Kyushu University Academic Staff Educational and Research Activities Database
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Atsushi Toramaru Last modified date:2018.06.21

Professor / Dynamics, Structure and Evolution of the Earth and Planets
Department of Earth and Planetary Sciences
Faculty of Sciences


Graduate School
Undergraduate School
Other Organization


Homepage
http://ganseki3.geo.kyushu-u.ac.jp/index.html
Hope page of Group of Physics of magmatic processes, Petrology and Chemical geodynamics .
Academic Degree
Doctor of Science
Field of Specialization
Volcanology, Physics of Magmatic Processes, Igneous Petrology, Sciences on Form
Outline Activities
1.Research
1-1.Study on the dynamics of igneous processes:Igneous processes are all processes concerning magmas sucha as the generation, segregation and migration processes of melts in the mantle, phenomena occuring in magma chambers, the magma intrusion into the crust, and the volcanic eruption. I study them from the view points of material science and physics; specially, the kinetics of crystallization and vesiculation (formation of bubbles in magmas) of magmas and the eruption mechanisms.
1-2.Study on the formation of igneous rock texture:Igneous rocks which are formed by the solidification of magmas, shows a wide variety of texture. "Texture" means the pattern characterized
by the geometrical interrelation among constituent minerals. I study the texture of igneous rocks from view points of the quantitative description of textures and the understandig of a fundamental process of crystallization during the magma solidification.
1-3.Study on the pattern formation: Interesting patters in natures are ubiquitous. Especially, I theoretically and experimentally study various patterns which are geologically interesting: the columnar joint formation by the solidification of magmas, the Liesegang ring phenomena as a kind of diffusion-reaction system, the layering formation by the flow of rocks or magmas.

2.Education
I contribute the education through the colaborating researches as mentioned above with students. Three undergraduate and two graduate classes, seminars, the field survey, laboratory experiments, and discussion.

