Chapter 14 Mapping of soil CO
            <sub>2</sub>
            diffuse degassing at São Miguel Island and its public health implications

Viveiros, Fátima; Gaspar, J. L.; Ferreira, Teresa; Silva, Catarina; Marcos, Márcio; Hipólito, Ana

doi:10.1144/m44.14

Cited by 15 publications

(18 citation statements)

References 33 publications

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“…In the first phase it is assumed that this volcano may have been an individual island and its joining to the central volcanoes to the east occurred through the development of the basaltic fissure volcanism associated with the PFVS. Current volcano-related phenomena are restricted to CO 2 soil diffuse degassing in some areas of the caldera floor and at Mosteiros Village, together with thermal springs offshore of Mosteiros and Ponta da Ferraria (Viveiros et al 2015).…”

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Chapter 7 Eruptive history and evolution of Sete Cidades Volcano, São Miguel Island, Azores

Queiroz

Gaspar

Guest

et al. 2015

Memoirs

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Sete Cidades is an active central volcano on the western part of São Miguel. The geological record reveals that subaerial activity started more than 250 ka ago. Stratigraphic units defined for Sete Cidades deposits reflect major events in the history of the volcano and are organized into two main groups: the Inferior Group and the Superior Group. Caldera formation resulted from three major paroxysmal events that occurred at about 36, 29 and 16 ka ago. Analysis of the eruptive history of Sete Cidades shows that effusive or moderately explosive eruptions, of Hawaiian and/or Strombolian styles, were located on the slopes of the central volcano. Conversely, trachytic explosive activity is mostly centred inside the caldera involving, in a first stage, predominantly Plinian and sub-Plinian phenomena, changing about 5 ka ago to a dominant hydromagmatic style. Trachytic effusive eruptions are represented by domes and associated lava flows that crop out in the inner caldera walls and on the western slopes of the volcano. Offshore submarine activity is represented by the historic Surtseyan eruptions of 1638 and 1811. In the last 5 ka Sete Cidades was the most active central volcano in the Azores with 17 explosive eruptions predominantly with hydromagmatic character. Scoria conesThese are the most common volcanic edifices on Sete Cidades massif and were formed as a result of the accumulation of basaltic † Deceased 19 May 2012.

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Chapter 7 Eruptive history and evolution of Sete Cidades Volcano, São Miguel Island, Azores

Queiroz

Gaspar

Guest

et al. 2015

Memoirs

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“…Nowadays the volcanic activity in the area is characterized not only by seismic swarms (Silva et al, 2012), but also by episodes of ground deformation (Okada et al, 2015) and the presence of secondary manifestations of volcanism, such as three main hydrothermal fumarolic fields (Caldeira Velha, Caldeiras da Ribeira Grande and Pico Vermelho), thermal and cold CO 2 -rich springs, as well as, several diffuse degassing areas (Ferreira et al, 2005;Caliro et al, 2015;Viveiros et al, 2015b). These manifestations are essentially found out in the north flank of the volcano, and seem to be tectonically controlled by the graben faults.…”

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confidence: 99%

“…The permanent soil CO 2 flux networks that have been set up in various volcanic areas of the world since then (Mori et al, 2002;Salazar et al, 2002;Granieri et al, 2003Granieri et al, , 2010Gurrieri et al, 2008;Padrón et al, 2008;Viveiros et al, 2008Viveiros et al, , 2015aHernández et al, 2012;Liuzzo et al, 2013;Laiolo et al, 2016) already contributed to identify geochemical signs that represent changes on the volcanic activity, namely by recognizing volcanic unrest episodes (Granieri et al, 2003(Granieri et al, , 2010Salazar et al, 2004;Pérez et al, 2006) or as precursors of eruptive periods (Brusca et al, 2004;Carapezza et al, 2004;Aiuppa et al, 2010;Pérez et al, 2012;Liuzzo et al, 2013;Inguaggiato et al, 2017). Some gas flux anomalies were also associated with seismic activity (Salazar et al, 2002) and the stations installed have also been used as proxy for indoor environments and showed to be useful for risk assessment in diffuse degassing areas (Viveiros et al, 2009(Viveiros et al, , 2015b.…”

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Automatic Filtering of Soil CO2 Flux Data; Different Statistical Approaches Applied to Long Time Series

et al. 2018

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Monitoring soil CO 2 diffuse degassing areas has become more relevant in the last decades to understand seismic and/or volcanic activity. These studies are specially valuable for volcanic areas without visible manifestations of volcanism, such as fumaroles or thermal springs. The development and installation of permanent soil CO 2 flux instruments has allowed to acquire long time series in different volcanic environments, and the results obtained highlight the influence of environmental variables on the gas flux variations. Filtering the influence of these external variables on the gas flux is crucial to understand deep processes on the volcanic system. This study focuses on the discussion of different statistical approaches applied to the long time series recorded in a diffuse degassing area of the Azores archipelago, mainly on the application of stepwise multivariate regression analysis, wavelets and Fast Fourier transforms to understand the CO 2 flux variations and to detect eventual anomalous periods that can represent deep changes in the volcano feeding reservoirs. A permanent soil CO 2 flux station is installed at Caldeiras da Ribeira Grande area since June 2010. This degassing site is located at Fogo Volcano, a polygenetic volcano at S. Miguel Island. The station performs measurements based on the accumulation chamber method and has coupled several environmental sensors. Average soil CO 2 flux and soil temperature values around 1,165 gm −2 d −1 and 33 • C, respectively, were measured in this site between June 2010 and June 2017. Multivariate regression analysis shows that about 47% of the soil CO 2 flux variations are explained by the effect of the soil and air temperature, wind speed, and soil water content. Spectral analysis highlights the existence of 24 h cycles in the soil CO 2 flux time series, mainly during the summer period. The filtered time series showed some anomalous periods and a correlation with the geophysical data recorded on the area was carried out. The models proposed have been applied on a near real-time automatic monitoring system and implementation of these approaches will be profitable in any volcano observatory of the world since it allows a fast understanding of the degassing processes and contribute to recognize unrest periods.

