Conduit processes of the Sf. Ana (TGS) sub-Plinian-Vulcanian eruption sequence of the Ciomadul volcano (SE Carpathians)

2021 ◽  
Author(s):  
Balázs Kiss ◽  
Dávid Karátson ◽  
László Aradi ◽  
János Szepesi ◽  
Tamás Biró ◽  
...  
Keyword(s):  
Bubble Nucleation ◽  
Small Scale ◽  
Eruption Column ◽  
Eruption Style ◽  
Innovation Fund ◽  
Volcanic Chain ◽  
Eastern Carpathians ◽  
Failure Event ◽  
Conduit Processes ◽  
Textural Evidence

<p>The Sf. Ana crater is the young volcanic crater of the dacitic Ciomadul volcano located at the SE end of the Călimani-Gurghiu-Harghita volcanic chain in the Eastern Carpathians. The crater was formed at ~60-30 kyr-s ago probably by several eruptions. The Sf. Ana also called as TGS eruption sequence was the main event that shaped the crater to the present form. The eruption produced fall and PDC deposits, but it is unclear what caused the change in the eruption style. The stratigraphically controlled analyses of the Mohos Layered Pyrolcalstic Sequence (MLPS) provide deep insight into the evolution of the eruption. Assuming that juvenile clast density is primarily controlled by the magma vesiculation within the conduit, the processes close to the fragmentation level can be studied. The vesicularity, vesicle texture, microlite texture, and glass H2O content of the juvenile pyroclasts were studied to reveal the conduit processes. The juvenile clasts show textural evidence for different stages of the vesiculation from bubble nucleation to collapse indicating degassing and outgassing processes in the conduit. The increase of the juvenile clast density upward in the MLPS and the sharp increase of the dense clasts in the PDC deposits indicate the effect of magma column heterogeneity on the eruption style. The conduit heterogeneity was induced by the effective outgassing of the slowly ascending magma portion due to the evolution of vesicle textures together with localized shearing. The eruption column collapse was preceded by a vent failure event which caused densification in the conduit. Banded pumices suggest that the observed conduit heterogeneity was small scale.</p><p> </p><p>The study is supported by the PD130214 project National Research, Development, and Innovation Fund of Hungary.</p>

A glacial refugium and zoogeographic boundary in the Slovak eastern Carpathians

2018 ◽  
Vol 91 (1) ◽  
pp. 383-398 ◽  
Author(s):  
Lucie Juřičková ◽  
Jitka Horáčková ◽  
Anna Jansová ◽  
Jiří Kovanda ◽  
Ján Harčár ◽  
...  
Keyword(s):  
Late Glacial ◽  
Glacial Refugium ◽  
Small Scale ◽  
Snail Species ◽  
The Holocene ◽  
Eastern Carpathians ◽  
Molluscan Fauna ◽  
Fossil Records ◽  
Glacial Periods ◽  
First Time

AbstractAlthough the Carpathians in Europe have often been considered a glacial refugium for temperate plants, vertebrates, and molluscs, the fossil records, the only indisputable evidence surviving glacial periods, are as yet scarce. Moreover, the distribution of fossil records is uneven, and some areas have remained unstudied. We present here three molluscan successions from such an area—the border between the western and eastern Carpathians. This area is not only a geographic border but also a border between the oceanic and continental climate in Europe, and the molluscan fauna reflects this. We found a fluctuation of this zoogeographical border during the late glacial period and the Holocene for several snail species with their easternmost or westernmost distribution situated at this border. Such a fluctuation could reflect a small-scale shifting of climate character during the Holocene. For the first time, we recorded the fossil shells of three local endemics, Carpathica calophana, Petasina bielzi, and Perforatella dibothrion. We also found a fully developed woodland snail fauna radiocarbon dated to the Bølling period. This early occurrence of canopy forest snails indicates a possible eastern Carpathian glacial refugium for them, including local endemics, and may reflect a more moderate glacial impact on local biota than expected.

scholarly journals Rapid eruptive transitions from low to high intensity explosions and effusive activity: insights from textural analysis of a small-volume trachytic eruption, Ascension Island, South Atlantic

