Bouncing Spallation Bombs During the 2021 La Palma Eruption, Canary Islands, Spain

Incandescent pyroclasts of more than 64 mm in diameter erupted from active volcanoes are known as bombs and pose a significant hazard to life and infrastructure. Volcanic ballistic projectile hazard assessment normally considers fall as the main transport process, estimating its intensity from bomb location and impact cratering. We describe ballistically ejected bombs observed during the late October 2021 episode of eruption at La Palma (Canary Islands) that additionally travelled downhill by rolling and bouncing on the steep tephra-dominated cone. These bouncing bombs travelled for distances >1 km beyond their initial impact sites, increasing total travel distance by as much as 100%. They left multiple impact craters on their travel path and frequently spalled incandescent fragments on impact with substrate, leading to significant fire hazard for partially buried trees and structures far beyond the range of ballistic transport. We term these phenomena as bouncing spallation bombs. The official exclusion zone encompassed this hazard at La Palma, but elsewhere bouncing spallation bombs ought to be accounted for in risk assessment, necessitating awareness of an increased hazard footprint on steep-sided volcanoes with ballistic activity

The influence of natural fire and cultural practices on island ecosystems: insights from a 4800 year record from Gran Canaria, Canary Islands

Aim: Long-term ecological data provide a stepped frame of island ecosystem transformation after successive waves of human colonization, essential to determine conservation and management baselines. However, the timing and ecological impact of initial human settlement on many islands is still poorly known. Here we report analyses from a 4800-year sedimentary sequence from Gran Canaria (Canary Islands), with the goal of disentangling forest responses to natural fire from early human pressure on the island.Location: La Calderilla, a volcanic maar caldera at 1770 m a.s.l. on Gran Canaria.Taxon: plants and fungi.Methods: A core from the caldera infill was analysed for sediment properties, pollen, micro- and macrocharcoal, with radiocarbon and biochronology dating. Fossil data were statistically zoned and interpreted with the help of cross-correlation and ordination analyses. Surface samples and a pollen–vegetation training set were used as modern analogues for vegetation reconstruction.Results: Before human settlement (4800–2000 cal. yr BP), pine (Pinus canariensis) pollen dominated. Extensive dry pine forests characterised the highlands, although with temporary declining phases, followed by prompt (sub-centennial scale) recovery. Towards 2280 cal. yr BP there was a shift to open vegetation, marked by an increase in coprophilous spores. Coincidental with independent evidence of human settlement in the pine belt (2000–470 cal. yr BP) there was a decline of pine and a peak in charcoal. Following historic settlement (470–0 cal. yr BP), pollen producers from anthropogenic habitats, secondary vegetation and coprophilous fungi increased in abundance, reflecting higher pressure of animal husbandry and farming. Modern moss polsters reflect extensive reforestation since 1950 CE (Common Era).Main conclusions: From 4800 cal. yr BP, the pristine vegetation covering the Gran Canaria highlands was a mosaic of dry pine forests and open vegetation. The pine forests sustained intense fires, which may well have promoted habitat diversity. Human interference was initiated around 2280 cal. yr BP probably by recurrent cultural firing and animal husbandry, triggering a steady trend of forest withdrawal and expansion of grasses and scrubs, until the final disappearance of the pine forest locally in the 20th century. Grasslands were found to be of ancient cultural origin in the summit areas of Gran Canaria, although they underwent an expansion after the Castilian Conquest

