scholarly journals Explosive caldera-forming eruptions and debris-filled vents: Gargle dynamics

Geology ◽  
2021 ◽  
Author(s):  
Greg A. Valentine ◽  
Meredith A. Cole
Keyword(s):  
Grain Size ◽  
Numerical Modeling ◽  
Volcanic Eruptions ◽  
Low Energy ◽  
Buoyant Plume ◽  
Entire Height ◽  
The World ◽  
Jet Behavior ◽  
Explosive Volcanic Eruptions ◽  
Caldera Subsidence

Large explosive volcanic eruptions are commonly associated with caldera subsidence and ignimbrites deposited by pyroclastic currents. Volumes and thicknesses of intracaldera and outflow ignimbrites at 76 explosive calderas around the world indicate that subsidence is commonly simultaneous with eruption, such that large proportions of the pyroclastic currents are trapped within the developing basins. As a result, much of an eruption must penetrate its own deposits, a process that also occurs in large, debris-filled vent structures even in the absence of caldera formation and that has been termed “gargling eruption.” Numerical modeling of the resulting dynamics shows that the interaction of preexisting deposits (fill) with an erupting (juvenile) mixture causes a dense sheath of fill material to be lifted along the margins of the erupting jet. This can cause an eruption that would otherwise produce a buoyant plume and fallout deposits to instead form pyroclastic currents as the dense sheath drives pulsing jet behavior. Increasing thickness of fill amplifies the time variation in jet height. Increasing the fill grain size relative to that of the juvenile particles can result in a much higher jet due to poorer mixing between the dense sheath and the dilute jet core. In all cases, material collapses along the entire height of the dense sheath rather than from the top of a simple fountain. These gargle dynamics provide strong backing for processes that have been inferred to result in intraplinian ignimbrites and simultaneous deposition from high- and low-energy pyroclastic currents.

scholarly journals Revisiting the statistical analysis of pyroclast density and porosity data

2015 ◽  
Vol 7 (1) ◽  
pp. 1077-1095 ◽  
Author(s):  
B. Bernard ◽  
U. Kueppers ◽  
H. Ortiz
Keyword(s):  
Grain Size ◽  
Volcanic Eruptions ◽  
Large Datasets ◽  
Grain Size Analysis ◽  
Size Analysis ◽  
Statistical Tools ◽  
Statistical Relevance ◽  
Volcanic Deposits ◽  
Working Groups ◽  
Explosive Volcanic Eruptions

Abstract. Explosive volcanic eruptions are commonly characterized based on a thorough analysis of the generated deposits. Amongst other characteristics in physical volcanology, density and porosity of juvenile clasts are some of the most frequently used characteristics to constrain eruptive dynamics. In this study, we evaluate the sensitivity of density and porosity data and introduce a weighting parameter to correct issues raised by the use of frequency analysis. Results of textural investigation can be biased by clast selection. Using statistical tools as presented here, the meaningfulness of a conclusion can be checked for any dataset easily. This is necessary to define whether or not a sample has met the requirements for statistical relevance, i.e. whether a dataset is large enough to allow for reproducible results. Graphical statistics are used to describe density and porosity distributions, similar to those used for grain-size analysis. This approach helps with the interpretation of volcanic deposits. To illustrate this methodology we chose two large datasets: (1) directed blast deposits of the 3640–3510 BC eruption of Chachimbiro volcano (Ecuador) and (2) block-and-ash-flow deposits of the 1990–1995 eruption of Unzen volcano (Japan). We propose add the use of this analysis for future investigations to check the objectivity of results achieved by different working groups and guarantee the meaningfulness of the interpretation.

scholarly journals The fate of volcanic ash: premature or delayed sedimentation?

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Eduardo Rossi ◽  
Gholamhossein Bagheri ◽  
Frances Beckett ◽  
Costanza Bonadonna
Keyword(s):  
Residence Time ◽  
Volcanic Ash ◽  
Volcanic Eruptions ◽  
Theoretical Description ◽  
Particle Sedimentation ◽  
Weather Modeling ◽  
Explosive Volcanic Eruptions ◽  
Travel Distances ◽  
Ash Dispersal

AbstractA large amount of volcanic ash produced during explosive volcanic eruptions has been found to sediment as aggregates of various types that typically reduce the associated residence time in the atmosphere (i.e., premature sedimentation). Nonetheless, speculations exist in the literature that aggregation has the potential to also delay particle sedimentation (rafting effect) even though it has been considered unlikely so far. Here, we present the first theoretical description of rafting that demonstrates how delayed sedimentation may not only occur but is probably more common than previously thought. The fate of volcanic ash is here quantified for all kind of observed aggregates. As an application to the case study of the 2010 eruption of Eyjafjallajökull volcano (Iceland), we also show how rafting can theoretically increase the travel distances of particles between 138–710 μm. These findings have fundamental implications for hazard assessment of volcanic ash dispersal as well as for weather modeling.

scholarly journals Volcanic Ash, Insecurity for the People but Securing Fertile Soil for the Future

