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  • 04. Solid Earth::04.08. Volcanology::04.08.05. Volcanic rocks  (13)
  • Geological Society of America  (7)
  • Elsevier Scientific Publishers  (2)
  • Nature Publishing Group  (2)
  • elsevier  (2)
  • La Habana
  • Santiago de Chile: Universidad de Chile, Departamento de Economía
  • Washington, DC: Inter-American Development Bank (IDB)
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Keywords
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  • 1
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    Dynamic feeder dyke systems in basaltic volcanoes: the exceptional example o fthe 1809 Etna eruption (Italy) (2015)
    Nature Publishing Group
    Details
    Publication Date: 2017-04-04
    Description: In this paper, we describe the 1809 eruption of Mt. Etna, Italy, which represents one historical rare case in which it is possible to observe details of the internal structure of the feeder system. This is possible thanks to the presence of two large pit craters located in the middle of the eruptive fracture field that allow studying a section of the shallow feeder system. Along the walls of one of these craters, we analysed well-exposed cross sections of the uppermost 15–20 m of the feeder system and related volcanic products. Here, we describe the structure, morphology and lithology of this portion of the 1809 feeder system, including the host rock which conditioned the propagation of the dyke, and compare the results with other recent eruptions. Finally, we propose the dynamic model of the magma behaviour inside a laterally-propagating feeder dyke, demonstrating how this dynamic triggered important changes in the eruptive style (from effusive/Strombolian to phreatomagmatic) during the same eruption. Our results are also useful for hazard assessment related to the development of flank eruptions, potentially the most hazardous type of eruption from basaltic volcanoes in densely urbanized areas, such as Mt. Etna.
    Description: Published
    Description: 1-11
    Description: 2T. Tettonica attiva
    Description: 2V. Dinamiche di unrest e scenari pre-eruttivi
    Description: 3V. Dinamiche e scenari eruttivi
    Description: 4V. Vulcani e ambiente
    Description: 6A. Monitoraggio ambientale, sicurezza e territorio
    Description: N/A or not JCR
    Description: open
    Keywords: feeder dyke ; basaltic volcanoes ; flank eruptions ; Etna ; volcanic hazards ; sill ; volcanic rift ; 04. Solid Earth::04.04. Geology::04.04.09. Structural geology ; 04. Solid Earth::04.07. Tectonophysics::04.07.07. Tectonics ; 04. Solid Earth::04.08. Volcanology::04.08.99. General or miscellaneous ; 04. Solid Earth::04.08. Volcanology::04.08.03. Magmas ; 04. Solid Earth::04.08. Volcanology::04.08.04. Thermodynamics ; 04. Solid Earth::04.08. Volcanology::04.08.05. Volcanic rocks ; 04. Solid Earth::04.08. Volcanology::04.08.08. Volcanic risk ; 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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  • 2
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    Hyaloclastite fragmentation below the glass transition: An example from El Barronal submarine volcanic complex (Spain) (2014)
    Geological Society of America
    Details
    Publication Date: 2020-12-14
    Description: Submarine felsic volcanoes are dominated by hyaloclastic piles hundreds of meters thick, the origin of which, in terms of how and when they form, is far from being completely understood. Here we present a study of the thermal remanent magnetization of the Miocene high-K dacitic El Barronal hyaloclastites (Cabo de Gata, Spain), showing that their formation is dominated by in situ fragmentation with small or negligible transportation and/or rotation of different clasts after their formation. Data indicate that fragmentation progressed down to 210–390 °C, well below the glass-transition temperature estimated at 560–750 ºC depending on the water content of the high-K dacite. Hence, hyaloclastite fragmentation in thick lavas may occur over most of the cooling history, as a result of the progressive access of sea water toward the lava interior by development of a complex network of contraction fractures.