The 2021 eruption of the Cumbre Vieja volcanic ridge on La Palma, Canary Islands

Almost exactly half a century after the eruption of the Teneguía Volcano on La Palma (26 October to 28 November 1971), a new eruption occurred on the island and lasted for 85 days from 19 September until 13 December 2021. This new eruption opened a volcanic vent complex on the western flank of the Cumbre Vieja rift zone, the N-S elongated polygenetic volcanic ridge that has developed on La Palma over the last c. 125 ka. The Cumbre Vieja ridge is the volcanically active region of the island and the most active one of the Canary Islands, hosting half of all the historically recorded eruptive events in the archipelago. The 2021 La Palma eruption has seen no direct loss of human life, thanks to efficient early detection and sensible management of the volcanic crisis by the authorities, but more than 2800 buildings and almost 1000 hectares of plantations and farmland were affected by lava flows and pyroclastic deposits. Satellite surveillance enabled accurate mapping of the progressive buildup of the extensive and complex basaltic lava field, which together with monitoring of gas emissions informed the timely evacuation of local populations from affected areas. Lava flows that reached the sea constructed an extensive system of lava deltas and platforms, similar to events during earlier historical eruptions such as in 1712, 1949 and 1971. Long-term challenges in the aftermath of the eruption include protection of drainage systems from potential redistribution of tephra during high rainfall events, the use of the large surplus quantities of ash in reconstruction of buildings and in agriculture, and the crucial concerns of where and how rebuilding should and could occur in the aftermath of the eruption. Finally, there remain strong financial concerns over insurance for properties consumed or damaged by the eruption in the light of future volcanic hazards from the Cumbre Vieja volcanic ridge.Peer reviewe

El registro geológico como herramienta para la evaluación de la peligrosidad volcánica: Estudio del caso de la erupción de hace 4200 años en Cerro Blanco (Catamarca, Puna Sur)

XXI Congreso Geológico Argentino, del 14 al 18 de marzo, 2022, Puerto Madryn (Chubut)En zonas volcánicas activas, entendiendo como tales aquellas que han tenido alguna erupción durante el Holoceno (aproximadamente en los últimos 11.700 años), el registro geológico nos permite identi ficar estas erupciones y acotar una gran cantidad de parámetros eruptivos. Esta información sirve no sólo para reconstruir las erupciones pasadas, sino que permite predecir, entre otros, el tipo de magma, el estilo eruptivo o el rango de magnitud del evento. En suma, el pasado es la clave del futuro. De esta manera, el registro geológico (particularmente el holoceno) se convierte en una herramienta de gran utilidad para evaluar la peligrosidad del volcanismo activo. En este contexto, un caso de estudio excepcional es la gran erupción del Complejo Volcánico de Cerro Blanco (CVCB), en la Zona Volcánica Central de los Andes, noroeste de Argentina, datada en 4410-4150 a cal AP. Este evento eruptivo es uno de los principales que han ocurrido durante el Holoceno en el mundo (Fernández-Turiel et al. 2019, Osterrieth et al. 2019). El registro geológico investigado en las provincias de Catamarca, Tucumán y Santiago del Estero evidencia una erupción explosiva riolítica que formó depósitos piroclásticos de caída en un área de aproximadamente 500,000 km2, acumulando >100 km3 de tefra (volu- men total bruto, equivalente a unos 70 km 3 de volumen DRE). Este último valor excede el umbral inferior del Índice de Explosión Volcánica (VEI) de 7. Los depósitos de caída cineríticos cubrieron extensas áreas localizadas a más de 400 km de la fuente y los depósitos deflujos piroclásticos inundaron los valles vecinos alcanzando distancias de varias decenas de kilómetros (Báez et al. 2020, Fernández-Turiel et al. 2019). El descubrimiento de la gran erupción holocena del Complejo Volcánico de Cerro Blanco ha puesto de manifiesto que el sur de la Puna es una zona volcánica muy activa y que, como tal, la evaluación de la peligrosidad volcánica debe ser reconsiderada, de la misma manera que las medidas de mitigación de riesgos relacionadas con futuras erupciones explosivas de gran magnitud. Esta investigación fue financiada por los Proyectos ASH y QUECA (MINECO, CGL2008-00099 y CGL2011- 23307). Agradecemos el apoyo analítico del Laboratorio de Geoquímica labGEOTOP (infraestructura cofinan- ciada por ERDF-EU Ref. CSIC08-4E-001) y el Laboratorio de DRX (infraestructura cofinanciada por ERDF-EU Ref. CSIC10-4E-141) de ICTJA-CSIC, y los laboratorios de EPMA y SEM de CCiTUB. Este estudio se realizó en el marco de los Grupos Consolidados de Investigación GEOVOL (Gobierno de Canarias) y GEOPAM (Generalitat de Catalunya, 2017SGR 1494).Esta investigación fue financiada por los Proyectos ASH y QUECA (MINECO, CGL2008-00099 y CGL2011- 23307). Agradecemos el apoyo analítico del Laboratorio de Geoquímica labGEOTOP (infraestructura cofinan- ciada por ERDF-EU Ref. CSIC08-4E-001) y el Laboratorio de DRX (infraestructura cofinanciada por ERDF-EU Ref. CSIC10-4E-141) de ICTJA-CSIC, y los laboratorios de EPMA y SEM de CCiTUB. Este estudio se realizó en el marco de los Grupos Consolidados de Investigación GEOVOL (Gobierno de Canarias) y GEOPAM (Generalitat de Catalunya, 2017SGR 1494)

