Comment on "Evidence from acoustic imaging for submarine volcanic activity in 2012 off the west coast of El Hierro (Canary Islands, Spain)" by Pérez NM, Somoza L, Hernández PA, González de Vallejo L, León R, Sagiya T, Biain A, González FJ, Medialdea T, Barrancos J, Ibáñez J, Sumino H, Nogami K and Romero C [Bull Volcanol (2014) 76:882-896]

Versión del editor2,205

Hydrography applied to the mapping of submarine volcanoes

Technical advances in hydrographic studies of the seafloor and the progressive use of these techniques in oceanographic expeditions with scientific objectives, is generating greater collaborations between the hydrographic and oceanographic institutions. Coordination between the different institutions and the use of IHO criteria in the acquisition of bathymetric data in oceanographic expeditions, allow regional hydrographic offices to have an additional source of data for the improvement of the navigation charts. Meanwhile the Oceanographic Institutions will benefit by having validated bathymetric data of high precision. This product is of great interest in studies of submarine geological hazards where is necessary to have a very detailed knowledge of the seabed to determine possible morphological changes associated with the risk processes and the possible active structures. In addition, monitoring of active volcanoes need to have a good knowledge of changes in the physico-chemical properties of the water column, the possible changes in low intensity emissions (hot water, gas) can be detected with these studies in the overlying water masses.Versión del edito

Explosive felsic volcanism on El Hierro (Canary Islands)

© 2014, Springer-Verlag Berlin Heidelberg. The Canary Islands consist of seven basaltic shield volcanoes whose submerged portion is much more voluminous than the subaerial part of each island. Like so many other volcanic oceanic islands, the indicative deposits of explosive felsic volcanism are not a common feature on the Canary archipelago. Hitherto, they have only been documented from the central islands of Gran Canaria and Tenerife, which are the largest volcanic complexes of the islands. On the other Canary Islands, the presence of felsic rocks is mostly restricted to intrusions and a few lava flows, generally within the succession in the oldest parts of individual islands. In this paper, we present a detailed stratigraphic, lithological and sedimentological study of a significant felsic pumice deposit on the island of El Hierro, referred here as the Malpaso Member, which represents the only explosive episode of felsic volcanism found on the Canary Islands (outside of Gran Canaria and Tenerife). The products of the eruption indicate a single eruptive event and cover an area of about 15 km2. This work provides a detailed stratigraphic and chronological framework for El Hierro, and four subunits are identified within the member on the basis of lithological and granulometric characteristics. The results of this study demonstrate the importance of an explosive eruption in a setting where the activity is typified by effusive basaltic events. Given the style and the spatial distribution of the Malpaso eruption and its products, a future event with similar characteristics could have a serious impact on the population, infrastructure and economy of the island of El Hierro.This research was partially funded by the MINECO grant CGL2011-16144-E and the European Commission (FT7 Theme: ENV.2011.1.3.3-1; grant 282759:VUELCO’ )Peer Reviewe

The 1909 Chinyero eruption on Tenerife (Canary Islands): insights from historical accounts, and tephrostratigraphic and geochemical data

The last eruption on Tenerife (Canary Islands, Spain) started on 18 November 1909 from the El Chinyero vent on the northwestern Santiago rift. This fissural eruption was well documented by scientists and eyewitnesses, but there is a lack of data on the high-energy phase that produced the most significant emissions of ash and lapilli at the onset of the eruption. Here, we review historical documents (e.g. newspapers, dispatches, telegrams); eyewitness accounts and scientific reports were reviewed from a volcanological perspective and integrated with data from the analysis of deposit features, allowing an accurate reconstruction of the eruption and its dynamics. The 1909 eruption of Chinyero was fed by a compositionally discrete magma batch that ascended rapidly within the crust, producing rather violent pulsating Strombolian explosive activity in the early phases of the eruption. This activity produced a ca. 80 m high scoria cone and heavy fallout of lapilli and ash over the entire northern sector of the island of Tenerife. The energy of explosive activity waned after 3 days, giving way to the weak Strombolian explosive activity that contributed to a lesser extent to the buildup of the pyroclastic pile. Eruptions such as those from the Chinyero vent in 1909 are representative of rift activity on Tenerife and constitute a volcanic hazard for present-day inhabitants.Published886V. Pericolosità vulcanica e contributi alla stima del rischioJCR Journa

Xenopumice erupted on 15 October 2011 offshore of El Hierro (Canary Islands): a subvolcanic snapshot of magmatic, hydrothermal and pyrometamorphic processes