3.Social activities
On the homepage, I make a propaganda of results of researches and the enlightenment.
Research
Research Interests
  • Study on the method of long-term prediction of large volcanic eruption by geology and material science
    keyword : volcanic eruption Long-term prediction
    2016.09~2026.09.
  • Study of columnar joint
    keyword : columar joint
    2000.03~2026.03.
  • An inverse method of CSD
    keyword : volcanic eruption, eruption style,microlite, crystallization kinetics
    2009.04~2026.04.
  • Study of factors controlling temporal change of eruption styles during volcanic eruption
    keyword : volcanic eruption, eruption style, vesiculation of magma, structure of magma chamber
    2009.04~2026.04.
  • Study on volcanic eruption using analog experiments
    keyword : experimental geyser, analog experiment, short term behavior, long term behavior, volcanic tremor, eruption style
    2010.04~2026.04.
  • Experimental and theoretical study of Liesegang ring
    keyword : Liesegang ring, pattern transition, periodic structure, branching structure, DLA
    1994.05~2026.05Experimental study of Liesegang ring. Using PbI2 precipitation system, I examine the precipitation patterns such as periodic pattern and branching structure, and the transtion between them, the influence of electric field on the pattern..
  • Earth science and physics on the structure formed by geological flows.
    keyword : deformation, flow, diffusion, streamline mixing, mantle convection, rhyolite, magma mixing
    1998.05~2026.05Physics and Petrological study on the layering structure formed by the deformation of magmas or rocks..
  • Kitchin experiments
    keyword : Kitchin earth science
    1996.05~2026.05Analogue experiments using material in kitchen..
  • Pattern formation and texture of igneous rocks
    keyword : magma, rock, pattern formation, crystallization, vesiculation, nonlinearity, nucleation, diffusion-reaction system
    1996.05~2026.05Texture of igneous rocks: the physics of ingeous textures and the crystallization of magmas..
  • Physics and earth science of magmatic processes
    keyword : magma, kinetics, crystallization,vesiculation,volcanic eruption, two-phase flow
    2000.04~2026.12Physics of magmatic processes: the study of the elemental prcoesses such as melting, crystallization, convection and vesiclutation included in magmatic processes from the generation of magmas at the mantle to the eruption on the surface ..
Academic Activities
Papers
1. Atsushi Toramaru, On the second nucleation of bubbles in magmas under sudden decompression, EARTH AND PLANETARY SCIENCE LETTERS, 10.1016/j.epsl.2014.07.035, 404, 190-199, 2014.10.
2. Atsushi Toramaru, 前田一樹, Mass and style of eruptions in experimental geysers, Journal of Volcanology and Geothermal Reserches, 257 (2013) 227–239., 2013.04, In the present study, we conducted laboratory experiments of geysers to reproduce the time predictability of
natural geysers in Yellowstone and other geothermal areas. We measured pressure and temperature in a hot
water chamber, flux from a cold water reservoir, and mass erupted by each eruption (total number of eruptions
are up to 100), varying experimental conditions such as the heating rate, water quality, and system
geometry. We observed two styles of eruptions, “jet” and “flow” depending on the maximum height reached.
Under some conditions, only jet events occurred, while under other conditions, jet and flow events
co-occurred. Based on the statistical analysis of the erupted mass, an experiment setup that produces only
jet events exhibits a narrower frequency distribution with a relatively large average mass. As the proportion
of flow events increases, the frequency distribution of the erupted mass widens with relatively small average
mass. The temperature measurements indicated that jet-dominated experimental setups had smaller
temperature fluctuations than flow-dominated setup. We proposed a triggering condition involving boiling
of water that defined the onset of an eruption. We assumed two thresholds of the efficiency of decompression
boiling that defined explosivity and eruption development on the basis of hydrodynamic energetics. Using
the triggering condition and the two thresholds, to explain experimental correlations between erupted
mass, eruption style, and the magnitude of thermal fluctuation, we conducted a Monte Carlo simulation in
a square consisting of 256 × 256 parcels with the superheating temperature as a stochastic variable by a
Gaussian probability density function (PDF). The results showed that when the PDF has a larger average
and smaller standard deviation, the event tends to be explosive and large fraction of water is evacuated, as
in jet events. Decreasing the average temperature or increasing the standard deviation of the PDF shifts the
events to an explosive style followed by an effusive event and to an event that produces only effusive flow.
This transition of eruption styles from explosive to effusive and the relationship with the erupted mass is
consistent with results of the laboratory experiments, suggesting that the spatial distribution pattern of
supersaturated portions just prior to an eruption is a factor controlling the style and transition of the
eruption..
3. A. Toramaru and M. Matsumoto, Numerical experiment of cyclic layering in a solidified binary eutectic melt, Journal of Geophysical Research, VOL. 117, B02209, doi:10.1029/2011JB008204, 2012, 2012.02, In shallow magmatic intrusions, a characteristic layering structure (hereafter referred to as cyclic layering) can sometimes be observed.
