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(searched for: doi:10.1007/s00445-015-0914-2)
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, David González-Santana, , Melchor González-Dávila, Celso A. Hernández, Carlos Sangil, José Carlos Hernández
Published: 9 March 2021
Biogeosciences, Volume 18, pp 1673-1687; https://doi.org/10.5194/bg-18-1673-2021

Abstract:
We present a new natural carbon dioxide (CO2) system located off the southern coast of the island of La Palma (Canary Islands, Spain). Like CO2 seeps, these CO2 submarine groundwater discharges (SGDs) can be used as an analogue to study the effects of ocean acidification (OA) on the marine realm. With this aim, we present the chemical characterization of the area, describing the carbon system dynamics, by measuring pH, AT and CT and calculating Ω aragonite and calcite. Our explorations of the area have found several emission points with similar chemical features. Here, the CT varies from 2120.10 to 10 784.84 µmol kg−1, AT from 2415.20 to 10 817.12 µmol kg−1, pH from 7.12 to 8.07, Ω aragonite from 0.71 to 4.15 and Ω calcite from 1.09 to 6.49 units. Also, the CO2 emission flux varies between 2.8 and 28 kg CO2 d−1, becoming a significant source of carbon. These CO2 emissions, which are of volcanic origin, acidify the brackish groundwater that is discharged to the coast and alter the local seawater chemistry. Although this kind of acidified system is not a perfect image of future oceans, this area of La Palma is an exceptional spot to perform studies aimed at understanding the effect of different levels of OA on the functioning of marine ecosystems. These studies can then be used to comprehend how life has persisted through past eras, with higher atmospheric CO2, or to predict the consequences of present fossil fuel usage on the marine ecosystem of the future oceans.
, Joaquín Escayo, Zhongbo Hu, Antonio G. Camacho, Sergey V. Samsonov, , Kristy F. Tiampo, Mimmo Palano, Jordi J. Mallorquí, Eumenio Ancochea
Published: 28 January 2021
Scientific Reports, Volume 11, pp 1-15; https://doi.org/10.1038/s41598-021-82292-3

Abstract:
La Palma island is one of the highest potential risks in the volcanic archipelago of the Canaries and therefore it is important to carry out an in-depth study to define its state of unrest. This has been accomplished through the use of satellite radar observations and an original state-of-the-art interpretation technique. Here we show the detection of the onset of volcanic unrest on La Palma island, most likely decades before a potential eruption. We study its current evolution seeing the spatial and temporal changing nature of activity at this potentially dangerous volcano at unprecedented spatial resolutions and long time scales, providing insights into the dynamic nature of the associated volcanic hazard. The geodetic techniques employed here allow tracking of the fluid migration induced by magma injection at depth and identifying the existence of dislocation sources below Cumbre Vieja volcano which could be associated with a future flank failure. Therefore they should continue being monitored using these and other techniques. The results have implications for the monitoring of steep-sided volcanoes at oceanic islands.
, Juanjo Ledo, Katarzyna Ślęzak, David Martínez Van Dorth, Iván Cabrera-Pérez, Nemesio M. Pérez
Published: 23 October 2020
Scientific Reports, Volume 10, pp 1-8; https://doi.org/10.1038/s41598-020-75001-z

Abstract:
The study of geothermal systems is nowadays a topic of great importance because of the huge amount of energy that could be converted in electricity for human consumption from such sources. Among the various geophysical methods employed to study geothermal reservoirs, the magnetotelluric (MT) method is capable to reveal the internal structures of the subsurface and interpret the geological structures from the electrical resistivity. We present the first 3D resistivity model of La Palma (Canary archipelago, Spain) obtained from a dataset of 44 broadband magnetotelluric soundings distributed around the island. Our results highlight the presence of resistivity anomalies, spatially coinciding with density anomalies present in literature. In the north of the island, a high resistivity anomaly can be interpreted as the signature of an old intrusive body beneath the Taburiente caldera. In the south, a complex resistivity structure around the Cumbre Vieja volcanic ridge could be indicative of presence of an active geothermal system. In particular, low-resistivity anomalies, located in a high-fractured zone, have values compatible with clay alteration caps (illite and illite–smectite). Such a result suggests the presence of hot rocks, or a dike system, heating fluids in the interior of Cumbre Vieja volcanic system.
Cynthia Werner, Tobias P. Fischer, Alessandro Aiuppa, Marie Edmonds, Carlo Cardellini, Simon Carn, Giovanni Chiodini, Elizabeth Cottrell, Mike Burton, Hiroshi Shinohara, et al.
Published: 31 October 2019
Sofía Viotti, Carlos Sangil, Celso Agustín Hernández,
Published: 9 September 2019
Marine Environmental Research, Volume 152; https://doi.org/10.1016/j.marenvres.2019.104789

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, , Natividad Luengo-Oroz, , Ilazkiñe Iribarren, M. José Blanco, Vicente Soler, Ana Jiménez-Abizanda,
Journal of Volcanology and Geothermal Research, Volume 381, pp 32-43; https://doi.org/10.1016/j.jvolgeores.2019.05.018