    Description: Published
    Description: 87-90
    Description: 1V. Storia e struttura dei sistemi vulcanici
    Description: JCR Journal
    Description: restricted
    Keywords: hyaloclastite ; volcanic fragmentation ; thermal magnetization ; Cabo de Gata ; 04. Solid Earth::04.08. Volcanology::04.08.05. Volcanic rocks
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 3
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    A study on the reproducibility of counting vesicles in volcanic rocks (2012)
    Geological Society of America
    Details
    Publication Date: 2017-04-04
    Description: Vesicle size distributions in two and three dimensions of two samples were independently measured by three different researchers to investigate whether or not such measurements are reproducible. Additionally, two different software programs were used to measure the three-dimensional vesicle size distributions: the 3D Object Counter plugin for ImageJ and Blob3D. Manual thresholding by each of the authors produced similar results for both samples using both programs; however, use of the automatic, maximum entropy technique for thresholding produced measurably different results because it did not discriminate between vesicles and plagioclase crystals in one case and between vesicles and some cracks in another. Use of asymmetric erosion and dilation processes on the images is shown to affect the vesicle size distribution, but it does not have a significant effect on the power-law exponent that describes intermediate-sized vesicles or on the vesicle number density in these samples. However, such a technique is not recommended.
    Description: Published
    Description: 70-78
    Description: 2.3. TTC - Laboratori di chimica e fisica delle rocce
    Description: JCR Journal
    Description: reserved
    Keywords: Volcanic rocks ; vesicle counting ; reproducibility ; 04. Solid Earth::04.08. Volcanology::04.08.05. Volcanic rocks ; 04. Solid Earth::04.08. Volcanology::04.08.07. Instruments and techniques
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 4
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    Early Miocene volcanic activity and paleoenvironment conditions recorded in tephra layers of the AND-2A core (southern McMurdo Sound, Antarctica) (2012)
    Geological Society of America
    Details
    Publication Date: 2017-04-04
    Description: The ANtarctic geological DRILLing program (ANDRILL) successfully recovered 1138.54 m of core from drillhole, AND-2A, in the Ross Sea sediments (Antarctica). The core is composed of terrigenous claystones, siltstones, sandstones, conglomerates, breccias, and diamictites with abundant volcanic material. In this work we present sedimentological, morphoscopic, petrographic, and geochemical data on pyroclasts recovered from core AND-2A, which provide insights on eruption styles, volcanic sources, and environments of deposition. One pyroclastic fall deposit, 12 resedimented volcaniclastic deposits and 14 volcanogenic sedimentary deposits record a history of intense explosive volcanic activity in southern Victoria Land during the Early Miocene. Tephra were ejected during Subplinian and Plinian eruptions fed by trachytic to rhyolitic magmas and during Strombolian to Hawaiian eruptions fed by basaltic to mugearitic magmas in submarine/subglacial to subaerial environments. The long-lived Mt. Morning eruptive centre, located c. 80 km south of the drillsite, was recognized as the probable volcanic source for these products on the basis of volcanological, geochemical, and age constraints. The study of tephra in the AND-2A core provides important paleoenvironment information by revealing that the deposition of primary and moderately reworked tephra occurred in a proglacial setting under generally open water marine conditions.
    Description: Published
    Description: 1342-1355
    Description: 3.7. Dinamica del clima e dell'oceano
    Description: JCR Journal
    Description: partially_open
    Keywords: Antarctica ; Volcaniclastic sediments ; Paleoenvironment ; Mt. Morning ; Victoria Land Basin ; 02. Cryosphere::02.03. Ice cores::02.03.05. Paleoclimate ; 04. Solid Earth::04.04. Geology::04.04.08. Sediments: dating, processes, transport ; 04. Solid Earth::04.08. Volcanology::04.08.05. Volcanic rocks
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  • 5
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    Rapid differentiation in a sill-like magma reservoir: a case study from the campi flegrei caldera (2012)
    Nature Publishing Group
    Details
    Publication Date: 2017-04-04
    Description: In recent decades, geophysical investigations have detected wide magma reservoirs beneath quiescent calderas. However, the discovery of partially melted horizons inside the crust is not sufficient to put constraints on capability of reservoirs to supply cataclysmic eruptions, which strictly depends on the chemical-physical properties of magmas (composition, viscosity, gas content etc.), and thus on their differentiation histories. In this study, by using geochemical, isotopic and textural records of rocks erupted from the high-risk Campi Flegrei caldera, we show that the alkaline magmas have evolved toward a critical state of explosive behaviour over a time span shorter than the repose time of most volcanic systems and that these magmas have risen rapidly toward the surface. Moreover, similar results on the depth and timescale of magma storage were previously obtained for the neighbouring Somma-Vesuvius volcano. This consistency suggests that there might be a unique long-lived magma pool beneath the whole Neapolitan area.