2021 ◽  
Vol 83 (9) ◽  
Author(s):  
Bridie V. Davies ◽  
Richard J. Brown ◽  
Jenni Barclay ◽  
Jane H. Scarrow ◽  
Richard A. Herd
Keyword(s):  
High Intensity ◽  
Small Volume ◽  
Early Stage ◽  
Eruption Dynamics ◽  
Eruption Style ◽  
Effusive Activity ◽  
Ascension Island ◽  
Explosive Phase ◽  
The Impact ◽  
Textural Evidence

AbstractProximal deposits of small-volume trachytic eruptions are an under-studied record of eruption dynamics despite being common across a range of settings. The 59 ± 4 ka Echo Canyon deposits, Ascension Island, resulted from a small-volume explosive-effusive trachytic eruption. Variations in juvenile clast texture reveal changes in ascent dynamics and transitions in eruption style. Five dominant textural types are identified within the pumice lapilli population. Early Strombolian-Vulcanian eruption phases are typified by macro- and micro-vesicular equant clast types. Sheared clasts are most abundant at the eruption peak, transitioning to dense clasts in later phases due to shear-induced coalescence, outgassing and vesicle collapse. Melt densification and outgassing via tuffisite veins increased plume density, contributing to partial column collapse and the explosive-effusive transition. Bulk vesicularity distributions indicate a shift in dominant fragmentation mechanism during the eruption, from early-stage bubble interference and rupture to late-stage transient fragmentation, with a transient peak of Plinian activity. Dome and lava groundmass crystallinities of up to 70% indicate near-complete degassing during effusive phases, followed by shallow over pressurisation and a final less explosive phase. We provide textural evidence for high-intensity explosive phases and rapid transitions in eruptive style during small-volume trachytic eruptions and consider the impact of trachytic melt compositions on underlying dynamics of these short-lived, explosive events. This analysis demonstrates the value of detailed stratigraphy in understanding critical changes in eruption dynamics and the timescales over which they may occur which is of particular value in anticipating future eruptions of this type.

scholarly journals Hybrid atomistic-continuum simulation of nucleate boiling with domain re-decomposition method

2017 ◽  
Author(s):  
◽  
Bo Zhang
Keyword(s):  
Molecular Dynamics ◽  
Nucleate Boiling ◽  
Bubble Nucleation ◽  
Coupling Method ◽  
Dynamics Simulation ◽  
Small Scale ◽  
Coupling Scheme ◽  
Atomistic Region ◽  
Continuum Mechanic Model ◽  
Promising Solution

The bubble nucleation plays a pivotal role in the boiling process. In order to have a comprehensive understanding of this phenomenon, a critical consideration on fluid-solid interaction at atomistic level is imperative. However, traditional Molecular Dynamics simulation requires prohibited amount of computational efforts to accomplish a full scale study. Hybrid atomistic-continuum method is a promising solution for this problem. It limits the atomistic region to a small scale where detailed information is preferable, while using continuum method for the rest of the domain. Nevertheless, none of the current hybrid method is suitable for solving a rapid expanding system like the bubble nucleation. In this study, a domain re-decomposition hybrid atomistic-continuum method is developed to conduct a multiscale/multiphase investigation on the bubble nucleation. In addition to the conventional coupling scheme, this method is capable to re-partition the molecular and continuum domain once it is necessary during the simulation. That is, the Computational Fluid Dynamics (CFD) and Molecular Dynamics (MD) regions are interchangeable on the fly such that the bubble is absolutely confined within MD region. Giving the fact that accurate modeling of interface tracking and phase change are still problematic for continuum mechanics on microscale, our coupling method directly avoids these issues since CFD domain takes care of a single-phase flow while the molecular domain simulates the bubble growth. With this idea in mind, this approach enables us to investigate the nucleate boiling on nanostructured surface with higher resolution than complete continuum mechanic model based simulation. In the present result, it is observed that bubble grows at a curved surface imposed with a constant super heat after nucleate boiling occurs. Meanwhile, the energy flux flows from solid to fluid is measured during the entire process. It is believed that this coupling method is very promising in studying nano-bubble related multiphase problems on microscale.

scholarly journals Thematic vent opening probability maps and hazard assessment of small-scale pyroclastic density currents in the San Salvador volcanic complex (El Salvador) and Nejapa-Chiltepe volcanic complex (Nicaragua)

