九州大学-研究者情報 [寅丸敦志 (教授) 理学研究院地球惑星科学部門]

地質学と物質科学による巨大噴火の長期予測
キーワード：火山噴火　長期予測
2016.09～2026.09.

柱状節理の研究
キーワード：柱状節理
2000.03～2026.03.

結晶サイズ分布の逆問題
キーワード：火山噴火，噴火様式，マイクロライト、結晶化カイネティックス
2009.04～2026.04.

噴火様式遷移の支配要因の研究
キーワード：火山噴火，噴火様式，マグマの発泡，マグマだまりの構造
2009.04～2026.04.

アナログ実験による火山噴火現象の解明
キーワード：実験間欠泉、アナログ実験、短時間挙動、長時間挙動、火山性微動、噴火様式
2010.04～2026.04.

リーゼガングリングの研究
キーワード：リーゼガングリング、パターン遷移、周期構造、枝分かれ構造、DLA
1994.05～2026.05.

地質学的流れによる構造形成の地球科学と物理学
キーワード：変形、流動、拡散、streamline mixing、マントル対流、流紋岩、マグマ混合
1998.05～2026.05.

食材を用いた実験
キーワード：キッチン地球科学
1996.05～2026.05.

火成岩の岩石組織学とパターン形成
キーワード：マグマ、岩石、パターン形成、結晶化、発泡、非線形、核形成、反応拡散系
1996.05～2026.05.

火成作用の地球科学と物理学
キーワード：マグマ、カイネティックス、結晶化、発泡、火山噴火、２相流
2000.04～2026.12.

地震予知・噴火予知計画
2018.04～2023.03, 代表者：寅丸敦志, 九州大学
地震予知・噴火予知に資する研究を行う。.

地震予知・噴火予知計画
2013.04～2018.03, 代表者：寅丸敦志, 九州大学
地震予知・噴火予知に資する研究を行う。.

地震予知・噴火予知計画
2008.04～2013.03, 代表者：寅丸敦志, 九州大学
地震予知・噴火予知に資する研究を行う。.

主要著書

全てを見る→

1.	Atsushi Toramaru, Vesiculation and Crystallization of Magma: Fundamentals of the Volcanic Eruption Process, Springer Nature, https://doi.org/10.1007/978-981-16-4209-8, ISBN: 978-981-16-4209-8 Book series Advances in Volcanology An Official Book Series of the International Association of Volcanology and Chemistry of the Earth’s Interior, 2021.12.
2.	寅丸敦志, マグマの発泡と結晶化：火山噴火過程の基礎, 東京大学出版会, 2019.03, 火山噴火現象の解明に向けて，火山噴出物が記録しているマグマの発泡と結晶化の素過程を，平衡論と非平衡論の２つの物質科学的視点から包括的に解説．式の導出や背後の基本的物理にいたるまで丁寧に詳述している．火山国日本で将来の火山噴火災害に備える際の基本となる一冊．.
3.	O. Namur, B. Abily, Atsushi Toramaru, Layered Intrusions, Springer, 2015.01.