The 4.2 ka cal BP major eruption of Cerro Blanco, Central Andes

Fernandez–Turiel, J.L., Perez–Torrado, F.J., Rodriguez–Gonzalez, A., Saavedra, J., Carracedo, J.C., Rejas, M., Lobo, A., Osterrieth, M., Carrizo, J.I., Esteban, G., Gallardo, J., Ratto, N., 2019. The large eruption 4.2 ka cal BP in Cerro Blanco, Central Volcanic Zone, Andes: Insights to the Holocene eruptive deposits in the southern Puna and adjacent regions. Estudios Geologicos 75, e088.; EGU2020: Sharing Geoscience Online, 4-8 may 2020The major eruption of the Cerro Blanco Volcanic Complex (CBVC), in the Central Volcanic Zone of the Andes, NW Argentina, dated at 4410–4150 a cal BP, was investigated confirming that is the most important of the three major Holocene felsic eruptive events identified in the southern Puna (Fernandez-Turiel et al., 2019). Identification of pre–, syn–, and post–caldera products of CBVC allowed us to estimate the distribution of the Plinian fallout during the paroxysmal syn–caldera phase of the eruption. Results provide evidence for a major rhyolitic explosive eruption that spread volcanic deposits over an area of about 500,000 km2, accumulating >100 km3 of tephra (bulk volume). This last value exceeds the lower threshold of Volcanic Explosive Index (VEI) of 7. Ash-fall deposits mantled the region at distances >400 km from source and thick pyroclastic-flow deposits filled neighbouring valleys up to several tens of kilometres from the vent. This eruption is the largest documented during the past five millennia in the Central Volcanic Zone of the Andes, and is probably one of the largest Holocene explosive eruptions in the world. The implications of the findings of the present work reach far beyond having some chronostratigraphic markers. Further interdisciplinary research should be performed in order to draw general conclusions on these impacts in local environments and the disruptive consequences for local communities. This is invaluable not just for understanding how the system may have been affected over time, but also for evaluating volcanic hazards and risk mitigation measures related to potential future large explosive eruptions.Financial support was provided by the ASH and QUECA Projects (MINECO, CGL2008–00099 and CGL2011–23307). We acknowledge the assistance in the analytical work of labGEOTOP Geochemistry Laboratory (infrastructure co–funded by ERDF–EU Ref. CSIC08–4E–001) and DRX Laboratory (infrastructure co–funded by ERDF–EU Ref. CSIC10–4E–141) (J. Ibañez, J. Elvira and S. Alvarez) of ICTJA-CSIC, and EPMA and SEM Laboratories of CCiTUB (X. Llovet and J. Garcia Veigas). This study was carried out in the framework of the Research Consolidated Groups GEOVOL (Canary Islands Government, ULPGC) and GEOPAM (Generalitat de Catalunya, 2017 SGR 1494)