2021 ◽  
Vol 21 (5) ◽  
pp. 1639-1665
Author(s):  
Andrea Bevilacqua ◽  
Alvaro Aravena ◽  
Augusto Neri ◽  
Eduardo Gutiérrez ◽  
Demetrio Escobar ◽  
...  
Keyword(s):  
El Salvador ◽  
Small Scale ◽  
Volcanic Complex ◽  
Pyroclastic Density Currents ◽  
Density Currents ◽  
Eruption Style ◽  
San Salvador ◽  
Low Intensity ◽  
Probability Maps ◽  
Cone Model

Abstract. The San Salvador volcanic complex (El Salvador) and Nejapa-Chiltepe volcanic complex (Nicaragua) have been characterized by a significant variability in eruption style and vent location. Densely inhabited cities are built on them and their surroundings, including the metropolitan areas of San Salvador (∼2.4 million people) and Managua (∼1.4 million people), respectively. In this study we present novel vent opening probability maps for these volcanic complexes, which are based on a multi-model approach that relies on kernel density estimators. In particular, we present thematic vent opening maps, i.e., we consider different hazardous phenomena separately, including lava emission, small-scale pyroclastic density currents, ejection of ballistic projectiles, and low-intensity pyroclastic fallout. Our volcanological dataset includes: (1) the location of past vents, (2) the mapping of the main fault structures, and (3) the eruption styles of past events, obtained from critical analysis of the literature and/or inferred from volcanic deposits and morphological features observed remotely and in the field. To illustrate the effects of considering the expected eruption style in the construction of vent opening maps, we focus on the analysis of small-scale pyroclastic density currents derived from phreatomagmatic activity or from low-intensity magmatic volcanism. For the numerical simulation of these phenomena we adopted the recently developed branching energy cone model by using the program ECMapProb. Our results show that the implementation of thematic vent opening maps can produce significantly different hazard levels from those estimated with traditional, non-thematic maps.

scholarly journals Thematic vent opening probability maps and hazard assessment of small-scale pyroclastic density currents in the San Salvador Volcanic Complex (El Salvador) and Nejapa-Chiltepe Volcanic Complex (Nicaragua)

2020 ◽  
Author(s):  
Andrea Bevilacqua ◽  
Alvaro Aravena ◽  
Augusto Neri ◽  
Eduardo Gutiérrez ◽  
Demetrio Escobar ◽  
...  
Keyword(s):  
El Salvador ◽  
Small Scale ◽  
Volcanic Complex ◽  
Pyroclastic Density Currents ◽  
Density Currents ◽  
Thematic Maps ◽  
Eruption Style ◽  
San Salvador ◽  
Low Intensity ◽  
Probability Maps

Abstract. San Salvador Volcanic Complex (El Salvador) and Nejapa-Chiltepe Volcanic Complex (Nicaragua) have been characterized by a significant variability in eruption style and vent location. Densely inhabited cities are in their surroundings, including the metropolitan areas of San Salvador (~2.4 M people) and Managua (~1.4 M people), respectively. In this study we present novel vent opening probability maps for these volcanic complexes, which are based on a multi-model approach that relies on kernel density estimators. Our volcanological dataset includes: (1) the location of past vents, (2) the mapping of the main fault structures, and (3) the eruption styles of past events, obtained from the critical analysis of literature and/or inferred from volcanic deposits and morphological features observed remotely and in the field. In particular, we present thematic vent opening maps, i.e. we consider different hazardous phenomena separately, including lava emission, small-scale pyroclastic density currents, ejection of ballistic projectiles, and low-intensity pyroclastic fallout. To illustrate the effects of considering the expected eruption style in the construction of vent opening maps, we focus on the analysis of small-scale pyroclastic density currents derived from phreatomagmatic activity or from low-intensity magmatic volcanism. For the numerical simulation of these phenomena we adopted the recently developed branching energy cone model by using the program ECMapProb. Our results show that the implementation of thematic maps of vent opening can produce significantly different hazard levels from those estimated with traditional, non-thematic, maps.

