scholarly journals Detection of volcanic unrest onset in La Palma, Canary Islands, evolution and implications

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
José Fernández ◽  
Joaquín Escayo ◽  
Zhongbo Hu ◽  
Antonio G. Camacho ◽  
Sergey V. Samsonov ◽  
...  
Keyword(s):  
Oceanic Islands ◽  
Volcanic Unrest ◽  
Art Interpretation ◽  
La Palma ◽  
Depth Study ◽  
Long Time ◽  
Potential Risks ◽  
Satellite Radar ◽  
Dislocation Sources ◽  
Cumbre Vieja

AbstractLa 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.

Diffuse H2 degassing studies: a useful geochemical tool for monitoring Cumbre Vieja volcano, La Palma, Canary Islands

2021 ◽  
Author(s):  
Nemesio M. Pérez ◽  
Gladys V. Melián ◽  
Pedro A. Hernández ◽  
María Asensio-Ramos ◽  
Eleazar Padrón ◽  
...  
Keyword(s):  
Canary Islands ◽  
Emission Rate ◽  
Monitoring Program ◽  
Hydrothermal Systems ◽  
Sequential Gaussian Simulation ◽  
Homogeneous Distribution ◽  
La Palma ◽  
Soil Degassing ◽  
Geothermal Activity ◽  
Cumbre Vieja

<p>Hydrogen (H<sub>2</sub>) is one of the most abundant trace species in volcano-hydrothermal systems and is a key participant in many redox reactions occurring in the hydrothermal reservoir gas. Although H<sub>2</sub> can be produced in soils by N<sub>2</sub>-fixing and fertilizing bacteria, soils are considered nowadays as sinks of molecular hydrogen (Smith-Downey et al. 2006). Because of its chemical and physical characteristics, H<sub>2</sub> generated within the crust moves rapidly and escapes to the atmosphere. These characteristics make H<sub>2</sub> one of the best geochemical indicators of magmatic and geothermal activity at depth. Cumbre Vieja volcano (La Palma, Canary Islands) is the most active basaltic volcano in the Canaries with seven historical eruptions being Teneguía eruption (1971) the most recent one. Cumbre Vieja volcano is characterized by a main north–south rift zone 20 km long, up to 1950 m in elevation and covering an area of 220 km<sup>2</sup> with vents located at the northwest and northeast. Cumbre Vieja does not show any visible degassing (fumaroles, etc.). For that reason, the geochemical volcano monitoring program at Cumbre Vieja volcano has been focused on soil degassing surveys.  Here we show the results of soil H<sub>2</sub> emission surveys that have been carried out regularly since 2001. Soil gas samples were collected in about 600 sampling sites selected to obtain a homogeneous distribution at about 40 cm depth using a metallic probe and 60 cc hypodermic syringes and stored in 10 cc glass vials. H<sub>2</sub> content was analysed later by a VARIAN CP4900 micro-GC. A simple diffusive emission mechanism was applied to compute the emission rate of H<sub>2</sub> at each survey. Diffuse H<sub>2</sub> emission values were used to construct spatial distribution maps by using sequential Gaussian simulation (sGs) algorithm, allowing the estimation of the emission rate from the volcano. Between 2001-2003, the average diffuse H<sub>2</sub> emission rate was ∼2.5 kg·d<sup>−1</sup> and an increase of this value was observed between 2013-2017 (∼16.6 kg·d<sup>−1</sup>), reaching a value of 36 kg·d<sup>−1</sup> on June 2017, 4 month before the first recent seismic swarm in October, 2017 at Cumbre Vieja volcano. Six additional seismic swarms had occurred at Cumbre Vieja volcano (February 2018, July-August 2020; October 8-10, 2020; October 17-19, 2020, November 21, 2020 and December 23-26, 2020) and changes of diffuse H<sub>2</sub> emission related to this unrest had been observed reaching values up to ∼70 kg·d<sup>−1</sup>. Diffuse H<sub>2</sub> emission surveys have demonstrated to be sensitive and excellent precursors of magmatic processes occurring at depth in Cumbre Vieja. Periodic diffuse H<sub>2</sub> emission surveys provide valuable information to improve and optimize the detection of early warning signals of volcanic unrest at Cumbre Vieja volcano.</p>

scholarly journals Persistent Scatterer Interferometry of Sentinel-1 time series to detect ground subsidence in the city of Recife, Brazil

