May 2025, https;kazan-g.sakura.ne.jp;age_tp;ml, Evolution of a large-scale phreatoplinian eruption: Constraints from the 40 ka caldera-forming eruption of Kutcharo volcano, eastern Hokkaido, Japan, J Volcanol Geotherm Res, 452, 108125., 日本火山学会
柴田翔平

Mar. 2025, Highlighted Papers of 2024, https://earth-planets-space.springeropen.com/highlighted-papers, Earth, Planets and Space (EPS)
Takeshi Hasegawa;Nobutatsu Mochizuki;Hidetoshi Shibuya;Ayumu Nishihara;Chie Kusu;Shohei Shibata;Makoto Okada;Kuniaki Nishiki;Yuki Sato

Sep. 2024, 研究奨励賞（受賞論文の共著、指導）, 福島県南部，二岐山火山の噴火史とマグマ供給系. 地質学雑誌, 129, 307–324., 日本地質学会
渡部将太

May 2023, Best Paper Award, Eruption Styles and Processes of the 7.6 ka Caldera-forming Eruption of Mashu Volcano, Eastern Hokkaido, Japan: Reconstruction of a High-resolution Eruption Sequence Based on Geologic, Petrologicand PaleomagneticMethods and Recognition of Low Aspect Ratio Ignimbrite (LARI), THE VOLCANOLOGICAL SOCIETY OF JAPAN
Takeshi HASEGAWA, Shohei S HIBATA, Tetuso KOBAYASHI, Nobutatsu M OCHIZUKI, Mitsuhiro NAKAGAWA and Hiroshi KISHIMOTO

Sep. 2021, 研究奨励賞（受賞論文のCorresponding author）, 栃木県北部，余笹川岩屑なだれ堆積物の層序・年代と運搬過程. 地質学雑誌，126, 293-310., 日本地質学会
菊地瑛彦

Sep. 2008, 日本地質学会研究奨励賞, 北海道東部，阿寒カルデラ周辺の前－中期更新世火砕堆積物の層序, 地質学雑誌, 113, 53-72., 日本地質学会
長谷川健

Preface: The 6^th International Conference on Environmental Resources Management (ICERM) 2024
Djati Mardiatno; Sayantan Das; Takeshi Hasegawa; Annisa Triyanti; Tsung-Yi Lin; Dian Nuraini Melati; Anabelle Moatty; Kyaw Zaya Htun, Anthropogenic pressure and climate change are the main issues of environmental degradation, posing significant challenges to sustainable landscape [1,2]. These issues are recognized as major global risks with long-lasting consequences [3]. Landscape management is an integrated approach that may be helpful to address these issues by combining policies and practices to address environmental degradation and promote sustainable land use planning [4]. This approach plays an important role in achieving sustainable livelihoods by integrating multiple objectives such as ecological, economic and social [5,6]. Proper landscape management can lead to numerous ecological benefits, including improved land restoration, increased forest cover, enhanced ecosystem services, and maintain the biodiversity [5,6,7]. In the economic and social context, land management can be beneficial for promoting food security, reducing vulnerability to climate change, and improving welfare [5,6,7].

Department of Environmental Geography, the Faculty of Geography Universitas Gadjah Mada, has a long history of conducting research on environmental management. The concept of sustainable land management aligns with the department’s research framework, which emphasizes the analysis of land, water, social, and economic factors to improve population welfare and reduce risk. To address current issues and discuss efforts related to sustainable land management, the department is organizing the 6^th International Conference on Environmental Resources Management (ICERM) to showcase the latest scientific advancements.

List of Conference Committee is available in this pdf., IOP Publishing
IOP Conference Series: Earth and Environmental Science, 20 Feb. 2025, [Reviewed]

Cooling timescale and process of welded facies of Youngest Toba Tuff, North Sumatra, Indonesia
Shohei Shibata; Gabriela Nogo Retnaningtyas Bunga Naen; Yasuaki Kaneda; Indranova Suhendro; Chie Kusu; Takeshi Hasegawa, Last, Abstract

The 74 ka Youngest Toba Tuff (YTT) super-eruption is one of the largest caldera-forming eruptions on Earth. Thick welded facies (~100 m) of the YTT are exposed 30 km northwest of the source caldera. In this outcrop, an entablature of columnar joints, consisting of multiple domains can be well observed. The domain is cracked by a vertical master joint (cooling plane), from which a chilled margin and many columnar joints developed laterally. In this study, the paleomagnetic method was applied to evaluate the cooling history and genetic processes of the YTT welded facies. Oriented samples were collected from both the cooling plane (CP) and the interior part of the domain (ID), and all samples were subjected to a thermal demagnetization experiment. Samples from CP and ID show slightly different directions that can be confirmed by the significance test. Compared to CP, the characteristic remanent magnetization (ChRM) mean direction of ID shows shallower inclination and northern declination (D_m=357.5°, I_m=2.2°, α₉₅=2.5°) that is consistent with previous data of YTT. The mean angular difference of CP and ID is calculated to be 3.2° ± 2.1°. To generate such an angular difference would take 22.8 ± 15.2 years, assuming the fastest changing rate of geomagnetic secular variation (0.14°/year). This suggests that there exists a time lag of tens of years for acquiring thermal magnetization between CP and ID. Temperature profiles of YTT calculated using the conductive cooling model support the result that the interior part of the ignimbrite remained hot at ~ 600 °C for 30 years after deposition. Based on these findings, we conclude that the slight difference in paleomagnetic directions indicates heterogeneity in cooling timescale between quenched (CP) and slowly cooled (ID) portions within thick the welded YTT., IOP Publishing
IOP Conference Series: Earth and Environmental Science, 20 Feb. 2025, [Reviewed]

Petrogenetic relationship of pre-caldera and caldera-forming magmas from Maninjau volcano, West Sumatera, Indonesia
Yasuaki Kaneda; Indranova Suhendro; Shohei Shibata; Gabriela Nogo Retnaningtyas Bunga Naen; Festus Tongwa Aka; Takeshi Hasegawa, Last, Abstract

The 220–250 km³ (VEI 7) caldera-forming eruption of Maninjau (West Sumatra, Indonesia) in 52 ±3 ka played a major role for changing the landscape in the Padang Volcanic Field. Besides forming thick and widespread ignimbrite plateau (especially in the vicinity of Bukttinggi), the eruption successfully exposed the stratigraphy of pre-caldera rocks which predominantly constructed of lava (hereafter referred to as somma lava). Since our knowledge regarding the relationship between the pre-caldera somma lavas and silicic caldera-forming activity is lacking, we aimed to study the petrological characteristics of these eruptive materials. Somma lavas are mostly classified as medium-K andesite to dacite (SiO₂ = 57–64 wt.%) except for one rhyolitic sample (SiO₂ = 77 wt.%). Although whole-rock chemistry of somma lavas largely shows coherent compositional trends that a priori suggest mixing with caldera-forming magmas, there are considerable compositional gaps between them on some SiO₂ against incompatible-element (e.g., Sr and Zr) diagrams. Rayleigh fractionation models suggest that it is difficult to generate the caldera-forming silicic magma by differentiation of somma lava magma. Considering the incoherences of petrological and chronological features between Maninjau somma lavas and ignimbrites, we suggest that the caldera-forming large silicic magma evolved as an independent system after the termination of pre-caldera magmatism., IOP Publishing
IOP Conference Series: Earth and Environmental Science, 20 Feb. 2025, [Reviewed]

Volcanic history and magma systems of Lake Monoun Polygenetic Maar, Noun Plain, Western part of the Cameroon Volcanic Line: Constraints from stratigraphy, chronology and geochemistry
Linus Anye Nche; Takeshi Hasegawa; Festus Tongwa Aka; Takeshi Ohba; George Teke Mafany; Károly Németh; Yasuo Miyabuchi; Yasuaki Kaneda; Asobo Nkengmatia Elvis Asaah; Patrick Mendi Wajiba; Caroline Neh Ngwa; Joseph Legrand Tchop; Pauline Wokwenmendam Nguet; Ntepe Nfomou; Cheo Emmanuel Suh; Wilson Yetoh Fantong; Farouk Oumar Mouncherou, Elsevier BV
Journal of Volcanology and Geothermal Research, Jan. 2025, [Reviewed]

Paleomagnetic study of the 30 ka Aira caldera-forming eruption and 60–45 ka Iwato pyroclastic flow deposits, southern Kyushu, Japan
Takeshi HASEGAWA; Nobutatsu Mochizuki; Hidetoshi Shibuya; Ayumu Nishihara; Chie Kusu; Shohei Shibata; Makoto Okada; Kuniaki Nishiki; Yuki Sato, Lead
Earth, Planets and Space, Dec. 2024, [Reviewed]

Application of a recently developed method of oriented drill coring to accumulative tephra layers: identification of the Matuyama–Brunhes geomagnetic reversal in Akan caldera-forming eruption deposits
Takeshi Hasegawa; Chie Kusu; Makoto Okada; Aoi Hiratsuka; Kuniaki Nishiki; Yuki Sato; Masaru Koshigai; Takuya Matsuzaki; Yuhji Yamamoto, Lead, Abstract

We adapted a recently developed technique of oriented drill coring (100 m in depth) for paleomagnetic measurements, including additional techniques such as half-cutting of the drill cores and accurate cube sampling using an apparatus that precisely guides the cube into the half-cut drill core surface. Our techniques were successfully applied to sequential tephra layers (including loess) at Akan Quaternary caldera volcano in eastern Hokkaido, Japan. Directions of remanent magnetization for a total of 129 specimens were measured by Spinner magnetometer with thermal and alternating field demagnetizations. We detected clear Matuyama–Brunhes geomagnetic reversal between the depths of 20.59 m and 21.30 m, where inclinations change from 65.1 to –44.3°. With these techniques, we can in future obtain useful geologic information (e.g., radiometric ages and absolute paleo-intensities) from volcanic rocks around the Matuyama–Brunhes boundary in Akan volcano. This will clarify more detailed processes of the geomagnetic polarity transition. Our study demonstrates the utility of oriented drill cores from successive tephra and loess layers for high resolution investigate of continuous paleo-geomagnetic records. The new techniques can be adopted to other geological fields on Earth, like in studies of marine sediments, providing continuous paleomagnetic direction data from drill core.

Graphical Abstract, Springer Science and Business Media LLC
Earth, Planets and Space, 31 Oct. 2024, [Reviewed]

マグマ噴出量階段図の標準的な作成手法の提案と有珠山での作成例
中川光弘; 松本亜希子; 宮縁育夫; 長谷川健; 古川竜太; 上澤真平; 長井雅史
火山, Oct. 2024, [Reviewed]

第8回IAVCEI陥没カルデラワークショップ研究集会報告
下司 信夫; 後藤 芳彦; 金子 克哉; 三浦 大助; 長谷川 健; 富島 千晴; 柴田 翔平
火山, Jul. 2024, [Reviewed]

Evolution of a large-scale phreatoplinian eruption: Constraints from the 40 ka caldera-forming eruption of Kutcharo volcano, eastern Hokkaido, Japan
Shohei Shibata; Takeshi Hasegawa
Journal of Volcanology and Geothermal Research, Jun. 2024, [Reviewed]

The genesis of Ba anomaly in pumice lapilli inferred from petrological features: A case study of the caldera-forming eruption of Nigorikawa volcano, Japan
Yasuaki Kaneda; Takeshi Hasegawa; Takumi Imura, The Geological Society of Japan
The Journal of the Geological Society of Japan, 22 Dec. 2023, [Reviewed]

Paleomagnetism and paleomagnetic dating to large volcanic bombs: an example from the historical eruption of Azuma–Jododaira volcano, NE Japan
Takeshi Hasegawa; Bunta Kikuchi; Shibata Shohei; Yuhji Yamamoto; Takumi Imura; Masao Ban; Kae Tsunematsu; Chie Kusu; Makoto Okada; Tsukasa Ohba, Lead, Abstract

Vulcanian activity is one of the most common eruption styles of arc andesitic volcanism on Earth. It ejects and deposits volcanic bombs around the source crater. Although paleomagnetic studies of volcanic bombs are limited, such studies can potentially provide more opportunities for high-resolution paleomagnetic dating of volcanic activity. In this study, paleomagnetic dating was applied to large (> 1 m) volcanic bombs around active craters in the Azuma volcano group, NE Japan. Oriented samples were collected from the interior parts of five large volcanic bombs situated on gentle slopes, a few hundred meters from the source crater. More than six core samples were collected from each bomb and all samples were subjected to a range of rock magnetic experiments, including anisotropy of magnetic susceptibility (AMS) and thermal/alternating field demagnetization (THD/AFD) analyses. The Characteristic Remanent Magnetization (ChRM) directions for specimens from all bombs were well-defined, have small α₉₅ (< 2.5º), and are in close agreement with each other. Comparing our measured overall mean direction (D_m = 355.5º, I_m = 49.8º, α₉₅ = 1.6º) with modeled geomagnetic field estimates and a reference secular variation curve for this area (using MATLAB-based archaeomagnetic dating tool), we suggest that the volcanic bombs were produced in the historical Meiji period (1893–1895 CE) eruption. In addition, a combination of the data of ChRM, AMS, thermomagnetic analyses, hysteresis measurement, and XRF analysis indicates that the volcanic bombs were derived from a plug of lava in the conduit under the solidification point (ca. 800 °C), but above the Curie point of the titanomagnetite remanence carrier (around 300 °C). We show that volcanic bombs can be powerful for paleomagnetic dating if certain sampling conditions, such as quantity, situation, size and portion are satisfied.

Graphical Abstract, Springer Science and Business Media LLC
Earth, Planets and Space, 16 Nov. 2023, [Reviewed]

Magma had ejected in CE 1893 eruption (Meiji eruption) at Azuma- Jododaira volcano, Fukushima: Inferred from paleomagnetic dating for large volcanic bombs around Tsubakurosawa craters
長谷川 健; 菊池 文太; 柴田 翔平; 井村 匠; 伴 雅雄; 常 松佳恵; 山本 裕二; 大場 司; 鈴木和馬; 戸丸淳晴; 楠 稚枝; 岡田 誠, Lead
火山, Sep. 2023, [Reviewed]

Multi-method constraints on the age and timescale of silicic small-volume eruptions of Puketerata Volcanic Complex, Taupō Volcanic Zone, New Zealand
Szabolcs Kósik; Takeshi Hasegawa; Martin Danišík; Károly Németh; Makoto Okada; Bjarne Friedrichs; Axel K. Schmitt, Abstract

Accurate dating of young eruptions from explosive volcanoes is essential for forecasting future eruptions and for defining the hazardscape of volcanic fields. However, precise dating of Quaternary eruptions is often challenging due to limited number of applicable dating methods or lack of datable eruptive phases. Moreover, small volume eruptions (e.g., monogenetic type), despite their significance on regional scale, have traditionally deserved less attention than their large volume counterparts. Puketerata is a maar-lava dome complex in the central Taupō Volcanic Zone (New Zealand), encompassing mafic and silicic phreatomagmatic eruptions with well-preserved pyroclastic deposits sourced from closely spaced vents. Its most recent activity is estimated to ca. 16 ka based on medial and distal stratigraphic surveys. Here, we carried out two independent age determinations and an additional paleomagnetic analysis on the volcanic succession of the Puketerata maar-lava dome complex with an aim to unravel the timing of volcanic activity. Combined U-Th disequilibrium and (U-Th)/He dating of zircon from two lava domes yielded eruption ages of 11.3 ± 2.6 ka and 11.3 ± 1.7 ka, which are concordant with the radiocarbon ages of 11.3–11.7 ka obtained on charcoal from the base of the pyroclastic sequence. Paleomagnetic data on the lavas from the two lava domes suggest at least ~ 100 years difference between their emplacements. Our geochronological results and new stratigraphic observations suggest that the volcanic/magmatic history of the Puketerata is complex with multiple eruptions within a small, confined area, where the most recent eruptions occurred only at ca. 11.5 ka, which is significantly younger than previously thought. This provides an additional datum for volcanic hazards assessment and stratigraphic correlations in New Zealand.