2019 ◽  
Vol 11 (11) ◽  
pp. 3072 ◽  
Author(s):  
Dian Fiantis ◽  
Frisa Ginting ◽  
Gusnidar ◽  
M. Nelson ◽  
Budiman Minasny
Keyword(s):  
Volcanic Ash ◽  
Volcanic Eruptions ◽  
Positive Outcome ◽  
Natural Event ◽  
Fertile Soil ◽  
The People ◽  
The World ◽  
The Future ◽  
Security View ◽  
Agricultural Areas

Volcanic eruptions affect land and humans globally. When a volcano erupts, tons of volcanic ash materials are ejected to the atmosphere and deposited on land. The hazard posed by volcanic ash is not limited to the area in proximity to the volcano, but can also affect a vast area. Ashes ejected from volcano’s affect people’s daily life and disrupts agricultural activities and damages crops. However, the positive outcome of this natural event is that it secures fertile soil for the future. This paper examines volcanic ash (tephra) from a soil security view-point, mainly its capability. This paper reviews the positive aspects of volcanic ash, which has a high capability to supply nutrients to plant, and can also sequester a large amount of carbon out of the atmosphere. We report some studies around the world, which evaluated soil organic carbon (SOC) accumulation since volcanic eruptions. The mechanisms of SOC protection in volcanic ash soil include organo-metallic complexes, chemical protection, and physical protection. Two case studies of volcanic ash from Mt. Talang and Sinabung in Sumatra, Indonesia showed the rapid accumulation of SOC through lichens and vascular plants. Volcanic ash plays an important role in the global carbon cycle and ensures soil security in volcanic regions of the world in terms of boosting its capability. However, there is also a human dimension, which does not go well with volcanic ash. Volcanic ash can severely destroy agricultural areas and farmers’ livelihoods. Connectivity and codification needs to ensure farming in the area to take into account of risk and build appropriate adaptation and resilient strategy.

Rising smoke-charged vortices in the mid-latitude stratosphere

2021 ◽  
Author(s):  
Bernard Legras ◽  
Hugo Lestrelin ◽  
Aurélien Podglajen ◽  
Mikail Salihoglu
Keyword(s):  
Fluid Mechanics ◽  
Forest Fires ◽  
Volcanic Eruptions ◽  
Radiative Heating ◽  
Dynamical Structure ◽  
The Past ◽  
Self Organized ◽  
The World ◽  
Lidar Observations ◽  
Meso Scale

<p>The two most intense wildfires of the last decade that took place in Canada in 2017 and Australia in 2019-2020 were followed by large injections of smoke in the stratosphere due to pyroconvection. It was discovered that, after the Australian event, part of this smoke self-organized as anticyclonic confined vortices that rose against the Brewer-Dobson circulation in the mid-latitude stratosphere up to 35 km (Khaykin et al., 2020, doi: 10.1038/s43247-020-00022-5).  Based on CALIOP lidar observations and the ECMWF ERA5 reanalysis, we analyze the Canadian case and find, similarly, that the large plume which penetrated the stratosphere on 12 August 2017 and reached 14 km got trapped thereafter within a meso-scale anticyclonic structure which travelled across the Atlantic. It then broke into three offsprings that could be followed until mid-October 2017, each performing  round the world journeys and rising up to 23 km for one of them. We analyze the dynamical structure of the vortices produced by these two wildfires in the ERA 5 and demonstrate how they are maintained by the assimilation of data from instruments measuring the signature of the vortices in the temperature and ozone field. We propose that these vortices can be seen as bubbles of very low potential vorticity carried vertically by their internal radiative heating across the stratosphere against the stratification. We will also present elements of a theory and first numerical simulations explaining the dynamics of such structures  and discuss possible occurrences after other forest fires and volcanic eruptions in the past as well as  future likely impacts. This new phenomenon in geophysical fluid mechanics has, to our knowledge, no reported analog (see reference: https://acp.copernicus.org/preprints/acp-2020-1201/).</p>

scholarly journals The concept of creating thrust based on angular momentum change

2021 ◽  
Author(s):  
Sergei Kupreev
Keyword(s):  
Angular Momentum ◽  
Vacuum Chamber ◽  
Loop Quantum Gravity ◽  
Low Energy ◽  
Practical Implementation ◽  
Material Body ◽  
The World ◽  
Classical And Quantum Mechanics ◽  
Physical Principles ◽  
Kinetic Moment

Abstract The change in the kinetic moment of a material body is considered regarding to classical and quantum mechanics. The possibility of creating the propulsion system in terms of energy efficiency exceeding the photon engine has been theoretically proved. The proposed new principle of motion is based on the law of conservation of angular momentum and is fully consistent with the basic fundamental laws of physics. It is proposed to use the emission/absorption of streams of low-energy particles with spin in the direction perpendicular to the movement of the material body. The practical implementation of this idea is confirmed by the presence of promising approaches to solving the problem of quantizing gravity (string theory, loop quantum gravity, etc.) recognized by the world scientific community and by the successful results of experiments conducted by the authors with the motion of bodies in a vacuum chamber. The proposed idea, the examples and experiments has given grounds for the formation of new physical concepts of the speed, mass and inertia of bodies. The obtained results can be used in experiments to search for elementary particles with low energy, to explain a number of physics phenomena and to develop transport of objects based on new physical principles.

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