2020 ◽  
Vol 10 (1) ◽  
pp. 1
Author(s):  
Enton Bedini
Keyword(s):  
Time Series ◽  
Ground Subsidence ◽  
Persistent Scatterer Interferometry ◽  
Persistent Scatterer ◽  
Radar Imagery ◽  
Long Time ◽  
Satellite Radar ◽  
Surrounding Areas ◽  
Satellite Radar Imagery ◽  
The City

Persistent Scatterer Interferometry (PSI) analysis of Sentinel-1 time series was carried out to detect ground subsidence in the city of Recife, Brazil. The dataset consisted of sixty-eight Sentinel-1A Interferometric Wide (IW) Single Look Complex (SLC) images of the time period April 2017 – September 2019. The images were acquired in descending orbit in VV (vertical transmitting, vertical receiving) polarization. The results of the PSI analysis show that in the city of Recife occur several ground subsidence areas. The largest ground subsidence area occurs between the neighborhoods of Afogados, Torrŏes and Cordeiro. The subsidence rates in this area range from few mm/year up to -15 mm/year. This ground subsidence could be a result of groundwater extraction or of subsidence processes in urbanized reclaimed lands. Similar but smaller ground subsidence areas occur in several localities in Recife. In some cases, subsidence with rates of up to -25 mm/year is noted in small zones where new buildings have been constructed in the last decade. This should be due to ground settlement processes, taking a long time due to the particular soils and geology of the locality. This study can serve as a first contribution for further research on the ground subsidence hazard in the city of Recife and the surrounding areas by means of satellite radar imagery.

scholarly journals Assessing the Potential Replacement of Laurel Forest by a Novel Ecosystem in the Steep Terrain of an Oceanic Island

2020 ◽  
Vol 12 (24) ◽  
pp. 4013
Author(s):  
Ram Sharan Devkota ◽  
Richard Field ◽  
Samuel Hoffmann ◽  
Anna Walentowitz ◽  
Félix Manuel Medina ◽  
...  
Keyword(s):  
Castanea Sativa ◽  
Oceanic Islands ◽  
Control Measures ◽  
Trade Wind ◽  
Suitable Habitat ◽  
Landsat 8 ◽  
Landsat Images ◽  
Laurel Forest ◽  
La Palma ◽  
Steep Terrain

Biological invasions are a major global threat to biodiversity and often affect ecosystem services negatively. They are particularly problematic on oceanic islands where there are many narrow-ranged endemic species, and the biota may be very susceptible to invasion. Quantifying and mapping invasion processes are important steps for management and control but are challenging with the limited resources typically available and particularly difficult to implement on oceanic islands with very steep terrain. Remote sensing may provide an excellent solution in circumstances where the invading species can be reliably detected from imagery. We here develop a method to map the distribution of the alien chestnut (Castanea sativa Mill.) on the island of La Palma (Canary Islands, Spain), using freely available satellite images. On La Palma, the chestnut invasion threatens the iconic laurel forest, which has survived since the Tertiary period in the favourable climatic conditions of mountainous islands in the trade wind zone. We detect chestnut presence by taking advantage of the distinctive phenology of this alien tree, which retains its deciduousness while the native vegetation is evergreen. Using both Landsat 8 and Sentinel-2 (parallel analyses), we obtained images in two seasons (chestnuts leafless and in-leaf, respectively) and performed image regression to detect pixels changing from leafless to in-leaf chestnuts. We then applied supervised classification using Random Forest to map the present-day occurrence of the chestnut. Finally, we performed species distribution modelling to map the habitat suitability for chestnut on La Palma, to estimate which areas are prone to further invasion. Our results indicate that chestnuts occupy 1.2% of the total area of natural ecosystems on La Palma, with a further 12–17% representing suitable habitat that is not yet occupied. This enables targeted control measures with potential to successfully manage the invasion, given the relatively long generation time of the chestnut. Our method also enables research on the spread of the species since the earliest Landsat images.

