scholarly journals Dynamics of large pyroclastic currents inferred by the internal architecture of the Campanian Ignimbrite

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Claudio Scarpati ◽  
Domenico Sparice ◽  
Annamaria Perrotta
Keyword(s):  
Leading Edge ◽  
Global Scale ◽  
Campi Flegrei ◽  
Explosive Eruptions ◽  
Transport Mechanisms ◽  
Campanian Ignimbrite ◽  
Lateral Variation ◽  
Time And Space ◽  
Ignimbrite Sheet ◽  
Internal Architecture

AbstractLarge ignimbrites are the product of devastating explosive eruptions that have repeatedly impacted climate and life on global scale. The assemblage of vertical and lateral lithofacies variations within an ignimbrite sheet, its internal architecture, may help to determine how the parental pyroclastic current evolves in time and space. The 39 ka Campanian Ignimbrite eruption, vented from Campi Flegrei caldera, laid down a thick ignimbrite over an area of thousands of km2. A detailed reconstruction of the vertical and lateral variation of the seven lithofacies recognised in the ignimbrite medial sequence constrains the behaviour of this event. The pyroclastic current flowed over a wide area around Campi Flegrei without depositing (bypass zone), and inundated a huge area during most of the paroxysmal, waxing phase, emplacing a mainly incipiently- to strongly- welded ignimbrite. Following this waxing phase, the leading edge of the current retreated back towards the source as the current waned, impacting a progressively smaller area and leaving an unconsolidated ash and lapilli deposit, later lithified. Our study illustrates how large pyroclastic currents can evolve in time and space and the importance of both internal (eruptive and transport mechanisms) and external (topography, surficial water and rain) factors in governing their behaviour.

Vorticity transport in the leading-edge vortex on a rotating blade

2014 ◽  
Vol 743 ◽  
pp. 249-261 ◽  
Author(s):  
Craig J. Wojcik ◽  
James H. J. Buchholz
Keyword(s):  
Leading Edge ◽  
Quasi Equilibrium ◽  
Transport Mechanisms ◽  
Leading Edge Vortex ◽  
Rotating Blade ◽  
Edge Vortex ◽  
Rotation Motion ◽  
Vorticity Transport ◽  
Control Volumes ◽  
Quiescent Fluid

AbstractVorticity transport is analysed within the leading-edge vortex generated on a rectangular flat plate of aspect ratio 4 undergoing a starting rotation motion in a quiescent fluid. Two analyses are conducted on the inboard half of the blade to better understand the vorticity transport mechanisms responsible for maintaining the quasi-equilibrium state of the leading-edge vortex. An initial global analysis between the $25$ and $50\, \%$ spanwise positions suggests that, although spanwise velocity is significant, spanwise convection of vorticity is insufficient to balance the flux of vorticity from the leading-edge shear layer. Subsequent detailed analyses of vorticity transport in planar control volumes at the $25$ and $50\, \%$ spanwise positions verify this conclusion and demonstrate that vorticity annihilation due to interaction between the leading-edge vortex and the opposite-sign layer on the plate surface is an important, often dominant, mechanism for regulation of leading-edge-vortex circulation. Thus, it provides an important condition for maintenance of an attached leading-edge vortex on the inboard portion of the blade.

scholarly journals Magma chamber evolution prior to the Campanian Ignimbrite and Neapolitan Yellow Tuff eruptions (Campi Flegrei, Italy)

2007 ◽  
Vol 70 (8) ◽  
pp. 961-976 ◽  
Author(s):  
Sonja Pabst ◽  
Gerhard Wörner ◽  
Lucia Civetta ◽  
Roberto Tesoro
Keyword(s):  
Magma Chamber ◽  
Campi Flegrei ◽  
Campanian Ignimbrite ◽  
Neapolitan Yellow Tuff

scholarly journals The permeability and elastic moduli of tuff from Campi Flegrei, Italy: implications for ground deformation modelling

