Characterization and correlation of the Hegawa‐Kasamori 5 tephra, a widespread tephra aged c . 450 ka associated with large‐scale pyroclastic flows from southern Kyushu, SW Japan

2019 ◽  
Vol 35 (1-2) ◽  
pp. 288-303 ◽  
Author(s):  
Fumikatsu Nishizawa ◽  
Takehiko Suzuki
Keyword(s):  
Large Scale ◽  
Pyroclastic Flows ◽  
Sw Japan

Flow behavior of large-scale pyroclastic flows ? Evidence obtained from petrofabric analysis

1989 ◽  
Vol 51 (2) ◽  
pp. 115-122 ◽  
Author(s):  
Tadahide Ui ◽  
Keiko Suzuki-Kamata ◽  
Rumi Matsusue ◽  
Kei Fujita ◽  
Hideya Metsugi ◽  
...  
Keyword(s):  
Large Scale ◽  
Flow Behavior ◽  
Pyroclastic Flows

scholarly journals Modelling erosion and deposition in geophysical granular mass flows

2021 ◽  
Vol 52 (1) ◽  
pp. 29-32
Author(s):  
Sylvain Viroulet ◽  
Chris Johnson ◽  
Nico Gray
Keyword(s):  
Debris Flows ◽  
Large Scale ◽  
Laboratory Experiments ◽  
Pyroclastic Flows ◽  
Small Scale ◽  
Snow Avalanches ◽  
Erosion And Deposition ◽  
Granular Rheology ◽  
Scale Models ◽  
Mass Flows

During hazardous geophysical mass flows, such as rock or snow avalanches, debris flows and volcanic pyroclastic flows, a continuous exchange of material can occur between the slide and the bed. The net balance between erosion and deposition of particles can drastically influence the behaviour of these flows. Recent advances in describing the non-monotonic effective basal friction and the internal granular rheology in depth averaged theories have enabled small scale laboratory experiments (see fig. 1) to be quantitatively reproduced and can also be implemented in large scale models to improve hazard mitigation.

Compressible particle-driven gravity currents

2001 ◽  
Vol 445 ◽  
pp. 305-325 ◽  
Author(s):  
MARY-LOUISE E. TIMMERMANS ◽  
JOHN R. LISTER ◽  
HERBERT E. HUPPERT
Keyword(s):  
Large Scale ◽  
Numerical Solutions ◽  
Volcanic Eruptions ◽  
Gravity Currents ◽  
Scale Height ◽  
Pyroclastic Flows ◽  
Water Model ◽  
Model Approximation ◽  
Particle Settling ◽  
Density Scale

Large-scale particle-driven gravity currents occur in the atmosphere, often in the form of pyroclastic flows that result from explosive volcanic eruptions. The behaviour of these gravity currents is analysed here and it is shown that compressibility can be important in flow of such particle-laden gases because the presence of particles greatly reduces the density scale height, so that variations in density due to compressibility are significant over the thickness of the flow. A shallow-water model of the flow is developed, which incorporates the contribution of particles to the density and thermodynamics of the flow. Analytical similarity solutions and numerical solutions of the model equations are derived. The gas–particle mixture decompresses upon gravitational collapse and such flows have faster propagation speeds than incompressible currents of the same dimensions. Once a compressible current has spread sufficiently that its thickness is less than the density scale height it can be treated as incompressible. A simple ‘box-model’ approximation is developed to determine the effects of particle settling. The major effect is that a small amount of particle settling increases the density scale height of the particle-laden mixture and leads to a more rapid decompression of the current.

scholarly journals GCOM-C (SHIKISAI) Second-generation Global Imager infrared observation of active volcanoes: Case studies from the Asia-Pacific region

2020 ◽  
Author(s):  
Takayuki Kaneko ◽  
Atsushi Yasuda ◽  
Kenji Takasaki ◽  
Shun Nakano ◽  
Toshitsugu Fujii ◽  
...  
Keyword(s):  
Case Studies ◽  
Large Scale ◽  
Second Generation ◽  
Lava Dome ◽  
Global Climate ◽  
Thermal Anomaly ◽  
Pyroclastic Flows ◽  
Asia Pacific ◽  
Small Scale ◽  
Infrared Observation