The importance of slope correction for studying Greenland ice change using radar altimetry (CryoSat-2)

2020 ◽  
Author(s):  
Katarzyna Sejan ◽  
Bert Wouters ◽  
Michiel van den Broeke
Keyword(s):  
Slope Angle ◽  
Greenland Ice Sheet ◽  
Correction Method ◽  
Surface Elevation ◽  
Laser Altimetry ◽  
Radar Altimetry ◽  
Slope Correction ◽  
Long Time ◽  
Elevation Changes ◽  
Satellite Radar

<p>Satellite radar altimetry is one of the most important tools for monitoring changes in the mass balance of the world's ice sheets. Acquiring long time series of elevation changes is crucial, and the long lifetime of the CryoSat-2 mission has contributed wonderfully to this effort. However, once the CryoSat-2 mission ends, it will be important to bridge the gap between CryoSat-2 and future radar altimetry missions. IceSat2 data can help aid this effort, assuming that the appropriate processing techniques are used to allow the comparison of radar and laser altimetry. Furthermore, different altimetry techniques come with their own pitfalls, in radar altimetry signal penetration into the snowpack introduces ambiguity in the origin of reflected echo, a major issue not present in laser altimetry. It is therefore important to minimize this ambiguity by developing processing algorithms for the radar altimetry form CryoSat-2 mission, with a special attention on relating it to the IceSat2 mission.  </p><p>Focusing on Greenland Ice Sheet (GIS), we have developed a processing chain for the estimation of surface elevations and elevation changes from the ESA level-1 product (L1b) Baseline D. As a first step, we investigated the importance of Digital Elevation Model (DEM) in the slope correction algorithm and how it affects the estimated surface elevation.</p><p> </p><p>The waveform retracker algorithm was developed following the method by Nilsson (2015) with a range of thresholds in the threshold retracker applied to the waveform. Knowing the estimated range and the altitude of the satellite at the time of the measurement, we calculated the corresponding surface elevation at the point of the wavelet reflection.</p><p>We apply a slope correction method by Hurkmans (2012), where displacement from the nadir location in x- and y- directions is calculated using the slope angle and aspect retrieved from a DEM, giving a new set of coordinates that represents the location of the estimated elevation. We use two sets of slope angle and aspect calculated from two DEMs, ArcticDEM Release 7 (Porter et al., 2018) and Greenland Ice Mapping Project (GIMP) DEM (Howat et al., 2017). Both DEMs are similar in terms of optical imagery data source, processing and resolution, however, they have been referenced to different laser altimetry data. We investigate this effect in the slope correction of radar altimetry from CryoSat2 mission.</p><p>We checked the two sets of slope correction data using IceSat-2 data (Smith et al., 2019) corresponding to the same time period, and selected by nearest point calculation. We analyze and discuss the differences between IceSat-2 data and CryoSat-2 data with slope correction using GIMP DEM or ArcticDEM.</p>

scholarly journals Far-Field Tsunami Impact in the North Atlantic Basin from Large Scale Flank Collapses of the Cumbre Vieja Volcano, La Palma

2015 ◽  
Vol 172 (12) ◽  
pp. 3589-3616 ◽  
Author(s):  
Babak Tehranirad ◽  
Jeffrey C. Harris ◽  
Annette R. Grilli ◽  
Stephan T. Grilli ◽  
Stéphane Abadie ◽  
...  
Keyword(s):  
North Atlantic ◽  
Large Scale ◽  
Far Field ◽  
Atlantic Basin ◽  
North Atlantic Basin ◽  
The North ◽  
La Palma ◽  
The North Atlantic ◽  
Cumbre Vieja

scholarly journals DETECCIÓN DEL INICIO DE REACTIVACIÓN VOLCÁNICA EN LA ISLA DE LA PALMA, ISLAS CANARIAS, Y ESTUDIO DE SU EVOLUCIÓN TEMPORAL

