J Volcanol Geotherm Res 166:106-116, ) in order to evaluate the potential extent of the main eruption hazards that could be expected from TPV. The simulated hazard scenarios show that the southern flank of Tenerife is protected by Las Cañadas caldera wall against lava flows and pyroclastic density currents, but not against ash fallout. The Icod Valley, and to a minor extent also the La Orotava valley, is directly exposed to most of TPV hazards, in particular to the gravity driven flows. This study represents a step forward in the evaluation of volcanic hazard at TPV with regard to previous studies, and the results obtained should be useful for intermediate and long-term land-use and emergency planning. [ABSTRACT FROM AUTHOR]

The Quaternary Bandas del Sur Formation in the south of Tenerife comprises a complex sequence of pyroclastic rocks and lavas. In contrast to the NW- and NE-Rift zone on Tenerife, the S-Rift zone comprises a number of characteristics with respect to the morphological features, eruption cyclicity and the geochemistry of the volcanic deposits. Various flank eruptions of the Las Cañadas volcano associated with basaltic lavas and the formation of cinder cones within the Bandas del Sur are important volcanic units for understanding the explosive volcanic cycles during the Pleistocene on Tenerife. A number of palaeomagnetic studies, as well as major and trace element geochemistry and two radio-isotope dates (K-Ar), have been carried out on prominent cinder cones, in order to discover their stratigraphic position. Combining our results with previous K-Ar data, the cones and lavas can be subdivided into three stratigraphic units. The first unit contains cinder cones with reverse magnetization and Y/Nb ratios between 0.37 and 0.41. Cinder cones which belong to the second unit show normal magnetization and Y/Nb ratios of < 0.35. The third unit comprises cinder cones with normal magnetization and Y/Nb ratios of about 0.47. The first two units were constructed between c. 0.948-0.779 Ma and 0.323-0.300 Ma. These units define volcanic cycles ending in violent Plinian eruptions. The third and youngest unit possibly marks the beginning of a further volcanic cycle that started c. 0.095 Ma ago. [ABSTRACT FROM AUTHOR]

Aim We report the first analysis of the long-term ecology of Tenerife, in order to establish a pre-colonization base-line and to assess the effect of human activity and the role of climatic variation on vegetation during the Late Holocene. Location A former lake bed in the city of La Laguna (Tenerife, Canary Islands, Spain). Methods A sedimentary sequence of over 2 m was obtained from the former lake bed. Fossil pollen and microfossil charcoal concentrations were analysed. Radiocarbon dating of the sequence indicates that it spans approximately the last 4700 years. The pollen diagram was zoned using optimal splitting withinpsimpoll 4.25. Results Three pollen zones were differentiated: (1) in Zone L1 ( c. 4700–2900 cal. yr bp) a mixed forest was dominated by Quercus, Carpinus, Myrica and Pinus; (2) in Zone L2 ( c. 2900–2000 cal. yr bp) the laurel forest taxa increased, while Pinus, Juniperus and Phoenix declined; and (3) Zone L3 ( c. 2000–400 cal. yr bp) was characterized by the decline of Carpinus and Quercus and the abundance of laurel forest taxa (e.g. Myrica). Neither Carpinus nor Quercus was hitherto considered to be native to the Canary Islands. Their decline started c. 2000 years ago, coinciding with microfossil charcoal evidence of increased burning and with archaeological evidence for the first human settlement on Tenerife. Main conclusions Between c. 4700 and 2000 cal. yr bp, the composition of the forest in the valley of La Laguna was very different from what it is at present. In particular, Quercus and Carpinus appear to have been significant components, alongside components of the present-day laurel forest, and the native pine ( Pinus canariensis) forest and thermophilous woodland were also more prevalent in the region (but probably not within the lake basin itself) until 3000 cal. yr bp. The subsequent decline of Quercus and Carpinus led to the establishment of the present laurel forest in the region and a shift to more open vegetation types. These changes indicate that the aboriginal inhabitants of the islands, the Guanches, had a far more profound impact on the vegetation of Tenerife than hitherto realized. [ABSTRACT FROM AUTHOR]

The article provides a non-controlled biogenetic gas emission survey to 280 sampling sites in Tenerife, Canary Islands during February and March, 2002 in order to evaluate the concentration of CH4 and CO2 in the soil gas of the landfill cover, efflux from the surface of the landfill, and to compare these with other similar landfills. The measurements of surface landfill CO2 efflux were carried out at each sampling site on the surface landfill along with the collection of soil gas and ground temperatures at a depth of 30-40 centimeters. The CH4 efflux was computed from CO2 efflux and from CH4/CO2 ratio in the soil gas. The results of the study suggest a non-uniform pattern of diffuse degassing.