This cyclic layering is different from what is observed as rhythmic layering caused by gravity.
Here, we present examples of cyclic layering in Japan and Scotland.
The cyclic layering is visualized as differential weathering in response to the differential stiffness caused by textural variations such as those in the volume fraction, number density, and size of vesicles or crystals.
The spacing of layers seems to increase according to a geometric progression, like as in Liesegang bands of a diffusion-precipitation system.
Their geological occurrences suggest an origin in which the interplay between double diffusion (mass and heat) and the kinetics of crystallization or vesiculation has an important role.
In order to understand the development condition for cyclic layering and the characteristics of textural variations, such as the spacing of layering in crystallized multi-component melts by conductive cooling, we carried out a numerical experiment on the 1D crystallization process of a binary eutectic melt.
This simulation took into account the cooling from contact with country rock as well as the compositional and thermal diffusion and the kinetics of diffusion-limited crystallization.
The governing equations include dimensionless control parameters describing the relative importance of thermal diffusion or compositional diffusion (Lewis number, $Le$) and the effective latent heat release (Stefan number, $St$).
From the results of the numerical experiments, it was found that the layering develops through eutectic oscillation (compositional and thermal oscillation below the eutectic point), suggesting that the bi-activating condition, whereby both phases cooperatively activate their crystallization rates, is essential for the development of layering.
No layering is observed at the margin, and the length of the region with no layering increases exponentially with decreasing $St$.
The amplitude of textural oscillation decreases with decreasing $St$.
Thus, practically no layering develops at small latent heat release.
Three types of layering structure or oscillatory profiles of spatial texture are observed (short, long and multiple types), depending mainly on $Le$.
Realistic values of $Le$ and $St$ suggest that natural cyclic layering is the multiple or long type of layering.
Assuming that the spacing of natural layering corresponds to the distance between adjoining local maxima of textural quantities, such as crystal number density or mean crystal radius, the spacing in numerical experiments is mathematically well described by a geometric progression with common ratios that are functions of the controlling parameters,namely $Le$, $St$, nucleation barrier, and crystal growth rate scale.
The common ratios converge with increasing $Le$ to constants in the range of approximately 1.02 - 1.05, which is similar to the range of the natural observations.
Experiments with no latent heat release by the second-phase simulated vesicles show similar oscillatory behaviors, suggesting that the latent heat release of the first crystallizing phase is an essential factor for the development of vesicle layering.
Applying the results to vesicle layering, we propose a revised formation scenario in which the thermal effect of first-phase crystallization below the eutectic point dominates the effect of volatile diffusion..
4. A. Toramaru, T. Miwa, Vesiculation and crystallization under instantaneous decompression: Numerical study and comparison with laboratory experiments, Journal of Volcanology and Geothermal Research, Volume 177, Issue 4, 20 November 2008, Pages 983-996
, 2008.11.
5. Toramaru, A., S. Noguchi, S. Oyoshihara, A. Tsune, MND(microlite number density) water exsolution rate meter, Journal of Volcanology and Geothermal Research, Volume 175, Issues 1-2, 30 July 2008, Pages 156-167
, 2008.07.
6. A. Toramaru, BND (bubble number density) decompression rate meter for explosive volcanic eruptions, Journal of Volcanology and Geothermal Research, 154 (2006) 303–316, 2006.05.
7. A. Toramaru and T. Matsumoto, Columnar joint morphology and cooling rate: a starch-water mixture experiment, Journal of Geophysical Research, 109, B02205, doi:10.1029/2003JB002686, 2004.02.
8. A. Toramarau, A numerical experiment of crystallization for a binary eutectic system with application to igneous textures, J. Geophys. Res., 106, 4037-4060, 2001.03.
9. A. Toramaru, E. Takazawa, T. Morishita, and K. Matsukage, Model of layering formation in a mantle peridotite (Horoman, Hokkaido, Japan), Earth Planet Sci. Lett., 185, 299-313, 2001.02.
10. A. Toramaru, T. Harada and T. Okamura, Experimental pattern transitions in a Liesegang system, Physica D, 183, 133-140, 2003.09.
Presentations
1. 佐野恭平, 寅丸 敦志, 和田恵治, Textural analysis of obsidian lava flow in Shirataki, Northern Hokkaido, Japan, IAVCEI (International Association of Volcanology and Chemistry of the Earth's Interior)2013 Scientific Assembly, 2013.07.
2. 寅丸 敦志, Laboratory geyser; Insights into predictability of mass and style of eruptions, IAVCEI (International Association of Volcanology and Chemistry of the Earth's Interior)2013 Scientific Assembly, 2013.07.
3. Microlite systematics: Origin and implications for the
conduit flow.
4. The effect of electric field on the Liesegang pattern.
5. , [URL].
Educational
Educational Activities
Undergraduate classes
1.Phase diagrams and kinetics in petrology
2.Volcanology
3.Introductory class for field research
Graduate classes
1.Dynamic analysis in petrology