2021 ◽  
Author(s):  
José Fernández ◽  
Joaquín Escayo ◽  
Zhongbo Hu ◽  
Antonio G. Camacho ◽  
Sergey V. Samsonov ◽  
...  
Keyword(s):  
La Palma ◽  
Cumbre Vieja

La isla de La Palma es de las de mayor riesgo potencial del archipiélago canario, siendo por tanto importante realizar unestudio en profundidad que permita definir su estado de actividad volcánica. Esto se ha realizado usando observacionesde radar de satélite y una técnica de interpretación original de última generación. Ambas cosas han permitido detectar elinicio de la reactivación volcánica en la isla de La Palma, probablemente décadas antes de una posible erupción. Suevolución temporal muestra una naturaleza cambiante de la deformación volcánica, tanto espacial como temporalmente.El uso de imágenes radar permite obtener resultados con una gran resolución espacial y en un periodo de tiempoprolongado (2009-2020), obteniendo información sobre la naturaleza dinámica de los procesos asociados. Las técnicasgeodésicas empleadas permiten detectar la migración de fluidos inducida por la inyección de magma en profundidad eidentificar la existencia de fuentes de dislocación bajo el volcán Cumbre Vieja que podrían estar asociadas con futurosdeslizamientos, siendo por tanto necesario continuar con la monitorización de este proceso de reactivación utilizandoestas y otras técnicas.

scholarly journals Levels And Risks of Antineoplastic Drugs In Households of Oncology Patients, Hospices And Retirement Homes

2021 ◽  
Author(s):  
Lucie Bláhová ◽  
Jan Kuta ◽  
Lenka Doležalová ◽  
Šárka Kozáková ◽  
Tereza Hojdarová ◽  
...  
Keyword(s):  
Family Members ◽  
Antineoplastic Drugs ◽  
Indoor Environments ◽  
Oncology Patients ◽  
Pilot Studies ◽  
Icp Ms ◽  
Long Time ◽  
Potential Risks ◽  
Exposure Risks ◽  
High Concentrations

Abstract BackgroundContamination of the indoor environment by the antineoplastic drugs (ADs) is known to pose health risks to the exposed staff in hospitals or pharmacies. ADs may also contaminate households of the patients receiving chemotherapy but the exposure levels and potential risks to family members have not been studied. The objective was to provide an in-depth research of surface contamination by ADs inside homes focusing on the households of oncology patients, hospices and retirement houses. ResultsThe main study included repeated samplings of surfaces (floors, desktops) in households of 17 ambulant oncology patients receiving different chemotherapies with cyclophosphamide (CP), platinum-based drugs (Pt), doxorubicin (DOX), 5-fluorouracil (FU) and others. Screening of AD contamination was further performed in 2 hospices and 2 retirement homes. The wipe samples were analyzed by HPLC-MS/MS and ICP-MS/MS for 11 organic ADs and total Pt as a marker of Pt-based ADs. Patients treated with chemotherapy were found to serve as a source of contamination for their households, representing thus a risk to sensitive family members such as children or elderly people. Carcinogenic CP was commonly found at relatively high concentrations, especially during the first 6 days after the chemotherapy (maximum 511 pg/cm2). Sweat seems to be a major medium for the spread of the contamination, and high and long-time persisting CP levels (traces still found after 6 months post-chemotherapy) were found on various desktops including kitchen dining tables. The pilot studies in hospices and retirement homes indicated rather lower exposure risks of the personnel but pointed to potential long-lasting contamination by Pt or some other persistent ADs such as ifosfamide, IF.ConclusionsThis is one of the first studies investigating the contamination by ADs in indoor environments outside of hospitals or pharmacies. Peak concentrations of the carcinogenic CP in households were comparable to those observed in hospitals. The information guidance flier with practical recommendations was prepared improving thus information as well as prevention of eventual risks for family members.

