Bulletin of the Volcanological Society of Japan最新文献

{"title":"Fluorine and Chlorine Contents of Volcanic Ash from the 2004 Eruption of Asama Volcano, Japan","authors":"K. Nogami, S. Onizawa","doi":"10.18940/KAZAN.65.1_1","DOIUrl":"https://doi.org/10.18940/KAZAN.65.1_1","url":null,"abstract":"Asama volcano in central Honshu, Japan, commenced four-month-long eruptive activity on September 1, 2004, with a phreatic explosion after approximately 20 years of quiescence. According to the mode of eruption, the activity is divided into three phases : Phase I, Phase II and Phase III, which are characterized by a phreatic explosion and plume activity, nonexplosive eruptions with swarms of BH-type earthquakes and explosions at short intervals, respectively. In Phase I, the ash samples are mainly composed of altered volcaniclastic material. Meanwhile, the ash samples in Phase II and Phase III are pristine and originated from new magma. The fluorine and chlorine contents of the ash samples in these phases are determined, and their behavior corresponding to the dramatic changes in the mode of eruption is examined. The ash samples in Phase I characteristically contain large amounts of fluorine and chlorine in watersoluble and water-insoluble forms. The prolonged reactions of HF, HCl and SO2 in volcanic gases with old volcaniclastic material within the crater during the noneruptive period prior to Phase I produced extraordinary amounts of water-soluble and water-insoluble F and Cl compounds. The intense degassing in Phase I and Phase II corresponding to the ascent of the magma near the surface sharply decreased the volatile contents of the uppermost part of the magma column; however, the water-insoluble F contents of the ash samples in Phase IIa are higher than those of the ash in Phase IIb. These results strongly suggest that volatiles were greatly concentrated in the uppermost part of the ascending magma prior to Phase I. Meanwhile, the water-insoluble Cl contents of the ash in Phase IIa are significantly lower than those of the ash in Phase IIb. Chlorine was degassed from the uppermost part of the ascending magma column far more intensely than fluorine because chlorine is more volatile than fluorine in magma, which probably decreased the chlorine content of the ash in Phase IIa significantly. Chlorine was degassed intensely, whereas fluorine was less degassed between Phase IIb and Phase IIIa. The intense degassing of chlorine from magma corresponded to the dramatic change in the mode of eruption from nonexplosive to explosive eruptions. The transition of the water-insoluble Cl contents of the ash samples in Phase III demonstrates steady degassing of chlorine from the effused lava. The significant increases in the water-soluble F and Cl contents of the ash samples in Phase III demonstrate that the effused lava gradually reacted with volcanic gases, although the ash was not subjected to obvious alteration. Water-soluble F compounds formed on the surface of the lava were partially converted to water-insoluble F compounds, which significantly increased the water-insoluble F contents of the ash samples in Phase III. Determination of the water-soluble and waterinsoluble F and Cl contents of volcanic ejecta enables clarification of their behavior through","PeriodicalId":321973,"journal":{"name":"Bulletin of the Volcanological Society of Japan","volume":"50 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-03-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129415687","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Multiple Vent-forming Phreatic Eruptions after AD 1663 in the Noboribetsu Geothermal Field, Kuttara Volcano, Hokkaido, Japan","authors":"Y. Goto, Yoshimasa Toriguchi, Hirotaka Sasaki, A. Hatakeyama","doi":"10.18940/KAZAN.60.2_241","DOIUrl":"https://doi.org/10.18940/KAZAN.60.2_241","url":null,"abstract":"The Noboribetsu geothermal field (area 1×1.5 km) is located in the western part of Kuttara volcano, southwestern Hokkaido, Japan. Seventy-one shallow trenches (<90 cm deep) were systematically dug within the geothermal field, in order to study the stratigraphy and distribution of the most recent phreatic fall deposit (the Nb-a deposit) erupted from the field. The Nb-a deposit (<68 cm thick) consists of altered dacitic lithic clasts in a fine-grained clay-rich matrix. The deposit overlies the Us-b tephra that was emplaced in AD 1663. Stratigraphic sections constructed from the 71 trenches indicate that the deposit is distributed within an elliptical area measuring 850×1250m across and extending NNWSSE. Isopach and maximum-grain-size isopleth maps indicate that the deposit increases in thickness and maximumgrain-size toward several explosion craters. These data suggest that phreatic eruptions, through multiple vents, occurred in the Noboribetsu geothermal field after AD 1663.","PeriodicalId":321973,"journal":{"name":"Bulletin of the Volcanological