Solid Earth ◽  
2014 ◽  
Vol 5 (1) ◽  
pp. 25-44 ◽  
Author(s):  
M. J. Heap ◽  
P. Baud ◽  
P. G. Meredith ◽  
S. Vinciguerra ◽  
T. Reuschlé
Keyword(s):  
Ultrasonic Wave ◽  
Elastic Moduli ◽  
Ground Deformation ◽  
Laboratory Data ◽  
Campi Flegrei ◽  
Pore Collapse ◽  
Campanian Ignimbrite ◽  
Wave Velocities ◽  
Neapolitan Yellow Tuff ◽  
Dynamic Elastic Moduli

Abstract. The accuracy of ground deformation modelling at active volcanoes is a principal requirement in volcanic hazard mitigation. However, the reliability of such models relies on the accuracy of the rock physical property (permeability and elastic moduli) input parameters. Unfortunately, laboratory-derived values on representative rocks are usually rare. To this end we have performed a systematic laboratory study on the influence of pressure and temperature on the permeability and elastic moduli of samples from the two most widespread lithified pyroclastic deposits at the Campi Flegrei volcanic district, Italy. Our data show that the water permeability of Neapolitan Yellow Tuff and a tuff from the Campanian Ignimbrite differ by about 1.5 orders of magnitude. As pressure (depth) increases beyond the critical point for inelastic pore collapse (at an effective pressure of 10–15 MPa, or a depth of about 750 m), permeability and porosity decrease significantly, and ultrasonic wave velocities and dynamic elastic moduli increase significantly. Increasing the thermal stressing temperature increases the permeability and decreases the ultrasonic wave velocities and dynamic elastic moduli of the Neapolitan Yellow Tuff; whereas the tuff from the Campanian Ignimbrite remains unaffected. This difference is due to the presence of thermally unstable zeolites within the Neapolitan Yellow Tuff. For both rocks we also find, under the same pressure conditions, that the dynamic (calculated from ultrasonic wave velocities) and static (calculated from triaxial stress-strain data) elastic moduli differ significantly. The choice of elastic moduli in ground deformation modelling is therefore an important consideration. While we urge that these new laboratory data should be considered in routine ground deformation modelling, we highlight the challenges for ground deformation modelling based on the heterogeneous nature (vertically and laterally) of the rocks that comprise the caldera at Campi Flegrei.

Eruptive history of Neapolitan volcanoes: constraints from 40Ar–39Ar dating

2012 ◽  
Vol 150 (3) ◽  
pp. 412-425 ◽  
Author(s):  
CLAUDIO SCARPATI ◽  
ANNAMARIA PERROTTA ◽  
SIMONE LEPORE ◽  
ANDREW CALVERT
Keyword(s):  
Volcanic Field ◽  
Campi Flegrei ◽  
Campanian Ignimbrite ◽  
Pyroclastic Deposits ◽  
Eruptive History ◽  
New Period ◽  
History Of ◽  
Tephra Layers ◽  
The City ◽  
Eruptive Cycles

AbstractThe city of Naples can be considered part of the Campi Flegrei volcanic field, and deposits within the urban area record many autochthonous pre- to post-caldera eruptions. Age measurements were carried out using 40Ar–39Ar dating techniques on samples from small monogenetic vents and more widely distributed tephra layers. The 40Ar–39Ar ages on feldspar phenocrysts yielded ages of c. 16 ka and 22 ka for events older than the Neapolitan Yellow Tuff caldera-forming eruption (15 ka), and ages of c. 40 ka, 53 ka and 78 ka for events older than the Campanian Ignimbrite caldera-forming eruption (39 ka). The oldest age obtained is 18 ka older than previous dates for pyroclastic deposits cropping out along the northern rim of Campi Flegrei. The results of this study allow us to divide the Campi Flegrei volcanic history into four main, geochronologically distinct eruptive cycles. A new period, the Paleoflegrei, occurred before 74–78 ka and has been proposed to better discriminate the ancient volcanism in the volcanic field. The eruptive history of Campi Flegrei extends possibly further back than this, but the products of previous eruptions are difficult to date owing to the lack of fresh juvenile clasts. These new geochronological data, together with recently published ages related to young volcanic edifices located in the city of Naples (Nisida volcano, 3.9 ka) testify to persistent activity over a period of at least 80 ka, with an average eruption recurrence interval of ~555 years within and adjacent to this densely populated city.