主要原著論文

全てを見る→

1.	Chrisian Huber, Atsushi Toramaru, Increase in magma supply to Sakurajima volcano’s (Japan) shallow magma chamber over the past 500 years, Geology, https://doi.org/10.1130/G51763.1, 2024.01.
2.	Atsushi Toramaru, Tsuyoshi Kichise, A New Model of Crystallization in Magmas: Impact of Pre‐Exponential Factor of Crystal Nucleation Rate on Cooling Rate Exponent and Log‐Linear Crystal Size Distribution, Journal of Geophysical Research: Solid Earth, https://doi. org/10.1029/2023JB026481, 10.1029/2023JB026481, 2023.10.
3.	Kyohei Sano, Atsushi Toramaru, Application of time–temperature–transformation and time–pressure–transformation diagrams for cooling- and decompression-induced crystallization to estimate the critical cooling rate required to form glassy obsidian, Journal of Volcanology and Geothermal Research, https://doi.org/10.1016/j.jvolgeores.2022.107643, Volume 435, March 2023, 2023.03.
4.	Gabriela Nogo Retnaningtyas Bunga Naen, Atsushi Toramaru, Saefudin Juhri, Kotaro Yonezu, Haryo Edi Wibowo, Rachmi Mustika Pertiwi Putri Gunawan, Tabegra Disando, Distinct pumice populations in the 74 ka Youngest Toba Tuff: Evidence for eruptions from multiple magma chambers, Journal of Volcanology and Geothermal Research, https://doi.org/10.1016/j.jvolgeores.2022.107643, Volume 437, May 2023, 2023.05.
5.	Ohashi, M. Maruishi, T., Toramaru, A., Coalescence of growing bubbles in highly viscous liquids, Geochemistry, Geophysics, Geosystems, e2022GC010618, 2022.10.
6.	Indranova Suhendro, Atsushi Toramaru, Agung Harijoko, Haryo Edi Wibowo, The origins of transparent and non-transparent white pumice: A case study of the 52 ka Maninjau caldera-forming eruption, Indonesia, Journal of Volcanology and Geothermal Research, https://doi.org/10.1016/j.jvolgeores.2022.107643, 431, 107643., 2022.07.
7.	Teshima, N., Toramaru, A., Ichihara, M., Precursory pressure oscillation in a laboratory geyser system, Journal of Volcanology and Geothermal Research, https://doi.org/10.1016/j.jvolgeores.2022.107613, 429, 107613., 2022.07.
8.	Takafumi Maruishi (丸石崇史), Atsushi Toramaru (寅丸敦志), Effect of bubble deformation on the coalescence of two ascending bubbles in a viscous liquid, Physics of Fluids, https://doi.org/10.1063/5.0082506, 2022.03.
9.	Masatoshi Ohashi1, Atsushi Toramaru, Atsuko Namiki, Coalescence of two growing bubbles in a Hele–Shaw cell, Scientific reports, https://doi.org/10.1038/S41598-022-05252-5, 2022.01.
10.	Indranova Suhendro, Atsushi Toramaru, Tomoharu Miyamoto, Yasuo Miyabuchi, Takahiro Yamamoto, Magma chamber stratification of the 1815 Tambora caldera-forming eruption, BULLETIN OF VOLCANOLOGY, 10.1007/s00445-021-01484-x, 83, 10, 83: 63, 2021.10.
11.	寅丸敦志, 小川裕江, 大橋正俊, 増山孝行, パンと軽石, 混相流, https://doi.org/10.3811/jjmf.2020.T012, 34, 3, 【特　集】地球惑星科学の混相流（1）－キッチン地球科学の視点から－, 2020.09.
12.	Ai HamadaAtsushi Toramaru, Analogue experiments on morphological transition from colonnade to entablature of columnar joints, Journal of Volcanology and Geothermal Research, 2020.07.
13.	Shunsuke YamashitaAtsushi Toramaru, Control of Magma Plumbing Systems on Long‐Term Eruptive Behavior of Sakurajima Volcano, Japan: Insights from Crystal‐Size‐Distribution Analysis, Dynamic Magma Evolution, Geophysical Monograph Series, 2020.07.
14.	Mizuki Nishiwaki, Atsushi Toramaru,, Inclusion of Viscosity Into Classical Homogeneous Nucleation Theory forWater Bubbles in Silicate Melts: Reexamination of Bubble Number Density in Ascending Magmas, Journal of Geophysical Research: Solid Earth, /10.1029/2019JB017796, 124, 8, 88250-8266, 2019.09, [URL], To evaluate the effect of melt viscosity on bubble nucleation, we formulated the homogeneous nucleation rate of water bubbles to explicitly include melt viscosity. The viscosity coefficient appears in the preexponential factor of the nucleation rate in terms of the Péclet number: the ratio of the bubble growth timescale by molecular diffusion and the viscous relaxation timescale. The preexponential factor is almost constant when viscosity is low (or a high Péclet number), whereas it linearly decreases with increasing viscosity (or a decreasing Péclet number) exceeding the crossover value of viscosity, under a given supersaturation. The crossover point depends on whether homogeneous or heterogeneous nucleation takes place.We numerically solved the evolution of bubble nucleation and growth processes in ascending magmas by using the new nucleation rate formula and a precise approximation of moment equations of the bubble size distribution function. The resultant bubble number density has two regimes, similar to the previous study, but the transition point between the diffusion-controlled regime and the viscosity-controlled regime moves to higher viscosity or higher decompression rates by 0.6 log units at the maximum. In the viscosity-controlled regime, the effect of the better approximation of bubble size distribution moment equations reduces bubble number density by a few orders of magnitude compared with the previous study. As a result of compiling the past laboratory experimental data, it turned out that all the experiments are conducted under the conditions equivalent to the diffusion-controlled regime.We propose an experimental condition to confirm the presence of the viscosity-controlled regime..
15.	Masatoshi Ohashi,Mie Ichihara,Atsushi Toramaru, Bubble deformation in magma under transient flow conditions, Journal of Volcanology and Geothermal Research, doi.org/10.1016/j.jvolgeores.2018.09.005, 364, 15, 59-75, 2018.09, [URL].