A COMPARATIVE ANALYSIS OF HISTORICAL FLOOD EVENTS (POST-1990) IN THE TREBEŞ-NEGEL REPRESENTATIVE BASIN FOR EASTERN CARPATHIANS AND SUBCARPATHIANS TRANSITION ZONE

2021 ◽  
Vol 16 (1) ◽  
pp. 31-46
Author(s):  
Larisa Elena PAVELUC ◽  
◽  
Alin MIHU-PINTILIE ◽  
Elena HUŢANU ◽  
Adrian GROZAVU
Keyword(s):  
Comparative Analysis ◽  
Transition Zone ◽  
Small Scale ◽  
Flood Events ◽  
European Network ◽  
Entire Region ◽  
Eastern Carpathians ◽  
Hydrological Hazards ◽  
Mitigation Effort ◽  
Heavy Rains

The European Network of Experimental and Representative Basins (ENERB) is the results of several experimental projects concerning the hydrological forecasting and flood mitigation effort which have been implemented within states member of European Union. In Romania, the hydrometric activity for ENERB it is currently composed of 14 representative basins (RB) of which the Trebeş-Negel (184 km2) was selected as RB for Eastern Carpathian and Subcarpathian transition zone. Located in one of the most affected territories by hydrological hazards, the Trebeş-Negel RB reacted as a small-scale flood sensor for the entire region. Using the well-documented discharge and pluviometric database collected at five gauge stations within the study area, we develop the first comparative analysis of historical flood events that occurred in the Trebeş-Negel RB post-1990. Five exceptional floods were selected: flood events from July 2 to July 8, 1991; flood events from June 16 to June 22, 1992; flood events from July 11 to July 14, 2005; flood events from July 26 to July 31, 2010; and flood events from June 28 to July 1, 2018. All flood events envisaged were caused by heavy rains, when significant amounts of precipitations were recorded which sometimes exceeded 100 mm/day.

Reasons to strike first

2019 ◽  
Vol 42 ◽  
Author(s):  
William Buckner ◽  
Luke Glowacki
Keyword(s):  
Intergroup Conflict ◽  
Small Scale

Abstract De Dreu and Gross predict that attackers will have more difficulty winning conflicts than defenders. As their analysis is presumed to capture the dynamics of decentralized conflict, we consider how their framework compares with ethnographic evidence from small-scale societies, as well as chimpanzee patterns of intergroup conflict. In these contexts, attackers have significantly more success in conflict than predicted by De Dreu and Gross's model. We discuss the possible reasons for this disparity.

Exploring Coronal Structures with SOHO

2000 ◽  
Vol 179 ◽  
pp. 403-406
Author(s):  
M. Karovska ◽  
B. Wood ◽  
J. Chen ◽  
J. Cook ◽  
R. Howard
Keyword(s):  
Solar Corona ◽  
Image Enhancement ◽  
Coronal Mass Ejections ◽  
Dynamical Evolution ◽  
Small Scale ◽  
Low Contrast ◽  
Contrast Structures ◽  
Scale Structures ◽  
Small Scale Structures ◽  
Coronal Structures

AbstractWe applied advanced image enhancement techniques to explore in detail the characteristics of the small-scale structures and/or the low contrast structures in several Coronal Mass Ejections (CMEs) observed by SOHO. We highlight here the results from our studies of the morphology and dynamical evolution of CME structures in the solar corona using two instruments on board SOHO: LASCO and EIT.

Scanning tunneling microscopy and atomic force microscopy: New tools for biology

1989 ◽  
Vol 47 ◽  
pp. 778-779
Author(s):  
CE Bracker ◽  
P. K. Hansma
Keyword(s):  
Physical Property ◽  
Scanning Probe ◽  
Scanning Tunneling ◽  
Small Scale ◽  
Tunneling Microscopy ◽  
Force Microscopy ◽  
New Family ◽  
Small Probe ◽  
Atomic Force ◽  
Transmission Electron

A new family of scanning probe microscopes has emerged that is opening new horizons for investigating the fine structure of matter. The earliest and best known of these instruments is the scanning tunneling microscope (STM). First published in 1982, the STM earned the 1986 Nobel Prize in Physics for two of its inventors, G. Binnig and H. Rohrer. They shared the prize with E. Ruska for his work that had led to the development of the transmission electron microscope half a century earlier. It seems appropriate that the award embodied this particular blend of the old and the new because it demonstrated to the world a long overdue respect for the enormous contributions electron microscopy has made to the understanding of matter, and at the same time it signalled the dawn of a new age in microscopy. What we are seeing is a revolution in microscopy and a redefinition of the concept of a microscope.Several kinds of scanning probe microscopes now exist, and the number is increasing. What they share in common is a small probe that is scanned over the surface of a specimen and measures a physical property on a very small scale, at or near the surface. Scanning probes can measure temperature, magnetic fields, tunneling currents, voltage, force, and ion currents, among others.

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