Texture and composition of pumices and scoriae from the Campi Flegrei caldera (Italy): Implications on the dynamics of explosive eruptions

2008 ◽  
Vol 9 (3) ◽  
pp. n/a-n/a ◽  
Author(s):  
M. Piochi ◽  
M. Polacci ◽  
G. De Astis ◽  
A. Zanetti ◽  
A. Mangiacapra ◽  
...  
Keyword(s):  
Campi Flegrei ◽  
Explosive Eruptions ◽  
Campi Flegrei Caldera

scholarly journals The origin of a zoned ignimbrite: Insights into the Campanian Ignimbrite magma chamber (Campi Flegrei, Italy)

2016 ◽  
Vol 449 ◽  
pp. 259-271 ◽  
Author(s):  
Francesca Forni ◽  
Olivier Bachmann ◽  
Silvio Mollo ◽  
Gianfilippo De Astis ◽  
Sarah E. Gelman ◽  
...  
Keyword(s):  
Magma Chamber ◽  
Campi Flegrei ◽  
Campanian Ignimbrite

scholarly journals The evolution of city life

2018 ◽  
Vol 285 (1884) ◽  
pp. 20181529 ◽  
Author(s):  
James S. Santangelo ◽  
L. Ruth Rivkin ◽  
Marc T. J. Johnson
Keyword(s):  
Urban Areas ◽  
Evolutionary Biology ◽  
Natural Populations ◽  
Leading Edge ◽  
Theoretical Models ◽  
Global Scale ◽  
Urban Environments ◽  
Ecological Communities ◽  
Natural Ecosystems ◽  
Evolutionary Mechanisms

Urbanization represents a dominant and growing form of disturbance to Earth's natural ecosystems, affecting biodiversity and ecosystem services on a global scale. While decades of research have illuminated the effects of urban environmental change on the structure and function of ecological communities in cities, only recently have researchers begun exploring the effects of urbanization on the evolution of urban populations. The 15 articles in this special feature represent the leading edge of urban evolutionary biology and address existing gaps in our knowledge. These gaps include: (i) the absence of theoretical models examining how multiple evolutionary mechanisms interact to affect evolution in urban environments; (ii) a lack of data on how urbanization affects natural selection and local adaptation; (iii) poor understanding of whether urban areas consistently affect non-adaptive and adaptive evolution in similar ways across multiple cities; (iv) insufficient data on the genetic and especially genomic signatures of urban evolutionary change; and (v) limited understanding of the evolutionary processes underlying the origin of new human commensals. Using theory, observations from natural populations, common gardens, genomic data and cutting-edge population genomic and landscape genetic tools, the papers in this special feature address these gaps and highlight the power of urban evolutionary biology as a globally replicated ‘experiment’ that provides a powerful approach for understanding how human altered environments affect evolution.

A FRACTAL APPROACH TO CLUSTERING OF THE 1983–1984 SEISMICITY IN THE CAMPI FLEGREI CALDERA, SOUTHERN ITALY

Fractals ◽  
1996 ◽  
Vol 04 (01) ◽  
pp. 29-34 ◽  
Author(s):  
G. LUONGO ◽  
A. MAZZARELLA ◽  
A. PALUMBO
Keyword(s):  
Critical State ◽  
Southern Italy ◽  
Power Laws ◽  
Limited Range ◽  
Campi Flegrei ◽  
Time And Space ◽  
Scale Invariant ◽  
Fractal Approach ◽  
Significant Power ◽  
Volcanic Seismicity

The volcanic seismicity occurring in Campi Flegrei during the 1983–1984 volcanic crisis is quantitatively analyzed by means of fractal (scale invariant) geometry in all its five dimensional set (magnitude, time and space). The significant power laws, relating the number of earthquakes to magnitude, time and space, within a limited range of scales, show that the Campi Flegrei region is in a critical state during the whole crisis.

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