16.	Yu Iriyama, Atsushi Toramaru, Tetsuo Yamamoto, Theory for Deducing Volcanic Activity From Size Distributions in Plinian Pyroclastic Fall Deposits, Journal of Geophysical Research: Solid Earth, 10.1002/2017JB014782, 123, 3, 2199-2213, 2018.03, [URL], Stratigraphic variation in the grain size distribution (GSD) of plinian pyroclastic fall deposits reflects volcanic activity. To extract information on volcanic activity from the analyses of deposits, we propose a one-dimensional theory that provides a formula connecting the sediment GSD to the source GSD. As the simplest case, we develop a constant-source model (CS model), in which the source GSD and the source height are constant during the duration of release of particles. We assume power laws of particle radii for the terminal fall velocity and the source GSD. The CS model can describe an overall (i.e., entire vertically variable) feature of the GSD structure of the sediment. It is shown that the GSD structure is characterized by three parameters, that is, the duration of supply of particles to the source scaled by the fall time of the largest particle, t_s/t_M, and the power indices of the terminal fall velocity p and of the source GSD q. We apply the CS model to samples of the Worzel D ash layer and compare the sediment GSD structure calculated by using the CS model to the observed structure. The results show that the CS model reproduces the overall structure of the observed GSD. We estimate the duration of the eruption and the q value of the source GSD. Furthermore, a careful comparison of the observed and calculated GSDs reveals new interpretation of the original sediment GSD structure of the Worzel D ash layer..
17.	Kyohei Sano, Atsushi Toramaru, Cooling and crystallization of rhyolite–obsidian lava Insights from micron-scale projections on plagioclase microlites, Journal of Volcanology and Geothermal Research, 10.1016/j.jvolgeores.2017.05.012, 341, 158-171, 2017.07, [URL], To reveal the cooling process of a rhyolite–obsidian flow, we studied the morphology of plagioclase microlites in the Tokachi–Ishizawa lava of Shirataki, northern Hokkaido, Japan, where the structure of the lava can be observed from obsidian at the base of the flow to the innermost rhyolite. Needle-like micron-scale textures, known as “projections” occur on the short side surfaces of the plagioclase microlites. Using FE–SEM we discovered a positive correlation between the lengths and spacings of these projections. On the basis of the instability theory of an interface between melt and crystal, and to understand the length and spacing data, we developed a model that explains the positive correlation and allows us to simultaneously estimate growth rates and growth times. Applying the model to our morphological data and the estimated growth rates and growth times, we suggest that the characteristics of the projections reflect the degree of undercooling, which in turn correlates with lava structure (the obsidian at the margin of the flow experienced a higher degree of undercooling than the interior rhyolite). The newly developed method provides insights into the degree of undercooling during the final stages of crystallization of a rhyolitic lava flow..
18.	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.
19.	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..
20.	Takahiro Miwa, Atsushi Toramaru, Conduit process in vulcanian eruptions at Sakurajima volcano, Japan: Inference from comparison of volcanic ash with pressure wave and seismic data, Bulletin of Volcanology, 75 (2013) 685:DOI 10.1007/s00445-012-0685-y, 2013.01, To elucidate the conduit processes controlling the amplitude of air pressure waves (Apw) from vulcanian eruptions at the Sakurajima volcano, Japan, we examine ash particles emitted by eruptions preceded by swarms of lowfrequency B-type earthquakes (BL-swarms). We measure the water content of glassy ash, an indicator of shallow magma storage pressure, and vesicle textures, such as vesicle number density (VND). These data allow us to reconstruct the shallow conduit by comparing vesicularity with inferred pressure, and therefore depth, of magma storage. The results show that VND increases with depth, implying formation of a dense, outgassed magma cap underlain by more-vesicular, less-outgassed, magma. The VND and water content in the glassy ash positively correlate with the duration of BL-swarms, suggesting that such seismic signals reflect upward migration of deep gas- and vesicle-rich magma. Finally, it is determined that Apw positively correlates with VND, suggesting that the amplitude of the air pressure waves is controlled by the amount of accumulated gas- and bubble-rich magma below the dense magma cap..
21.	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..
22.	T. Miwa, M. Iguchi, A. Toramaru, Correlations of volcanic ash texture with explosion earthquakes from vulcanian eruptions at Sakurajima volcano, Japan, Journal of Volcanology and Geothermal Research, 10.1016/j.jvolgeores.2009.05.012, 184, 3-4, 473-486, 2009.07.
23.	Satoshi Noguchi, Atsushi Toramaru, Setsuya Nakada, Relation between microlite textures and discharge rate during the 1991–1995 eruptions at Unzen, Japan, Journal of Volcanology and Geothermal Research, Volume 175, Issues 1-2, 30 July 2008, Pages 141-155, 2008.11.
24.	Satoshi Noguchi, Atsushi Toramaru, Setsuya Nakada, Groundmass crystallization in dacite dykes taken in Unzen Scientific Drilling Project (USDP-4), Journal of Volcanology and Geothermal Research, Volume 175, Issues 1-2, 30 July 2008, Pages 71-81, 2008.11.