    Description: Published
    Description: article 712
    Description: 2.3. TTC - Laboratori di chimica e fisica delle rocce
    Description: 3.5. Geologia e storia dei vulcani ed evoluzione dei magmi
    Description: 3.6. Fisica del vulcanismo
    Description: 4.3. TTC - Scenari di pericolosità vulcanica
    Description: N/A or not JCR
    Description: open
    Keywords: magma ; campi flegrei caldera ; 04. Solid Earth::04.04. Geology::04.04.05. Mineralogy and petrology ; 04. Solid Earth::04.08. Volcanology::04.08.03. Magmas ; 04. Solid Earth::04.08. Volcanology::04.08.05. Volcanic rocks ; 04. Solid Earth::04.08. Volcanology::04.08.08. Volcanic risk
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  • 6
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    Quantitative analysis of X-ray microtomography images of geomaterials: Application to volcanic rocks (2011)
    Geological Society of America
    Details
    Publication Date: 2021-01-27
    Description: X-ray computed microtomography is an excellent tool for the three-dimensional analysis of rock microstructure. Digital images are acquired, visualized, and processed to identify and measure several discrete features and constituents of rock samples, by means of mathematical algorithms and computational methods. In this paper, we present digital images of volcanic rocks collected with X-ray computed microtomography techniques and studied by means of a software library, called Pore3D, custom-implemented at the Elettra Synchrotron Light Laboratory of Trieste (Italy). Using the Pore3D software, we analyzed the fabrics and we quantified the characteristics of the main constituents (vesicles, crystals, and glassy matrix) of four different types of pyroclasts: frothy pumice, tube pumice, scoria, and “crystalline” scoria. We identified the distinctive features of these different types of volcanic rocks. The frothy pumices show vesicles that coalesce in isotropic aggregates, especially toward the sample interior, while the scoriae have a low porosity and an abundance of isolated vesicles. In the “crystalline” scoria sample most of the vesicle separation is due to the presence of crystals of different types, while the tube pumice shows an anisotropic distribution of vesicles and crystals at the microscale, as also observed at the scale of the hand sample. Quantitative analysis and textural information may supply an additional tool to investigate the eruptive processes and the origin of volcanic rocks.