Abstract The GCOM-C (SHIKISAI) satellite was developed to understand the mechanisms of global climate change. The Second-generation Global Imager (SGLI) onboard GCOM-C is an optical sensor observing wavelengths from 380 nm to 12.0 µm in 19 bands. One of the notable features is that the resolution of the 1.63-, 10.8-, and 12.0-µm bands is 250 m, with an observation frequency of 2–3 days. To investigate the effective use and potential of the 250-m resolution of these SGLI bands in the study of eruptive activities, we analyzed four practical cases. As an example of large-scale effusive activity, we studied the 2018 Kilauea eruption. By analyzing the series of 10.8-µm band images using cumulative thermal anomaly maps, we could observe that the lava effused on the lower East Rift Zone, initially flowed down the southern slope to the sea, and then moved eastward. As an example of lava dome growth and generation of associated pyroclastic flows, the activity at Sheveluch between December 2018 and December 2019 was analyzed. The 1.63- and 10.8-µm bands were shown to be suitable for observing growth of the lava dome and occurrence of pyroclastic flows, respectively. We found that the pyroclastic flows occurred during periods of rapid lava dome expansion. For the study of an active crater lake, the activity of Ijen during 2019 was analyzed. The lake temperature was found to rise rapidly in mid-May and reach 38 °C in mid-June. We also analyzed the intermittent activities of small-scale Vulcanian eruptions at Sakurajima in 2019. The 1.63-µm band was useful for detecting activities that are associated with Vulcanian eruptions. Analytical results for these case studies demonstrated that the GCOM-C SGLI images are beneficial for observing various aspects of volcanic activity, and their real-time use may contribute to reducing eruption-related disasters.

scholarly journals Lahars in Java: Initiations, Dynamics, Hazard Assessment And Deposition Processes

2016 ◽  
Vol 21 (1) ◽  
Author(s):  
Franck Lavigne ◽  
Jean-Claude Thouret ◽  
Danang Sri Hadmoko ◽  
Bambang Sukatja
Keyword(s):  
Debris Flows ◽  
Large Scale ◽  
Debris Avalanche ◽  
Pyroclastic Flows ◽  
Direct Result ◽  
Small Scale ◽  
Average Intensity ◽  
Turbulent Regime ◽  
Eruptive Activity ◽  
High Concentration

Lahar has been applied as a general term for rapidly flowing, high-concentration, poorly sorted sediment-laden mixtures of rock debris and water (other than normal streamflow) from a volcano. Lahars are one of the most destructive phenomena associated with composite volcanoes, which are dominant in Java Island. Resulting deposits of lahar are poorly sorted, massive, made up of clasts (chiefly of volcanic composition), that generally include a mud-poor matrix. The aim of this research is threefold: to discuss the initiation of lahars occurrences, their dynamics, to assess the hazard and to analyse the deposition. Lahars are either a direct result of eruptive activity or not temporally related to eruptions. Syn-eruptive lahars may result from the transformation on pyroclastic flows or debris avalanches which transform to aqueous flows (e.g. at Papandayan in November 2002); They may be also generated through lake outburst or breaching (e.g. at Kelut in 1909 or 1966), and through removal of pyroclastic debris by subsequent heavy rainstorms. Post-eruptive lahar occurs during several years after an eruption. At Merapi, lahars are commonly rain-triggered by rainfalls having an average intensity of about 40 mm in 2 hours. Most occur during the rainy season from November to April. Non-eruptive lahars are flows generated without eruptive activity, particularly in the case of a debris avalanche or a lake outburst (e.g., Kelut). A lahar may include one or more discrete flow processes and encompass a variety of rheological flow types and flow transformations. As such, lahars encompass a continuum between debris flows and hyperconcentrated flows, as observed at Merapi, Kelut and Semeru volcanoes. Debris flows, with water contents ranging from 10 to no more than about 25% weight, are non-newtonian fluids that move as fairly coherent masses in what is thought to be predominantly laminar fashion. However, the relative importance of laminar versus turbulent regime is still debatable. Hyperconcentrated streamflows contain 25- to about 40%-weight-water; these flows possess some yield stress, but they are characteristically turbulent. Hazard-zone maps for lahar were produced for most of the the Javanese volcanoes, but these maps are on too small-scale to meet modern zoning requirements. More recently, a few large-scale maps (1/10,000 and 1/2,000-scale) and risk assessments have been completed for a few critical river systems at Merapi.

scholarly journals Large-scale experiments on the mechanics of pyroclastic flows: Design, engineering, and first results

2007 ◽  
Vol 112 (B4) ◽  
Author(s):  
Pierfrancesco Dellino ◽  
Bernd Zimanowski ◽  
Ralf Büttner ◽  
Luigi La Volpe ◽  
Daniela Mele ◽  
...  
Keyword(s):  
Large Scale ◽  
Pyroclastic Flows ◽  
Design Engineering ◽  
First Results

scholarly journals A new infrared volcano monitoring using GCOM-C (SHIKISAI) satellite: Applications to the Asia-Pacific region