25.	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.
26.	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.
27.	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.
28.	S. Noguchi, A. Toramaru and T. Shimano, Crystallization of microlites and degassing during magma ascent: Constraints on the fluid mechanical behavior of magma during the Tenjo Eruption on Kozu Island, Japan, Bulletin of Volcanology, 68, 432-449, 2006. DOI: 10.1007/s00445-005-0019-4, 2006.02.
29.	津根　明, 寅丸敦志, 斜長石累帯構造が示すマグマ溜まりの分化過程, 火山, 5, 2004.11.
30.	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.
31.	A. Toramaru, T. Harada and T. Okamura, Experimental pattern transitions in a Liesegang system, Physica D, 183, 133-140, 2003.09.
32.	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.
33.	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.
34.	A. Toramaru, A. Iochi, Transition between periodic precipitation and tree-like crystal aggregates: a detail experimental study, Forma, 15, 365-376, 2000.01.
35.	A. Toramaru, A. Ishiwatari, M. Matsuzawa, N. Nakamura, S. Arai, Vesicle layering in solidified intrusive magma bodies: A newly recognized type of igneous structure, Bulletin of Volcanology, 10.1007/s004450050147, 58, 5, 393-400, 1996.12, We report a novel type of layering structure in igneous rocks. The layering structure in the Ogi picrite sill in Sado Island, Japan, is spatially periodic, and appears to be caused by the variation in vesicle volume fraction. The gas phase forming the vesicles apparently exsolved from the interstitial melt at the final stage of solidification of the magma body. We call this type of layering caused by periodic vesiculation in the solidifying magma body "vesicle layering." The presence of vesicle layering in other basic igneous bodies (pillow lava at Ogi and dolerite sill at Atsumi, Japan) implies that it may be a fairly common igneous feature. The width of individual layers slightly, but regularly, increases with distance from the upper contact. The layering plane is perpendicular to the long axes of columnar joints, regardless of gravitational direction, suggesting that the formation of vesicles is mainly controlled by the temperature distribution in the cooling magma body. We propose a model of formation of vesicle layering which is basically the same as that for Liesegang rings. The interplay between the diffusion of heat and magmatic volatiles in melt, and the sudden vesiculation upon supersaturation, both play important roles..
36.	A. Toramaru, Numerical study of nucleation and growth of bubbles in viscous magmas, Journal of Geophysical Research, 10.1029/94JB02775, 100, B2, 1913-1931, 1995.02, The nucleation and growth processes of bubbles in viscous magmas with a constant decompression rate have been numerically investigated based on a formulation which accounts for effects of viscosity, as well as diffusivity, interfacial tension, and decompression rate. The numerical solutions show two regimes in the nucleation and growth process, a diffusion-controlled regime and a viscosity-controlled regime, mainly depending on the decompression rate, initial saturation pressure and viscosity. The transition between the two regimes dramatically occurs when the value of the above parameter decreases below about 2 × 10 . In the viscosity-controlled regime abundant tiny bubbles (exceeding 10 (m )) form with a relatively high internal pressure. In basaltic eruptions the vesiculation is essentially controlled by diffusion, and the viscosity-controlled regime is limited to very high decompression rate and very small water content. When andesitic magma saturated by water at 10 MPa is decompressed through the propagation of rarefaction wave induced by a landslide, the vesiculation is controlled by the viscosity up to 100 m depth. In a rhyolitic magma for the same situation, vesiculation is controlled by the viscosity over the whole depth of the magma column. -from Author 3 14 -3.
37.	Atsushi Toramaru, Keisuke Ito, Shoichi Kai, The Liesegang model of the Titius-Bode's law, Forma, 6, 247-266, 1991.12.
38.	Atsushi Toramaru, Model of nucleation and growth of crystals in cooling magmas, Contributions to Mineralogy and Petrology, 10.1007/BF00307330, 108, 1-2, 106-117, 1991.07, The nucleation and growth of liquidus phases in cooling magmas at constant rates are modeled taking into account homogeneous nucleation, diffusion-limited growth, and depletion of crystallizing component from melt, and the temperature-dependent diffusivity. The formulation of governing equations shows that four dimensionless parameters, whose physical meanings are the nucleation difficulty, the fusion enthalpy, the ratio of the growth rate to the cooling rate, and the activation energy of diffusion, control the crystallization phenomena. The nucleation behavior with time (or temperature) is determined primarily by the competition between increasing nucleation rate with cooling and the reduced supersaturation with depletion by progressive growth of crystals previously nucleated. The maximum nucleation rate and the number density of crystals increase with decreasing interfacial tension and diffusivity, and with increasing fusion enthalpy and cooling rate. Quantitative expressions of the time or temperature interval for which the nucleation remains appreciable, the peak nucleation rate, the number density of crystals and the mean crystal radius are derived as functions of controlling parameters, and can be used to estimate the cooling rate or other unknown parameters from the number density of crystals of a rock. © 1991 Springer-Verlag..
