Eruptive dynamics and petrological evolution of recent volcanism on the El Hierro Island : Implications for volcanic hazard assessment

[eng] The Canarian archipelago, extends over approximately 500 km in total along the passive continental margin off NW Africa, comprises seven major and four minor islands, and it is part of the so called Macaronesia region, together with the archipelagos of Azores, Madeira, Salvajes and Cape Verde. Within the oceanic geodynamic context, the Canary archipelago is located on oceanic crust of the big African plate, specifically upon the passive continental margin, with thickness exceeding 20 km. It is a good example of oceanic intraplate alkaline volcanism. According the radioisotopic data available (Carracedo et al., 1998) the archipelago has been formed during the last 60 Ma and is still volcanically active. Multiple periods of volcanic activity accompanied with extreme range in magma compositions and eruptive styles have been exhibited during the evolution. A wide variety of models have been proposed for the origin of the Canary Islands, such as, hot spot, decompressing fusion, Atlas generated propagating fracture, or the "block" model based on regional fractures that helped elevate the islands. Holocene sub-aerial activity has occurred on all islands, except La Gomera, with 18 eruptions in the last 520 years (historic activity) on Tenerife, La Palma, Lanzarote and El Hierro. All these eruptive events consist of monogenetic basaltic eruptions along structures or zones identified as rifts (only the 1798 of Montaña Chahorra in Tenerife, expulsed intermediate composition magma and was located at the base of the Teide-Pico Viejo volcanic complex). Although monogenetic volcanism is the most extended type of volcanic activity on the planet (Walker 2000) and is characterized by a large diversity of eruptive styles and products, it is generally associated to low level volcanic hazard and many times it is underestimated in the hazard assessment. The main structures generated by these type of eruptions (concentrated as volcanic fields or long rift zones) are cinder cones, formed by the pyroclastic products and lava flows, that can reach several kilometres length. Eventually, can generate phreatomagmatic deposits, when an interaction between magma and water occurs (shallow submarine volcanism or littoral cones). These eruptions, traditionally, are associated with a single batch and pulse of magma and are greatly influenced by local and regional stress fields. Other parameters that can be important in the evolution of the activity, as in any other volcanic activity, are magma composition, volume, and rheological contrast beneath the surface. Recent studies have revealed that, even in a monogenetic eruption, an internal geochemical evolution could be possible, mainly because of the multiple batches involved and the importance of the local stress controls in the migration and finally eruption of magma. Complexity, derived from these internal and external conditions in combination with the depth where magmas are stored and transported, is reflected in the difficulty to anticipate and forecast these types of eruptions and their evolution, especially, for areas with long quiescent periods and a variety of magmas as in the Canary Islands, where a new volcano could come up in any location. The reconstruction of the structure, geometry, composition and plumbing system conditions of pre- existed monogenetic eruptions on the Canary Islands along with the data obtained (petrological, seismological, geodetical, etc.) of an eruption in course such was the 2011 El Hierro eruption will help us obtain a significant progress in understanding the processes that take place, improve our knowledge on monogenetic eruptions and as a consequence enhance hazard assessment and reduce the risk to human lives.[spa] La última erupción en la isla de El Hierro (2011-12) representa una excelente oportunidad para estudiar el volcanismo monogenético basáltico. La comparación de los productos emitidos durante esa erupción con los emitidos en erupciones anteriores y la interpretación de los resultados petrológicos junto con los datos obtenidos por la red multiparamétrica de vigilancia volcánica del IGN de vigilancia (estaciones sísmicas, GNSS, gravimétricas,…) nos ha permitido lograr un conocimiento integral de los procesos que ocurren antes y durante este tipo de erupciones basáticas monogenéticas, que son las más probables a corto y medio plazo en Canarias. Este enfoque multidisciplinar nos ha proporcionado nueva información sobre el ascenso del magma, las condiciones y procesos internos, los mecanismos de las erupciones basálticas, los mecanismos de deposición y los escenarios de interacción. La interpretación conjunta de todos los datos obtenidos permitirá una mejor evaluación del riesgo volcánico, no solo para la isla de El Hierro, sino para todo el archipiélago canario. En esta tesis, junto con el estudio de la erupción de 2011-12, se han estudiado dos más erupciones; la que ha dado el depósito de productos evolucionados en el centro de la isla (área del Malpaso) donde la dinámica y evolución de ella se ha ligado en la interacción magma/agua y la erupción de Chinyero (1909, Tenerife) que con rasgos similares a la de El Hierro (basáltica) pero con menor volumen de magma involucrado, ha tenido una dinámica más explosiva de lo que se había creído hasta hoy. Por lo tanto, las evaluaciones de riesgo volcánico a largo y corto plazo para el conjunto de las islas Canarias deben tener en cuenta posibles escenarios que no solo incluyen la erupciones basálticas submarinas, como es el caso de 2011-2012, sino también las erupciones sub-aéreas de corta vida como la del Chinyero o las erupciones como la del Malpaso, donde la intrusión basáltica y la interacción con el agua son procesos que aumentan la explosividad de una erupción y como consecuencia, al área afectado de sus productos

Multiteide Project: Multiparametric characterization of the activity of Teide-Pico Viejo volcanic system