    Description: Published
    Description: 793-804
    Description: 2.3. TTC - Laboratori di chimica e fisica delle rocce
    Description: JCR Journal
    Description: reserved
    Keywords: X-ray tomography ; 3D imaging ; volcanic rocks ; 04. Solid Earth::04.08. Volcanology::04.08.05. Volcanic rocks ; 04. Solid Earth::04.08. Volcanology::04.08.07. Instruments and techniques
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  • 7
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    Late Miocene submarine volcanism in ANDRILL AND-1B drill core, Ross Embayment, Antarctica (2011)
    Geological Society of America
    Details
    Publication Date: 2017-04-04
    Description: The ANDRILL McMurdo Ice Shelf initiative recovered a 1285-m-long core (AND-1B) composed of cyclic glacimarine sediments with interbedded volcanic deposits. The thickest continuous volcanic sequence by far is ∼175 m long and is found at mid-core depths from 584.19 to 759.32 m below seafloor. The sequence was logged, and initial interpretations of lithostratigraphic subdivisions were made on ice during drilling in late 2006. Subsequent observations, based on image, petrographic, and scanning electron microscopy–energy dispersive spectroscopy analyses, provide a more detailed, revised interpretation of a thick submarine to emergent volcanic succession. The sequence is subdivided into two main subsequences on the basis of sediment composition, texture, and alteration style. The ∼70-m-thick lower subsequence consists mostly of monothematic stacked volcanic-rich mudstone and sandstone deposits, which are attributed to epiclastic gravity flow turbidite processes. This subsequence is consistent with abundant active volcanism that occurred at a distal site with respect to the drill site. The ∼105-m-thick upper subsequence consists mainly of interbedded tuff, lapilli tuff, and volcanic diamictite. A Late Miocene (6.48 Ma) 2.81-m-thick subaqueously emplaced lava flow occurs within the second subsequence. This second subsequence is attributed to recurring cycles of submarine to emergent volcanic activity that occurred proximal to the drill site. This new data set provides (1) the first rock evidence of significant Late Miocene submarine volcanic activity in the Ross Embayment during a period of no to limited glaciation, and (2) a rich stratigraphic record that elucidates submarine volcano-sedimentary processes in an offshore setting.
    Description: Published
    Description: 524-536
    Description: 2.3. TTC - Laboratori di chimica e fisica delle rocce
    Description: 3.5. Geologia e storia dei vulcani ed evoluzione dei magmi
    Description: 3.8. Geofisica per l'ambiente
    Description: JCR Journal
    Description: reserved
    Keywords: Antarctica ; Andrill ; Ice-Volcano interactions ; Submarine Volcanism ; Volcanoclastic rocks ; 04. Solid Earth::04.04. Geology::04.04.04. Marine geology ; 04. Solid Earth::04.04. Geology::04.04.08. Sediments: dating, processes, transport ; 04. Solid Earth::04.08. Volcanology::04.08.05. Volcanic rocks
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  • 8
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    40Ar/39Ar and 14C geochronology of the Albano maar deposits: Implications for 2 defining the age and eruptive style of the most recent explosive activity at Colli 3 Albani Volcanic District, Central Italy (2010)
    elsevier
    Details
    Publication Date: 2021-06-16
    Description: New 40Ar/39Ar and 14C ages have been found for the Albano multiple maar pyroclastic units and underlying 25 paleosols to document the most recent explosive activity in the Colli Albani Volcanic District (CAVD) near 26 Rome, Italy, consisting of seven eruptions (Albano 1 27 ^ = ^ oldest). Both dating methodologies have been applied on several proximal units and on four mid-distal fall/surge deposits, the latter correlated, according to two 28 current different views, to either the Albano or the Campi di Annibale hydromagmatic center. The 40Ar/39Ar 29 ages on leucite phenocrysts from the mid-distal units yielded ages of ca. 72 ka, 73 ka, 41 ka and 36 ka BP, 30 which are indistinguishable from the previously determined 40Ar/39Ar ages of the proximal Albano units 1, 2, 31 5 and 7, thus confirming their stratigraphic correspondence. 32 Twenty-one 14C ages of the paleosols beneath Albano units 3, 5, 6 and 7 were found for samples collected 33 from 13 proximal and distal sections, some of which were the same sections sampled for 40Ar/39Ar 34 measurements. The 14C ages were found to be stratigraphically inconsistent and highly scattered, and were 35 systematically younger than the 40Ar/39Ar ages, ranging 36 ^ from 35 ka ^ to 3 ka. Considering the significant consistence of the 40Ar/39Ar chronological framework, we interpret the scattered and contradictory 14C ages 37 to be the result of a variable contamination of the paleosols by younger organic carbon deriving from the 38 superficial soil horizons. 39 These results suggest that multiple isotopic systems anchored to a robust stratigraphic framework may need 40 to be employed to determine accurately the geochronology of the CAVD as well as other volcanic districts. 41