39.	Atsushi Toramaru, Measurement of bubble size distributions in vesiculated rocks with implications for quantitative estimation of eruption processes, Journal of Volcanology and Geothermal Research, 10.1016/0377-0273(90)90045-H, 43, 1-4, 71-90, 1990.10, This paper outlines methods for determining a bubble size distribution (BSD) and the moments of the BSD function in vesiculated clasts produced by volcanic eruptions. It reports the results of applications of the methods to 11 natural samples and discusses the implications for quantitative estimates of eruption processes. The analysis is based on a quantitative morphological (stereological) method for 2-dimensional imaging of cross-sections of samples. One method determines, with some assumptions, the complete shape of the BSD function from the chord lengths cut by bubbles. The other determines the 1st, 2nd and 3rd moments of distribution functions by measurement of the number of bubbles per unit area, the surface area per unit volume, and the volume fraction of bubbles. Comparison of procedures and results of these two distinct methods shows that the latter yields rather more reliable results than the former, though the results coincide in absolute and relative magnitudes. Results of the analysis for vesiculated rocks from eleven subPlinian to Plinian eruptions show some interesting systematic correlations both between moments of the BSD and between a moment and the eruption column height or the SiO content of magma. These correlations are successfully interpreted in terms of the nucleation and growth processes of bubbles in ascending magmas. This suggests that bubble coalescence does not predominate in sub-Plinian to Plinian explosive eruptions. The moment-moment correlations put constraints on the style of the nucleation and growth process of bubbles. The scaling argument suggests that a single nucleation event and subsequent growth with any kind of bubble interaction under continuous depressurization, which leads to an intermediate growth law between the diffusional growth (R ∝ t ) at a constant depressurization rate and the Ostwald ripening (R ∝ t ) under a constant pressure, where R and t are the mean radius of bubble and the effective time of diffusion respectively, occurred in the eruptions. It is emphasized that the BSD in vesiculated rocks from terrestrial volcanoes can be used to estimate quantitatively eruption processes such as the initial saturation pressure and magma ascent velocity in a volcanic conduit. © 1990. 2 m m m 2 3 1 3.
40.	Atsushi Toramaru, Formation of propagation pattern in two‐phase flow systems with application to volcanic eruptions, Geophysical Journal, 10.1111/j.1365-246X.1988.tb06707.x, 95, 3, 613-623, 1988.12, The hydrodynamic behaviour of a two‐phase system with different densities and viscosities is investigated, assuming that both phases are continuous phases and incompressible and that no phase change occurs. Mass and momentum conservation equations describe the relative motion of the two phases under the gravitational force when the inertia term is not negligible. Using the derived equations the stability of a spatially constant structure along gravity is examined in the one‐dimensional case for an infinite system without boundaries, where the basic state is taken as constant velocity and volume fractions. Two special cases are considered: the first is a gas‐liquid system where the density of one of the phases is neglected; the second is a deformable solid‐liquid system where the densities of the two phases are taken to be the same except for the calculation of the buoyancy force. The linear stability analysis shows that a small perturbation always generates a propagating wave which grows unstably with a characteristic wavelength. Since the spatially uniform structure of a two‐phase system is always unstable, the growth pattern should be observed in nature if the growth rate and spatial scale of the system are suitable. The dependence of the wavelength and growth rate on parameters is divided into two regimes. In one regime the wavelength, which equals the compaction length, and growth rate depend on the typical pore size. In the other regime, on the other hand, they do not depend on the typical pore size but only on the kinematic viscosity of the liquid phase and the volume fraction, given the frictional law. Which regime a real system chooses depends on a nondimensional parameter. The first case (gas—liquid system) is applied to magma effusion in an eruption‐style volcano. The system consisting of a silicate liquid phase and a gas phase can have a wavelength from metres to tens of metres and a growth rate from the order of less than a second to 1 week depending on viscosities, typical pore size and volume fraction. As a result, the rhythm and discreteness of magma effusion observed at volcanic eruptions may be explained by the mechanism presented here. The theory provides a relation between the observed period of the magma effusion rate, the mixture exit velocity of gas plus magma and the volume fraction of magma, given the frictional law. Using the relation, the mixture exit velocity is estimated from the observed period for the 1986 Izu‐Oshima eruption. The applicability to partially molten systems in the mantle and the core and basic assumptions are discussed. Copyright © 1988, Wiley Blackwell. All rights reserved.
41.	Toramaru, A, N. Fujii, Connectivity of melt phase in a partially molten peridotite, J. Geophys. Res., 91, 9239-9252, 1986.10.