Society of Japan","volume":"40 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126580120","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Geology and Evolution of the Nakajima Islands (Toya Caldera, Hokkaido, Japan) Inferred from Aerial Laser Mapping and Geological Field Surveys","authors":"Y. Goto, Satoru Matsuzuka, Seiji Kameyama, T. Danhara","doi":"10.18940/KAZAN.60.1_17","DOIUrl":"https://doi.org/10.18940/KAZAN.60.1_17","url":null,"abstract":"Aerial high-resolution laser-scanner mapping and geological field surveys were performed over the Nakajima Islands within Toya caldera, southwestern Hokkaido, Japan, to study the evolutional history of the islands. The laserscanner mapping survey covered the entirety of the Nakajima Islands, an area of 3×3 km. A three-dimensional digital map produced from the laser-scanning data revealed detailed topographic features of the islands. Geological field surveys were carried out over the whole area of the Nakajima Islands, to determine how their topography relates to the geological and lithological features. These surveys suggest that the islands consist of a tuff cone, eight lava domes, and a cryptodome. The tuff cone has a low profile and wide crater and consists of dacitic pyroclastic deposits, suggesting that the cone was produced by explosive eruptions resulting from the interaction of dacitic magma and groundwater. The lava domes are conical or pancake-shaped and composed of dacitic to andesitic lavas, suggesting that the domes formed by extrusions of high-viscosity, dacitic to andesitic magmas. The cryptodome consists of coherent dacite overlain by mudstone and sandstone, suggesting that the dome formed by the uplift of caldera-floor deposits following the intrusion of high-viscosity dacitic magma. Mudstones and sandstones are present along the northeastern and southwestern parts of the islands, implying that the caldera floor was uplifted during or prior to the volcanism, forming a bulge (small resurgent dome) at the center of the caldera. We infer that the Nakajima Islands have evolved from caldera resurgence related to the ascent of voluminous dacitic to andesitic magma, followed by subsequent formation of multiple dacitic to andesitic domes and phreatomagmatic eruptions on the resurgent dome.","PeriodicalId":321973,"journal":{"name":"Bulletin of the Volcanological Society of Japan","volume":"50 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-03-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133483003","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Internal Structure of Kuttara Caldera, Hokkaido, Japan","authors":"Y. Goto, A. Johmori","doi":"10.18940/KAZAN.60.1_35","DOIUrl":"https://doi.org/10.18940/KAZAN.60.1_35","url":null,"abstract":"A controlled-source audio-frequency magnetotelluric (CSAMT) survey was conducted across the caldera of Kuttara volcano, Hokkaido, Japan, to investigate its subsurface structure. The caldera is 3 km in diameter and contains a circular lake (Lake Kuttara) 2.5 km across. The CSAMT survey was conducted along a 12-km-long east‒west-trending transect that crossed the volcano and passed over the caldera. A total of 23 receiver stations were distributed along the survey line, including 7 stations in the caldera. Unique on-boat measurements were obtained at the surface of Lake Kuttara. A two-dimensional inversion of the CSAMT data, which revealed the resistivity structure to depths of up to 1000m beneath the caldera, suggested the existence of a low-resistivity region (<30Ω・m) beneath the eastern caldera floor, extending subvertically for>1000m and with a width of 1300-1500m. The structure is interpreted to be a region filled with lava blocks and pyroclasts, which subsided during collapse of the caldera and which has been affected by hydrothermal alteration. The location of the low-resistivity region corresponds to an oval basin in the eastern part of the lake, implying that caldera subsidence occurred mainly beneath this basin. The western part of the caldera floor tilts gently to the east and has a rugged surface, suggesting that the western caldera rim was significantly enlarged as a result of landsliding during caldera formation. We thus infer that the Kuttara caldera was produced by asymmetric caldera collapse, which is attributed to the geological heterogeneity of the Kuttara volcano, with an eastern part comprised mainly of andesitic lavas and a western part comprised mainly of dacitic pyroclastic deposits.","PeriodicalId":321973,"journal":{"name":"Bulletin of the Volcanological Society of Japan","volume":"112 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-03-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123099848","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Resistivity Structure of the Showa-Shinzan Dome at Usu Volcano, Hokkaido, Japan","authors":"Y. Goto, A. Johmori","doi":"10.18940/KAZAN.59.1_1","DOIUrl":"https://doi.org/10.18940/KAZAN.59.1_1","url":null,"abstract":"A