Detailed studies on the lichen genus Porina in Macaronesia have led to a reappraisal of the genuine identity of Porina atlantica (Erichsen) P. M. J∅rg., a characteristic species that has previously been confused with P. guaranitica, P. heterospora, P. nucula, P. mastoidea or P. rhodostoma in the literature, and is here reported from Madeira, the Canary Islands, Ireland, France and Portugal. Two new species are described: P. effilata Brand & Sérus. sp. nov. (known from Madeira, the Canary Islands, Great Britain, Ireland and Portugal) and P. ocoteae Brand & Sérus. sp. nov. (restricted to La Palma, Canary Islands, and São Jorge in the Azores). Porina leptospora Nyl. is recognized at the species level, and P. isidiata KaIb & Hafellner is reduced into synonymy with P. atlantica. A key to all known species of Porina in Macaronesia is provided. [ABSTRACT FROM AUTHOR]

The Granadilla eruption at 600 ka was one of the largest phonolitic explosive eruptions from the Las Cañadas volcano on Tenerife, producing a classical plinian eruptive sequence of a widespread pumice fall deposit overlain by an ignimbrite. The eruption resulted in a major phase of caldera collapse that probably destroyed the shallow-level magma chamber system. Granadilla pumices contain a diverse phenocryst assemblage of alkali feldspar + biotite + sodian diopside to aegirine–augite + titanomagnetite + ilmenite + nosean/haüyne + titanite + apatite; alkali feldspar is the dominant phenocryst and biotite is the main ferromagnesian phase. Kaersutite and partially resorbed plagioclase (oligoclase to sodic andesine) are present in some eruptive units, particularly in pumice erupted during the early plinian phase, and in the Granadilla ignimbrite at the top of the sequence. Associated with the kaersutite and plagioclase are small clots of microlitic plagioclase and kaersutite interpreted as quenched blebs of tephriphonolitic magma within the phonolite pumice. The Granadilla Member has previously been recognized as an example of reverse-then-normal compositional zonation, where the zonation is primarily expressed in terms of substantial variations in trace element abundances with limited major element variation (cryptic zonation). Evidence for cryptic zonation is also provided by the chemistry of the phenocryst phases, and corresponding changes in intensive parameters (e.g. T, f O2, f  H2O). Geothermometry estimates indicate that the main body of phonolite magma had a temperature gradient from 860 °C to ∼790 °C, with hotter magma (≥900 °C) tapped at the onset and terminal phases of the eruption. The reverse-then-normal chemical and thermal zonation reflects the initial tapping of a partially hybridized magma (mixing of phonolite and tephriphonolite), followed by the more sequential tapping of a zoned and relatively large body of highly evolved phonolite at a new vent and during the main plinian phase. This suggests that the different magma types within the main holding chamber could have been laterally juxtaposed, as well as in a density-stratified arrangement. Correlations between the presence of mixed phenocryst populations (i.e. presence of plagioclase and kaersutite) and coarser pumice fall layers suggest that increased eruption vigour led to the tapping of hybridized and/or less evolved magma probably from greater depths in the chamber. New oxygen isotope data for glass and mineral separates preclude syn-eruptive interaction between the vesiculating magma and hydrothermal fluids as the cause of the Sr isotope disequilibrium identified previously for the deposit. Enrichment in radiogenic Sr in the pumice glass has more likely been due to low-temperature exchange with meteoric water that was enriched in 87Sr by sea spray, which may be a common process affecting porous and glassy pyroclastic deposits on oceanic islands. [ABSTRACT FROM AUTHOR]