Graphical Abstract, Springer Science and Business Media LLC
Earth, Planets and Space, 12 Jul. 2023, [Reviewed]

Report on the IAVCEI 2023 Scientific Assembly (Part 2): Field trips and impressions of the conference
松本恵子; コンウェイ クリス; 畑 真紀; 伊藤久敏; 岩橋くるみ; 片岡香子; 森田雅明; 西原 歩; 三反畑修; 渡部将太; 山﨑誠子; 長谷川健, Last, 内部査読
火山, Jun. 2023, [Reviewed]

Report on the IAVCEI 2023 Scientific Assembly (Part 1): Overview of Sessions and Workshops　　　　　　　　　　　　　　　
長谷川健; 松本恵子; 橋本武志; 畑 真紀; 岩橋くるみ; 無盡真弓; 村松 弾; 大橋正俊; 三反畑修; 嶋野岳人; 田中 良; 安田裕紀, Lead, 内部査読
火山, Jun. 2023, [Reviewed]

Varying stages of ecological succession in lakes subdivided by volcanic eruptions at Akan Caldera, Japan
Isamu Wakana; Yasuro Kadono; Jotaro Urabe; Yuki Tamura; Yoshifusa Suzuki; Hiroyuki Yamada; Yoichi Oyama; Keiji Wada; Takeshi Hasegawa; Masashi Ohara, Abstract

Ecological succession within lakes generally proceeds as eutrophication and shallowing occur and the aquatic biota of the lakes is altered. The eutrophication rate depends on the lake size and the area and fertility of the watershed. If the watershed fertility of several different lakes is equivalent and the lakes’ formation time and initial environment are similar, the trophic status of each lake is expected to increase over time depending on the ratio of the watershed area to lake size. To test this supposition, we surveyed the topography and water quality of 10 lakes of varying sizes in Akan Caldera, Japan, which were formed thousands of years ago by fragmentation due to volcanic eruptions within the caldera. The ratio of the accumulated watershed area to lake size was positively correlated with total phosphorus concentration, an indicator of trophic status, and lake types were classified as oligotrophic, mesotrophic, eutrophic, and dystrophic. In addition, 21 species of macrophytes were found in the lakes, and the species composition of each lake was divided into five types corresponding to combinations of the lake types. The discovery of such diversity in a group of lakes with a similar origin paves the way for new comparative studies., Springer Science and Business Media LLC
Hydrobiologia, 23 Apr. 2023, [Reviewed]

Eruption history and magma plumbing system of Futamatayama Volcano, southern Fukushima, Japan
Shota Watanabe; Takeshi Hasegawa; Naoya Obata; Shin Toyoda; Takeshi Imayama, The Geological Society of Japan
The Journal of the Geological Society of Japan, 06 Apr. 2023, [Reviewed]

Paleomagnetic constraint of the age and duration of the Taupō Eruption, New Zealand
Takeshi Hasegawa; Annika Greve; Darren M. Gravley; Chie Kusu; Yasuaki Kaneda; Shohei Shibata; Makoto Okada; Szabolcs Kósik; Nobutatsu Mochizuki; Gillian Turner, Lead
Earth, Planets and Space, Feb. 2023

Chronology and Magmatic Evolution of Shiobara Caldera-Forming Eruption Deposits, Tochigi Prefecture
Yuki Nishino; Takeshi Hasegawa; Hisatoshi Ito; Akihiko Kikuchi; ndShinzou Ooi, Corresponding
J. Geol. Soc. Japan, Feb. 2023, [Reviewed]

Geological, geophysical and geochemical constraints on the time-space evolution of Akan composite caldera, Hokkaido, Japan
Hasegawa, T.; Nakagawa, M.; Kamiyama, H.; Yamamoto, A., Lead
Frontiers in Earth Sciences, Sep. 2022, [Reviewed]

The complexities of assessing volcanic hazards along the Cameroon Volcanic Line using spatial distribution of monogenetic volcanoes
Christoph Schmidt; Christian Laag; Melody Whitehead; Jörn Profe; Festus Aka; Takeshi Hasegawa; Gabor Kereszturi
Journal of Volcanology and Geothermal Research, Jul. 2022, [Reviewed]

Eruption Ssequence of 40 ka Ccaldera-forming Eeruption (Kp I) from Kutcharo Vvolcano, Eeastern Hokkaido, Japan: Generation pProcesses of Llarge-scale Pphreatoplinian Eeruption
Shibata, S; Hasegawa, T, 日本火山学会
BULLETIN OF THE VOLCANOLOGICAL SOCIETY OF JAPAN, Jun. 2022, [Reviewed]

No evidence for tephra in Greenland from the historic eruption of Vesuvius in 79 CE: implications for geochronology and paleoclimatology
Gill Plunkett; Michael Sigl; Hans F. Schwaiger; Emma L. Tomlinson; Matthew Toohey; Joseph R. McConnell; Jonathan R. Pilcher; Takeshi Hasegawa; Claus Siebe, Abstract. Volcanic fallout in polar ice sheets provides important opportunities to date and correlate ice-core records as well as to investigate the
environmental impacts of eruptions. Only the geochemical characterization of volcanic ash (tephra) embedded in the ice strata can confirm the source
of the eruption, however, and is a requisite if historical eruption ages are to be used as valid chronological checks on annual ice layer
counting. Here we report the investigation of ash particles in a Greenland ice core that are associated with a volcanic sulfuric acid layer previously
attributed to the 79 CE eruption of Vesuvius. Major and trace element composition of the particles indicates that the tephra does not derive from
Vesuvius but most likely originates from an unidentified eruption in the Aleutian arc. Using ash dispersal modeling, we find that only an eruption
large enough to include stratospheric injection is likely to account for the sizable (24–85 µm) ash particles observed in the Greenland
ice at this time. Despite its likely explosivity, this event does not appear to have triggered significant climate perturbations, unlike some other
large extratropical eruptions. In light of a recent re-evaluation of the Greenland ice-core chronologies, our findings further challenge the previous
assignation of this volcanic event to 79 CE. We highlight the need for the revised Common Era ice-core chronology to be formally accepted by the wider
ice-core and climate modeling communities in order to ensure robust age linkages to precisely dated historical and paleoclimate proxy records., Copernicus GmbH
Climate of the Past, 18 Jan. 2022, [Reviewed]

Syn- and Post- caldera-forming Eruption Sequence of Nigorikawa Volcano, Southwestern Hokkaido, Japan
Kaneda, Y; Hasegawa, T
BULLETIN OF THE VOLCANOLOGICAL SOCIETY OF JAPAN, 2022, [Reviewed]

Geochemical composition of dykes along the Cameroon Line (CL): Petrogenesis and similarities with the Central Atlantic Magmatic Province
Asobo Nkengmatia Elvis Asaah; Tetsuya Yokoyama; Hikaru Iwamori; Festus Tongwa Aka; Jules Tamen; Takeshi Kuritani; Tomohiro Usui; Takeshi Hasegawa; Eric Martial Fozing, We report whole-rock geochemistry and Sr–Nd–Pb isotopic compositions of mafic dykes intruded in the Precambrian granito-gneissic basement complex, exposed at Nyos, Batibo, Dschang and Foumban on the Cameroon Line. The dykes are alkaline (Batibo), transitional (Foumban), and subalkaline (Nyos, Batibo and Dschang) with SiO2 of 45–54 wt% and MgO of 2–9 wt%, similar to dykes reported in other areas of the Cameroon Line (CL) and the Central Atlantic Magmatic Province (CAMP). The abundances of rare earth elements (REE) and the Primitive Mantle normalised patterns for the Nyos, Batibo and Dschang dykes are similar to those of MORB, indicating that the dykes formed at shallower depths by a higher degree of partial melting relative to the Foumban dykes and the alkaline lavas of the CL. The transitional basaltic dykes with steeper REE patterns have their sources at deeper levels in the lithospheric mantle, possibly the garnet-spinel transition zone and were generated by a lower degree partial melting of the lithospheric and plume components. The Nyos and Batibo subalkaline dykes show similar isotopic compositions with a spectrum extending from depleted (DMM-like) to enriched (EM1-like) mantle, indicating the similarity in their source components. The Dschang dykes show distinct isotopic characteristics with relatively unradiogenic Nd-Pb isotope compositions compared to the Batibo and Nyos dykes. The Foumban transitional dykes with characteristic wide ranges in Sr-Nd-Pb isotopic compositions reveal varying contributions from enriched mantle components (EM1 and EM2) in addition to its plume signature similar to those of CL lavas. The Nyos and Batibo dykes alongside other dykes on the CL have low TiO2 abundances (<2 wt%), negative PM-normalised Nb-anomalies, and moderately to strongly enriched REE patterns, and isotopic composition that overlaps with those of CAMP, suggesting a similar lithospheric origin., Elsevier BV
Geochemistry, Jan. 2022, [Reviewed]

High–μ signature in lavas of Mt. Oku: Implications for lithospheric and asthenospheric contributions to the magmatism of the Cameroon Volcanic Line (West Africa)
A.N.E. Asaah; T. Yokoyama; H. Iwamori; F.T. Aka; T. Kuritani; T. Usui; J. Tamen; M. Gountié Dedzo; B. Chako-Tchamabé; T. Hasegawa; L.A. Nche; T. Ohba, This study presents geochemical data for mafic lavas from Mt. Oku to investigate the mantle source for Mt. Oku lavas and regional variations in isotopic ratios along the Cameroon Volcanic Line (CVL). The investigated mafic lavas present trace element and isotope signatures akin to ocean island basalts (OIB) and cover the entire range of the CVL. Major and trace element compositions of the studied lavas indicates that they have undergone fractionation of olivine + clinopyroxene + Fe-Ti oxide ± Cr–spinel with insignificant crustal contamination. The lavas were generated by <2% partial melting from a heterogeneous source containing less than 4% garnet. Major and trace elements abundances indicate the presence of hydrous minerals indicative of modal metasomatism. The highest value of radiogenic 206Pb/204Pb (20.7) so far measured along the CVL is reported in this study. The isotopic features of the lavas suggest that the HIMU signatures are dominantly inherited from the asthenosphere (primary source) and melting of enriched components hosted in the subcontinental lithospheric mantle (SCLM; secondary source). Lavas from Mt. Oku present more comprehensive ranges of Sr–Nd–Pb isotopic composition than those from the continent-ocean-boundary (COB). The isotopic composition of Mt. Oku lavas with 206Pb/204Pb > 19.5 differs from those of the COB but are similar to FOZO. The isotopic composition of Mt. Oku lavas (87Sr/86Sr = 0.7030–0.7036, 143Nd/144Nd = 0.5127–0.5129, 206Pb/204Pb = 17.9–20.7) suggest that the lavas are the result of contributions from the asthenosphere and the SCLM. Using a combination of Sr–Nd–Pb isotope display on a 3D plot and Sm/Yb, we identify four essential components denoted; A, B, C and D involved in the petrogenesis of Mt. Oku lavas and the approximate melting depth. While A and B are from the asthenosphere with HIMU mantle flavour, C and D owe their origin from the SCLM with EM1 and DMM characteristics, respectively. Although depleted in Sr-Nd isotopes, D is radiogenic in 206Pb/204Pb, indicating the influence of metasomatism. Therefore, the petrogenesis of Mt. Oku lavas involves the mixing of at least three mantle end-members: HIMU–DMM–EM1. The “fanning” of samples from”A" towards the other components (B, C and D) indicates a HIMU–like end–member dominance in Mt. Oku magmatism. Considering the geophysical studies on mantle convection and plumes, we have developed a schematic model that explains the petrogenesis of the CVL lavas. The continuous spectrum from relatively depleted to HIMU characteristics of CVL lavas is associated with the progressive change in source components (i) SCLM with ± pockets of enriched metasomes to (ii) SCLM + asthenosphere sources and finally to (iii) typically asthenospheric source material ± pockets of enriched metasomes. Lavas derived from stage (i) exhibit geochemical variability involving DMM–like and EM1–like signatures. The magma generated at Stage (iii) is dominated by the HIMU mantle component and accounts for over 85% of CVL lavas., Elsevier BV
Lithos, Nov. 2021, [Reviewed]

A tephra-based approach to calibrating relative geomagnetic paleointensity stacks to absolute values
Nobutatsu Mochizuki; Satomu Fujii; Takeshi Hasegawa; Yuhji Yamamoto; Tadahiro Hatakeyama; Daisuke Yamashita; Makoto Okada; Hidetoshi Shibuya, Elsevier BV
Earth and Planetary Science Letters, Oct. 2021, [Reviewed]

Eruption Styles and Processes of the 7.6 ka Caldera-forming Eruption of Mashu Volcano, Eastern Hokkaido, Japan: Reconstruction of a High-resolution Eruption Sequence Based on Geologic, Petrologic and Paleomagnetic Methods and Recognition of Low Aspect Ratio Ignimbrite (LARI)
Takeshi Hasegawa; Shohei Shibata; Tetuso Kobayashi; Nobutatsu Mochizuki; Mitsuhiro Nakagawa; Hiroshi Kishimoto, Lead, Based on detailed fieldwork, petrological and paleomagnetic investigations, we present a revised stratigraphy of deposits from the 7.6 ka eruption at Mashu volcano and the formation process of its summit caldera, eastern Hokkaido, Japan. As previously described, the eruption products consist of an initial phreatomagmatic unit (Ma-j) and the overlying three pumice-fall layers (Ma-i, -h, and -g), which are in turn overlain by pyroclastic-flow deposits (Ma-f). In the present study, we divide Ma-f into 4 subunits: Ma-f1/2, Ma-fAc, Ma-f3a and Ma-f3b in descending order. Ma-f3b is a valley-ponding, pumice-flow deposit with limited distribution. Ma-f3a comprises clast-supported facies (fines-depleted ignimbrite: FDI) and matrix-supported (normal ignimbrite) facies, the two changing across topography. The FDI is characterized by a gray, fines-depleted, lithic-breccia-rich layer with materials incorporated from the substrate. Impact sag structures from large (>50 cm) dacite ballistic blocks were recognized at the base of the Ma-f3a within 10 km from the source. Ma-fAc is a minor eruption unit consisting of accretionary lapilli. Ma-f1/2 is a most voluminous (8.8 km³), widely distributed and weakly stratified ignimbrite. Both Ma-f3a and Ma-f1/2 can be classified as “low aspect ratio ignimbrite (LARI)”. Dacite lithic fragments are ubiquitously observed throughout the sequence and are not considered to be juvenile; they have distinctly different chemical compositions from the pumice fragments in the early pumice-fall (Ma-g～Ma-i) and pyroclastic-flow (Ma-f3b) deposits, but those of pumice clasts in the late pyroclastic-flow units (Ma-f3a and Ma-f2) lie between the two on a FeO*/MgO vs. SiO₂ diagram. The 7.6 ka caldera-forming eruption of the Mashu volcano was initiated by Plinian fall (Ma-j～-g), and then, a small-volume high aspect ratio ignimbrite (Ma-f3b) was deposited by a valley-confined pyroclastic flow that was generated by partial column collapse. After that, a violent pyroclastic flow was generated probably during a strong explosion of a dacite lava edifice on the summit of Mashu volcano. This flow emplaced Ma-f3a. The caldera collapse that followed the explosion generated a climactic pyroclastic flow that emplaced Ma-f1/2. Ma-f3a flow was extremely fast. Ma-f1/2 flow was related to sustained flow due to low settling velocity and high discharge volume. These are supported by field observations and numerical simulation that shows the ability of the flow to surmount high topographic obstacles and spread widely. The 7.6 ka caldera-forming process of Mashu volcano was driven not only by subsidence of roof block but also by violent explosions., The Volcanological Society of Japan
Bulletin of the Volcanological Society of Japan, Sep. 2021, [Reviewed]

ヤチカンバ花粉の識別と北海道東部の西別湿原における6500年前以降の植生史　　　　　　　　　　　　　　　
吉川昌伸; 鈴木三男; 佐藤雅俊; 小林和貴; 長谷川健; 吉川純子; 戸田博史
植生史研究, Feb. 2021, [Reviewed]

Lithostratigraphy and geochemistry of Aojiki volcano and Sumiyoshiike and Yonemaru maars, Kamo Volcanic Field (Southern Kyushu), Japan
Nche, L.A; Hasegawa, T; Aka, F.T; Kobayashi, T; Nemeth, K; Asaah, A.N.E; Kaneda, Y; Nishihara, A; Etakah, B-T.E; Lebga, A.K; Tiabou, A.F; Ngwa, C.N; Suh, C.E, Corresponding
Journal of Volcanolgy and Geothermal Research, Dec. 2020, [Reviewed]

Repetitive duality of rhyolite compositions, timescales, and storage and extraction conditions for Pleistocene caldera-forming eruptions, Hokkaido, Japan　　　　　　　　　　　　　　　
Pitcher, B; Gualda, G.A; Hasegawa, T
Journal of Petrology, Dec. 2020, [Reviewed]