controlled source audio frequency magnetotelluric (CSAMT) survey was conducted over Showa-Shinzan Dome at Usu Volcano, Hokkaido, Japan, in order to investigate its internal structure. The Showa-Shinzan Dome (800-1000m across, 350m high) is a partly extruded cryptodome that formed in AD 1943-45 due to the uplift of pre-existing rocks and sediments by the intrusion of dacitic magma. The dome comprises a flat-topped cryptodome called ‘Yaneyama’ and a dacitic lava dome projecting above the Yaneyama cryptodome. The CSAMT survey was carried out on a 1600-mlong line that crosses the Showa-Shinzan Dome in an east-west orientation. Two-dimensional inversion of the CSAMT data revealed the resistivity structure at depths less than 1000m beneath the dome. The resistivity structure suggests the existence of a sub-spherical dacite intrusion (resistivity 50-130Ω・m; ~400m across) below the summit of the ShowaShinzan Dome. The dacite intrusion may represent the solidified dacitic magma emplaced in AD 1943-45. The Yaneyama cryptodome only comprises pre-existing rocks and sediments uplifted by the intrusion of dacite magma. The upper zone of the Yaneyama cryptodome consists of the Usu Somma Lava (>100Ω・m), whereas the lower zone consists of Quaternary pyroclastic flow deposits and sedimentary rocks (<30Ω・m), such as the Toya pyroclastic flow deposits, the Fukaba Formation, the Takinoue welded tuff, the Sobetsu pumice flow deposits, and the Yanagihara Formation. There is no dacite intrusion beneath the Yaneyama cryptodome. This structural model is consistent with the distribution of active fumaroles on the Showa-Shinzan Dome, and also with historical records of dome growth. The geophysical data provide new insights into the formation mechanism of the Showa-Shinzan Dome.","PeriodicalId":321973,"journal":{"name":"Bulletin of the Volcanological Society of Japan","volume":"17 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-03-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131853190","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The 18-19ka Andesitic Explosive Eruption at Usu Volcano, Hokkaido, Japan","authors":"Y. Goto, Y. Sekiguchi, S. Takahashi, Hayuru Ito, T. Danhara","doi":"10.18940/KAZAN.58.4_529","DOIUrl":"https://doi.org/10.18940/KAZAN.58.4_529","url":null,"abstract":"Mount Usu is a Quaternary composite volcano located in southwestern Hokkaido, Japan. Here we report on an andesitic pyroclastic fall deposit (the Usu-Kaminagawa [Us-Ka] tephra) erupted during the initial stage of activity at Usu Volcano. The tephra extends from the volcano to the east, and comprises a lower andesitic pumice-fall deposit and an upper ash-fall deposit. The tephra overlies the Nj-Os tephra, which was erupted from the Nakajima Islands, and is overlain by the Usu Somma Lava, which was extruded during the early stages of activity at Usu Volcano. Radiocarbon dating of buried soils located immediately beneath the Us-Ka tephra yields ages of 18-19 cal ka BP. The distribution, stratigraphy, and lithology of the tephra, and the radiocarbon ages of the buried soils beneath the tephra, suggest that an andesitic explosive eruption occurred at Usu Volcano at ca. 18-19 ka. This eruption was probably an early manifestation of activity at Usu Volcano.","PeriodicalId":321973,"journal":{"name":"Bulletin of the Volcanological Society of Japan","volume":"11 21 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2013-12-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132569036","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"History of Phreatic Eruptions in the Noboribetsu Geothermal Field, Kuttara Volcano, Hokkaido, Japan","authors":"Y. Goto, Hirotaka Sasaki, Yoshimasa Toriguchi, A. Hatakeyama","doi":"10.18940/KAZAN.58.3_461","DOIUrl":"https://doi.org/10.18940/KAZAN.58.3_461","url":null,"abstract":"A 6.3-m-deep trench was dug in the Noboribetsu Geothermal Field, Kuttara Volcano, Hokkaido, Japan, to clarify the history of phreatic eruptions in the field. The stratigraphic section in the trench consists of (from lower to upper): the Kt-1 pyroclastic surge deposit, nine phreatic fall deposits (Nb-l to Nb-d), the B-Tm tephra, two phreatic fall deposits (Nb-c, Nb-b), the Us-b tephra, and a phreatic fall deposit (Nb-a). The 12 phreatic fall deposits (Nb-l to Nb-a) are 3-100 cm thick and consist of altered dacitic lithic fragments in a clay-rich fine-grained matrix. These deposits are inferred to have been erupted from the Noboribetsu Geothermal Field. Buried soil layers occur between the deposits. Radiocarbon dating of buried soil samples from immediately below each of the phreatic fall deposits suggests that phreatic eruptions occurred at ca. BC6450, BC 5370, BC 3980, BC 3440, BC 1990, BC 1710, BC 1280, BC 900, BC 200, AD 980, AD 1480, and after AD 1663, corresponding to an average eruption interval of 〜700 