The Holocene volcanism of El Hierro, Canary Islands

EGU2020: Sharing Geoscience Online, 4-8 may 2020El Hierro is, together with La Palma, the youngest island of the Canarian Archipelago. Both islands are in the shield stage of their volcanic growth, which implies a high volcanic activity during the Holocene period. The submarine eruption occurred in October 2011 in the SSE rift of El Hierro evidenced the active volcanic character of the island. Even so, despite the numerous scientific works published following the submarine eruption (most of them centered to understand such volcanic event), there is still a lack of precise knowledge about the Holocene subaerial volcanism of this island. The LAJIAL Project focuses on solving this knowledge gap. The Holocene subaerial volcanism of El Hierro generates fields of monogenetic volcanoes linked to the three systems of rifts present on the island. Its eruptive mechanisms are typically Strombolian although there are also phreato-Strombolian events. The most recent eruptions frequently form lava on coastal platforms, which are considered after the last glacial maximum (approx. 20 ka BP). The most developed coastal platforms in El Hierro are at the ends of the rifts and in the interior of the El Golfo depression. This geomorphological criterion shows that more than thirty subaerial eruptions have taken place in El Hierro since approx. 20 ka BP. In addition, there are many apparently recent volcanic edifices far from the coast. The research of the most recent volcanism of the island, the last 11,700 years of the Holocene, covers a long enough period whereas it is close to the present day. Thus, this period is the best to model the eruptive processes that will allow us to evaluate the future scenarios of the eruptive dynamics in El Hierro. The Project LAJIAL combines methodologies of geological mapping, geomorphology, GIS, chronostratigraphy, paleomagnetism, petrology and geochemistry to solve the Holocene eruptive recurrence rate in El Hierro, and to constrain the rift model of intraplate ocean volcanic islands.Financial support was provided by the Project LAJIAL (ref. PGC2018-101027-B-I00, MCIU/AEI/FEDER, EU). This study was carried out in the framework of the Research Consolidated Groups GEOVOL (Canary Islands Government, ULPGC) and GEOPAM (Generalitat de Catalunya, 2017 SGR 1494)

La erupción submarina de La Restinga en la isla de El Hierro, Canarias: Octubre 2011-Marzo 2012