The present study focuses on the development of a standard methodology for selection of suitable sites for offshore (exposed) marine fish-cage farming (floating cages) of seabream ( Sparus aurata) and seabass ( Dicentrarchus labrax) in an island environment, using Tenerife as an example. Site selection is a key factor in any aquaculture operation, affecting both success and sustainability and can solve conflicts between different activities, making a rational use of the coastal space. Site selection was achieved by using geographical information systems (GIS)-based models and related technology to support the decision-making process. The framework for spatial multicriteria decision analysis used in this study began with a recognition and definition of the decision problem. Subsequently, 31 production functions (factors and constraints) were identified, defined and subdivided into eight submodels. These were then integrated into a GIS database in the form of thematic layers and later scored for standardization. At this stage, the database was verified by field sampling to establish the quality of data used. The decision maker's preferences were incorporated into the decision model by assigning weights of relative importance to the evaluation under consideration. These, together with the thematic layers, were incorporated using multicriteria evaluation techniques and simple overlays to provide an overall assessment of possible alternatives. The integration, manipulation and presentation of the results by means of GIS-based models in this sequential and logical flow of steps proved to be very effective for helping the decision-making process of site selection. Tenerife has very favourable environmental conditions for culture of marine fish and there are no totally unsuitable sites for cage farming identified in this study. On the other hand, there are few very suitable sites (high scores) either, principally due to the heavy use of the coastline and the conflicts between different users. From the 228 km2 of available area for siting cages in the coastal regions with depth less than 50 m, the total area suitable for siting cages (scores 6–8) was 37 km2. There are only 0.51 km2 of very suitable areas (score 8) and approximately 5.37 km2 of suitable (score 7), most of these being located in the southeast of the island. These relatively small areas of suitability should be put into the context of the wider use of the coastal environment around Tenerife. [ABSTRACT FROM AUTHOR]

The Bandas del Sur Formation preserves a Quaternary extra-caldera record of central phonolitic explosive volcanism of the Las Can˜adas volcano at Tenerife. Volcanic rocks are bimodal in composition, being predominantly phonolitic pyroclastic deposits, several eruptions of which resulted in summit caldera collapse, alkali basaltic lavas erupted from many fissures around the flanks. For the pyroclastic deposits, there is a broad range of pumice glass compositions from phonotephrite to phonolite. The phonolite pyroclastic deposits are also characterized by a diverse, 7–8-phase phenocryst assemblage (alkali feldspar + biotite + sodian diopside + titanomagnetite + ilmenite + nosean–hau¨yne + titanite + apatite) with alkali feldspar dominant, in contrast to interbedded phonolite lavas that typically have lower phenocryst contents and lack hydrous phases. Petrological and geochemical data are consistent with fractional crystallization (involving the observed phenocryst assemblages) as the dominant process in the development of phonolite magmas. New stratigraphically constrained data indicate that petrological and geochemical differences exist between pyroclastic deposits of the last two explosive cycles of phonolitic volcanism. Cycle 2 (0·85–0·57 Ma) pyroclastic fall deposits commonly show a cryptic compositional zonation indicating that several eruptions tapped chemically, and probably thermally stratified magma systems. Evidence for magma mixing is most widespread in the pyroclastic deposits of Cycle 3 (0·37–0·17 Ma), which includes the presence of reversely and normally zoned phenocrysts, quenched mafic glass blebs in pumice, banded pumice, and bimodal to polymodal phenocryst compositional populations. Syn-eruptive mixing events involved mostly phonolite and tephriphonolite magmas, whereas a pre-eruptive mixing event involving basaltic magma is recorded in several banded pumice-bearing ignimbrites of Cycle 3. The periodic addition and mixing of basaltic magma ultimately may have triggered several eruptions. Recharge and underplating by basaltic magma is interpreted to have elevated sulphur contents (occurring as an exsolved gas phase) in the capping phonolitic magma reservoir. This promoted nosean–hau¨yne crystallization over nepheline, elevated SO3 contents in apatite, and possibly resulted in large, climatologically important SO2 emissions. [ABSTRACT FROM PUBLISHER]