Major/trace elements and Sr–Nd–Pb isotope systematics of lavas from lakes Barombi Mbo and Barombi Koto in the Kumba graben, Cameroon volcanic line: Constraints on petrogenesis
A. N.E. Asaah; T. Yokoyama; F. T. Aka; H. Iwamori; T. Kuritani; T. Usui; M. Gountie Dedzo; J. Tamen; T. Hassegawa; E. M. Fozing; M. J. Wirmvem; A. L. Nche, © 2019 Elsevier Ltd This study presents major elements, trace elements and Sr–Nd–Pb isotope data for fifteen (15) representative volcanic rock samples from volcanic edifices of Lakes Barombi Mbo (n = 9) and Barombi Koto (n = 6), located in the Kumba graben along the Cameroon Volcanic Line (CVL). The samples are dominantly basalts and trachy-basalts with MgO ranging from 7 to 9 wt.%. The lavas from the edifice of Lake Barombi Mbo are slightly richer in TiO2 (mean 3.3 wt%) and lower in CaO (mean 9.2 wt%) relative to those from the edifice of Lake Barombi Koto (2.9 wt% and 10.3 wt%, respectively). Trace element characteristics of the lavas suggest an enrichment of the source by carbonatitic metasomatism and melting of a heterogeneous source at varying depth in the garnet-spinel transition zone. Trace elements and isotopic composition of the lavas suggest insignificant crustal contamination. Modelling of the degree of partial melting suggest that the magmas were formed at varying depth (60–80 km) and by ~2% partial melting of a source containing less than 4% garnet. Samples from Lake Barombi Mbo formed at a higher degree of partial melting (2%–0.5%) and at a shallower depth relative to those from the volcanic edifice of Lake Barombi Koto (mostly <0.5%) and Mt. Cameroon. Interestingly, the relationship of Zr/Hf and 206Pb/204Pb suggests that the magma was affected by carbonatitic metasomatism whose effect decreased from Mt. Cameroon to Lake Barombi Mbo. Our results suggest that Lakes Barombi Mbo and Barombi Koto lavas are typical of lavas with HIMU-like signature and involved contributions from a dominantly sublithospheric mantle (SLM) and minor contributions from the sub-continental lithospheric mantle (SCLM). The SLM material rose and was hosted in the SCLM prior to melting., Elsevier {BV}
Journal of African Earth Sciences, Jan. 2020, [Reviewed]

Stratigraphy, age and depositional processes of Yosasagawa Debris Avalanche deposit, North Tochigi Prefecture, Japan
菊地瑛彦; 長谷川健, Corresponding
地質学雑誌, 2020, [Reviewed]

Eruption history and petrogenesis of rocks from Nyos volcano (NW Cameroon): Evidence from lithostratigraphy and geochemistry
Takeshi Hasegawa; Festus Tongwa Aka; Yasuo Miyabuchi; Linus Anye Nche; Tetsuo Kobayashi; Katsuya Kaneko; Asobo Nkengmatia; Elvis Asaah; Boniface Kankeu; Issa; Takeshi Ohba; Minoru Kusakabe; Joseph Victor Hell, Lead, Even though ca 1746 people and over 3000 cattle were killed in 1986 by sudden release of about 800 million m(3) of CO2 from Lake Nyos volcano in northwest Cameroon, the lake's formation history is not known. Here we report results of a lithostratigraphic and petrogenetic study of Nyos volcano that allows us to confirm its phreatomagmatic (maar) origin. Eruptive products are divided into 2 units, the phases of each of which are closely related in time. Unit A comprises 4 phases, the last (A-4) represents the cataclysmic phreatomagmatic formation of Nyos maar and may have been triggered by collapse of the vent system of the previous (A-1 to A-3) phases, and/or reactivation of basement faults. After a repose period, activity shifted NE of the maar to form Unit B products. The B-1 phase of this unit deposited the scoria now covering most of the Lake Nyos area. Unit B-2 constructed the Fon's cone. A small lava flow (Unit B-3) represents the latest phase of volcanic activity of Nyos volcano. Based on area-thickness estimation methods, a total of ca 0.8 km(3) of eruptive material was produced from the volcano. Geochemical data suggest that magma of the 2 units probably formed by melting of the same garnet-bearing OIB-like asthenospheric mantle source, and evolved mainly by crustal contamination and fractional crystallization in independent magma batches that erupted without mixing. Our results provide a basis for advice on general hazard mitigation in the Lake Nyos area. (C) 2019 Elsevier B.V. All rights reserved., ELSEVIER SCIENCE BV
Journal of Volcanology and Geothermal Research, Jun. 2019, [Reviewed]

Upper Triassic mafic dykes of Lake Nyos, Cameroon (West Africa) I: K-Ar age evidence within the context of Cameroon Line magmatism, and the tectonic significance
Festus Tongwa Aka; Takeshi Hasegawa; Linus Anye Nche; Asobo Nkengmatia Elvis Asaah; Mumbfu Ernestine Mimba; Isidore Teitchou; Caroline Ngwa; Yasuo Miyabuchi; Tetsuo Kobayashi; Boniface Kankeu; Tetsuya Yokoyama; Gregory Tanyileke; Takeshi Ohba; Joseph Victor Hell; Minoru Kusakabe, The hydrodynamic fragmentation that formed Lake Nyos in northwest Cameroon did not only make it the most unpopular lake in the world from a gas disaster perspective, it also opened a rare and formidable window through which much of the geology of Cameroon can be studied in a single locality. The Cambrian quartz monzonite cliff excavated by the maar-forming explosion and exposed in its northeastern shore is intruded by mafic dykes, two of which we dated. Even though close to one another, the dykes are different in composition. The alkaline dyke yields a slightly older (Carnian) K-Ar fedspar age of 231.1 ± 4.8 Ma, while the sub alkaline dyke yields an age of 224.8 ± 4.7 Ma (Norian). Based on radioisotopic age data available over the last 48 years (347 data) for the Cameroon Line magmatism comprising eruptives and volcano-plutonic complexes, the Nyos dykes are way older than the Cameroon Line, and even pre-date the Lower Cretaceous initiation of west Gondwana fragmentation in Equatorial Atlantic domain. They would therefore not have been directly linked to the formation of the Cameroon Line. Alternatively, they might be associated with the development of intra-continental rift systems in West Central Africa that pre-dated west Gondwana breakup to form the Atlantic Ocean., Elsevier Ltd
Journal of African Earth Sciences, 01 May 2018, [Reviewed]

Petrology of the 120 ka Caldera-Forming Eruption of Kutcharo Volcano, Eastern Hokkaido, Japan: Coexistence of Multiple Silicic Magmas and their Relationship with Mafic Magmas
Matsumoto Akiko; Hasegawa Takeshi; Nakagawa Mitsuhiro, 担当：現地調査・試料採取
JOURNAL OF PETROLOGY, Apr. 2018, [Reviewed]

Large-scale Caldera-forming Eruption and Active Post-caldera Volcano: General Geology and Representative Outcrops of Toya Caldera and Usu Volcano, Southwestern Hokkaido, Japan
HASEGAWA Takeshi; MATSUMOTO Akiko; TOMIYA Akihiko; NAKAGAWA Mitsuhiro, Lead,

 Toya caldera, eastern Hokkaido, was formed approximately 110 ka, and has two post-caldera volcanoes, Nakajima and Usu volcano. Caldera-forming eruptions ejected a large-scale Toya pyroclastic flow, and related co-ignimbrite ash which covered a wide area in northern Japan. Usu volcano is one of the most active volcanoes in Japan, and has had repeated magmatic eruptions during historical time since AD 1663. The latest major eruption occurred in AD 2000. General geology and representative outcrops of eruptive deposits from Toya caldera and its post-caldera volcanoes are introduced, on the basis of a training field course at the 6^th IAVCEI Collapse Caldera Workshop held in September 2016.

, Tokyo Geographical Society
Journal of Geography (Chigaku Zasshi), 2018, [Reviewed]

Methods of Estimating the Durations of Super Large Eruptions Based on Pyroclastic Deposits
Hasegawa Takeshi; Mochizuki Nobutatsu; Oiwane Hisashi, Lead, The durations of caldera-forming eruptions that produce large volumes (>100 km(3)) of pyroclastic ejecta are poorly understood due to the absence of direct observations. However, clarifying the timescale of these catastrophic hazardous events is essential for understanding associated eruption dynamics and links with the eruptible portions of the underlying magma system. Case studies addressing the time scale of caldera-forming eruptions are reviewed. Three Quaternary large volume caldera-forming eruption deposits from Yellowstone (US), Taupo (New Zealand) and Kutcharo (Japan) volcanoes are inferred from deposits to have lasted for periods of at least for months to years. However, these estimations are generally based on geological evidence, such as re-worked deposits between eruption units, and not quantitative evidence. Proposed here is a new method of timescale estimation based on paleomagnetic secular variation. A sampling procedure was developed for accurate oriented samples of pyroclastic deposits including volcanic ash. This procedure makes it possible to obtain the mean remanent magnetization of a tephra layer with a 95% confidence limit of about 2 degrees, which is comparable to those of well-determined directions for lava. Based on this procedure, the 7.3 ka Kikai caldera-forming eruption was investigated as a trial. Samples for paleomagnetic measurement were collected from the basal ash-rich part of the lowermost plinian pumice fall (Koya pumice fall) at Satsuma Iwo-jima, Kyushu. The difference of 6.9 degrees in the remanent magnetizations between Koya pumice and reported data of the uppermost co-ignimbrite ash-fall(Kikai. Akahoya Ash) suggests the caldera-forming eruption of a considerable duration (>50 years) on the basis of average rate of secular variation. Paleomagnetic directions from pyroclastic deposits could be a powerful tool for estimating timescales of large explosive eruptions., TOKYO GEOGRAPHICAL SOC
JOURNAL OF GEOGRAPHY-CHIGAKU ZASSHI, 2018, [Reviewed]

Re-evaluation of the history of phreatic eruptions from Atosanupuri Volcano, eastern Hokkaido, Japan: Inferred from 14C ages and borehole cores of Japan Meteorological Agency
長谷川健; 中川光弘; 宮城磯治, Lead,

Atosanupuri Volcano is one of the active volcanoes, located in the Akan-Shiretoko Volcanic Chain, eastern Hokkaido. Tephro-stratigraphic and tephro-chronologic studies were conducted on two drill cores and new outcrops around the volcano to reveal a recent history of the explosive eruptions. Widespread tephra layers, such as the 10th century B-Tm tephra, and the 2.7 cal. ka BP Ta-c2 tephra were distinguished by the geochemical composition of volcanic glass. In addition, ¹⁴C ages of organic samples underlying the eruption deposits were obtained. Using these data, we identified seven phreatic eruption deposits, At-ph1 to At-ph7, overlying the T-c2 tephra; these include the previously described At-a and At-b tephras. At-ph7 yields the oldest ¹⁴C calibrated age (2.5-2.7 cal. ka), and the deposition ages of At-ph6 to At-ph1 range from cal. AD 554 to 1678. At-ph4 (At-b) is the thickest phreatic ejecta, with a volume of ~3 × 10⁶ m³. Five phreatic eruptions occurred from Atosanupuri Volcano between 1,500 and 1,000 cal. BP. The youngest eruption, At-ph1 (At-a) occurred at 300 ~ 400 cal. BP, which might be documented in historical records.

, The Geological Society of Japan
地質学雑誌, May 2017, [Reviewed]

Report of the IAVCEI 2017 Scientific Assembly
HASHIMOTO Takeshi; TANAKA Ryo; UESAWA Shimpei; YAMADA Taishi; HASEGAWA Takeshi; KOZONO Tomofumi; MANNEN Kazutaka; NAKAMICHI Haruhisa; SUMITA Mari; SUZUKI Yuki; TAJIMA Yasuhisa; TAKAGI Akimichi, 担当部執筆（解説・紹介）, The Volcanological Society of Japan
BULLETIN OF THE VOLCANOLOGICAL SOCIETY OF JAPAN, 2017, [Reviewed]

Superconductivity and Non-Fermi-Liquid Behavior in the Heavy-Fermion Compound CeCo1−xNixIn5
Ryo Otaka; Makoto Yokoyama; Hiroaki Mashiko; Takeshi Hasegawa; Yusei Shimizu; Yoichi Ikeda; Kenichi Tenya; Shota Nakamura; Daichi Ueta; Hideki Yoshizawa; Toshiro Sakakibara, The effect of off-plane impurity on superconductivity and non-Fermi-liquid
(NFL) behavior in the layered heavy-fermion compound CeCo$_{1-x}$Ni$_x$In$_5$
is investigated by specific heat, magnetization, and electrical resistivity
measurements. These measurements reveal that the superconducting (SC)
transition temperature T$_c$ monotonically decreases from 2.3 K (x=0) to 0.8 K
(x=0.20) with increasing x, and then the SC order disappears above x=0.25. At
the same time, the Ni substitution yields the NFL behavior at zero field for
x=0.25, characterized by the -ln T divergence in specific heat divided by
temperature, C$_p$/T, and magnetic susceptibility, M/B. The NFL behavior in
magnetic fields for x=0.25 is quite similar to that seen at around the SC upper
critical field in pure CeCoIn$_5$, suggesting that both compounds are governed
by the same antiferromagnetic quantum criticality. The resemblance of the
doping effect on the SC order among Ni- , Sn-, and Pt-substituted CeCoIn5
supports the argument that the doped carriers are primarily responsible for the
breakdown of the SC order. The present investigation further reveals the
quantitative differences in the trends of the suppression of superconductivity
between Ce(Co,Ni)In$_5$ and the other alloys, such as the rates of decrease in
T$_c$, dT$_c$/dx, and specific heat jump at T$_c$, d($\Delta$C$_p$/T$_c$)/dx.
We suggest that the occupied positions of the doped ions play an important role
in the origin of these differences.
Journal of the Physical Society of Japan, 15 Sep. 2016, [Reviewed]

Superconductivity and non-Fermi-liquid behavior in the heavy-fermion compound CeCo$_{1-x}$Ni$_x$In$_5$
Ryo Otaka; Makoto Yokoyama; Hiroaki Mashiko; Takeshi Hasegawa; Yusei Shimizu; Yoichi Ikeda; Kenichi Tenya; Shota Nakamura; Daichi Ueta; Hideki Yoshizawa; Toshiro Sakakibara, 担当：化学分析
JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN, 29 Jul. 2016, [Reviewed]

Evolution of the 120 ka caldera-forming eruption of Kutcharo volcano, eastern Hokkaido, Japan: Geologic and petrologic evidence for multiple vent systems and rapid generation of pyroclastic flow
Takeshi Hasegawa; Akiko Matsumoto; Mitsuhiro Nakagawa, Lead, We investigated the eruptive sequence and temporal evolution of juvenile materials during the 120 ka Kutcharo pumice flow IV (Kp IV) eruption, which was the most voluminous (175 km(3): bulk volume) caldera-forming eruption of Kutcharo volcano. The eruptive deposits are divided into four units in ascending order. Unit 1 is widely dispersed and consists of silt-sized, cohesive ash. Unit 2 is a thin, moderately sorted pumice fall deposit with a restricted distribution and small volume (<0.2 km(3)). Unit 3, consisting of widely distributed ignimbrite, is the most voluminous. Unit 4 is also composed of pyroclastic flow deposits, but its distribution is limited to the northwest side of the caldera. Juvenile materials consist mainly of rhyolite pumice (74%-78% SiO2) associated with a minor amount of scoria (52%-73% SiO2) that are found only northwest of the caldera in Unit 3 and Unit 4. These scoriae can be classified on the basis of the P2O5 contents of their matrix glass into low-P, medium-P, and high-P types, which are almost entirely restricted to the lower part of Unit 3, Unit 4, and the upper part of Unit 3, respectively. These three types display distinct mixing trends with the rhyolitic compositions in SiO2-P2O5 variation diagrams. This evidence indicates that three distinct mafic magmas were independently and intermittently injected into the main body of silicic magma to erupt from the northwestern part of the magma system. Mafic injections did not occur in the southern part of the magma system. This petrologic evidence implies that the northwestern and southeastern flows of Unit 3 are heterotopic, contemporaneous products derived from multiple vent systems. Although Unit 2 was derived from an eruptive column, its volume is very small compared to Plinian fall deposits of typical caldera-forming eruptions. In our interpretation, the activity of the Kp IV eruption reached its climax rapidly, depositing Unit 3, without first producing a stable Plinian column. The presence of multiple vent systems could have allowed the system to bypass an initial eruptive stage with a stable Plinian column and begin its climactic stage, represented by Unit 3, rapidly. Multiple vents could have been the result of sequential injections of mafic magma in the early stages of the Kp IV eruption. (C) 2016 Elsevier B.V. All rights reserved., ELSEVIER SCIENCE BV
JOURNAL OF VOLCANOLOGY AND GEOTHERMAL RESEARCH, Jul. 2016, [Reviewed]