主要総説, 論評, 解説, 書評, 報告書等

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主要学会発表等

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1.	丸石崇史寅丸敦志, 浮力による気泡の変形と合体の理論的研究, 日本火山学会, 2021.10.
2.	寅丸敦志, マグマの発泡と結晶化, 日本火山学会, 2018.09.
3.	Atsushi Toramaru,Shunsuke Yamashita , Method of CSD for long-term prediction of eruptions at Sakurajima volcano, Cities on Volcanoes 10, 2018.09.
4.	寅丸敦志、山下俊介, 巨大噴火の長期予測への戦略, JpGU-AGU Joint Meeting 2017, 2017.05.
5.	寅丸敦志, マグマにおける結晶成長と結晶中の累帯構造, JpGU-AGU Joint Meeting 2017, 2017.05.
6.	Toramaru A, Masotta M, Model of Bubble Coalescence in Initially Mono-Dispersed System and Experimental Observations, Goldschmidt Conference, 2016.06.
7.	Atsushi Toramaru, 吉瀬毅, Log-linear CSDの新しい結晶化カイネティックモデル, 日本鉱物科学会, 2015.09.
8.	Atsushi Toramaru, Tsuyoshi Kichise, New model of crystallization kinetics and CSD: its applications to Shinmoedake 2011 eruptions, Goldschmidt conference 2015, 2015.08.
9.	寅丸敦志, 濱田藍, 柱状節理形成過程における熱弾性の基本的側面, 地球惑星科学連合大会, 2015.05.
10.	寅丸敦志, マグマの結晶化モデルにおける問題点について, 日本火山学会秋季大会, 2013.09.
11.	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.
12.	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.
13.	寅丸敦志, 火山噴出物の組織解析についての展望噴出物のミクロな組織からマクロなダイナミクスを理解するための手法について , 地球惑星科学連合大会, 2013.05, 噴出物の組織や化学組成のミクロな特徴は、目に見えない火道中でのマグマの運動の歴史を記録している。その記録を、化学組成・組織のデータから定量的に読み解く手法の開発が、この10年で格段に進んできた。その中には、マイクロライト組成、気泡やマイクロライトのサイズ分布に基づくマグマの飽和深度や上昇の際の減圧速度、マグマ滞在時間の推定などが含まれる。そして、その応用の成果として、リアルタイムで取得されている地表での地球物理的・化学的観測データと併せて、マグマが移動を開始してから噴出に至るまでのマグマの運動のイメージがより現実的に描けるようになってきた。こうした手法の発達は、噴出物の組織や化学組成を再現する実験的研究、観察・測定技術、実験結果や観察結果を物理化学的に解釈する理論的研究が、相補的に進歩してきた結果である。しかし、そうした進歩にもかかわらず、物質科学的手法を利用して、マグマの運動を的確に予想し、また、地質学的情報と併せて、過去の噴火の推移を定量的に復元できるまでには至っていない。ましてや、噴出量や噴火様式の推移の指標となる観測量の発見さらにはそれらの間の関係性など、火山噴火研究の一つの目標である噴火現象に関する物質科学的基本法則の発見には程遠い状況である。こうした困難を意識したうえで、物質科学研究の現状を省みると、天然で見られる噴出物の組織や化学組成の特徴が定性的にも定量的にもおおかた理解できた訳では決してなく、その背後にある根本的な問題が数多く残されていることに気づく。例えば、気泡やマイクロライトのサイズ分布関数のさまざまな形の成因や、非平衡下で結晶化する際の結晶組成決定性の問題である。本講演では、それらの問題の一つであるマイクロライトの結晶サイズ分布（CSD）に関して現状と展望を語る。 CSDは、指数分布すなわち、横軸を結晶サイズ、縦軸をpopulation density（決まった結晶サイズの範囲にある結晶数）として片対数でプロットすると、直線的になる場合がしばしばある。指数分布になるには、時間の指数関数として結晶核形成速度が増加する必要があるが、その増加速度を決める時間の係数は、均質核形成理論と減圧結晶化実験から予想される値よりはるかに小さくなる。また、多くのCSDは、大きいサイズでは指数分布よりpopulation densityが大きくなり、小さいサイズでは小さくなり、指数分布からずれてくる。すなわち、指数分布のCSDは近似でしかなく、それと数学的に一致することの物理的理由を探ることに定量的意味はない。とはいえ、CSDが、結晶の核形成と成長の歴史を表していることに間違いはない。物理的にはCSDは、実効的冷却速度が大きくなれば傾きの絶対値と切片の値が大きくなる（細かい結晶が沢山形成することに相当する）から、傾きや切片の値は、時間スケールすなわち実効的冷却速度（減圧速度）や滞在時間の指標である。それ故、よく用いられるCSD法では、指数分布を仮定して、状況証拠的時間スケールを与えて、その傾きから結晶成長速度を推定するが、これは本末転倒と言える。講演者らは、結晶化のモデルを順問題として解き、その結果から、実効的冷却速度と結晶数密度（CSDの0次のモーメント）の関係を導き、それを用いて、結晶数密度から、実効的冷却速度を推定する方法を提案した。この方法では、核形成速度最大時の瞬間的な線形の冷却速度や減圧速度が推定できるが、CSDの最大値付近の接線の傾きと切片の情報しか利用していないことになる。しかし、CSDの形自体に、マグマの温度・圧力の時間変化に関してもっと多くの情報があるはずである。その情報を定量的に推定するために、Lagrange的なCSDの記述方法から出発し、温度圧力の非線形な時間変化を特徴づけるパラメータを未知数とした、逆問題を定式化する。講演では、その定式化と応用を示し、CSDインバージョンンの方法を提案しその可能性について議論したい。 .