Mantle xenoliths from Tenerife show evidence of metasomatism and recrystallization overprinting the effects of extensive partial melting. The evidence includes: recrystallization of exsolved orthopyroxene porphyroclasts highly depleted in incompatible trace elements into incompatible-trace-element-enriched, poikilitic orthopyroxene with no visible exsolution lamellae; formation of olivine and REE–Cr-rich, strongly Zr–Hf–Ti-depleted clinopyroxene at the expense of orthopyroxene; the presence of phlogopite; whole-rock CaO/Al2O3 ≫ 1 (Ca metasomatism) in recrystallized rocks; and enrichment in incompatible elements in recrystallized rocks, relative to rocks showing little evidence of recrystallization. The ‘higher-than-normal’ degree of partial melting that preceded the metasomatism probably results from plume activity during the opening of the Central Atlantic Ocean. Sr–Nd isotopic compositions are closely similar to those of Tenerife basalts, indicating resetting from the expected original mid-ocean ridge basalt composition by the metasomatizing fluids. Metasomatism was caused by silicic carbonatite melts, and involved open-system processes, such as trapping of elements compatible with newly formed acceptor minerals, leaving residual fluids moving to shallower levels. The compositions of the metasomatizing fluids changed with time, probably as a result of changing compositions of the melts produced in the Canary Islands plume. Spinel dunites and wehrlites represent rocks where all, or most, orthopyroxene has been consumed through the metasomatic reactions. [ABSTRACT FROM PUBLISHER]

The petrology, geochemistry and petrogenesis of the active Teide–Pico Viejo volcanic complex provide information about the evolution and internal structure of the Tenerife central magma system during its most recent volcanic cycle. Two petrologically distinct basaniten–phonolite lineages are identified, which correlate essentially with the products of the Pico Teide and Pico Viejo stratovolcanoes. Geochemical modelling supports the evolution of both series from a common evolved basanite parent, by crystal fractionation under different physico-chemical conditions. Pico Viejo series intermediate magmas fractionated mainly kaersutite and low-Or plagioclase at high PH2O, whereas Teide series examples fractionated mainly high–Or plagioclase and clinopyroxene at low PH2O, resulting in lower Ba, Sr, Eu/Eu* and MREE/HREE, and less peralkaline phonolitic residua. The Pico Viejo series shows smooth modal, mineralogical and whole-rock chemical variations, whereas the Teide series shows the additional effects of mineral accumulation, magma mixing, assimilation of hydrothermally altered crust and contamination by felsic magmas. Pyroxene barometry suggests that parental basanites and Pico Viejo series intermediate magmas evolved in the lower crust and uppermost mantle at 6–12 kbar Ptotal. Teide series intermediate magmas experienced polybaric fractionation, also differentiating extensively within a shallow chamber beneath Teide, where low PH2O conditions resulted from low Ptotal and, on the basis of F and Cl systematics, from open–system degassing. Hygrometry and melt-inclusion data from phonolites suggest a shallow Teide chamber at ∼1.5 kbar Ptotal, whereas Pico Viejo series phonolites evolved in a separate shallow chamber at ∼1 kbar Ptotal. [ABSTRACT FROM AUTHOR]

This study explores the spatiotemporal variability of extreme wave storms around the Canary archipelago, with special focus on the southern coastal flank of Tenerife island, a strategic beach tourism destination of large socioeconomic importance. To this end, experimental and simulated data of winds and waves are used to study the severity, seasonality, and directionality of wave storms with considerable potential to cause significant impact on beaches. Furthermore, tidal experimental records are employed to test the joint occurrence of wave storms and significantly high sea levels. Long-term statistical analysis of extreme wave storms at different locations reveals a complex spatial pattern of wave storminess around the islands and in the southern flank of Tenerife, due to the intricacy of the coastline geometry, the presence of deep channels between islands, the high altitude and complex topography of the islands, and the sheltering effects exerted by each island over the others, depending on the directionality of the incident wave fields. In particular, south of Tenerife, the energy content and directionality of wave storms show substantial spatial variability, while the timing of extreme wave storms throughout the year exhibits a marked seasonal character. A specific extreme storm is examined in detail, as an illustrative case study of severe beach erosion and infrastructure damage. [ABSTRACT FROM AUTHOR]