Large scale explosive eruptions of Akan volcano, eastern Hokkaido, Japan: A geological and petrological case study for establishing tephro-stratigraphy and -chronology around a caldera cluster
Takeshi Hasegawa; Mitsuhiro Nakagawa, Lead, Akan volcano, in eastern Hokkaido in the southern Kurile arc, occupies a rectangular caldera (24 x 13 km) with a long (1.7-0.2 Ma) and complex history. This paper combines tephrostratigraphy, tephrochronology, and petrological and geochemical evidence to elucidate the eruptive history and evolution of the caldera. Pyroclastic deposits from Akan caldera are divided into at least 40 "eruptive units", separated by paleosols, that constitute 17 "eruptive groups" (Ak1 to Ak17, in descending stratigraphic order) that are petrologically distinct and separated by indicators of longer dormancy periods such as thick (> 30 cm) paleosols and angular unconformities. The estimated volumes of most eruptive groups are less than 10 km(3) dense rock equivalent, and four groups (Ak2, Ak4, Ak7, and Ak13) are larger. Group Ak2, exceeding 50 km3, is the largest. Pyroclastic deposits from Akan caldera are intercalated with pyroclastic deposits from the adjacent Kutcharo caldera and distal air-fall ash layers from central Hokkaido, suggesting that caldera-forming episodes overlapped in central and eastern Hokkaido. Radiometric ages from these exotic deposits range from 1.46 to 0.21 Ma, indicating that caldera-forming eruptions occurred at Akan volcano for more than 1 million years at an average magma discharge rate of approximately 10(-1) km(3)/kyr. Juvenile materials in Akan caldera pyroclastics consist of dominantly aphyric, two-pyroxene dacite to rhyolite. They are characterized by a wide range of K2O compositions (0.8-2.8 wt.%) within a narrow range of SiO2 compositions (67-73 wt.%). Plots of SiO2 vs. K2O suggest that each eruptive group is the product of a distinct, ephemeral magma system rather than a single long-lived magma system. These magma systems appear to have been generated and erupted successively beneath the caldera for more than 1 million years. Each magma system thus appears to represent a relatively short period of activity, and they were separated by relatively long dormancy periods before the next magma system. In particular, a long dormancy of 400 kyr preceded eruptive group Ak2, which consists of the most voluminous and compositionally varied silicic magmas. (C) 2015 Elsevier Ltd and INQUA. All rights reserved., PERGAMON-ELSEVIER SCIENCE LTD
QUATERNARY INTERNATIONAL, Mar. 2016, [Reviewed]

茨城県日立市,宮脇A・泉前遺跡から出土した黒曜石製石器の産地推定
長谷川健; 猪狩俊哉; 大平達雄; 田切美智雄; 向井正幸; 和田恵治, Lead, 筆頭, 日本文化財科学会
考古学と自然科学, Feb. 2016, [Reviewed]

第5回陥没カルデラワークショップ報告
長谷川健; 下司信夫; 石川敦代, Lead, 筆頭（解説・紹介）, Volcanological Society of Japan
火山, Jun. 2015, [Reviewed]

Effective Method for Tephra Correlation on the Basis of Petrological Characteristics: Outcrop Database of Large Scale Pyroclastic Flow Deposits around Akan and Kutcharo Volcanoes, Eastern Hokkaido, Japan
長谷川健; 中川光弘, Lead, This paper introduces a practical use of outcrop data in determining the correlation, stratigraphy and distribution of large-scale pyroclastic flow deposits (PFL). The studied area is the Akan and Kutcharo volcanic zone in Eastern Hokkaido, Japan, which have had a long and complex history of more than 20 caldera-forming eruptions during the Quaternary. A database of the stratigraphy and glass chemistry for the more than 20 PFL can be established by studying a sufficient number of representative outcrops. We found representative outcrops where stratigraphic relationships between several PFL can be observed at the same time. We analyzed glass chemistry of juvenile pumices (>10 clasts) of the PFL. The database enables to identify all exposed PFL in this area, thus allowing us to draw detailed maps of the distribution for each PFL. The database can be also used for correlation and chrono-stratigraphic determination of reworked volcanic deposits, such as terrigenous marine deposits in Kushiro region, located on the plains at the foot of Akan and Kutcharo volcanoes., Volcanological Society of Japan
火山, Dec. 2014, [Reviewed]

Sequence of the 120 ka Adatara-Dake Eruption from Adatara Volcano, Fukushima, Japan: Based on Correlations between the Outcrops of Pyroclastic Fall Deposits at the Summit and Flow Deposits on the Flank and Foot of the Volcano
藤原健一郎; 長谷川健; 藤縄明彦, Corresponding, We performed systematic sampling and description of the Adatara-Dake tephra outcrop on the summit of Adatara volcano, Fukushima Prefecture, Japan in order to reveal the detailed eruption sequence and temporal evolution of the magma system of this volcano that erupted 120ka BP. Even though there is no recognizable eruption hiatus represented by a paleosoil layer, pyroclastic fall characteristics at the outcrop permit to divide Adatara-Dake tephra into 19 layers: A to R; from bottom to top. The earlier layers (A to L) are characterized by successive pumice fall deposits, intercalated by thin volcanic sand layers. The later layers (M to R) are rich in scoria fall and are partly welded, with agglutinate found in layers O and R. Representative clasts from each layer were analyzed to determine the grain size distribution, componentry, modal composition and whole rock chemistry. Layer M can be correlated petrologically and petrographically with the lower part of Yugawa pyroclastic flow deposit on the eastern foot and the Motoyama pyroclastic flow deposit on the western flank of the volcano. Similarly, the upper part of Yugawa pyroclastic flow correlate with layer N, meanwhile the upper part of Motoyama pyroclastic flow correlate with layers O or R. There is an increase in the lithic fraction with decreasing sorting in layer M, which we interpret to indicate increasing enlargement of vent during the phase of this layer. The scoria/pumice volume ratio also increases remarkably in layer M, suggesting that vent enlargement and sudden increase of mafic magma during phase M caused the column collapse that generated the Yugawa and Motoyama pyroclastic flows. The mafic magma composition changed after layer O, with the FeO*/MgO ratios becoming less than 2.1. After this change in chemistry in phases O to R, pyroclastic flows were continuously generated and agglutinated deposits were formed at the summit. This suggests that the eruption style of the final phase abruptly changed to relatively low column height., Volcanological Society of Japan
火山, Dec. 2014, [Reviewed]

Possible Evolution of Antiferromagnetism in Zn-Doped Heavy-Fermion Superconductor CeCoIn5
Makoto Yokoyama; Kenji Fujimura; Sara Ishikawa; Masashi Kimura; Takeshi Hasegawa; Ikuto Kawasaki; Kenichi Tenya; Yohei Kono; Toshiro Sakakibara, We have succeeded in growing single crystals of the heavy-fermion
superconductor CeCo(In1-xZnx)5 with x<=0.07. Measurements of specific heat,
electrical resistivity, dc magnetization and ac susceptibility revealed that
the superconducting (SC) transition temperature Tc decreases from 2.25 K (x=0)
to 1.8 K (x=0.05) by doping Zn into CeCoIn5. Furthermore, these measurements
indicate a development of a new ordered phase below T_o ~ 2.2 K for x=>0.05,
characterized by the reduced magnetization and electrical resistivity in the
ordered phase, and the enhancement of specific heat at T_o. This phase
transition can be also recognized by the shoulder-like anomaly seen at H_o ~ 55
kOe in the field variations of the magnetization at low temperatures, which is
clearly distinguished from the superconducting critical fields Hc2=49 kOe for
x=0.05 and 42 kOe for x=0.07. We suggest from these results that the
antiferromagnetic (AFM) order is generated by doping Zn, and the interplay
between the SC and AFM orders is realized in CeCo(In1-xZnx)5.
J. Phys. Soc. Jpn, 04 Feb. 2014, [Reviewed]

Recognition and its significance of Tarumai-d tephra in Kushiro region, eastern Hokkaido, Japan
長谷川健; 花岡正光; 古川竜太; 重野聖之; 七山太; 中川光弘; 安藤寿男, Lead, The Ta-d tephra (8.7–9.2 cal. ka) from Tarumai Volcano in south-western Hokkaido has been newly recognized at two archeological sites and in cores taken from a bay in the Kushiro–Nemuro area, eastern Hokkaido, Japan. Identification of the tephra is based on chronological data, stratigraphic relationships (it is overlain by the 2.5 cal. kyr old Ta-c2 tephra), lithofacies, and petrological correlation (modal mineralogy and glass chemistry) with proximal Ta-d tephra deposits. In particular, the relatively high TiO₂ and low K₂O contents of the tephra are distinctive. The Ta-d tephra comprises lower pumiceous and upper scoriaceous parts, and is well preserved in the distal Kushiro region as a 5-cm-thick tephra layer. The Ta-d tephra may be a useful chronostratigraphic marker for the early Holocene in eastern Hokkaido and bordering regions of the Pacific Ocean., The Geological Society of Japan
地質学雑誌, Jul. 2013, [Reviewed]

Development history and magma plumbing systems of Takakura Volcano, Sengan geothermal field, Tohoku, Japan
中谷咲子; 長谷川健; 藤縄明彦; 照井肇子, Corresponding, Takakura Volcano is located at the southern end of the Senzan geothermal field of the northeastern Japan arc, in the central part of the volcanic chain comprising Kotakakura, Takakura, and Marumori volcanoes. We have carried out a detailed geological and petrological investigation of Takakura Volcano in order to reveal its volcanic history and evolution of the magmatic plumbing system beneath the volcano. In addition, a K–Ar dating study of rock samples from the volcano was carried out. Takakura Volcano comprises two lava series: an older series (Takinosawa lava series) of the lower and eastern part of the volcano, and a younger series (Takakurasan lava series) from the present-day summit down to the southeastern and southern foot of the volcano. On the basis of field and petrological data, the Takinosawa and Takakurasan lava series can be divided into 13 (TS1–13; oldest to youngest) and 17 (TK1–17) units, respectively. One of the oldest samples of the TS1 has a K–Ar age of 0.44 ± 0.14 Ma.
Rocks of Takakura Volcano typically belong to the low-K tholeiitic series, and predominantly comprise basaltic andesite, andesite, and rare dacite. The tholeiitic lavas can be further divided into two groups on the basis of incompatible element concentrations such as Zr and Nb (i.e., high- and low-Zr groups). Although the two groups have been erupted continuously throughout the volcano's history, the high- and low-Zr groups have distinct compositional variation trends on geochemical diagrams. Furthermore, a different modal phenocryst assemblage is evident in each group. These observations suggest that the two groups were derived from independent magma plumbing systems, which have persisted throughout the lifetime of Takakura Volcano., The Geological Society of Japan
地質学雑誌, Jul. 2013, [Reviewed]

Calderas and Active Volcanoes in Central to Eastern Hokkaido
Hasegawa, T; Nakagawa, M; Kishimoto, H, Lead, 筆頭
Bull. Volcanol. Soc. Japan, Jun. 2013, [Reviewed]

Reconstructed Holocene sea level curve from the Akkeshi barrier system in eastern Hokkaido, Japan
Shigeno Kiyoyuki; Nanayama Futoshi; Sudo Yusuke; Sagayama Tsumoru; Hasegawa Takeshi; Ando Hisao, An active barrier system is present in Akkeshi Bay and a lagoonal area along the Pacific coast of eastern Hokkaido, Japan. This rare feature consists of a so-called lagoon (the Akkeshi-ko lagoon), a flood tidal delta, a barrier, and a tidal inlet that leads into the outer sea of Akkeshi Bay and the Pacific Ocean. Large oyster reefs were living on the flood tidal delta until their sudden extinction in the early 1980s. The processes involved in the formation of this barrier system during a postglacial transgression period are not well understood. Here, we use sedimentological, paleontological, and radiocarbon dating methods to analyze Holocene drillcore obtained from the Akkeshi fishing port in 2009 and borehole log data previously obtained from public works around the Akkeshi lowlands. The data obtained from both drillcore and borehole logs indicates that: (1) postglacial transgression occurred in this area some 11,400 years ago and reached 50 m below the present sea water level, with the barrier system in the study area established 8800 years ago. (2) The preservation of this barrier system is due to the stable sea level in this area. The sea level has been constant for the past 5500 years, and has led to the development of oyster reefs on the tidal flood delta. (3) The current topographically distinctive barrier system has been affected by sudden uplifts associated with giant earthquakes. These events occur every few hundred years, with the barrier undergoing prolonged but relatively rapid post-earthquake subsidence at about 1 cm/year, as observed after a giant 17th century earthquake., The Geological Society of Japan
The Journal of the Geological Society of Japan, 2013, [Reviewed]

High-temperature volcanic gas flow from the summit lava dome of Tarumai Volcano, Hokkaido, Japan
Hasegawa Takeshi; Miyamura Jun'ichi; Fushiya Yuji; Takahashi Yuji, Lead, 筆頭, The Geological Society of Japan
The Journal of the Geological Society of Japan, 2013, [Reviewed]

The eruption history and silicic magma systems of caldera-forming eruptions in eastern Hokkaido, Japan
Takeshi Hasegawa; Mitsuhiro Nakagawa; Hiroshi Kishimoto, Lead, The eruptive history and magma systems of large-scale explosive eruptions (VEI>5) in eastern Hokkaido, Japan, are reviewed on the basis of recently reported high-resolution tephrostratigraphy. More than 70 large-scale explosive eruptions have been recorded from the Akan, Kutcharo, Atosanupuri, and Mashu caldera volcanoes in the past 1.7 Ma. The total tephra volume of these eruptions is estimated to be approximately 1000 km(3). The discharge rate increases remarkably from 0.2 km(3)/kyr to 2.0 km(3)/kyr at approximately 0.2 Ma. The discharge rate is still high owing to the recent frequent activity of the Mashu caldera. The silicic magma systems of the Akan, Kutcharo, and Mashu calderas formed independently. On the other hand, the magma olAtosanupuri is associated with that of Kutcharo caldera., JAPAN ASSOC MINERALOGICAL SCIENCES
JOURNAL OF MINERALOGICAL AND PETROLOGICAL SCIENCES, Feb. 2012, [Reviewed]

Tephrostratigraphy and petrological study of Chikurachki and Fuss volcanoes, western Paramushir Island, northern Kurile Islands: Evaluation of Holocene eruptive activity and temporal change of magma system
Takeshi Hasegawa; Mitsuhiro Nakagawa; Mitsuhiro Yoshimoto; Yoshihiro Ishizuka; Wataru Hirose; Sho-ichi Seki; Vera Ponomareva; Rybin Alexander, A tephrostratigraphic and petrological study of the Chikurachki (1816 m)-Tatarinov-Lomonosov volcanic chain (CTL volcanic chain) and Fuss (1772 m), located at the southern part of Paramushir Island in the northern Kurile Islands, was carried out to reveal the explosive eruption history during the Holocene and the temporal change of the magma systems of these active volcanoes. Tephra successions were described at 54 sites, and more than 20 major eruptive units were identified, consisting of pumice fall, scoria fall and ash fall deposits, each of which are separated by paleosol or peat layers. The source volcano of each recognized tephra layer was confirmed by correlation with proximal deposits of each eruption center with respect to petrography and whole-rock and glass chemistry. The age of each layer was determined by radiocarbon dating and the stratigraphic relationship with the dated, widespread tephra from Kamchatka according to the thickness of paleosols bracketed between tephra layers. The Holocene activity in this region was initiated by eruptions from the Tatarinov and Lomonosov volcanoes. After the eruptions, the Fuss and Chikurachki volcanoes started their explosive activities at ca. 7.5 ka BP, soon after the deposition of widespread tephra from the Kurile Lake caldera in southern Kamchatka. Compared with Fuss located on the back-arc side, Chikurachki has frequent, repeated explosive and voluminous eruptions. Whole-rock compositions of the rocks of the CTL volcanic chain and Fuss are classified into medium-K and high-K groups, respectively. These suggest that magma systems beneath the CTL volcanic chain and Fuss differ from each other and have been independently constructed. The rocks of the Chikurachki volcano are basalt-basaltic andesite and have gradually evolved their chemical compositions; when graphed on a SiO(2)-oxide diagram, these form smooth trends from mafic to more felsic. This suggests that the magma system evolved mainly by fractional crystallization. In contrast, matrix glass chemistries for Fuss pumices are distinct for each eruption and show different K(2)O levels on a SiO(2)-K(2)O diagram. This implies that the magma system of Fuss has been frequently replaced. Both volcanoes have been active under the same subduction system. However, the Chikurachki volcano will continue eruptive activity under a stable magma system with a higher magma discharge rate, whereas Fuss may continue construction with an intermittent supply of distinct, small magma batches. (C) 2011 Elsevier Ltd and INQUA. All rights reserved., PERGAMON-ELSEVIER SCIENCE LTD
QUATERNARY INTERNATIONAL, Dec. 2011, [Reviewed]