14.	入山宙, 寅丸敦志, 山本哲生, テフラ堆積物の粒径サイズ分布の高さ変化と初期サイズ分布の関係, 地球惑星科学連合大会, 2013.05.
15.	吉瀬毅, 寅丸敦志, 過冷却によって結晶成長する斜長石マイクロライトのサイズ分布と化学組成の関係について, 地球惑星科学連合大会, 2013.05.
16.	Atsushi Toramaru Kazuki Maeda, STATISTICAL CHARACTERISTICS OF EXPERIMENTAL GEYSERS: FACTORS CONTROLLING MASS　AND STYLE OF ERUPTION, American Geophysical Meeting Fall Meeting 2011, 2011.12.
17.	寅丸敦志前田一樹, 実験間欠泉における噴出様式と噴出量の数理モデル, 日本火山学会秋季大会, 2011.10.
18.	Atsushi Toramaru, Factors controlling styles and intensity of eruption from the textural and chemical analysis of bubbles and microlites, 2011 International Union of Geodesy and Geophysics (IUGG) General Assembly, 2011.07.
19.	寅丸敦志市原美恵, Rayleigh-Plesset 方程式と流体系振動方程式のカップリング , 地球惑星科学連合大会, 2011.05.
20.	Atsushi Toramaru, Pattern transition in a precipitation-diffusion system in gels: Insights into pattern transition in thermal fracturing of columnar joints, CNRS/JSPS Joint Seminar on Deformation, Flow and Rupture of Soft Matter, 2010.07.
21.	寅丸敦志、前田一樹、児浪愛, 間欠泉実験からみた火山噴火の長期予測・短期予測可能性, 産業技術総合研究所　火山談話会, 2010.05.
22.	Atsushi Toramaru Mitsuo Matsumoto, Occurrence of cyclic layering: natural examples and numerical simulations, American Geophysical Meeting Fall Meeting 2009, 2009.12.
23.	寅丸敦志松本光央, 貫入岩におけるCyclic Layeringの特徴と発達条件, 日本火山学会, 2009.10.
24.	Atsushi Toramaru, Mitsuo Matsumoto, Makiko Yoshida, Cyclic layering in solidified magma bodies: Pattern　formation in the diffusion-crystallization system, IAVCEI2008, 2008.08.
25.	Atsushi Toramaru, Takahiro Miwa, Microlite systematics: Origin and implications for the conduit flow, IAVCEI2008, 2008.08.
26.	寅丸敦志・山内沙耶香, リーゼガングパターンに及ぼす電場の影響, 地球惑星科学連合大会, 2008.05.
27.	寅丸敦志・三輪学央, 結晶数密度―結晶度マイクロライト・システマティックスの意味, 地球惑星科学連合大会, 2008.05.
28.	寅丸敦志, 減圧するマグマにおける膨張する気泡の暴走合体, 日本火山学会秋季大会, 2007.11.
29.	Toramaru, A., Miwa, T, Vesiculation and Crystallization under Constant Amout of Decompression: Numerical Study and its comparison with Laboratory Experiments, COV5 (Cities on Volcano 5th meeting), 2007.11.
30.	Atsushi Toramaru, Experimental study of pattern transition in a Liesegang Ring, Workshop on Experimental and Theoretical Studies of Precipitation Patterns, 2007.06.
31.	寅丸敦志, マグマの発泡によって励起される低周波地震, 地球惑星科学関連学会合同大会, 2007.05.
32.	Atsushi Toramaru, BND (bubble number density) decompression rate meter for explosive volcanic eruptions, American Geophysical Union, Fall Meeting, 2006.12, [URL].
33.	Atsushi Toramaru, Satoshi Noguchi, Shinobu Oyoshihara, Akira Tsune, MND(microlite number density) water exsolution rate meter, American Geophysical Union, Fall Meeting, 2006.12.
34.	寅丸敦志, Bubble Number Density (BND) Decompression Rate Meter, International workshop on volcanic explosion in KOBE, Japan, 2005.01.

