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    Publication Date: 2021-06-15
    Description: Villarrica volcano (Chile) is one of the most active volcanoes in South America. Its activity is currently characterized by continuous degassing from a summit lava lake/vent punctuated by explosive events. During November 2004 a multidisciplinary experiment was deployed for a 10-d period to define the style of emission and infer shallow conduit dynamics at this basaltic center. This involved collection of thermal, seismic and infrasonic data to describe the background activity confined inside the crater, and use of samples to texturally and chemically characterize the ejecta from more energetic explosions able to attain the crater rim. The background activity was characterized by gas bursting with a frequency of 9 events per minute. This involved emission of gas puffs fed by bubble bursting, with larger bursts emplacing sheets of magma onto the lower crater walls. The ejecta population from the more energetic events was characterized by the coexistence of both scoriae and golden pumice. These two types of clasts have different textures but identical glass compositions, suggesting that they underwent different conduit histories. The golden pumice is interpreted as the expanding inner part of a short-lived jet fed by a rapidly ascending, magma batch. The scoria forms the outer portion of the jet and comprises degassed material entrained during passage of the fresh batch through material residing in the upper-most portion of the conduit. We thus have a largely degassed upper column that feeds persistent bubble bursting, through which fresh batches occasionally rise to feed events of relatively higher energy.
    Description: Published
    Description: B08206
    Description: 2.3. TTC - Laboratori di chimica e fisica delle rocce
    Description: JCR Journal
    Description: reserved
    Keywords: basaltic activity ; remote sensing ; 05. General::05.02. Data dissemination::05.02.03. Volcanic eruptions
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 3
    Publication Date: 2020-05-29
    Description: The Campi Flegrei (CF) caldera is one of the most dangerous quiescent volcanic systems in the world. Its activity mostly resulted in low magnitude explosive eruptions, such as that of the Monte Nuovo tuff cone that represents the last eruptive event within the caldera (AD 1538). However, there have been more energetic Plinian events, i.e., the Agnano Monte Spina eruption (4.1 ky), and very highly-explosive, caldera-forming eruptions, i.e., the Campanian Ignimbrite eruption (39 ky). Here, we integrate new and literature data on the groundmass texture and composition of pyroclastic products from the three above eruptions with the aim of unraveling how volatiles content, degassing mechanisms and crystallization processes influence magma explosivity and eruption dynamics at CF. Previous studies indicate that the investigated rocks share similar major element bulk and phenocryst chemistry; also similar is the water content of their trapped melt inclusions. These observations suggest that the magmas feeding these eruptions had comparable physico-chemical properties during storage in the shallow crust. However, our investigations indicate that the studied rocks differ in texture and composition of the groundmass and viscosity of the related magmas. We ascribe such differences to the variable style of volatile exsolution and outgassing from the melt, primarily in response to changes of the rate of magma ascent to the surface. We conclude that the magma ascent rate was the key-parameter in driving explosive eruptions at CF and we suggest that this parameter may be influenced by magma/water interaction and/or magma chamber geometry and replenishment.
    Description: Published
    Description: Q03013
    Description: 1.5. TTC - Sorveglianza dell'attività eruttiva dei vulcani
    Description: JCR Journal
    Description: reserved
    Keywords: Campi Flegrei ; products ; 04. Solid Earth::04.08. Volcanology::04.08.05. Volcanic rocks
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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