2020 ◽  
Author(s):  
Takayuki Kaneko ◽  
Atsushi Yasuda ◽  
Kenji Takasaki ◽  
Shun Nakano ◽  
Toshitsugu Fujii ◽  
...  
Keyword(s):  
Large Scale ◽  
Lava Dome ◽  
Global Climate ◽  
Thermal Anomaly ◽  
Pyroclastic Flows ◽  
Asia Pacific ◽  
Small Scale ◽  
Effusive Activity ◽  
Lake Temperature ◽  
Satellite Applications

Abstract The GCOM-C (SHIKISAI) satellite was developed to understand the mechanisms of global climate change. The Second-generation Global Imager (SGLI) onboard GCOM-C is an optical sensor observing wavelengths from 380 nm to 12.0 μm in 19 bands. One of the notable features is that the resolution of the 1.63-, 10.8-, and 12.0-µm bands is 250 m, with an observation frequency of 2-3 days. To investigate the effective use and potential of the 250-m resolution of these SGLI bands in the study of eruptive activities, we analyzed four practical cases. As an example of large-scale effusive activity, we studied the 2018 Kilauea eruption. By analyzing the series of 10.8-μm band images using cumulative thermal anomaly maps, we could observe that the lava effused on the lower East Rift Zone, initially flowed down the southern slope to the sea, and then moved eastward. As an example of lava dome growth and generation of associated pyroclastic flows, the activity at Sheveluch between December 2018 and December 2019 was analyzed. The 1.63- and 10.8-µm bands were shown to be suitable for observing growth of the lava dome and occurrence of pyroclastic flows, respectively. We found that the pyroclastic flows occurred during periods of rapid lava dome expansion. For the study of an active crater lake, the activity of Ijen during 2019 was analyzed. The lake temperature was found to rise rapidly in mid-May and reach 38 °C in mid-June. We also analyzed the intermittent activities of small-scale Vulcanian eruptions at Sakurajima in 2019. The 1.63-µm band was useful for detecting activities that are associated with Vulcanian eruptions. Analytical results for these case studies demonstrated that the GCOM-C SGLI images are beneficial for observing various aspects of volcanic activity, and their real-time use may contribute to reducing eruption-related disasters.

Some comments about observations and image processing of comet 29P/Schwassmann-Wachmann 1

1999 ◽  
Vol 173 ◽  
pp. 243-248
Author(s):  
D. Kubáček ◽  
A. Galád ◽  
A. Pravda
Keyword(s):  
Image Processing ◽  
Large Scale ◽  
Harvard College ◽  
Oak Ridge ◽  
Large Scale Structures ◽  
Short Period Comet ◽  
Short Period ◽  
Scale Structures ◽  
Harvard College Observatory ◽  
Period Comet

AbstractUnusual short-period comet 29P/Schwassmann-Wachmann 1 inspired many observers to explain its unpredictable outbursts. In this paper large scale structures and features from the inner part of the coma in time periods around outbursts are studied. CCD images were taken at Whipple Observatory, Mt. Hopkins, in 1989 and at Astronomical Observatory, Modra, from 1995 to 1998. Photographic plates of the comet were taken at Harvard College Observatory, Oak Ridge, from 1974 to 1982. The latter were digitized at first to apply the same techniques of image processing for optimizing the visibility of features in the coma during outbursts. Outbursts and coma structures show various shapes.

Evolution of Large-Scale Coronal Structures

1994 ◽  
Vol 144 ◽  
pp. 29-33
Author(s):  
P. Ambrož
Keyword(s):  
Magnetic Field ◽  
Field Line ◽  
Large Scale ◽  
Coronal Magnetic Field ◽  
Source Surface ◽  
Solar Cycles ◽  
Characteristic Relationship ◽  
The Magnetic Field ◽  
Coronal Structures

AbstractThe large-scale coronal structures observed during the sporadically visible solar eclipses were compared with the numerically extrapolated field-line structures of coronal magnetic field. A characteristic relationship between the observed structures of coronal plasma and the magnetic field line configurations was determined. The long-term evolution of large scale coronal structures inferred from photospheric magnetic observations in the course of 11- and 22-year solar cycles is described.Some known parameters, such as the source surface radius, or coronal rotation rate are discussed and actually interpreted. A relation between the large-scale photospheric magnetic field evolution and the coronal structure rearrangement is demonstrated.

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