years.","PeriodicalId":321973,"journal":{"name":"Bulletin of the Volcanological Society of Japan","volume":"22 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2013-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134255446","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Resistivity Structure of the Hiyoriyama Cryptodome at Kuttara Volcano, Hokkaido, Japan","authors":"Y. Goto, A. Johmori","doi":"10.18940/KAZAN.58.2_365","DOIUrl":"https://doi.org/10.18940/KAZAN.58.2_365","url":null,"abstract":"Direct current (DC) electrical and controlled source audio-frequency magnetotelluric (CSAMT) surveys were performed over the Hiyoriyama Cryptodome in Kuttara Volcano, Hokkaido, Japan. Both surveys were performed on the same survey line across the cryptodome in a NE‒SW orientation. Two-dimensional joint inversion of the DC electrical and CSAMT data revealed the underground resistivity structure at depths less than 400m beneath the cryptodome. The resistivity structure suggests that the cryptodome comprises a dacite intrusion of 150m wide and 80m thick (20-50Ω・ m), and overlying pyroclastic deposits that are 10-30m thick (>100Ω・m). The dacite intrusion is underlain by a convex-shaped, low-resistivity layer (<5Ω・m) that is interpreted to be smectite-rich, altered pyroclastic deposits that have been subjected to low-temperature (<200°C) hydrothermal alteration. The low-resistivity layer is underlain by a slightly higher-resistivity layer (10-30Ω・m) that is interpreted to be altered pyroclastic deposits that were subjected to higher-temperature (> 200°C) hydrothermal alteration in a relatively deep, hot region near the conduit of the cryptodome.","PeriodicalId":321973,"journal":{"name":"Bulletin of the Volcanological Society of Japan","volume":"28 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2013-06-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"120958121","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Parasitic Eruptions on Sakurajima Volcano(＜Special Section＞Sakurajima Special Issue)","authors":"I. Yokoyama","doi":"10.18940/KAZAN.58.1_91","DOIUrl":"https://doi.org/10.18940/KAZAN.58.1_91","url":null,"abstract":"","PeriodicalId":321973,"journal":{"name":"Bulletin of the Volcanological Society of Japan","volume":"200 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2013-03-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116702160","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Processes Prior to Outbursts of Vulcanian Eruption at Showa Crater of Sakurajima Volcano(＜Special Section＞Sakurajima Special Issue)","authors":"A. Yokoo, M. Iguchi, Takeshi Tameguri, Keigo Yamamoto","doi":"10.18940/KAZAN.58.1_163","DOIUrl":"https://doi.org/10.18940/KAZAN.58.1_163","url":null,"abstract":"Showa crater of Sakurajima volcano became active in June 2006 after 58 years of quiescence. From multiparametric geophysical observations, we have identified the processes that typically occur prior to an explosive eruption at the crater. A few hours prior to the onset of an eruption, magma starts to migrate and accumulates at a depth of about 1 km. This accumulation of magma can be clearly observed in strain change records as an inflation process. Several tens of minutes prior to an eruption, the SO2 gas emission rate gradually decreases, indicating that a sealing process is taking place in the crater bottom as the eruption nears. During the same time period, the volcanoʼs inflation rate starts to accelerate due to the formation of a plug above the conduit that prevents the gas from escaping, with the result that a gas pocket forms beneath the crater. In nighttime events, a volcanic glow is also seen, which weakens and then disappears. A few minutes prior to an eruption, a small tremor starts to occur. Its amplitude grows as the strain changes from inflation to deflation as the stored gas is released through new fractures within the plug that had been confining the gas pocket, leading to a minor depressurization in the conduit. Then, an expansion process starts, that could explain seismically the first motion of an explosion earthquake. This is probably when the effect of depressurization downward from the crater bottom reaches the magma head and a sudden magma expansion with degassing starts. After a short period (about half a second), this expanding magma rises and pushes the gas pocket upward, leading to a swelling of the crater ground along with the radiation of the preceding phase of infrasound waves, and then a breakup occurs. After the plug fails due to deformation, the accumulated gasses and expanding magma are ejected together from the crater as the surface eruption phenomena starts.","PeriodicalId":321973,"journal":{"name":"Bulletin of the Volcanological Society of Japan","volume":"22 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2013-03-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114790977","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}