Depositional ages of Quaternary sequences in the Kushiro region, eastern Hokkaido, Japan: Correlations and chronology on the basis of high-resolution tephro-stratigraphy
長谷川健; 中川光弘; 伊藤順一; 山元孝広, Lead, We investigated the correlation between pyroclastic materials in terrigenous marine deposits of the Kushiro region and pyroclastic deposits in the Akan volcanic area, eastern Hokkaido, with respect to Quaternary stratigraphy, glass chemistry, contents and assemblages of phenocrysts, and age determinations using tephro-chronology. A high-resolution Pleistocene tephro-stratigraphy of the Akan volcano was previously established for the Ak1–Ak17 sequence (youngest–oldest). The Akan eruptive deposits are intercalated with time-marker tephras derived from the adjacent Kutcharo volcano (KpI–KpVIII, youngest to oldest), central Hokkaido, and from unknown sources. In this study, pyroclastic materials in marine deposits in the Quaternary Otanoshike Formation, Kushiro region, were sampled at four type localities.
The Otanoshike Formation, covered by two pyroclastic flow deposits, contains two volcanic ashes, one in the lower part and one in the upper part of the formation. The lower and upper ashes correlate with the LowK-1 (source unknown) and Ak5 tephras, respectively. The overlying lower and upper pyroclastic flow deposits correlate with the KpVI and KpIV, respectively. The ages of the LowK-1 and KpIV tephras were estimated at ca. 0.8 and 0.1 Ma, respectively. These ages indicate that deposition of the Otanoshike Formation started by at least 0.8 Ma and finished before 0.1 Ma.
The Kushiro Formation, composed of the lower Takkobu and the upper Toro members, contains many reworked tephras, all originating from the Ak13–Ak17 tephras, implying that the Kushiro Formation formed before the Ak12 eruption. The Ak14 and Ak10 eruption ages are estimated at ca. 1.5 and 1.0 Ma, respectively, suggesting that deposition of the Kushiro Formation spanned the 1.5–1.0 Ma time period., The Geological Society of Japan
地質学雑誌, Dec. 2011, [Reviewed]

Bandai, Azuma, Adatara volcanoes: The three "rank-B" active volcanoes in Fukushima Prefecture
Hasegawa Takeshi; Fujinawa Akihiko; Ito Taku, Lead, 筆頭, 一般社団法人 日本地質学会
The Journal of the Geological Society of Japan, 2011, [Reviewed]

14Cages for the ejecta from Kutcharo and Mashu calderas, eastern Hokkaido, Japan.
山元孝広; 伊藤順一; 中川光弘; 長谷川健; 岸本博志, Eruption ages of the ejecta from Kutcharo and Mashu calderas were systematically determined by ¹⁴C dating. 16 charred samples were newly obtained from the Mashu and Nakashumbetsu Tephra Formations around the calderas and dated by AMS and β-counting methods. Examined units are Ma-d, Ma-e, Ma-f, Ma-j, Ma-k, Ma-l and Ml-a in the Mashu ejecta and 6 Nakashumbetsu tephra layers including Kutcharo Pumice Flow Deposit I (KpI), which is the youngest caldera-forming product from Kutcharo caldera. Results of the ¹⁴C dating range from 3,660 ±40 yBP to 36,080±1,300 yBP, and are consistent with the tephrostratigraphy. Calendar age for KpI was newly calculated at almost 40 ka and this age shows there was about 70,000 years recurrence interval between KpI and KpIV caldera-forming eruptions. Mashu caldera has appeared on the eastern part of Kutcharo caldera immediately after the KpI eruption, and calendar age for its main caldera-forming eruption were determined at ca. BC 5,600., National Institute of Advanced Industrial Science and Technology, Geological Survey of Japan
地質調査研究報告, Feb. 2010, [Reviewed]

Eruptive history of post-caldera volcanoes of Kutcharo caldera, eastern Hokkaido, Japan, as inferred from tephrostratigraphy in the Konsen and Shari areas for the period 35-12ka.
長谷川健; 岸本博志; 中川光弘; 伊藤順一; 山元孝広, Lead, The eruptive history of post-caldera volcanoes of Kutcharo caldera (Atosanupuri, Nakajima, and Mashu), eastern Hokkaido, Japan, was re-examined based on tephrostratigraphy above the layer KpI (35 ka), which is the youngest caldera-forming ignimbrite produced from the caldera. The studied areas are located to the east (Konsen) and north (Shari) of Kutcharo caldera. Between KpI and Ma-l (12 ka; the first eruption of the caldera-forming stage of Mashu volcano), at least 24 explosive eruptions Ml-a to (M1-d, Ch-a to Ch-d, and Nu-a to Nu-r, in descending order) are recognized in the Konsen area, and 10 (KoP, NaP, WTfl-2, KgSc, WTfl-1, KuSc, TyP, HkP, Ds-Oh, and YmP) are recognized in the Shari area. In addition, more than 20 thin scoria layers were found. Eight tephra layers in the Shari area can be correlated with those in the Konsen area, based on stratigraphy and petrology (e.g., glass chemistry and the mineralogy of juvenile materials) . The main phenocryst phases in these tephras are plagioclase, two pyroxenes, and Fe-Ti oxides, although some layers contain olivine and Nu-q includes hornblende. These tephras are divided into the following three groups based on the K₂O content of glass: Low-K (K₂O=0.4-0.9 wt.%), Medium-K (1.6-2.5 wt.%), and High-K (4.2-4.9 wt.%) . Nu-q, characterized by the presence of hornblende and a High-K composition, was possibly produced by the Daisetsu Ohachidaira caldera of central Hokkaido. The Medium-K group consists of 10 porphyritic (>11% phenocrysts), white-colored tephra layers. All other tephras, including the thin scoria layers, are assigned to the Low-K group. Based on geological and petrological data, and correlations with proximal deposits and edifices of each post-caldera volcano, we infer that the source volcanoes of the Medium-K and Low-K groups were the Atosanupuri/ Nakajima volcanoes and Mashu volcano, respectively. These results indicate that 10 explosive eruptions occurred at the Atosanupuri/Nakajima volcanoes over the period from 25 to 13 ka, with a total tephra volume of 16 km³. Mashu volcano produced more than 50 plinian eruptions (total tephra volume >90 km³) over the period from 35 to 1 ka, with no dormant periods exceeding several thousand years in duration., The Geological Society of Japan
地質学雑誌, Aug. 2009, [Reviewed]

Gravity structure of Akan composite caldera, eastern Hokkaido, Japan: Application of lake water corrections
Takeshi Hasegawa; Akihiko Yamamoto; Hiroyuki Kamiyama; Mitsuhiro Nakagawa, Lead, Akan volcano, eastern Hokkaido, Japan, is characterized by a rectangular-shaped caldera (Akan caldera: 24 kin by 13 km) with a complex history of caldera-forming eruptions during the Quaternary. A new Bouguer anomaly map of the caldera is presented on the basis of a gravity survey around Akan volcano. As part of and in addition to this survey, we applied gravimetry over the frozen caldera lake including lake water corrections. The Bouguer map shows the distribution of at least three sub-circular minima indicative of multiple depressions inside the caldera. Lake water corrections, performed by a numerical integration method using rectangular prisms, sharpen edges of the sub-circular minima. This gravity feature is consistent with geological investigations suggesting that caldera-forming eruptions of Akan volcano occurred from at least three different sources. It is concluded that Akan caldera can be described as a composite caldera with three major depressed segments., TERRA SCIENTIFIC PUBL CO
EARTH PLANETS AND SPACE, 2009, [Reviewed]

Tephrostratigraphy and Eruption Style of Mashu Volcano, During the Last 14,000 years, Eastern Hokkaido, Japan
KISHIMOTO Hiroshi; HASEGAWA Takeshi; NAKAGAWA Mitsuhiro; WADA Keiji, Corresponding, The eruptive history of Mashu volcano, located at the southeastern rim of Kutcharo caldera in eastern Hokkaido, Japan, has been divided into three stages: stratovolcano building, caldera-forming and central cone building. Tephrostratigraphy and eruption styles of the latter two stages were reinvestigated in conjunction with petrological analysis. We found new evidence of several eruptions from the volcano. These data, combined with recent ¹⁴C ages and the presence of wide-spread tephras, allow us to evaluate the temporal evolution of eruptive activity and styles of Mashu volcano during the last 14,000 years. After the formation of the stratovolcano, activity of the caldera forming stage started with plinian eruption (Ma-l) about 14cal ka. Approximately 7.5cal ka, climactic caldera-forming activity began with a phreatomagmatic eruption (Ma-j) followed by plinian falls (Ma-i～g), and a catastrophic pyroclastic flow (Ma-f) occurred resulting to the formation of the summit caldera, 7.5×5.5km in diameter. Total volume of the climactic eruption deposit is estimated to be 18.6km³. Temporal variation of pumice/lithic fragment and white (silicic)/gray (mafic) pumice ratio with eruption sequence suggest withdrawal of a zoned magma chamber with more silicic magma overlying more mafic one through the newly opened and enlarging vent. In the central cone building stage, at least eight eruptions (Ma-e, Ma-e´, Ma-d, Ma-c4～-c1 and Ma-b, in ascending order) have occurred repeatedly during the last 6,000 years. The latest eruption (Ma-b: ca. 0.9cal ka) was the largest one in this stage. Although most of the tephra layers in this stage are composed of pyroclastic fall deposits, thin pyroclastic flow deposits can also be recognized from the two eruptions (Ma-e and-d). Juvenile materials in the Mashu tephras are commonly pyroxene dacite (SiO₂=64-72wt.%, K₂O=0.5-0.7wt.% in whole-rock compositions). The pumice of the caldera-forming stage are nearly aphyric (1～6wt.%), whereas those of the central cone building stage are more porphyritic (13～24wt%). They can be also distinguished in SiO₂-oxides diagrams. Most of Mashu tephras consist of gray fine ash layers including blocky lithic/pumice fragments and accretionary lapilli, indicative of magma-water interactions. In the case of large eruptions, such as the climactic caldera-forming eruption (Ma-j～f) and Ma-b, eruptive styles changed from the wet to dry due to increase of the magma/water ratio. The long-term magma discharge rate was 0.8 and 0.3km³ DRE/ky during the last 14,000 and 6,000 years, respectively. Mashu volcano can be interpreted as one of the most productive and active volcanoes in Japan during Holocene., The Volcanological Society of Japan
BULLETIN OF THE VOLCANOLOGICAL SOCIETY OF JAPAN, 2009, [Reviewed]

Correlations of distal ash layers in the Akan pyroclastic deposits, eastern Hokkaido, with large-scale pyroclastic flow deposits distributed in central Hokkaido, Japan
HASEGAWA Takeshi; ISHII Eiichi; NAKAGAWA Mitsuhiro, Lead, Six distal rhyolitic ash layers (HR-1∼HR-6 in descending order) are interbedded in the pile of large-scale pyroclastic flow and pumice fall deposits derived from Akan volcano, eastern Hokkaido, during Pleistocene. These layers characteristically contain hydrous minerals such as hornblende and biotite, which are not common in the rocks of Quaternary volcanoes in eastern Hokkaido. Based on mineral assemblage, glass chemistry, and stratigraphy, these can be correlated with the early to middle Pleistocene large-scale pyroclastic flow deposits (pfld) distributed in central Hokkaido. The HR-5 and -6 layers have been already correlated with the Tokachi pfld (1.3∼1.46 Ma) in the central Hokkaido. In addition, we have newly correlated these ash layers to pfld in the central Hokkaido, as follows: HR-4 to the Tokachimitsumata pfld (1 Ma), HR-2 to the Kamishikaribetsu pfld and, HR-1 to the Kamiasahigaoka pfld, respectively. K-Ar ages for plagioclase in pumice of Kamiasahigaoka pfld is determined to be 0.51±0.14 Ma. These dates suggest that the large-scale felsic explosive volcanism had continued in both of central and eastern Hokkaido for at least eight hundred thousand years long during the early to middle Pleistocene. Especially, there is no evidence for dormancy, such as paleosol and erosional gap, between Ak14 and intercalating HR-5, indicating that large explosive eruptions simultaneously occurred in central and eastern Hokkaido. HR-1∼HR-6 could be Quaternary good time markers not only in eastern Hokkaido but also in Pacific Ocean and Kurile Islands because these tephras are more than 50 cm in thickness around Akan volcano., The Geological Society of Japan
The Journal of the Geological Society of Japan, 15 Jul. 2008, [Reviewed]

Inception of anticline growth near the Omagari Fault, northern Hokkaido, Japan
ISHII Eiichi; YASUE Ken-ichi; OHIRA Hiroto; FURUSAWA Akira; HASEGAWA Takeshi; NAKAGAWA Mitsuhiro, To know the beginning age of the anticline growth near the Omagari Fault in Neogene siliceous rocks, northern Hokkaido, Japan, this study is focused on determining differences in sedimentation rate as the anticline grew during sedimentation, at the sites of two boreholes, which are proximal (HDB-11) and distal (HDB-10), respectively, with respect to the anticlinal axis. We have investigated i) the petrographic and chronologic characteristics of tuff layers within mudstones in terms of several parameters: modal compositions, glass refractive indexes, glass chemical compositions and fission track ages; ii) the depth distribution of the opal-A/opal-CT diagenetic boundary between diatomaceous mudstone and siliceous mudstone; and iii) the effective porosity of the mudstones. Two tuff layers as key beds, HT1 and HT2, were found at HDB-10 and HDB-11, and yielded fission track ages of 2.9 Ma and 2.2 Ma, respectively. The sedimentation rates at HDB-10 and HDB-11 between HT1 and HT2 were estimated to match with the inferred basin trend or to have been nearly equal, based on their fission track ages, the thicknesses and the effective porosity of the mudstones. The depth distribution of the opal-A/opal-CT boundary and the effective porosity indicated that the maximum burial depth of HT2 was significantly shallower at HDB-11 than at HDB-10. Previous studies have found that maximum burial occurred at/before 1.0 Ma, suggesting that the sedimentation rate at HDB-11 was slower than at HDB-10 for the 2.2∼1.0 Ma period overall. We therefore infer that the anticline began to grow between 2.2 and 1.0 Ma. The inception of the anticline growth might be caused by the beginning of the active tectonism in and around this area., The Geological Society of Japan
The Journal of the Geological Society of Japan, 15 Jun. 2008, [Reviewed]

Stratigraphy of Early to Middle Pleistocene pyroclastic deposits around Akan caldera, eastern Hokkaido, Japan
HASEGAWA Takeshi; NAKAGAWA Mitsuhiro, Lead, Stratigraphy of pyroclastic deposits around Akan and Kutcharo calderas in eastern Hokkaido was investigated in order to reconstruct the eruptive history of the Akan volcano, and to clarify the stratigraphic relationships among pyroclastic deposits of Akan and other volcanoes. In addition to the geological data, source volcano of each deposit was identified using petrological features of juvenile materials, such as their phenocryst assemblages, whole-rock and glass chemistry. On the basis of the presence of significant time intervals, indicated by paleosol and erosional gap, we recognized at least 40 eruptive units of pyroclastic deposits (Akan pyroclastic deposits). Many of them are successions of pyroclastic fall deposits followed by pyroclastic flow deposits. Based on petrological features of juvenile materials of each unit, we grouped these units into 17 eruptive groups (Ak1 to Ak17 in descending order). Each group is composed of a single or sequential series of eruptive units. Whole-rock chemistry of juvenile materials is different from one group to another. This suggests that activities of each eruptive group were derived from distinct magma system.
We found several exotic pyroclastic flow deposits and distal air-fall ash layers within the Akan pyroclastic deposits. Pyroclastic flow deposits from adjacent Kutcharo caldera are interbedded between Ak2 and Ak3. One of them was dated to be 0.34 Ma. Distal rhyolitic ash layers from central Hokkaido (1.3−1.46 Ma) are recognized within Ak14. These dates suggest that the large-scale explosive volcanism at Akan volcano started in the Early Pleistocene and repeated many times for more than one million years. During the activity, the magma system was repeatedly renewed to produce eruptive group characteristics. This complex and long-term eruptive history of Akan volcano is probably reflected in the rectangle shape of Akan caldera. The shape of the possible composite caldera is different from the circular shapes of many other calderas.
, The Geological Society of Japan
The Journal of the Geological Society of Japan, 15 Feb. 2007, [Reviewed]