European Geosciences Union General Assembly (2017. Viena)Teide-Pico Viejo complex stands for one of the major natural volcanic hazards in the Canary Islands, due to the expected types of eruptions in the area and the high number of inhabitants in Tenerife Island. Therefore, it is necessary to have a volcanic alert system able to afford a precise assessment of the current state of the complex. For this purpose, the knowledge of the expected signals at each volcanic activity level is required. Moreover, the external effects that can affect the measurements shall be distinguished, external influences as the atmosphere are qualitatively known but have not been quantified yetCentro Geofísico de Canarias, Instituto Geográfico Nacional, EspañaObservatorio Geofísico Central, Instituto Geográfico Nacional, EspañaInstituto Geológico y Minero de España, EspañaLaboratoire GéoSciences Réunion, Institut de Physique du Globe de Paris, Centre National de la Recherche Scientifique, EspañaPeer reviewe

Geology of El Hierro Southern Rift, Canary Islands, Spain

The geological survey has been carried out in El Hierro with the aim to produce a new Geological Map at 1:12,500 scale for the Southern Rift. Almost 70 km2 have been mapped providing a detailed stratigraphic and volcano-tectonic reconstruction of its evolution. Our work focused on the last Rift Volcanism phase, where hundreds of cinder cones, associated with thin lava flows, cover most of the island’s surface. Lava flows fields (40), monogenetic volcanic edifices (>90), and volcano–tectonic structures (69), such as dykes, eruptive fissures, and faults have been surveyed and stored in the Geological Map. The map poses fundamental constraints on the Southern Rift geological evolution, mainly concerning its recent activity and allowing the definition of 4 main stages during the last 40 ka. Moreover, this 1:12,500 scale detailed map represents a primary tool for the volcanic hazard assessment of the Island, volcanic monitoring, urban planning, and further stratigraphic data-based investigations.The authors thank E. De Beni, B. Marston, and J. Szepesi for their useful revisions and suggestions, and the associated editor M. Pondrelli for managing the manuscriptPeer reviewe

Volcanic edifice slip events recorded on the fault plane of the San Andrés Landslide, El Hierro, Canary Islands

International audienc

New Insights into the Internal Structures and Geotechnical Rock Properties of the Giant San Andrés Landslide, El Hierro Island, Spain

peer reviewedThe San Andrés landslide on El Hierro (Canary Islands) represents a rare opportunity to study an incipient volcanic island flank collapse with an extensive onshore part. The presented research improves the knowledge of the internal structure and rock characteristics of a mega-landslide before its complete failure. The investigation combines multiple geophysical measurement techniques (active and passive seismic) and remotely sensed, high spatial resolution surveys (unmanned aerial vehicle) with in situ and laboratory geotechnical descriptions to characterize the rock properties inside and outside the San Andrés landslide. The available geophysical and geological data have been integrated into 3D geomodels to enhance their visual interpretation. The onshore geophysical investigations helped detect the possible San Andrés landslide sliding surfaces at depths between 320 m and 420 m, with a rather planar geometry. They also revealed that rocks inside and outside of the landslide had similar properties, which suggests that the previous fast movements of the landslide did not affect the bulk properties of the displaced rocks as the failure chiefly occurred along the weakened sliding plane. Uniaxial strength tests on basalt rocks further indicate a high variability and spatial heterogeneity of the rock strength properties due to the different types of volcanic rocks and their texture. The new information on the rock properties and structural setting of the San Andrés landslide can now be used to develop realistic geotechnical slope models of the onshore part of the flank collapse that are possibly applicable for slope stability or deformation calculations. It will also help assess related hazards marked by a low occurrence probability and a high impact potential.Mobility Plus project of the Czech Academy of Science

New insight into the 2011-2012 unrest and eruption of El Hierro Island (Canary Islands) based on integrated geophysical, geodetical and petrological data

A shallow water eruption started on October 10, 2011, ~2 km south off the coast of El Hierro (Canary Islands, Spain). The eruption lasted about five months and ended by early March 2012. Three months of unrest preceded this event with more than 10,000 localized earthquakes and up to 6 cm of vertical ground deformation. In the Canary Islands, this is the first eruption to be monitored by the network of Instituto Geográfico National (IGN) since the very beginning of the seismic unrest. This provided unprecedented time series that include geophysical (seismic and gravimetric), geodetic, geochemical and petrological data. In this work we discuss and interpret these data in order to describe the mechanisms of 2011-2012 El Hierro eruption, including ascent from magmatic source, a crustal storage, and the final intrusion in the South Rift before the eruption. Our research approach provides a multidisciplinary view of the dynamics of magma ascent and improves previous interpretations formulated during or shortly after the end of the eruption. According to our results, a major intrusion occurred beneath and around preexisting high-density magmatic bodies, localized at depth below the central part of the island. After a failed attempt to reach the surface through a low fractured zone located below the central-northern part of the island, the ascending magma finally found its way nearby the El Hierro South Rift Zone and erupted off the coast of La Restinga village, 350 m below sea level. The eruption was fed by the ascent of an important volume of material from the upper mantle that was emplaced near the crust-mantle boundary and progressively tapped during the eruption

Informe Científico-Técnico de la Campaña Oceanográfica VULCANA0515

Report on the environmental monitoring (geophysics, seabed sampling, physical and chemical characteristics, and planton) made on the submarine volcano of Tagoro (El Hierro Islands) to evaluate the degree of affection and recovery on the marine ecosystem of the last volcanic eruption in the Canary region, making it extendable to other regions of the Canary Islands of possible hydrothermal or volcanological interest. In this sense, the "Enmedio" volcano has been investigated, between the islands of Gran Canaria and Tenerife.Instituto Español de Oceanografí