    Description: Published
    Description: 203-213
    Description: 3.5. Geologia e storia dei vulcani ed evoluzione dei magmi
    Description: JCR Journal
    Description: open
    Keywords: 40Ar/39Ar 14C geochronology Albano maar Central Italy ; 04. Solid Earth::04.08. Volcanology::04.08.05. Volcanic rocks
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 9
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    Late Miocene Submarine Volcanism in the Ross Embayment, Antarctica (2010)
    Geological Society of America
    Details
    Publication Date: 2017-04-04
    Description: Abstract: The ANDRILL McMurdo Ice Shelf (MIS) initiative recovered a 1285 m-long core (MIS AND-1B) composed of cyclic glacimarine sediments with interbedded volcanic deposits. By far the thickest continuous volcanic sequence is about 175 m long and is found at midcore depths from 584.19 to 759.32 meters below sea floor (mbsf). The sequence was logged and initial interpretations of lithostratigraphic subdivisions were made on-ice during drilling in late 2006. Subsequent observations, based on image, petrographic, and SEM-EDS analyses, provide a more detailed, revised interpretation of a thick submarine to emergent volcanic succession. The sequence is subdivided into two main subsequences on the basis of sediment composition, texture and alteration style. The ~70 m thick lower subsequence consists mostly of monothematic stacked volcanic-rich mudstone and sandstone deposits, which are attributed to epiclastic gravity flow turbidite processes. This subsequence is consistent with abundant active volcanism that occurred at a distal site with respect to the drill site. The ~105 m thick upper subsequence consists mainly of interbedded tuff, lapilli tuff, and volcanic diamictite. A late Miocene (6.48 Ma) 2.81 m-thick subaqueously emplaced lava flow occurs within the second subsequence. This second subsequence is attributed to recurring cycles of submarine to emergent volcanic activity that occurred proximal to the drill site. This new dataset provides 1) the first rock evidence of significant late Miocene submarine volcanic activity in the Ross Embayment during a period of no to limited glaciation , and 2) a rich stratigraphic record that elucidates submarine volcano-sedimentary processes in an off-shore setting.
    Description: In press
    Description: 2.3. TTC - Laboratori di chimica e fisica delle rocce
    Description: 3.5. Geologia e storia dei vulcani ed evoluzione dei magmi
    Description: 3.8. Geofisica per l'ambiente
    Description: JCR Journal
    Description: open
    Keywords: ANDRILL ; AND1-B core ; McMurdo Sound ; submarine volcanism ; 04. Solid Earth::04.04. Geology::04.04.08. Sediments: dating, processes, transport ; 04. Solid Earth::04.04. Geology::04.04.10. Stratigraphy ; 04. Solid Earth::04.08. Volcanology::04.08.05. Volcanic rocks
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  • 10
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    Volcanological and structural evolution of the Ischia resurgent caldera (Italy) over the past 10 ka. (2008)
    Geological Society of America | GEOLOGICAL SOCIETY OF AMERICA
    Details
    Publication Date: 2020-11-17
    Description: Volcanic activity on the island of Ischia included both effusive and explosive eruptions, mainly occurred in the eastern sector of the island. Vent location, eruption dynamics, transport mechanisms and depositional processes, have been reconstructed for each recognized unit. In the past 10 ka, periods of quiescence alternated with periods of very intense volcanism, which was mainly concentrated at about 5.5 and over the past 2.9 ka. Volcanism was not continuous and strongly influenced by the mechanism of a resurgence phenomenon, which affects the island since about 33 ka. Therefore, it has been hypothesized that magma intrusion and uplift events occurred intermittently. In the past 5.5 ka, volcanic activity has been invariably accompanied by the emplacement of slope instability-related deposits testifying that also slope instability was induced by reactivation of vertical movements, likely related to resurgence.