Gravity structure of the Akan Caldera and its vicinity, Eastern Hokkaido, Japan
Takeshi Hasegawa; Akihiko Yamamoto; Hiroyuki Kamiyama; Mitsuhiro Nakagawa, Lead, We performed gravity surveys and compiled pre-existing gravity data to obtain gravity anomalies of the Akan Caldera, eastern Hokkaido, and a new gravity map around the caldera was produced. In particular, we conducted gravity surveys on the frozen lake surface in winter to reveal a fine gravity structure. A new Bouguer anomaly map shows that the Akan Caldera is characterized by three closed mimima and takes its minimum value (∼70 mgal) in the central area of the caldera. It is consistent with our geologic studies suggesting that the Akan Caldera is multiple caldera. Characteristic low anomalies in the Akan Caldera gradually increase towards topographic rim outside and reach their maximum around the rims. Post-caldera volcanoes are distributed not along topographic caldera rim but along a periphery of the low-anomaly region, which is situated inside the topographic rim.
Journal of the Hokkaido University, Faculty of Science, Series VII: Geophysics, Dec. 2006, [Reviewed]

Gravity anomaly and intrusive style of the tilted Tottabetsu plutonic complex, Hidaka Mountains, Northern Japan
Hiroyuki Kamiyama; Akihiko Yamamoto; Takeshi Hasegawa; Takanori Kajiwara; Toru Mogi, 担当：現地調査・重力測定

査読は内部査読
Journal of the Hokkaido University, Faculty of Science, Series VII: Geophysics, Dec. 2006, [Reviewed]

Gravity and density variations of the tilted Tottabetsu plutonic complex, Hokkaido, northern Japan: implications for subsurface intrusive structure and pluton development
H Kamiyama; A Yamamoto; T Hasegawa; T Kajiwara; T Mogi, An exposed cross section of the tilted Tottabetsu plutonic complex allows direct evaluation of its original 2-D cross-sectional shape and pretilting vertical density variations in both the pluton and the country rocks, which serves as a strong constraint in gravity modeling that complements information on the 'missing' pretilting horizontal dimension of this tilted pluton. The pluton is stratified with the uppermost thin granitic unit (similar to 1-km thick) and the underlying thick gabbro-diorite units (similar to 9-km thick) that preserve a stratigraphic record of numerous hotter replenishments in the form of alternation of originally horizontal mafic sheets and cumulate layers. Both the pluton and the country rocks show systematic density increase with pretilting crustal depth, but density contrast of the pluton with the country rocks varies between each unit. The 2-D cross-sectional shape and gravity analysis revealed that the pluton had a vertically-elongated shape with vertical side walls before tilting. The vertical side walls, together with the stack of the originally horizontal sheets and cumulate layers, suggests that the pluton grew only vertically by piston mechanism. The very thick, exposed cross section provides unequivocal evidence for development of such a pluton with this unusual shape and mass distribution, which has been inferred elsewhere only by some geophysical studies., TERRA SCIENTIFIC PUBL CO
EARTH PLANETS AND SPACE, 2005, [Reviewed]

Magma Discharge Step-diagram (Step-diagram) of Chausudake, Nasu Volcano Group, NE Japan-Evaluation for long- to middle-term activities-
長谷川健; 渡部将太; 北原遼太; 北原遼太; 吉川洸希; 井上結莉乃
防災科学技術研究所研究資料(Web), 2024

沈み込み初期における北西インドNidarオフィオライト層火成岩類の成因
佐藤成修; 今山武志; DRIPTA Dutta; 金田泰明; 渡部将太; 長谷川健; 南雅代; 若杉勇輝; 若木重行
名古屋大学年代測定研究, 2022

那須火山群の熱ルミネッセンス年代
長谷川 健; 渡部; 小畑 直也; 豊田 新; ハセガワ タケシ; ワタナベ; オバタ ナオヤ; トヨダ シン
岡山理科大学古生物学・年代学研究センター事業報告, Mar. 2021

アトサヌプリのボーリングコア
長谷川健; 中川光弘; 宮城磯治
気象庁火山観測点ボーリングコアの解析2016（平成28）年度成果報告書, Mar. 2017

CONNECTING MARINE AND ON-LAND PALEOINITENSITY STUDIES
Hidetoshi Shibuya; Nobutatsu Mochizuki; Takeshi Hasegawa; Makoto Okada
Geological Society of America Abstracts with Programs, 2017, [Invited]

The history of caldera-forming eruptions in eastern Hokkaido, Japan
長谷川 健; 中川 光弘; 岸本 博志
月刊地球, Dec. 2011

秋田駒ケ岳のボーリングコア
藤縄明彦; 長谷川健; 林信太郎; 伊藤順一
気象庁火山観測点ボーリングコアの解析～成果報告書～, Mar. 2011

アトサヌプリのボーリングコア
長谷川健; 中川光弘; 宮城磯治
気象庁火山観測点ボーリングコアの解析～成果報告書～, Mar. 2011

東日本大震災調査報告「地質災害」　　　　　　　　　　　　　　　
天野一男; 安藤寿男; 藤縄明彦; 宮下芳; 岡田誠; 河原 純; 本田尚正; 長谷川健; 他
東日本大震災調査報告書, 2011

2008年11月に噴火した雌阿寒岳の調査報告
石丸聡; 田村慎; 廣瀬亘; 村山泰司; 岡崎紀俊; 柴田智郎; 中川光弘; 吉本充宏; 長谷川健; 上澤真平; 西本潤平; 小杉安由美; 松本亜希子; 馬場彰; 佐々木寿; 高橋浩晃; 一柳昌義; 山口照寛; 河野裕希; 本多亮; 笠原稔
北海道立地質研究所報告, 31 Mar. 2009

カルデラ生成噴火―準備過程の理解にむけて―北海道東部のテフラ層序からみた後屈斜路カルデラ火山活動
長谷川健; 岸本博志; 中川光弘; 伊藤順一; 山元孝広
月刊地球, 01 Dec. 2008

カルデラ生成噴火―準備過程の理解にむけて―北海道東部,屈斜路軽石流堆積物IVの岩相変化からみるカルデラ形成噴火の噴火推移とマグマ供給系
松本亜希子; 長谷川健; 中川光弘
月刊地球, 01 Dec. 2008

カルデラ生成噴火―準備過程の理解にむけて―斑晶累帯構造および斑晶ガラス包有物に基づく屈斜路火山及び摩周火山のマグマプロセスの解明に関する研究
宮城磯治; 伊藤順一; NGUYEN Hoang; 山元孝広; 長谷川健; 岸本博志; 中川光弘
月刊地球, 01 Dec. 2008

Preliminary report on volcanological research of KBP 2007–2008 Cruise by Japanese volcanology group
Mitsuhiro Nakagawa; Yoshihiro Ishizuka; Takeshi Hasegawa; Akira Baba; Ayumi Kosugi
31 Mar. 2008

Eruptive sequence and magma plumbing system during Kutcharo caldera-forming eruption (Kp 4) inferred from facis variation of Kutcharo pumice flow deposit 4
松本 亜希子; 長谷川 健; 中川 光弘
Chikyu Monthly, 2008

Eruptive history of the post-caldera volcanoes of Kutcharo caldera, inferred from tephrostratigraphy in eastern Hokkaido, Japan
長谷川 健; 岸本 博志; 中川 光弘
Chikyu Monthly, 2008

The eruption on March 2006 at Meakandake volcano, Hokkaido, northern Japan: eruption process and ash fall survey
廣瀬亘; 岡崎紀俊; 石丸聡; 長谷川健; 藤原伸也; 中川光弘; 佐々木寿; 佐藤十一
北海道立地質研究所報告, 30 Mar. 2007

長方形カルデラの形成機構の解明~北海道東部阿寒カルデラを例として~
長谷川健
深田研究助成研究報告, 25 Oct. 2006

活火山における噴火様式の時代的変遷と長期噴火予測 降下軽石層に含まれる石質岩片から類推する阿寒カルデラの形成過程
長谷川健; 石井英一; 中川光弘
月刊地球, 01 May 2006

降下軽石層に含まれる石質岩片から類推する阿寒カルデラの形成過程 (総特集 活火山における噴火様式の時代的変遷と長期噴火予測(上))
長谷川 健; 石井 英一; 中川 光弘
月刊地球, May 2006

Gravity anomaly and intrusive style of the tilted Tottabetsu plutonic complex, Hidaka Mountains, Northern Japan
KAMIYAMA Hiroyuki; YAMAMOTO Akihiko; HASEGAWA Takeshi; KAJIWARA Takanori; MOGI Toru
Geophysical bulletin of Hokkaido University, Mar. 2006

Gravity Structure of the Akan Caldera and Its Vicinity, Eastern Hokkaido, Japan
HASEGAWA Takeshi; YAMAMOTO Akihiko; KAMIYAMA Hiroyuki; NAKAGAWA Mitsuhiro
Geophysical bulletin of Hokkaido University, Mar. 2006

安達太良山沼ノ沢火口の地殻変動及び全磁力の繰り返し観測1997-2002年
高木朗充; 重野伸昭; 山本哲也; 大和田毅; 福井敬一; 藤原健治; 坂井孝行; 長谷川浩; 瀧沢倫明
日本火山学会講演予稿集, 2002

「最新」地学事典
地学団体研究会; 地学団体研究会最新地学事典編集委員会, Contributor
平凡社, Mar. 2024
9784582115086

富士山噴火に備える　　　　　　　　　　　　　　　
科学; 編集部, Joint work
岩波書店, Feb. 2023
9784000063425

５万分の一地質図幅および説明書「網走」　　　　　　　　　　　　　　　
廣瀬 亘; 川上源太郎; 長谷川健; 林 圭一; 渡辺真人, Contributor
地質調査所, 2018

釧路叢書「The Great Nature of Akan 阿寒の大自然誌」　　　　　　　　　　　　　　　
HASEGAWA Takeshi, Contributor
釧路市, 2017

フィールド活用ハンドブック「阿寒の自然と文化－阿寒の魅力再発見 自然史の最新研究を学ぶ―」　　　　　　　　　　　　　　　
HASEGAWA Takeshi, Contributor
釧路市, 2016

特集「日本をおそった巨大噴火」 雑誌『科学』　　　　　　　　　　　　　　　
中川 光弘; 長谷川 健; 松本 亜希子, Contributor
岩波書店, Jan. 2014

Holocene: Perspectives, Environmental Dynamics and Impact Events　　　　　　　　　　　　　　　
Takeshi Hasegawa, Contributor
Nova Science Publishers, Feb. 2013
9781622577224

Arctic Circle　　　　　　　　　　　　　　　
HASEGAWA Takeshi, Contributor
財団法人北方文化振興協会, 2012

『日本地方地質誌 北海道地方』日本地質学会編　　　　　　　　　　　　　　　
長谷川健; 中川光弘, Contributor
朝倉書店, Nov. 2010
9784254167818

Estimation of the Eruptive Process of Ak2 from Akan Caldera Using Paleomagnetic Techniques　　　　　　　　　　　　　　　
佐藤勇輝; 西来邦章; 長谷川健; 柴田翔平; 楠稚枝; 岡田誠
日本火山学会講演予稿集, 2024
2024, 2024

Tephrostrathigraphy around Kutcharo caldera and their petrological characteristics, eastern Hokkaido, Japan
柴田翔平; 長谷川健
日本火山学会講演予稿集, 2024, The Volcanological Society of Japan
2024, 2024

Reconstruction of the sequence of 1893-1895CE Meiji eruption at Azuma-Jododaira volcano, Fukushima prefecture, based on historical records and field survey　　　　　　　　　　　　　　　
甲野藤ゆうな; 長谷川健; 及川輝樹
日本火山学会講演予稿集, 2024
2024, 2024

Re-investigation of the eruptive history of Chausu-dake volcano, Nasu Volcanic Group　　　　　　　　　　　　　　　
石射一希; 渡部将太; 長谷川健
日本火山学会講演予稿集, 2024
2024, 2024

Component analysis and characteristics of hydrothermally altered minerals in the 1408-1410CE eruption deposit from Nasu-Chausudake volcano, Northeast, Japan　　　　　　　　　　　　　　　
北原遼太; 鈴木里玖; 長谷川健
日本火山学会講演予稿集, 2024
2024, 2024

Matuyama-Brunhes reversal in oriented drill cores from Akan caldera-forming eruption deposits, east Hokkaido, Japan　　　　　　　　　　　　　　　
長谷川健; 楠稚枝; 岡田誠; 平塚葵; 西来邦章; 佐藤勇輝
日本地球惑星科学連合大会予稿集(Web), 2023
2023, 2023

Generation and magma fragmentation process of a large-scale phreatoplinian eruption inferred from the water content of volcanic glass　　　　　　　　　　　　　　　
柴田翔平; 長谷川健
日本地球惑星科学連合大会予稿集(Web), 2023
2023, 2023

Proposal of the procedure of creating the time -accumulated eruption volume step diagram　　　　　　　　　　　　　　　
中川光弘; 宮縁育夫; 長谷川健; 古川竜太; 上澤真平; 長井雅史
日本地球惑星科学連合大会予稿集(Web), 2023
2023, 2023

Origin of magma from Futamatayama volcano, Nasu volcano group, NE Japan: Evolution processes of crust-mantle interaction　　　　　　　　　　　　　　　
渡部将太; 長谷川健; 松本亜希子; AKA Festus Tongwa; 中川光弘
日本地球惑星科学連合大会予稿集(Web), 2023
2023, 2023

Componentry of lithic fragments in the 120 ka Kutcharo caldera-forming eruption deposit (KpIV), eastern Hokkaido, Japan　　　　　　　　　　　　　　　
長田美里; 長谷川健; 柴田翔平
日本地球惑星科学連合大会予稿集(Web), 2023
2023, 2023

Evolution of stress state in the crust beneath Aira caldera since the 1914 eruption of Sakurajima volcano: Inferences from viscoelastic volcano deformation model constrained by geodetic and geophysical data　　　　　　　　　　　　　　　
山崎雅; 長谷川健; LI Siqi; SIGMUNDSSON Freysteinn
日本火山学会講演予稿集, 2023
2023, 2023

Paleomagnetic directions of Kutcharo pumice flow deposits II/III and Aso-4 tephra: investigation of the duration time and simultaneity for caldera-forming eruptions　　　　　　　　　　　　　　　
柴田翔平; 長谷川健; 谷元瞭太; 望月伸竜; 岡田誠
日本火山学会講演予稿集, 2023
2023, 2023

Pyroclastic eruptive history of Azuma-Jododaira volcano during the last 700 years　　　　　　　　　　　　　　　
井村匠; 伴雅雄; 大津好秋; 井上朋紀; 常松佳恵; 長谷川健; 大場司
日本火山学会講演予稿集, 2023
2023, 2023

Structural evolution of small caldera in light of eruption sequence and drill core of Nigorikawa Caldera, southwest Hokkaido, Japan.
金田泰明; 長谷川健
日本火山学会講演予稿集, 2023, The Volcanological Society of Japan
2023, 2023

Time breaks during caldera-forming eruption: inferred from paleomagnetic directions of Plinian fall deposit and overlying ignimbrite
長谷川健; 望月伸竜
日本火山学会講演予稿集, 2023, The Volcanological Society of Japan
2023, 2023

Spacial-temporal distribution of the Miocene adakitic volcanic rocks in Daigo, Hitachi-omiya and Motegi districts, Ibaraki and Tochigi Prefectures, Northeast Japan　　　　　　　　　　　　　　　
小坂日奈子; 長谷川健; 内山玄基; 田切美智雄; 細井淳
日本地質学会学術大会(Web), 2023
2023, 2023

The genesis of Ba anomaly in pumice from the Nigorikawa volcano, southwestern Hokkaido, Japan: Identifying altered recycled pumice in caldera-forming eruption.　　　　　　　　　　　　　　　
金田泰明; 長谷川健; 井村匠
日本地質学会学術大会(Web), 2023
2023, 2023