On 15 October 2011, a submarine eruption offshore of El Hierro Island gave rise to floating volcanic products, known as xenopumices, i.e., pumiceous xenoliths partly mingled and coated with the juvenile basanitic magma. Over the last few years, no consensus in the scientific community in explaining the origin of these products has been reached. In order to better understand the formation of xenopumice, we present a textural, mineralogical, and geochemical study of the possible magmatic, hydrothermal, and pyrometamorphic processes, which usually operate in the plumbing systems of active volcanoes. We carried out a comprehensive SEM investigation and Sr-Nd-Pb isotope analyses on some samples representative of three different xenopumice facies. All the data were compared with previous studies, new data for El Hierro extrusives and a literature dataset of Canary Islands igneous and sedimentary rocks. In the investigated xenopumices, we emphasize the presence of restitic magmatic phases as well as crystallization of minerals (mainly olivine+pyroxene+magnetite aggregates) as pseudomorphs after pre-existing mafic phenocrysts, providing evidence of pyrometamorphism induced by the high-T juvenile basanitic magma. In addition, we identify veins consisting of zircon+REE-oxides+mullite associated with Si-rich glass and hydrothermal quartz, which indicate the fundamental role played by hydrothermal fluid circulation in the xenopumice protolith. The petrological data agree with a pre-syneruptive formation of the xenopumice, when El Hierro basanite magma intruded hydrothermally altered trachyandesite to trachyte rocks and triggered local partial melting. Therefore, the El Hierro xenopumice represents a snapshot of the transient processes at the magma-wall rock interface, which normally occurs in the feeding system of active volcanoes

Xenopumices from the 2011–2012 submarine eruption of El Hierro (Canary Islands, Spain): Constraints on the plumbing system and magma ascent

Textures, petrography and geochemical compositions of products emitted during the onset of the 2011–2012 submarine eruption (15 October, 2011) off the coast of El Hierro have been investigated to get information on interaction mechanism between the first rising magma and the crust during the onset of the eruption as well as to get information on magma storage and plumbing systems beneath El Hierro volcano. Studied products consist of 5–50 cm bombs with an outer black to greenish, vesicular crust with bulk basanite composition containing pumiceous xenoliths (xenopumices). Our results show that xenopumices are much more heterogeneous that previously observed, since consist of a macro-scale mingling of a gray trachyte and white rhyolite. We interpreted xenopumices as resulting from the interaction (heating) between the basanitic magma feeding the eruption, a stagnant trachytic magma pocket/s and an associated hydrothermally altered halo with rhyolitic composition. Our findings confirm the importance of the study of the early products of an eruption since they can contain crucial information on the plumbing system geometry and the mechanism of magma ascent

Xenopumices from the 2011–2012 submarine eruption of El Hierro (Canary Islands, Spain): Constraints on the plumbing system and magma ascent

Textures, petrography and geochemical compositions of products emitted during the onset of the 2011–2012 submarine eruption (15 October, 2011) off the coast of El Hierro have been investigated to get information on interaction mechanism between the first rising magma and the crust during the onset of the eruption as well as to get information on magma storage and plumbing systems beneath El Hierro volcano. Studied products consist of 5–50 cm bombs with an outer black to greenish, vesicular crust with bulk basanite composition containing pumiceous xenoliths (xenopumices). Our results show that xenopumices are much more heterogeneous that previously observed, since consist of a macro-scale mingling of a gray trachyte and white rhyolite. We interpreted xenopumices as resulting from the interaction (heating) between the basanitic magma feeding the eruption, a stagnant trachytic magma pocket/s and an associated hydrothermally altered halo with rhyolitic composition. Our findings confirm the importance of the study of the early products of an eruption since they can contain crucial information on the plumbing system geometry and the mechanism of magma ascent.PublishedL173022.3. TTC - Laboratori di chimica e fisica delle rocce3.3. Geodinamica e struttura dell'interno della Terra3.6. Fisica del vulcanismoJCR Journalrestricte

Nueva visión estructural, hidrogeológica e hidrotermal mediante potencial espontáneo en Cumbre Vieja (La Palma, Islas Canarias)

Since last 1 Ma, the La Palma island volcanic activity concentrates at its southern half, on the Cumbre Vieja volcanic rift-zone. During the 1949 San Juan eruption a N-S fault system, facing west, developed close to the rift summit area, indicating a potential zone of deformation on the western flank that may provoke future failures and landslides. In this context, a geophysical Self Potential (SP) study was carried out with the aim of to characterize major structural limits influencing volcanic hydrothermal activity and underground meteoric circulations. Our study, which integrates also the soil temperature measurements, provides new information to characterize and place the limits guiding upward or downward fluid circulation shown as a change in SP polarity and intensity. A clear asymmetry of the self-potential signal was found between the eastern and the western flanks of Cumbre Vieja, where strong infiltration of meteoric water seems to affect most of the summit axis. On the eastern flank, a negative SP values suggest a usual vertical water infiltration. However, the poor variation in the self-potential values observed on the western flank could be explained by a constant thickness of its vadose zone, limited by the presence of an impermeable layer controlling the water inflow in a parallel direction relative to the surface. This boundary could be linked with the interface debris-solid rock created after the previous Cumbre Nueva edifice collapse, above which the new Cumbre Vieja is currently growing. However, if the fault system results from a local extension or from larger scale instability, it remains unclear.Peer Reviewe