    Description: Published
    Description: 193-239
    Description: 6V. Pericolosità vulcanica e contributi alla stima del rischio
    Description: reserved
    Keywords: Volcanological ; Ischia resurgent ; 04. Solid Earth::04.08. Volcanology::04.08.05. Volcanic rocks ; 04. Solid Earth::04.08. Volcanology::04.08.08. Volcanic risk ; 05. General::05.02. Data dissemination::05.02.03. Volcanic eruptions
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 11
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    Slope processes in weathered volcaniclastic deposits within the city of Naples: The Camaldoli Hill case (2007)
    elsevier
    Details
    Publication Date: 2017-04-04
    Description: We describe the slope processes acting on Camaldoli Hill, the main volcanic feature of the Neapolitan area whose geological evolution and setting have been reconstructed. The backbone of the hill includes the remnants of two partially superposed tuff cones, lying between the Campanian Ignimbrite (CI) and the Neapolitan Yellow Tuff (NYT). This sequence is mantled by pyroclastic, anthropogenic and epiclastic deposits, with abrupt thickness and facies variations. The structural setting of the hill mainly results from several phases of reactivation of the CI caldera faults which were active until about 9.5 ka. Deformation younger than 15 ka is evidenced by landslide deposits, caused by slope instability from volcano-tectonism, and by a high-angle erosional unconformity, formed in response to a base-level lowering. A stratigraphic analysis of the reworked deposits at the foot of the slopes allowed us to define both depositional mechanisms and sedimentation rates. The results of combined volcanological, geomorphological and engineering-geological studies permitted us to constrain and quantify past geological processes and hypothesis about the future evolution of the hill. Present-day slope processes on Camaldoli Hill are largely controlled by the presence of weathered and reworked deposits, whose nature and thickness have been analysed and mapped in detail. Four main kinds of slope processes have been recognized: falls and toppling failures from NYT; small-scale slides in the weathered and pedogenized loose cover; mixed events, represented by slides evolving to hyperconcentrated flows, mud flows and debris flows; and areal and linear erosion. Consequently, a high number of mass movements not previously documented have been mapped. At the same time, an insight into the sedimentation rate due to the overall slope processes, covering a time-span of about 5 ka, was given. Some final considerations regarding landslide hazard are presented in the context of the most suitable remedial works.
    Description: Published
    Description: 132–157
    Description: 3.5. Geologia e storia dei sistemi vulcanici
    Description: 4.4. Scenari e mitigazione del rischio ambientale
    Description: JCR Journal
    Description: reserved
    Keywords: Slope processes ; Weathering ; Volcaniclastic rocks ; Hazard ; Risk ; 04. Solid Earth::04.04. Geology::04.04.03. Geomorphology ; 04. Solid Earth::04.04. Geology::04.04.07. Rock geochemistry ; 04. Solid Earth::04.04. Geology::04.04.08. Sediments: dating, processes, transport ; 04. Solid Earth::04.08. Volcanology::04.08.05. Volcanic rocks
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  • 12
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    Interaction between particles transported by fallout and surge in the deposits of the Agnano-Monte Spina eruption (Campi Flegrei, Southern Italy) (2006)
    Elsevier Scientific Publishers
    Details
    Publication Date: 2017-04-04
    Description: The Agnano^Monte Spina Tephra (AMST) is a complex sequence of beds generated by contrasting fragmentation and transportation dynamics. The 4.1 ka eruption was accompanied by a volcano-tectonic collapse, part of which is the present Agnano plain. The pyroclastic sequence is subdivided into members and submembers, each characterized by different lithological and sedimentological features. Plinian/subplinian fallout deposits frequently alternate with base-surge beds of phreatomagmatic origin. Analysis of lateral facies variations and vertical facies associations of correlated layers of submembers B2, D2 and E2 reveals that during some eruption phases the contrasting eruptive dynamics were almost contemporaneous. Base-surge deposits of submember B2 formed during the declining stage of a plinian column. They resulted from highly energetic and steady pyroclastic density currents that traveled long distances from the vent area and surmounted topographic obstacles such as the Posillipo hill (V150 m) and the northern sector of the Camaldoli hill (V250 m). Submember D2 pyroclastic density currents formed when contemporaneous fallout from an eruptive column was present. Coarse particles from the column settled throughout the pyroclastic density current, determining a significant increase of the solid load of the base surge. The consequent increase of supply rate from the transportation to the depositional zone of the base surge led to the formation of unsteady flows that could not efficiently transport the solid load and did not have the ability to travel long distances. Base-surge deposits of submember E2 were fed by a pulsating phreatomagmatic activity, which was punctuated by a short-lived fallout phase. Fallout material, which was incorporated as an additional load to the base surges, was partially transported by low-energy, steady pyroclastic density currents that traveled over the Agnano plain but did not surmount either the Camaldoli or the Posillipo hills. Only the very fine material, in continuous suspension in the upper, no-shearing part of the base-surge cloud, was dispersed higher in the atmosphere and quietly settled over a large area outside the caldera rim. The phreatomagmatic origin of base surges, which contrasts with the magmatic origin of fallout activity, suggests that the pyroclastic density currents of the Agnano^Monte Spina eruption did not result from eruption column collapses. They were most likely related to radially spreading clouds which were contemporaneous with fallout activity but issued from distinct zones in the vent area. The turbulent nature and the high expansion of base surges made them capable, under certain conditions, of passing over high topographic obstacles, with hazardous effects in distal areas.