Magma plumbing system of youngest magmatic eruption products of Azuma Volcano, NE Japan　　　　　　　　　　　　　　　
伴雅雄; 菅野舜; 佐藤初洋; 井村匠; 常松佳恵; 長谷川健
日本地質学会学術大会(Web), 2023
2023, 2023

A preliminary study of primary magma and mantle melting condition below Futamata Volcano, Nasu Volcano Group, Japan
Watanabe Shota; Hasegawa Takeshi; Aka Festus T.; Matsumoto Akiko; Nakagawa Mitsuhiro
PROGRAMME AND ABSTRACTS THE VOLCANOLOGICAL SOCIETY OF JAPAN, 2023, The Volcanological Society of Japan
2023, 2023

Eruption sequence and style of the Azumakofuji pyroclastic cone, Azuma-Jododaira Volcano, Japan　　　　　　　　　　　　　　　
鈴木和馬; 戸丸淳晴; 長谷川健
日本火山学会講演予稿集, 2022
2022, 2022

Stratigraphy and eruptive history of Azumakofuji, Azuma Volcanic Group, Fukushima, Japan　　　　　　　　　　　　　　　
鈴木和馬; 戸丸淳晴; 長谷川健
日本地質学会学術大会(Web), 2022
2022, 2022

Petrological and mineralogical investigation of tephra layers from Nasu Chausudake volcano, Japan　　　　　　　　　　　　　　　
吉川洸希; 長谷川健; CONWAY Chris; 谷健一郎
日本火山学会講演予稿集, 2022
2022, 2022

Paleomagnetic dating of large volcanic bombs around Tsubakurosawa craters, Azuma volcano, NE Japan: Was the 1893 eruption magmatic?　　　　　　　　　　　　　　　
長谷川健; 菊池文太; 柴田翔平; 山本裕二; 井村匠; 伴雅雄; 岡田誠; 相部達郎
日本地球惑星科学連合大会予稿集(Web), 2022
2022, 2022

Phreatomagmatic stratigraphy and eruptive history of maar cluster at the southern coastal area, Miyakejima Volcano, Japan　　　　　　　　　　　　　　　
渡部将太; 及川輝樹; 下司信夫; 長谷川健
日本地球惑星科学連合大会予稿集(Web), 2022
2022, 2022

The generation process of phreatoplinian eruption seen from 40 ka eruption (Kp I) from Kutcharo volcano, Eastern Hokkaido, Japan: About the contact conditions of magma with external water　　　　　　　　　　　　　　　
柴田翔平; 長谷川健
日本地球惑星科学連合大会予稿集(Web), 2022
2022, 2022

Evaluation of Post-caldera Activity of Nigorikawa Volcano, SW Hokkaido　　　　　　　　　　　　　　　
金田泰明; 長谷川健
日本火山学会講演予稿集, 2021
2021, 2021

Paleomagnetic dating of Taupo eruption, New Zealand　　　　　　　　　　　　　　　
長谷川健; GREVE Annika; GRAVLEY Darren; 楠稚枝; 岡田誠; KOSIK Szabolcs; 望月伸竜; 金田泰明
日本火山学会講演予稿集, 2021
2021, 2021

Eruptive stratigraphy and petrological characteristics during 4.0-2.5 ka of Miyakejima Volcano, Japan: Magmatic evolution process from dormant to active stages　　　　　　　　　　　　　　　
渡部将太; 長谷川健; 及川輝樹; 下司信夫
日本火山学会講演予稿集, 2021
2021, 2021

Eruption history and magma plumbing system of Futamatayama Volcano, southern Fukushima, Japan　　　　　　　　　　　　　　　
渡部将太; 長谷川健; 小畑直也; 豊田新; 今山武志
日本地質学会学術大会(Web), 2021
2021, 2021

富士火山北東麓に分布する最新期テフラの層序　　　　　　　　　　　　　　　
古屋海砂; 吉本充宏; 馬場 章; 長谷川 健
日本火山学会2020年秋季大会, 09 Oct. 2020
20201008, 20201010

給源近傍層序からみた屈斜路火山 40 ka噴火 ( KpI ) のカルデラ形成過程　　　　　　　　　　　　　　　
柴田 翔平; 長谷川 健; 渡部将太
日本火山学会2020年秋季大会, 08 Oct. 2020
20201008, 20201010

古地磁気方位と永年変化を利用した大規模カルデラ噴火の継続時間の推定：姶良カルデラとMamaku/Ohakuri ignimbritesの例　　　　　　　　　　　　　　　
長谷川 健; 望月 伸竜; Gravley Darren; 楠 稚枝; 岡田 誠; 下司 信夫; Kosik Szabolcs; 柴田 翔平; 金田 泰明
JpGU-AGU Joint Meeting 2020, Chiba, 13 Jul. 2020
20200712, 20200715

北海道東部，屈斜路火山40 ka噴火 (KpⅠ)の層序と噴火様式　　　　　　　　　　　　　　　
柴田 翔平; 長谷川 健
JpGU-AGU Joint Meeting 2020, 12 Jul. 2020
20200712, 20200715

北海道南西部，濁川火山における地質学・岩石学的研究　　　　　　　　　　　　　　　
金田 泰明; 長谷川 健
JpGU-AGU Joint Meeting 2020, 12 Jul. 2020
20200712, 20200715

三宅島火山，南部地域における坪田期（4.0〜2.5 ka）の噴火層序とマグマ組成の特徴　　　　　　　　　　　　　　　
渡部 将太; 長谷川 健; 及川 輝樹; 下司 信夫
JpGU-AGU Joint Meeting 2020, 12 Jul. 2020
20200712, 20200715

Caldera-forming process of 40 ka KpI eruption of Kutcharo Volcano, inferred from proximal deposits　　　　　　　　　　　　　　　
柴田翔平; 長谷川健; 渡部将太
日本火山学会講演予稿集, 2020
2020, 2020

Eruptive stratigraphy and magma compositions of the Tsubota stage (4.0-2.5 ka) in the southern part of the Miyakejima Volcano, Japan　　　　　　　　　　　　　　　
渡部将太; 長谷川健; 及川輝樹; 下司信夫
日本地球惑星科学連合大会予稿集(Web), 2020
2020, 2020

Stratigraphy and eruption styles of 40 ka Kp I eruption, Kutcharo Volcano, Eastern Hokkaido, Japan　　　　　　　　　　　　　　　
柴田翔平; 長谷川健
日本地球惑星科学連合大会予稿集(Web), 2020
2020, 2020

Magma plumbing system of the pre-climactic activity of a large silicic caldera-forming eruption: Case studies from 7.3 ka Kikai (K-Ah) and 120 ka Kutcharo (Kp IV) eruptions
Matsumoto Akiko; Nakagawa Mitsuhiro; Maeno Fukashi; Hasegawa Takeshi
PROGRAMME AND ABSTRACTS THE VOLCANOLOGICAL SOCIETY OF JAPAN, 2019, The Volcanological Society of Japan
2019, 2019

大規模珪長質噴火の先行活動-鬼界7.3ka噴火および屈斜路120ka噴火の例-　　　　　　　　　　　　　　　
松本亜希子; 中川光弘; 前野深; 長谷川健
日本火山学会講演予稿集, 2019
2019, 2019

千島海溝沿岸の地震性バリアーシステムに認められる17世紀超巨大地震による海岸隆起と大津波の発生時期の前後関係
七山太; 七山太; 渡辺和明; 深津恵太; 長谷川健; 重野聖之; 石井正之; 石渡一人; 猪熊樹人
日本地球惑星科学連合大会予稿集(Web), 2019

北海道南西部,濁川火山のカルデラ形成期噴出物の岩石学的特徴
金田泰明; 長谷川健
日本地球惑星科学連合大会予稿集(Web), 2019

那須火山群,二岐火山の地質と岩石
渡部将太; 長谷川健
日本地球惑星科学連合大会予稿集(Web), 2019

北海道東部,摩周火山における7.6kaカルデラ形成噴火の推移
柴田翔平; 長谷川健
日本地球惑星科学連合大会予稿集(Web), 2019

那須茶臼岳火山,1408年~1410年噴火(室町噴火)の推移
長谷川健; 北原遼太
日本火山学会講演予稿集, 26 Sep. 2018

栃木県北部,高原火山におけるカルデラ形成期の活動年代とマグマ系
西野佑紀; 長谷川健
日本火山学会講演予稿集, 26 Sep. 2018

栃木県,高原火山におけるカルデラ形成期初期噴出物の年代
西野佑紀; 伊藤久敏; 長谷川健; 菊地瑛彦
日本第四紀学会講演要旨集, 24 Aug. 2018

支笏カルデラ噴火堆積物の古地磁気学的測定:大規模噴火堆積物の時間間隙の推定へ向けて　　　　　　　　　　　　　　　
望月伸竜; 長谷川健; 中川光弘
日本地球惑星科学連合大会予稿集(Web), 2018
2018, 2018

野付崎バリアースピッツの現行過程から読み解く過去と未来
七山太; 七山太; 渡辺和明; 重野聖之; 石井正之; 長谷川健; 内田康人; 石渡一人
日本地球惑星科学連合大会予稿集(Web), 2018

鬼界カルデラ形成噴火における時間間隙:古地磁気方位と地磁気永年変化からの推定
長谷川健; 望月伸竜; 大岩根尚
日本地球惑星科学連合大会予稿集(Web), 2018

北海道東部,摩周火山東麓のボーリングコア記載とその特徴
岸本博志; 長谷川健; 中川光弘
日本地球惑星科学連合大会予稿集(Web), 2018

日本火山学会60周年事業を契機とした現状把握と将来への取り組み
井口正人; 奥村聡; 竹内晋吾; 長谷川健; 鈴木雄治郎; 中村仁美; 市原美恵
日本地球惑星科学連合大会予稿集(Web), 2018

栃木県,高原火山におけるカルデラ形成期の火砕堆積物の層序と年代
西野佑紀; 長谷川健; 藤縄明彦; 菊地瑛彦
日本火山学会講演予稿集, 21 Sep. 2017

福島県南部,鎌房山における火砕堆積物をもたらしたマグマ供給系
関根大輔; 長谷川健; 藤縄明彦
日本火山学会講演予稿集, 21 Sep. 2017

北海道東部,摩周火山で7,600年前に発生したカルデラ形成噴火の推移
長谷川健; 長谷川弘樹; 小林哲夫; GRAVLEY Darren
日本火山学会講演予稿集, 21 Sep. 2017

5万分の1地質図幅「網走」の概要
川上源太郎; 廣瀬亘; 林圭一; 渡辺真人; 長谷川健
日本地質学会学術大会講演要旨, 10 Sep. 2017

野付崎バリアースピッツの現行過程の視点から読み解く現在・過去・未来
七山太; 七山太; 渡辺和明; 重野聖之; 石井正之; 長谷川健; 内田康人; 石渡一人
日本第四紀学会講演要旨集, 26 Aug. 2017

大規模珪長質マグマ系の多様性とその成因
中川光弘; 松本亜希子; 長谷川健
日本地球惑星科学連合大会予稿集(Web), 2017

福島県南部,鎌房山火砕堆積物・岩屑なだれ堆積物の給源
関根大輔; 長谷川健
日本地球惑星科学連合大会予稿集(Web), 2017

野付崎バリアースピッツの地形発達史から読み解く根室海峡沿岸域の完新世地殻変動
七山太; 渡辺和明; 重野聖之; 長谷川健; 石渡一人; 和田直人; 小野哲也
日本地質学会学術大会講演要旨, 05 Sep. 2016

モンゴル西部の湖沼堆積物を用いた完新世後期の古環境変動解析　　　　　　　　　　　　　　　
早川翼; 勝田長貴; 國分(齋藤)陽子; 長谷部徳子; 村上拓馬; 宮田佳樹; 長谷川精; 長尾誠也; 川上紳一; 柏谷健二
日本地球惑星科学連合大会予稿集(Web), 2016
2016, 2016

福島県南部,鎌房山における火砕堆積物・岩屑なだれ堆積物の層序
関根大輔; 長谷川健
日本火山学会講演予稿集, 2016

伊豆大島テフラの自然残留磁化の基礎研究
望月伸竜; 長谷川健
地球電磁気・地球惑星圏学会総会及び講演会(Web), 2016

北海道東部,アトサヌプリ溶岩円頂丘における水蒸気噴火の発生履歴
長谷川健; 中川光弘; 宮城磯治
日本地質学会学術大会講演要旨, 10 Sep. 2015

阿寒湖沼群における水環境と水生植物群落の多様性
若菜勇; 尾山洋一; 田村由紀; 山田浩之; 和田恵治; 長谷川健; 大原雅
日本植物学会大会研究発表記録, 01 Sep. 2015

P70 Eruption history and magma systems of Nyos volcano, northwestern Cameroon
Hasegawa T.; Ohba T.; Kusakabe M.; G Tanyileke; J.V. Hell; Miyabuchi Y.; Kobayashi T.; F.T. Aka; K. Boniface; Issa; L.A. Nche; C.S.F. Nguemhe; Kaneko K.
PROGRAMME AND ABSTRACTS THE VOLCANOLOGICAL SOCIETY OF JAPAN, 2015, The Volcanological Society of Japan
2015, 2015

カメルーン北西部,ニオス火山の噴火史とマグマ系
長谷川健; 宮縁育夫; 小林哲夫; AKA F.T; BONIFACE K; ISSA; NCHE L.A; NGUEMHE C.S.F; 金子克哉; 大場武; 日下部実; TANYILEKE G; HELL J.V
日本火山学会講演予稿集, 2015

絶対古地磁気強度とテフロクロノロジー:相対古地磁気強度変動曲線の絶対較正
望月伸竜; 藤井哲夢; 長谷川健; 岡田誠; 渋谷秀敏
日本地球惑星科学連合大会予稿集(Web), 2015, [Invited]

カメルーン北西部,ニオス火山の噴火史
長谷川健; 宮縁育夫; 小林哲夫; AKA Festus; BONIFACE Kankeu; ISSA; MICHE Linus; FILS Salomon; 金子克哉; 大場武; 日下部実; GREGORY Tanyileke; JOSEPH Hell
日本地球惑星科学連合大会予稿集(Web), 2015

P2-13 Geological characteristics and emplacement mechanism of the Yosasagawa Debris Avalanche Deposit from Nasu Volcanic Group, North Tochigi Prefecture　　　　　　　　　　　　　　　
Kikuchi Akihiko; Hasegawa Takeshi
Programme and abstracts the Volcanological Society of Japan, 02 Nov. 2014, Volcanological Society of Japan
20141102, 20141102

B1-22 Eruption history of Nyos volcano, northwestern Cameroon : Preliminary report　　　　　　　　　　　　　　　
Hasegawa T.; Miyabuchi Y.; Kobayashi T.; Aka Festus T.; Boniface Kankeu; Kaneko K.; Ohba T.; Kusakabe M.; Tanyileke Gregory; Hell Joseph
Programme and abstracts the Volcanological Society of Japan, 02 Nov. 2014, Volcanological Society of Japan
20141102, 20141102

地殻変動によって規制された完新世走古丹バリアースピットの堆積様式
七山太; 重野聖之; 渡辺和明; 吉川秀樹; 長谷川健; 池田保夫; 五十嵐八枝子; 秋葉文雄; 内田康人; 石渡一人
日本地質学会学術大会講演要旨, 10 Sep. 2014

風蓮湖,走古丹バリアースピットの地形発達史から読み解く根室海峡沿岸域の完新世海面変動と地殻変動
重野聖之; 七山太; 渡辺和明; 吉川秀樹; 長谷川健; 池田保夫; 五十嵐八枝子; 秋葉文雄; 内田康人; 石渡一人
日本第四紀学会講演要旨集, 05 Sep. 2014

栃木県北部,那須火山群を給源とする余笹川岩屑なだれの地質学的特徴と運搬・堆積機構
菊地瑛彦; 長谷川健
日本火山学会講演予稿集, 2014

カメルーン北西部,ニオス火山の噴火史(序報)
長谷川健; 宮縁育夫; 小林哲夫; AKA Festus T; BONIFACE Kankeu; 金子克哉; 大場武; 日下部実; TANYILEKE Gregory; HELL Joseph
日本火山学会講演予稿集, 2014

走古丹バリアースピットの地形発達史から読み解く根室海峡沿岸域の過去5500年間の海面変動と地殻変動
七山太; 渡辺和明; 吉川秀樹; 重野聖之; 長谷川健; 池田保夫; 境智洋; 石渡一人; 内田康人
日本地質学会学術大会講演要旨, 10 Sep. 2013