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, Nemesio M. Pérez, Raúl Alberto Mora Amador, Pedro A. Hernández, Carlos Ramírez, Hirochicka Sumino, Guillermo E. Alvarado, Mario Fernández
Published: 17 March 2019
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, Germán Padilla, José Barrancos, , Eleazar Padrón, María Asensio-Ramos, , Nemesio Pérez, Mar Alonso, David Calvo
Published: 1 April 2017
Bulletin Volcanologique, Volume 79; https://doi.org/10.1007/s00445-017-1109-9

Abstract:
We report the results of 49 soil CO2 efflux surveys by the accumulation chamber method at the North West Rift (NWR) Zone of Tenerife Island, Canary Islands. The surveys were carried out from 2000 to 2016 to evaluate the temporal and spatial variations of CO2 efflux and their relationships with the volcanic and seismic activity at Tenerife. Soil CO2 efflux values ranged from non-detectable (<0.5 g m−2 day−1) up to 141 g m−2 day−1, with the highest values measured in May 2005, whereas total CO2 emission rates ranged between 52 and 867 t day−1 (metric tons per day). Isotopic analyses of soil gas in carbon dioxide (δ13C–CO2) suggest a mixing between organic and atmospheric CO2 with a small contribution of deep-seated CO2. The main temporal variation in the total CO2 output does not seem to be driven by external factors; it shows a clear temporal correlation with the onsets of seismic activity. Subsurface magma degassing affecting the central part of the island is proposed as a cause for the observed changes in the total output of diffuse CO2 emission, as well as for the spatial distribution of soil CO2 efflux.
C.A. Hernández, C. Sangil,
Published: 1 August 2016
Marine Pollution Bulletin, Volume 109, pp 419-426; https://doi.org/10.1016/j.marpolbul.2016.05.040

Abstract:
Natural CO2 vents are considered the gold standard of ocean acidification (OA) studies. In coastal areas these rare vents have only been investigated at the Mediterranean temperate rocky reefs and at Indo-Pacific coral reefs, although there should be more at other volcanic shores around the world. Substantial scientific efforts on investigating OA effects have been mostly performed by laboratory experiments. However, there is a debate on how acute this kind of approach truly represents the responses to OA scenarios, since it generally involves short-term, rapid perturbation and single variable and species experiments. Due to these limitations, world areas with natural CO2 vents are essential to understand long-term marine ecosystem responses to rising human derived atmospheric CO2 concentrations. Here, we presented a new vent found in the subtropical North East Atlantic reefs (28°N, La Palma Island) that shows moderate CO2 emission (900 ppm), reducing pH values to an annual average of 7.86 ± 0.16.
Published: 18 February 2016
Bulletin Volcanologique, Volume 78; https://doi.org/10.1007/s00445-016-1008-5

Abstract:
We measured diffuse carbon dioxide (CO2) flux and soil temperature around the summit of Asama volcano, Japan to assess the diffuse degassing structure around the summit area. Soil CO2 flux was measured using an accumulation chamber method, and the spatial distributions of CO2 flux and soil temperature were derived from the mean of 100 sequential Gaussian simulations. Results show that soil CO2 flux was high on the eastern flank of Kamayama cone and the eastern rim of Maekake crater, the outer cone. These areas mostly correspond to high-temperature anomalies. The average emission rate of diffuse CO2 was calculated to be 12.6 t day−1 (12.2–14.6 t day−1). Such diffuse emissions account for 12 % of the total (diffuse and plume) CO2 emissions from the summit area. The diffuse CO2 anomalies probably reflect permeable zones controlled by local topography and hidden fractures bordering Maekake crater. The permeable zones are connected to the low-electrical-resistivity zone inferred to indicate both a hydrothermal fluid layer and an upper sealed layer made of clay minerals. Magmatic gas from the main conduit ascends to the volcano surface through this fluid layer and the permeable zones. These insights emphasize that the pathways and the connection between the pathways and the source of diffuse CO2 combine to create the pattern of heterogeneous diffuse CO2 emission seen at the surface. Only by using a combination of gas measurements and geophysical tools can we begin to understand the dynamics of this system as a whole.
, Nemesio M Pérez, , , , , , Jose Barrrancos, Germán D Padilla, Paulo Fernandes, et al.
Published: 10 April 2015
Earth, Planets and Space, Volume 67; https://doi.org/10.1186/s40623-015-0219-x

Abstract:
Diffuse CO2 emission surveys were carried out at São Vicente, Brava, and Fogo islands, Cape Verde, archipelago to investigate the relationship between diffuse CO2 degassing and volcanic activity. Total amounts of diffuse CO2 discharged through the surface environment of the islands of São Vicente, Brava, and Fogo were estimated in 226, 50, and 828 t d−1, respectively. The highest CO2 efflux values of the three volcanic islands systems were observed at the summit crater of Pico do Fogo (up to 15.7 kg m−2 d−1). Statistical graphical analysis of the data suggests two geochemical populations for the diffuse CO2 emission surveys. The geometric mean of the peak population, expressed as a multiple of the geometric mean of the background population, seems to be the best diffuse CO2 emission geochemical parameter to correlate with the volcanic activity (age of the volcanism) for these three island volcanic systems at Cape Verde. This observation is also supported by helium isotopic signature observed in the Cape Verde’s fluids, fumaroles, and ground waters. This study provides useful information about the relationship between diffuse CO2 degassing and volcanic activity at Cape Verde enhancing the use of diffuse CO2 emission as a good geochemical tool, for volcanic monitoring at Cape Verde as well as other similar volcanic systems.
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