The first signs of renewed volcanic activity at El Hierro began in July 2011 with the occurrence of abundant, low-magnitude earthquakes. The increasing seismicity culminated on October 10, 2011, with the onset of a submarine eruption about 2 km offshore from La Restinga, the southernmost village on El Hierro. The analysis of seismic and deformation records prior to, and throughout, the eruption allowed the reconstruction of its main phases: 1) ascent of magma and migration of hypocentres from beneath the northern coast (El Golfo) towards the south rift zone, close to La Restinga, probably marking the hydraulic fracturing and the opening of the eruptive conduit; and 2) onset and development of a volcanic eruption indicated by sustained and prolonged harmonic tremor whose intensity varied with time. The features monitored during the eruption include location, depth and morphological evolution of the eruptive source and emission of floating volcanic bombs. These bombs initially showed white, vesiculated cores (originated by partial melting of underlying pre-volcanic sediments upon which the island of El Hierro was constructed) and black basanite rims, and later exclusively hollow basanitic lava balloons. The eruptive products have been matched with a fissural submarine eruption without ever having attained surtseyan explosiveness. The eruption has been active for about five months and ended in March 2012, thus becoming the second longest reported historical eruption in the Canary Islands after the Timanfaya eruption in Lanzarote (1730-1736). This eruption provided the first opportunity in 40 years to manage a volcanic crisis in the Canary Islands and to assess the interpretations and decisions taken, thereby gaining experience for improved management of future volcanic activity. Seismicity and deformation during the eruption were recorded and analysed by the Instituto Geográfico Nacional (IGN). Unfortunately, a lack of systematic sampling of erupted pyroclasts and lavas, as well as the sporadic monitoring of the depth and growth of the submarine vent by deployment of a research vessel, hampered a comprehensive assessment of hazards posed during volcanic activity. Thus, available scientific data and advice were not as high quality as they could have been, thereby limiting the authorities in making the proper decisions at crucial points during the crisis. The response in 2011-12 to the El Hierro eruption has demonstrated that adequate infrastructure and technical means exist in the Canary Islands for the early detection of potential eruptive hazards. However, it also has taught us that having detailed emergency management plans may be of limited value without an accompanying continuous, well-integrated scientific monitoring effort (open to national and international collaboration) during all stages of an eruption.Los primeros indicios de una posible erupción volcánica en El Hierro se percibieron a partir de julio de 2011 en forma de sismos de baja intensidad pero anormalmente numerosos. La intensificación de la sismicidad culminó con el inicio de la erupción submarina el 10 de octubre de 2011 a unos 2 km al sur de La Restinga. La sismicidad y deformación del terreno que precedieron y acompañaron a esta erupción han permitido reconstruir las principales fases de actividad volcánica: 1) generación y ascenso del magma con migración de los hipocentros sísmicos desde el norte, en el Golfo, hasta el rift sur, en La Restinga, marcando la apertura hidráulica del conducto magmático; y 2) inicio y continuidad de la erupción volcánica evidenciada por un tremor armónico continuo de intensidad variable en el tiempo. Las características observadas a lo largo de la erupción, principalmente localización, profundidad y evolución morfológica del foco emisor, así como emisión de materiales volcánicos flotantes, inicialmente con un núcleo blanco poroso (procedentes de la fusión parcial de sedimentos de la capa superior de la corteza oceánica anteriores a la construcción del edificio insular de El Hierro) envuelto por una corteza basanítica y después huecas (lava balloons), se han correspondido con una erupción submarina fisural profunda sin que nunca hayan intervenido mecanismos más explosivos tipo surtseyano. La erupción se mantuvo activa durante unos cinco meses, dándose por finalizada en marzo del 2012, convirtiéndose de este modo en la segunda erupción histórica más longeva de Canarias después de la de Timanfaya (1730-36) en Lanzarote. Esta erupción ha supuesto la primera oportunidad en 40 años de gestionar una crisis volcánica en Canarias y de analizar las observaciones e interpretaciones y las decisiones adoptadas, con objeto de mejorar la gestión de futuras crisis volcánicas. El Instituto Geográfico Nacional (IGN) se encargó de adquirir y analizar la información sísmica y de deformación durante todo el proceso. Sin embargo, no se dispuso inicialmente de un barco oceanográfico que realizara estudios sistemáticos de la profundidad y progresión de la erupción, así como de toma de muestras de los materiales emitidos (piroclastos y lavas), elementos claves para la determinación de la peligrosidad eruptiva. Estas deficiencias en el seguimiento científico del proceso eruptivo dificultaron en algunos momentos la toma de decisiones de protección civil. El análisis de la crisis ha puesto de manifiesto que, aunque se disponga de una infraestructura técnica adecuada para la detección temprana de crisis eruptivas en el archipiélago, de poco valen las medidas administrativas planificadas sin un seguimiento científico continuo e integrador del proceso eruptivo, abierto a la colaboración científica nacional e internacional.Por último, agradecemos a la ULPGC la financiación de las campañas Guayota, a Antonio González Ramos (SIANI, ULPGC) el apoyo logístico y científico durante la toma de imágenes del ROV y a la tripulación del B/O Atlantic Explorer el trato dispensado. Este trabajo forma parte del proyecto SolSubC20081000047 financiado por el Gobierno de Canarias

Bouncing Spallation Bombs During the 2021 La Palma Eruption, Canary Islands, Spain

Incandescent pyroclasts of more than 64 mm in diameter erupted from active volcanoes are known as bombs and pose a significant hazard to life and infrastructure. Volcanic ballistic projectile hazard assessment normally considers fall as the main transport process, estimating its intensity from bomb location and impact cratering. We describe ballistically ejected bombs observed during the late October 2021 episode of eruption at La Palma (Canary Islands) that additionally travelled downhill by rolling and bouncing on the steep tephra-dominated cone. These bouncing bombs travelled for distances >1 km beyond their initial impact sites, increasing total travel distance by as much as 100%. They left multiple impact craters on their travel path and frequently spalled incandescent fragments on impact with substrate, leading to significant fire hazard for partially buried trees and structures far beyond the range of ballistic transport. We term these phenomena as bouncing spallation bombs. The official exclusion zone encompassed this hazard at La Palma, but elsewhere bouncing spallation bombs ought to be accounted for in risk assessment, necessitating awareness of an increased hazard footprint on steep-sided volcanoes with ballistic activity