Dynamics of diffuse carbon dioxide emissions from Cumbre Vieja volcano, La Palma, Canary Islands

2015 ◽  
Vol 77 (4) ◽  
Author(s):  
Eleazar Padrón ◽  
Nemesio M. Pérez ◽  
Fátima Rodríguez ◽  
Gladys Melián ◽  
Pedro A. Hernández ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Canary Islands ◽  
Carbon Dioxide Emissions ◽  
La Palma ◽  
Cumbre Vieja

Diffuse H2 and He degassing survey to study of hidden potential geothermal systems in La Palma, Canary Islands

2020 ◽  
Author(s):  
Fátima Rodríguez ◽  
Antonio Polo Sánchez ◽  
Katherine Dale ◽  
Chloe Codner ◽  
Alba Martín ◽  
...  
Keyword(s):  
Rift Zone ◽  
Average Distance ◽  
Hydrothermal Systems ◽  
Soil Gas ◽  
Geothermal Systems ◽  
Soil Matrix ◽  
North West ◽  
The North ◽  
La Palma ◽  
Cumbre Vieja

<p>La Palma is one of the eastern islands of the Canary Archipelago located off the West African continental margin. Volcanic activity in the last 123 ka has taken place exclusively at the southern part of the island, where Cumbre Vieja volcano has been formed. Cumbre Vieja, one of the most active basaltic volcano in the Canaries, host seven historical eruptions being Teneguía eruption (1971) the most recent one. Cumbre Vieja volcano, characterized by a main north–south rift zone 20 km long and covering an area of 220 km<sup>2</sup>, does not show any visible degassing that show the existence of active geothermal systems. For that reason, geochemical prospecting of soil gases and volatiles in the soil matrix itself of Cumbre Vieja can provide useful information to investigate the presence of permeable areas and potential upflow areas for the degassing of geothermal systems at depth.</p><p>We report herein the results of an intensive soil gas study, focused on non-reactive and/or highly mobile gases such as helium (He) and hydrogen (H<sub>2</sub>), in Cumbre Vieja, with geothermal exploration purposes. He has unique characteristics as a geochemical tracer: it is chemically inert and radioactively stable, non-biogenic, highly mobile and relatively insoluble in water. H<sub>2</sub> is one of the most abundant trace species in volcano-hydrothermal systems and is a key participant in many redox reactions occurring in the hydrothermal reservoir gas.</p><p>Soil gas samples were collected at 1,201 sites selected from June 2019 to September 2019, with an average distance between sites of ≈ 250 m, at ≈ 40 cm depth using a metallic probe. He content was analyzed by means of a quadrupole mass spectrometer (QMS; Pfeiffer Omnistar 422) and hydrogen concentrations by a micro-gas chromatograph (microGC; VARIAN CP490). Soil He concentration showed values up to 23.9 ppm with an average of 5.73 ppm. Soil H<sub>2</sub> concentrations measured ranged from typical atmospheric values (≈ 0.5 ppm) up to 19.8 ppm. The mean value measured for H<sub>2</sub> was 0.78 ppm. Although He concentration values showed high spatial variability, the highest values can be observed in the north–south rift zone of Cumbre Vieja and around the surface contact with Cumbre Nueva ridge. Spatial distribution of H<sub>2</sub> concentration showed the highest values in the north-west area of Cumbre Vieja volcano. The results showed here are useful to identify the possible existence of permeable portions of deep-seated actively degassing geothermal reservoirs. However, a multidisciplinary approach is essential to obtain additional information about possible geothermal systems underlying at Palma island with the last goal of the selection of appropriate locations for future exploratory wells.</p>

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