福島県南部白河地域,鎌房山火砕流堆積物の噴火層序とマグマ系
長谷川健; 松浦奈央; 伴雅雄
日本地質学会学術大会講演要旨, 10 Sep. 2013

千島列島の完新世テフラ層序の確立とその意義
中川光弘; 馬場章; 石塚吉浩; 長谷川健; 小杉安由美
日本海洋学会大会講演要旨集, 30 Aug. 2013

那須茶臼岳火山,1408-1410年噴火における噴出物と噴火推移の再検討　　　　　　　　　　　　　　　
長谷川健; 伴雅雄
日本火山学会講演予稿集, 2013
2013, 2013

那須茶臼岳火山,1408‐1410年噴火における噴出物と噴火推移の再検討
長谷川健; 伴雅雄
日本火山学会講演予稿集, 2013

広域テフラに対比される溶結凝灰岩による絶対古地磁気強度測定:相対古地磁気強度との対比と絶対値較正
藤井哲夢; 望月伸竜; 長谷川健; 岡田誠; 渋谷秀敏
地球電磁気・地球惑星圏学会総会及び講演会予稿集(CD-ROM), 2013

完新世バリアーシステムと海水準変動の復元:北海道東部厚岸沿岸低地の例
重野聖之; 七山太; 内田康人; 嵯峨山積; 長谷川健; 安藤寿男
堆積学研究, 28 Dec. 2012
20121228, 20121228

P37 Petrologic study of pyroclastic flow deposits from Narugo volcano, Miyagi Prefecture, northeast Japan　　　　　　　　　　　　　　　
Ito Natsumi; Fujinawa Akihiko; Hasegawa Takeshi
Programme and abstracts the Volcanological Society of Japan, 14 Oct. 2012, Volcanological Society of Japan
20121014, 20121014

P34 Geology and magma plumbing system of Marumori volcano, Takakura volcanic field, Iwate prefecture　　　　　　　　　　　　　　　
Tsuchiya Saab; Fujinawa Akihiko; Hasegawa Takeshi
Programme and abstracts the Volcanological Society of Japan, 14 Oct. 2012, Volcanological Society of Japan
20121014, 20121014

北海道東部,屈斜路火山の最大規模カルデラ形成噴火(KpIV)の噴火推移とマグマプロセス
長谷川健; 松本亜希子; 中川光弘
日本地質学会学術大会講演要旨, 10 Sep. 2012

完新世バリアーシステムと海水準変動の復元:北海道東部厚岸沿岸低地の例
重野聖之; 七山太; 内田康人; 嵯峨山積; 長谷川健; 安藤寿男
日本堆積学会大会プログラム・講演要旨, 15 Jun. 2012

岩手県高倉火山列,丸森火山の地質とマグマ供給系
土屋沙亜武; 藤縄明彦; 長谷川健
日本火山学会講演予稿集, 2012

北海道東部,アトサヌプリ火山の爆発的噴火史の再検討
長谷川健; 中川光弘; 宮城磯治
日本火山学会講演予稿集, 2012

宮城県鳴子火山起源の火砕流堆積物の岩石学的検討
伊藤なつみ; 藤縄明彦; 長谷川健
日本火山学会講演予稿集, 2012

B1-11 Reinvestigation of explosive eruption history of Atosanupuri volcano, eastern Hokkaido, Japan
Hasegawa T; Nakagawa M; Miyagi I
PROGRAMME AND ABSTRACTS THE VOLCANOLOGICAL SOCIETY OF JAPAN, 2012

Geology and petrology of Marumori volcano, Takakura volcanic field, Iwate prefecture　　　　　　　　　　　　　　　
TSUCHIYA Saab; FUJINAWA Akihiko; HASEGAWA Takeshi
日本鉱物科学会年会講演要旨集, 05 Sep. 2011
20110905, 20110905

安達太良火山12万年前の噴火復元
藤原健一郎; 藤縄明彦; 長谷川健
日本鉱物科学会年会講演要旨集, 05 Sep. 2011

The history of caldera-forming eruptions in eastern Hokkaido, Japan
HASEGAWA Takeshi; KISHIMOTO Hiroshi; NAKAGAWA Mitsuhiro
Abstracts for Annual Meeting of Japan Association of Mineralogical Sciences, 05 Sep. 2011

岩手県高倉火山群,丸森火山の地質と岩石　　　　　　　　　　　　　　　
土屋沙亜武; 藤縄明彦; 長谷川健
日本鉱物科学会年会講演要旨集, 2011
2011, 2011

北海道東部,釧路地域における樽前d層(Ta-d)の発見　　　　　　　　　　　　　　　
長谷川健; 花岡正光; 重野聖之; 古川竜太; 七山太; 中川光弘; 安藤寿男
日本火山学会講演予稿集, 2011
2011, 2011

北海道東部,釧路地域における樽前d層(Ta‐d)の発見
長谷川健; 花岡正光; 重野聖之; 古川竜太; 七山太; 中川光弘; 安藤寿男
日本火山学会講演予稿集, 2011

北海道東部・屈斜路火山カルデラ形成噴火のマグマ供給系の変遷
宮坂瑞穂; 長谷川健; 中川光弘; 松本亜希子
日本火山学会講演予稿集, 2011

B2-19 Change of magmatic system of caldera-forming eruptions of Kutcharo volcano, Eastern Hokkaido
Miyasaka M Amma; Hasegawa T; Nakagawa M; Matsumoto A
PROGRAMME AND ABSTRACTS THE VOLCANOLOGICAL SOCIETY OF JAPAN, 2011

P41 Recognition of Ta-d tephra in Kushiro region, eastern Hokkaido, Japan
Hasegawa T; Hanaoka M; Shigeno K; Furukawa R; Nanayama F; Nakagawa M; Ando H
PROGRAMME AND ABSTRACTS THE VOLCANOLOGICAL SOCIETY OF JAPAN, 2011

北海道における後期更新世の火山活動の時空変遷と関連テクトニクス
中川光弘; 小杉安由美; 長谷川健; 石井英一; 石塚吉浩
日本地質学会学術大会講演要旨, 15 Sep. 2010

Sequence of the largest caldera-forming eruption (KpIV) of Kutcharo volcano, eastern Hokkaido, Japan
HASEGAWA Takeshi; MATSUMOTO Akiko; NAKAGAWA Mitsuhiro
日本鉱物科学会年会講演要旨集, Sep. 2010, [Invited]

北海道東部,屈斜路火山の最大規模カルデラ形成噴火(KpIV)の推移　　　　　　　　　　　　　　　
長谷川健; 松本亜希子; 中川光弘
日本鉱物科学会年会講演要旨集, 2010
2010, 2010

後屈斜路カルデラ火山噴出物の,3万5千年間における時間変化
武田研太郎; 岸本博志; 長谷川健; 本間宏樹; 中川光弘; 和田恵治
日本火山学会講演予稿集, 2009

A37 Temporal Evolution of Juvenile Ejecta of the Post-Caldera Volcanoes of Kutcharo Caldera during the Last 35,000 years
Takeda Kentarou; Kishimoto Hiroshi; Hasegawa Takeshi; Honma Hiroki; Nakagawa Mitsuhiro; Wada Keiji
PROGRAMME AND ABSTRACTS THE VOLCANOLOGICAL SOCIETY OF JAPAN, 2009

O-54 Formation and evolution of silicic magma systems during caldera-forming eruptions of Akan volcano, eastern Hokkaido, Japan : Petrological study on the basis of fine-scaled tephrostratigraphy
Hasegawa Takeshi; Nakagawa Mitsuhiro
日本地質学会学術大会講演要旨, 15 Sep. 2008

北海道東部,屈斜路カルデラ形成噴火KpIVにおける噴出マグマの特徴と時間変化
松本亜希子; 長谷川健; 中川光弘
日本火山学会講演予稿集, 2008

A13 Temporal change of magma type during Kutcharo caldera forming eruption (KpIV), eastern Hokkaido
MATSUMOTO Akiko; HASEGAWA Takeshi; NAKAGAWA Mitsuhiro
PROGRAMME AND ABSTRACTS THE VOLCANOLOGICAL SOCIETY OF JAPAN, 2008

P81 Small eruption on March 2006 at Meakan-dake volcano, Hokkaido(THE VOLCANOLOGICAL SOCIETY OF JAPAN 2006 FALL MEETING)
Hirose W; Okazaki N; Ishimaru S; Tajika J; Nakagawa M; Takahashi H; Hasegawa K; Fujiwara S; Imano E; Nagasawa K; Shigeno N; Sato J; Endo H; Inaba C; Sasaki H
PROGRAMME AND ABSTRACTS THE VOLCANOLOGICAL SOCIETY OF JAPAN, 2006

北海道雌阿寒岳2006年3月の小噴火
廣瀬亘; 岡崎紀俊; 石丸聡; 田近淳; 中川光弘; 高橋浩晃; 長谷川健; 藤原伸也; 今野英慈; 永澤幸; 重野伸昭; 佐藤十一; 遠藤仁; 稲葉千秋; 佐々木寿
日本火山学会講演予稿集, 2006

日高山脈トッタベツ深成岩体の重力異常と貫入形態
神山裕幸; 山本明彦; 長谷川健; 梶原崇憲; 茂木透
日本地震学会秋季大会講演予稿集, 01 Oct. 2005

重力異常から考察する阿寒カルデラの地下構造と形成過程
長谷川健; 神山裕幸; 山本明彦; 中川光弘
日本火山学会講演予稿集, 2005

A15 Subsurface Structure and Caldera-forming processes of Akan Caldera, inferred from Gravity Anomalies(THE VOLCANOLOGICAL SOCIETY OF JAPAN 2005 FALL MEETING)
HASEGAWA Takeshi; KAMIYAMA Hiroyuki; YAMAMOTO Akihiko; NAKAGAWA Mitsuhiro
PROGRAMME AND ABSTRACTS THE VOLCANOLOGICAL SOCIETY OF JAPAN, 2005

北海道中央部十勝地域と北海道東部阿寒・屈斜路地域の大規模珪長質噴火の指交関係
長谷川健; 中川光弘; 石井英一
日本火山学会講演予稿集, 2004

A13 Interfingering of large-scale felsic volcanism between Tokachi and Akan-Kussharo regions, Central and Eastern Hokkaido
HASEGAWA Takeshi; NAKAGAWA Mitsuhiro; ISHII Eiichi
PROGRAMME AND ABSTRACTS THE VOLCANOLOGICAL SOCIETY OF JAPAN, 2004

茨城大学

茨城大学

茨城大学

茨城大学

茨城大学

茨城大学

IAVCEI (International Association of Volcanology and Chemistry of the Earth's Interior)

Japan Association of Mineralogical Sciences

JAPAN SOCIETY FOR SCIENTIFIC STUDIES ON CULTURAL PROPERTIES

The Volcanological Society of Japan

JAPAN GEOSCIENCE UNION

The Geological Society of Japan

AGU (The American Geophysical Union)

房総半島における古地磁気―酸素同位体複合層序を活用した前期更新世広域テフラの高精度年代決定　　　　　　　　　　　　　　　
Jan. 2025 - Mar. 2025

International joint research for enhancing gas disaster management of composite maar volcanoes based on geological and geochemical approach　　　　　　　　　　　　　　　
Apr. 2024 - Mar. 2025

低頻度大規模噴火に関するインドネシアとの共同研究　　　　　　　　　　　　　　　
Feb. 2024 - Mar. 2025

ミョウバン石を用いた水蒸気噴火の推移予測法の開発　　　　　　　　　　　　　　　
災害対策分野
茨城大学
Apr. 2023 - Mar. 2025

超巨大噴火は本当に存在し、将来起こるのか？古地磁気・地球物理・岩石鉱物学的検証
挑戦的研究(萌芽)
茨城大学
Jun. 2022 - Mar. 2025

The prediction of eruption-sequence after phreatic explosions: Investigation for magmatic–hydrothermal systems based on geology, petrology and paleomagnetism
Grant-in-Aid for Scientific Research (B)
Ibaraki University
Apr. 2021 - Mar. 2025

火山噴火の予測技術の開発「噴火履歴調査による火山噴火の中長期予測と噴火推移調査に基づく噴火事象系統樹の作成」　　　　　　　　　　　　　　　
北海道大学（代表）ほか
Nov. 2016 - Mar. 2025

Establishing a standard curve for Holocene geomagnetic variations around Japan
Grant-in-Aid for Scientific Research (B)
Kochi University
01 Apr. 2021 - 31 Mar. 2024

大規模噴火現象の時間進展プロセスに関する研究に係る残留磁化方位データ作成
茨城大学
Sep. 2022 - Mar. 2023

Inverting Cameroon Line geochemical data for primary magmas and mantle potential temperatures: Toward the elucidation of plume-lithosphere interaction and global geodynamics　　　　　　　　　　　　　　　
Apr. 2022 - Mar. 2023

大陸プレートにおけるマントルプルームの進化とダイナミクス　　　　　　　　　　　　　　　
Apr. 2022 - Mar. 2023

超大規模水蒸気プリニー式噴火の国際比較研究： 地質学的・物質科学的手法による噴火推移モデルの構築　　　　　　　　　　　　　　　
Apr. 2020 - Mar. 2021

A basic study on remanent magnetization of volcanic ash layer
Grant-in-Aid for Scientific Research (C)
Kumamoto University
01 Apr. 2017 - 31 Mar. 2020

Quantitative verification of simultaneous super eruptions by using paleomagnetic directions and secular variation
Grant-in-Aid for Scientific Research (C)
Ibaraki University
01 Apr. 2016 - 31 Mar. 2020

古地磁気学的手法を用いた噴火現象の時間進展プロセスに関する研究　　　　　　　　　　　　　　　
茨城大学, 熊本大学, University of Canterbury
Jul. 2019 - Mar. 2020

Volcano-geological approach towards high-resolution reconstructions of explosive eruption phenomena and their utilization to the volcanic hazard mitigations
Grant-in-Aid for Scientific Research (C)
Ibaraki University
01 Apr. 2015 - 31 Mar. 2019

マグマ溜まりの形成・噴火プロセスの時間スケールに関する研究　　　　　　　　　　　　　　　
茨城大学, 熊本大学, Vanderbilt University
May 2018 - Mar. 2019

Comparative Study of Risk Assessment for Super Eruptions between New Zealand and Japan(Fostering Joint International Research)
Fund for the Promotion of Joint International Research (Fostering Joint International Research)
Ibaraki University
2017 - 2019

マグマ溜まりの形成・噴火プロセスの時間スケールに関する研究　　　　　　　　　　　　　　　
Jul. 2017 - Mar. 2018

石英結晶を利用したマグマ滞留時間推定に関する予察的研究　　　　　　　　　　　　　　　
Jul. 2016 - Mar. 2017

Development of the new method for tephra identification using the paleomagnetic directions
Grant-in-Aid for Young Scientists (B)
Ibaraki University
01 Apr. 2014 - 31 Mar. 2016

カメルーン火口湖ガス災害防止の総合対策と人材育成
Apr. 2011 - Mar. 2016

Joint research of Japan and Russia for investigation of magma system and its eruption mechanism of the arc-type basaltic eruptive activity
Grant-in-Aid for Scientific Research (A)
Hokkaido University
01 Apr. 2010 - 31 Mar. 2014

Transportation and deposition processes of lahar deposits from Nasu volcano、Japan: Toward a prevention of disaster in Naka River area
Grant-in-Aid for Young Scientists (B)
Ibaraki University
2011 - 2012

長方形カルデラの形成機構の解明~北海道東部阿寒カルデラを例として~　　　　　　　　　　　　　　　
Apr. 2005 - Mar. 2006

美幌の地質学
lecturer
美幌博物館, 美幌博物館講座, 31 Aug. 2024

吾妻山の噴火
lecturer
福島県, 福島県火山防災シンポジウム, 25 Aug. 2024 - 25 Aug. 2024

Caldera volcanoes in Japan and Indonesia
lecturer
ガジャマダ大学地理学部, 10 Oct. 2023

噴火予測のいま
lecturer
ときわサイエンスカフェ, 17 Jun. 2017

阿寒地域における火山灰の堆積史
lecturer
釧路市, 智のおもてなし創生事業セミナー「阿寒湖の魅力発見 最新研究を学ぶ」, 08 Oct. 2014

キッチン火山学
demonstrator
茨城大学, サイエンステクノロジーフェスタ