Mantle source characteristics and magmatic processes during the 2021 La Palma eruption

The 2021 eruption of La Palma (September 19-December 13) was the first subaerial eruption in the Canary Islands in 50 years. Approximately 0.2 km3 of lava erupted from a newly formed, broadly basaltic composite volcanic edifice on the northwestern flank of the Cumbre Vieja volcanic ridge. Comprehensive sampling of the olivine-and clinopyroxene-phyric lavas over the eruption period reveals temporal changes in mineralogy and bulk rock geochemistry from tephrite to basanite. Initial tephrite lavas have low MgO (-6 wt.%) and elevated TiO2 (-4 wt.%) and contain amphibole crystals and gabbroic micro -xenoliths. In contrast, lavas with progressively more mafic compositions erupted to approximately day 20 of the eruption and thereafter remained as basanite (-8 wt.% MgO; 3.7 wt.% TiO2) until eruption termination. Temporal changes in lava chemistry reflect initial eruption of fractionated magmas that crystallized 5-10% olivine and clinopyroxene, as well as minor spinel, sulfide, and magnetite, followed by later eruption of deeper-sourced and more primitive magma. Vanadium-in-olivine oxybarometry indicates parental magmas were oxidized (fO2 = +1.5 to +2 FMQ) with 8.2 +/- 0.8 wt.% MgO and were generated from between 2.5-3% partial melting of a mantle source potentially containing a pyroxenite component (Xpx = 0.31 +/- 0.12). Day 1-20 tephrites have more radiogenic 187Os/188Os (0.143-0.148) and lower Pd, Pt, Ir and Os contents than post day 20 basanites (187Os/188Os = 0.141-0.145). Combined with available seismic data, the lavas provide a high-resolution record of eruptive evolution. Initial fractionated tephrite magma was stored in the upper lithosphere up to four years prior to eruption, consistent with pre-cursor seismicity and the presence of partially reacted amphibole and micro-xenoliths. The later lavas of the eruption were fed by more primitive basanitic parental magmas that were likely sourced from the deeper portion of the magma storage system that is underplating the island. Precursor events to the 2021 La Palma eruption involved seismicity and magma emplacement, storage and differentiation, which was followed by mobilisation, eruption, and eventual exhaustion of stored magma and partial melts. This magmatic progression is similar to that documented from the 1949 and 1971 Cumbre Vieja eruptions. Ocean islands with limited basaltic magma supply show similarities to the magmatic evolution observed in large silicic systems, where initial magma emplacement and differentiation is followed by later magma remobilisation that induces volcanic activity

Cenozoic volcanism II: the Canary Islands

The authors thank C. Stillman, R. Tilling and A. Kerr for long hours dedicated to the careful revision of this chapter and for their very helpful comments.Book Description This book provides the first comprehensive account in English of the geology of mainland Spain and the Balearic and Canary Islands. It has been written by 159 research-active, mostly Spanish authors working together in teams from over 20 universities and other centres of research excellence. The 19 chapters begin with an overview of Spanish geology prepared by the editors, followed by a detailed examination of Iberian Precambrian and Palaeozoic rocks in Spain, Variscan magmatism and tectonics, and the Mesozoic and Cenozoic sedimentary and fossil record. Subsequent chapters deal with the Alpine orogeny in the Pyrenees, Betics and other mountain ranges of Spain and the Balearic Islands, and with Cenozoic magmatism, including the classic hot spot-related volcanism of the Canary Islands. The final chapter focuses on economic and environmental geology, emphasising metallic deposits and industrial minerals, hydrocarbon energy resources, water supply, and modern seismic hazard. Finally a bibliography of around 4000 references provide a uniquely valuable information source. Encompassing subjects as diverse as the origin of Spanish granites, the palaeogeographic and tectonometamorphic history of the Iberian plate, human evolution in the SW Mediterranean, and modern volcanism and earthquake activity, The Geology of Spain is a key reference work suitable not only for libraries across the world, but of interest to all researchers, teachers and students of SW European geology.Peer reviewe