所属学会名

アメリカ地球物理学連合

形の科学会

日本鉱物学会

日本火山学会

学協会役員等への就任

2010.07～2012.06, 日本火山学会, 理事.

2006.04～2008.03, 日本火山学会, 各賞選考委員会.

2006.04～2008.03, 日本火山学会, 大会運営委員.

学会大会・会議・シンポジウム等における役割

2021.12.13～2021.12.17, American Geophysical Union Fall Meeting 2021, Session convener.

2016.06.26～2016.07.01, Goldschmidt 2016, Session convener.

2015.05.24～2015.05.28, Japan Geoscience Union Meeting 2015, 座長（Chairmanship）.

2013.09.29～2013.10.01, 日本火山学会2013年度秋季大会, 座長（Chairmanship）.

2005.02, Unzen International Workshop at Shimabara, 座長（Chairmanship）.

2015.05.24～2015.05.27, 日本地球惑星科学連合2015年大会, Co-convener.

学会誌・雑誌・著書の編集への参加状況

2010.07～2014.06, 日本火山学会誌「火山」, 国内, 編集委員長.

学術論文等の審査

年度	外国語雑誌査読論文数	日本語雑誌査読論文数	国際会議録査読論文数	国内会議録査読論文数	合計
2015年度	2	3			5
2014年度	3				3
2013年度	3				3
2012年度	4				3
2010年度	3				3
2009年度	2	1			3
2007年度	6	1			7
2006年度	1	0	0	0	1
2005年度	0	1	0	0	1
2004年度	3	2	0	0	5

海外渡航状況, 海外での教育研究歴

University of Lausanne, Switzerland, 2016.04～2016.04.

St Helens 火山, Washington, USA, USGS Cascades Volcano Observatory, Washington, USA, Newberry crater, Oregon, USA, UnitedStatesofAmerica, 2015.09～2015.09.

St Helens 火山, Colombia River Basalt, Yellowstone, Stillwater igneous complex, UnitedStatesofAmerica, 2010.09～2010.09.

Ecole Normale Supérieure de Lyon, France, 2010.07～2010.07.

University of Bristol, UnitedKingdom, 2001.03～2001.11.

Arizona State University, UnitedStatesofAmerica, 1991.03～1993.03.

外国人研究者等の受入れ状況

2023.03～2023.05, Brown University (USA), Switzerland.

日本火山学会賞, 日本火山学会, 2018.05.


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