    Description: Published
    Description: 193-210
    Description: partially_open
    Keywords: base-surge deposits ; Campi Flegrei ; phreatomagmatism ; fallout deposits ; 04. Solid Earth::04.04. Geology::04.04.08. Sediments: dating, processes, transport ; 04. Solid Earth::04.08. Volcanology::04.08.05. Volcanic rocks
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 13
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    Turbulent boundary layer shear flows as an approximation of base surges at Campi Flegrei (Southern Italy) (2006)
    Elsevier Scientific Publishers
    Details
    Publication Date: 2017-04-04
    Description: Small-volume base-surge deposits of Astroni and Agnano^Monte Spina eruptions at Campi Flegrei consist of sets of beds formed by the passage of multiple pyroclastic density currents. Each set is made by a fining-upward sequence consisting, from base to top,of : (1) an inversely graded layer made of bombs and lapilli; (2) a finely laminated layer with wavy bedforms made of coarse ash and fine lapilli; (3) a structureless fine-ash bed. Lack of discontinuities at layer contacts allows us to hypothesize that each set of beds represents the passage of one pyroclastic density current. The sequence formed as a function of the decreasing particle transportation capability of the base surge during the waxing^sustained^waning phases of flowage. We make the simplifying assumptions that the flow,on passing from the deposition of the inversely graded layer to the deposition of the finely laminated layer,had low particle concentration,was quasi-steady and incompressible. By such assumptions,some of the equations that regulate sediment mechanics are applicable to the base surges of Campi Flegrei to reconstruct flow density and shear velocity in between the deposition of the two layers. Structural and textural features of deposits stress the importance of shear and turbulence during transportation and suggest that the turbulent boundary layer shear flow is a good approximation to such pyroclastic density currents. We used the Coles formula to reconstruct velocity as a function of flow height during the formation of the finely laminated layer of Astroni and Agnano^Monte Spina base surges. The methodology we used allows the reconstruction of flow parameters just at a particular point in time and space of base-surge evolution,and does not provide the complete picture of the flow history of pyroclastic density currents. Nevertheless,flow velocity and density data, as obtained with the proposed approach,point to dynamic pressure values that are compatible with those reported for similar currents on other volcanoes. We conclude therefore that the results obtained give approximate but helpful information on the nature of such hazardous events at Campi Flegrei.
    Description: Published
    Description: 221-228
    Description: partially_open
    Keywords: base-surge deposits ; boundary layer ; pyroclastic density current ; phreatomagmatic eruptions ; 04. Solid Earth::04.04. Geology::04.04.08. Sediments: dating, processes, transport ; 04. Solid Earth::04.08. Volcanology::04.08.05. Volcanic rocks
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
    Format: 497 bytes
    Format: 1071902 bytes
    Format: text/html
    Format: application/pdf
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