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“…Several hundreds of deaths have been reported in volcanic and non-volcanic environments due to deep-derived CO 2 emissions (Hansell and Oppenheimer, 2004) and high CO 2 concentrations have been reported in buildings located on CO 2 anomalous zones (Baxter et al, 1999;Viveiros et al, 2009Viveiros et al, , 2016a. This fact highlights the importance of identifying CO 2 anomalous areas by producing degassing maps, which should constitute valuable tools for land-use planners (Beaubien et al, 2003;Viveiros et al, 2009Viveiros et al, , 2010Viveiros et al, , 2015Viveiros et al, , 2016a. Building in high CO 2 degassing areas should be avoided, or, depending on the soil gas concentrations measured, buildings should follow few "gasresistant" construction rules as the ones defined by Viveiros et al (2016a).…”

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Soil CO2 Degassing Path along Volcano-Tectonic Structures in the Pico-Faial-São Jorge Islands (Azores Archipelago, Portugal)

Viveiros

Marcos²,

Faria

et al. 2017

Front. Earth Sci.

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The Azores archipelago is composed of nine volcanic islands located at the triple junction between the North American, Eurasian, and Nubian plates. Nowadays the volcanic activity in the archipelago is characterized by the presence of secondary manifestations of volcanism, such as hydrothermal fumaroles, thermal and cold CO 2 -rich springs as well as soil diffuse degassing areas, and low magnitude seismicity. Soil CO 2 degassing (concentration and flux) surveys have been performed at Pico, Faial, and São Jorge islands to identify possible diffuse degassing structures. Since the settlement of the Azores in the fifteenth Century these three islands were affected by seven onshore volcanic eruptions and at least six destructive earthquakes. These islands are crossed by numerous active tectonic structures with dominant WNW-ESE direction, and less abundant conjugate NNW-SSE trending faults. A total of 2,855 soil CO 2 concentration measurements have been carried out with values varying from 0 to 20.7 vol.%. Soil CO 2 flux measurements, using the accumulation chamber method, have also been performed at Pico and Faial islands in the summer of 2011 and values varied from absence of CO 2 to 339 g m −2 d −1 . The highest CO 2 emissions were recorded at Faial Island and were associated with the Pedro Miguel graben faults, which seem to control the CO 2 diffuse degassing and were interpreted as the pathways for the CO 2 ascending from deep reservoirs to the surface. At São Jorge Island, four main degassing zones have been identified at the intersection of faults or associated to WNW-ESE tectonic structures. Four diffuse degassing structures were identified at Pico Island essentially where different faults intersect. Pico geomorphology is dominated by a 2,351 m high central volcano that presents several steam emissions at its summit. These emissions are located along a NW-SE fault and the highest measured soil CO 2 concentration reached 7.6 vol.% with a maximum temperature of 77 • C. The diffuse degassing maps show that anomalous CO 2 degassing areas are controlled essentially by the tectonic structures and the lithology of the sites since the youngest volcanic systems are characterized by very low CO 2 emissions.

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Chapter 14 Mapping of soil CO ₂ diffuse degassing at São Miguel Island and its public health implications

Cited by 15 publications

References 33 publications

Chapter 7 Eruptive history and evolution of Sete Cidades Volcano, São Miguel Island, Azores

Chapter 7 Eruptive history and evolution of Sete Cidades Volcano, São Miguel Island, Azores

Automatic Filtering of Soil CO2 Flux Data; Different Statistical Approaches Applied to Long Time Series

Soil CO2 Degassing Path along Volcano-Tectonic Structures in the Pico-Faial-São Jorge Islands (Azores Archipelago, Portugal)

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Chapter 14 Mapping of soil CO 2 diffuse degassing at São Miguel Island and its public health implications

Cited by 15 publications

References 33 publications

Chapter 7 Eruptive history and evolution of Sete Cidades Volcano, São Miguel Island, Azores

Chapter 7 Eruptive history and evolution of Sete Cidades Volcano, São Miguel Island, Azores

Automatic Filtering of Soil CO2 Flux Data; Different Statistical Approaches Applied to Long Time Series

Soil CO2 Degassing Path along Volcano-Tectonic Structures in the Pico-Faial-São Jorge Islands (Azores Archipelago, Portugal)

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Chapter 14 Mapping of soil CO ₂ diffuse degassing at São Miguel Island and its public health implications