1,721,249 research outputs found
First evidence of hydromagmatism at Colima volcano (Mexico)
No full textHere we report for the first time evidences of hydromagmatism at Colima volcano (western sector of Trans-Mexican Volcanic Belt). The studied location exposes 9 m of fine ash deposits dated at around 15 cal kyr BP by C-14 measurement on organic matter collected at the very base of the stratigraphic succession. The ash deposits rest directly on the top of a debris avalanche deposit. The morphology and grain size distribution of ash samples from the basal part of the stratigraphic succession testify for an explosive magma-water interaction, which produced finely bedded layers with blocky fragments characterized by adhering particles, quenching cracks and chemical pitting. The availability of ground water was hypothesized to be in close relationship with the amelioration of climate conditions at the end of the Last Glacial period, with rising temperatures that induced melting of glaciers and snow previously accumulated on the volcano summit slopes. This recognition demonstrates how, even a "dry" volcano like Colima, can experience hydromagmatism under adequate climatic conditions. (C) 2012 Published by Elsevier B.V
Volcaniclastic debris flows in the Clanio Valley (Campania, Italy): Inshight for hazard assement.
No full textThe rugged and steep slopes of the Clanio Valley (Campania, Southern Italy), mantled by volcaniclastic deposits from explosive eruptions of Somma-Vesuvius and Phlegraean Fields volcanoes, have a great potential for generating volcaniclastic debris flows. During the well-known meteorological event of May 5-6, 1998, which triggered tens of debris flows causing enormous damage and casualties in the area of Sarno-Quindici-Siano-Bracigliano (SQSB), the Clanio Valley was also affected by these hazardous phenomena. Debris flows were triggered by the failure of the volcaniclastic cover of the carbonate relief in the form of soil slips, mainly on the sides of steep valleys (slope between 26degrees and 45degrees). A map of the hazard potential was created on the basis of both field and computer-assisted morphometric data. Three classes, characterised by a high, medium and low hazard potential, were distinguished. Within the higher class, a better and more detailed zonation was obtained by studying the shape of the disrupted and undisrupted basins during the May 5-6, 1998 event in the nearby Sarno-Quindici-Siano-Bracigliano area. This type of morphometric analysis can be applied rapidly by using a digital elevation model (DEM), which allows a rapid investigation of large-scale areas. Such an approach can be useful in areas characterised by similar geological and geomorphological settings
Comment on: “The dark nature of Somma-Vesuvius volcano: Evidence from the 3,5 ka BP Avellino eruption” by Mialia A., Raspini M.M.
No full textWe present here some criticism to the scientific content of the paper of Milia et al. [2007. The dark nature of Somma-Vesuvius volcano: evidence from the 3.5 ka B.P. Avellino eruption. Quaternary International, 173–174, 57–66] published in Quaternary International. Milia et al. (2007) interpreted seismic lines in the Gulf of Naples (southern Italy), and inferred the presence of deposits from a large debris avalanche which occurred just before the Avellino eruption of Somma-Vesuvius volcano. The authors supported their seismic profile interpretation with on-land stratigraphies and logs. However, we present here different on-land data that demonstrate the inconsistency of the occurrence of any debris avalanche before or after the Avellino eruption, and we provide also an alternative interpretation for the observed seismic facies offshore of Somma-Vesuvius
Tefrostratigraphic study for the last 18000 14C years in a dep sea sediment sequence for the south Adriatic
No full textThe late Pleistocene pyroclastic deposits of the Campanian Plain: new insights on the esplosive activity of Neapolitan volcanoes
No full textThe lithological and compositional characteristics of eighteen different pyroclastic deposits of Campanian origin, dated between 125 cal ky BP and 22 cal ky BP, were described. The pyroclastic deposits were Correlated among different outcrops mainly located on the Apennine slopes that border the southern Campanian Plain. They were grouped in two main stratigraphic and chronologic intervals of regional significance: a) between Pomici di Base (22.03 cal ky BP; Somma-Vesuvius) and Campanian Ignimbrite (39 cal ky BP: Campi Flegrei) eruptions; and b) older than Campanian Ignimbrite eruption. Three new (14)C AMS datings support the proposed correlations. Six eruptions were attributed to the Pomici di Base-Campanian Ignimbrite stratigraphic interval, while twelve eruptions are older than Campanian Ignimbrite. Of the studied deposits two originated from Ischia island, five are related to Campi Flegrei, and three to Somma-Vesuvius. Two eruptions have an uncertain correlation with Somma-Vesuvius or Campi Flegrei, while six eruptions remain of uncertain source. Minimum volumes of five eruptions were assessed, ranging between 0.5 km(3) and 4 km(3). Two of the studied deposits were correlated with Y-3 and X-5 tephra layers, which are widely dispersed in the central Mediterranean area. The new stratigraphic and chronologic data provide an upgraded chrono-stratigraphy for the explosive activity of Neapolitan volcanoes in the period between 125 and 22 cal ky BP
Carta Geologica del Vesuvio alla scala 1:15.000
No full textSELCA Firenze, carta geologica senza note illustrativ
Computational fluid dynamic simulations of granular flows: Insights on the flow-wall interaction dynamics
Full text linkDry volcanic granular flows are gravity-driven currents composed of solid particles where particle-particle interactions dominate the motion. The interaction with topography is a relevant factor controlling the propagation of such flows. In this paper we investigate the dynamics of channelised volcanic granular flows by comparing large-scale experiments with multiphase computational fluid dynamic simulations using the Two-Fluid Model approach, with an emphasis on the dynamics regulating the flow-wall interactions. We use the software MFIX to carry out sensitivity analysis of the boundary conditions for the solid phase implemented in the numerical code. The sensitivity analysis shows how the choice of the boundary condition and of the relevant parameters controlling the boundary conditions highly affect the dynamics of the whole flow. Finally, a preliminary benchmark of the MFIX boundary conditions with one large-scale experiment is presented, showing good agreement between the simulated and experimental flow front velocities
A map for volcaniclastic debris flow hazards in Apennine areas surrounding the Vesuvius volcano (Italy)
No full textVolcaniclastic debris flows are dangerous natural phenomena that originate in volcanic areas not only during or shortly after an eruption but also during a period of volcanic quiescence, when heavy and/or persistent rains remobilize unconsolidated pyroclastic deposits. In Italy, one of the areas most affected by these phenomena is that of the Apennine Mountains which border the southern Campania Plain surrounding the Vesuvius volcano. Historical accounts record in these areas that more than 500 debris flow events occurred during the last five centuries. These events caused very dangerous consequences such as loss of life and serious damage to property. An example is the devastating event of Sarno of 5 May 1998 which caused the death of more than 150 people and considerable damage to villages located at the foot of the Apennine Hills. In order to contribute to the assessment and mitigation of the debris flow risk, we propose a zonation map that identifies the areas more prone to generation and invasion by volcaniclastic flows. This map is based on field investigations and morphometric analyses derived from a digital elevation model with spatial resolution of 10 meters
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