Sequence of the 1895 eruption of the Zao volcano, Tohoku Japan

Miura, Kanako; Ban, Masao; Ohba, Takayoshi; Fujinawa, Akihiko

doi:10.1016/j.jvolgeores.2012.08.005

Cited by 15 publications

(10 citation statements)

References 16 publications

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“…We investigate tephra sedimentation by assessing temporal variations in the grain size distribution (GSD) of tephra, which reflects the sedimentation process (e.g., Iriyama et al 2018;Koyaguchi and Ohno 2001b). The deposit from a single Vulcanian eruption is generally too thin to examine its temporal variations from the internal stratigraphy (Imura 1991(Imura , 1995Miura et al 2012;Miyabuchi et al 2013). Therefore, high-temporal resolution sampling of falling ash is required to obtain the temporal variation in GSD during a Vulcanian eruption (Bagheri et al 2016;Bonadonna et al 2002).…”

Section: Introductionmentioning

confidence: 99%

Sedimentation process of ashfall during a Vulcanian eruption as revealed by high-temporal-resolution grain size analysis and high-speed camera imaging

Miwa

Iriyama

Nagai

et al. 2020

Prog Earth Planet Sci

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We here examined the sedimentation process of falling ash particles during a short-lived Vulcanian eruption at Sakurajima volcano, Japan, using high-speed camera imaging of airborne ash particles, as well as grain size analyses of ash samples collected at high temporal resolution. Ashfalls from a sequence of two Vulcanian eruptions at 10:44 and 11:26 JST (Japan Standard Time) on 26 March 2016 were investigated. The field site for imaging and sampling was located approximately 3.5 km from the vent. The ash particles collected exhibit bimodal grain size distributions (GSDs). The median particle size of the main subpopulation decreased throughout the ashfall owing to sizedependent segregation of ash particles from a single source released from a constant height. The volume fraction of the subordinate subpopulation is interpreted to represent a component of ash aggregates and shows an increase in its volume fraction after the eruption onset. High-speed camera imaging reveals that the mean particle density decreased over time as the ashfall continued. These data suggest an increasing contribution of low-density aggregates during the course of the ashfall. The temporal changes in the density of airborne ash particles and in the GSD of ash samples demonstrate that the sedimentation process during a Vulcanian eruption at Sakurajima volcano is characterized by sedimentation of ash particles from transient eruption plumes at constant height, in which ash aggregation increases over time. Moreover, time series analysis of the ash falling rate shows that secondary thickening occurred during these Vulcanian eruptions and that this can be triggered by the settling of ash aggregates.

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Section: Introductionmentioning

confidence: 99%

Sedimentation process of ashfall during a Vulcanian eruption as revealed by high-temporal-resolution grain size analysis and high-speed camera imaging

Miwa

Iriyama

Nagai

et al. 2020

Prog Earth Planet Sci

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“…These explosions occur at many different volcanoes; Soufrière de Guadeloupe (Le Guern et al 1980), Meakandake (Ogiso and Yomogida 2012), Usu (Miura et al 2012), Bandai (Glicken and Nakamura 1988), Karkar (Barberi et al 1992), Nyos (Neri et al 1999), Kilauea (Dvorak 1992), Mayon, Pinatubo, Mount St Helens (Newhall et al 2001), Ruapehu and Poás (Fischer et al 2015) are just a few examples. However, as their magnitude is generally smaller than that of magmatic events, phreatic eruptions are comparatively understudied.…”

Section: Introductionmentioning

confidence: 99%

Phreatic eruptions at crater lakes: occurrence statistics and probabilistic hazard forecast

et al. 2017

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Phreatic eruptions, although posing a serious threat to people in crater proximity, are often underestimated and have been comparatively understudied. The detailed eruption catalogue for Ruapehu Volcano (New Zealand) provides an exceptional opportunity to study the statistics of recurring phreatic explosions at a crater lake volcano. We performed a statistical analysis on this phreatic eruption database, which suggests that phreatic events at Ruapehu do not follow a Poisson process. Instead they tend to cluster, which is possibly linked to an increased heat flow during periods of a more shallow-seated magma column. Larger explosions are more likely to follow shortly after smaller events, as opposed to longer periods of quiescence. The absolute probability for a phreatic explosion to occur at Ruapehu within the next month is about 10%, when averaging over the last 70 years of recording. However, the frequency of phreatic explosions is significantly higher than the background level in years prior to magmatic episodes. Combining clast ejection simulations with a Bayesian event tree tool (PyBetVH) we perform a probabilistic assessment of the hazard due to ballistic ejecta in the summit area of Ruapehu, which is frequently visited by hikers. Resulting hazard maps show that the absolute probability for the summit to be affected by ballistics within the next month is up to 6%. The hazard is especially high on the northern lakeshore, where there is a mountain refuge. Our results contribute to the local hazard assessment as well as the general perception of hazards due to steam-driven explosions.

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“…Phreatic eruptions pose a significant hazard to areas in proximity of the erupting crater and occasionally lead to larger-scale deadly density currents (e.g., Yamamoto et al 1999;Fujinawa et al 2006). Low-temperature pyroclastic flows (pyroclastic density currents) accompanying phreatic eruptions have been reported in Japan, Tongariro (New Zealand), and La Soufriere (Guadeloupe) (e.g., Fujinawa et al 2008;Lube et al 2014;Miura et al 2012;Nakamura and Glicken 1988;Sheridan 1980;Yamamoto et al 1999). Low-temperature pyroclastic density currents accompanying phreatic eruptions are steam driven and usually laterally directed by the phreatic explosion .…”

Section: Introductionmentioning

confidence: 99%

Reconstruction of the 2014 eruption sequence of Ontake Volcano from recorded images and interviews

et al. 2016

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A phreatic eruption at Mount Ontake (3067 m) on September 27, 2014, led to 64 casualties, including missing people. In this paper, we clarify the eruption sequence of the 2014 eruption from recorded images (photographs and videos obtained by climbers) and interviews with mountain guides and workers in mountain huts. The onset of eruption was sudden, without any clear precursory surface phenomena (such as ground rumbling or strong smell of sulfide). Our data indicate that the eruption sequence can be divided into three phases. Phase 1: The eruption started with dry pyroclastic density currents (PDCs) caused by ash column collapse. The PDCs flowed down 2.5 km SW and 2 km NW from the craters. In addition, PDCs moved horizontally by approximately 1.5 km toward N and E beyond summit ridges. The temperature of PDCs at the summit area partially exceeded 100 °C, and an analysis of interview results suggested that the temperature of PDCs was mostly in the range of 30-100 °C. At the summit area, there were violent falling ballistic rocks. Phase 2: When the outflow of PDCs stopped, the altitude of the eruption column increased; tephra with muddy rain started to fall; and ambient air temperature decreased. Falling ballistic rocks were almost absent during this phase. Phase 3: Finally, muddy hot water flowed out from the craters. These models reconstructed from observations are consistent with the phreatic eruption models and typical eruption sequences recorded at similar volcanoes.

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Sequence of the 1895 eruption of the Zao volcano, Tohoku Japan

Cited by 15 publications

References 16 publications

Sedimentation process of ashfall during a Vulcanian eruption as revealed by high-temporal-resolution grain size analysis and high-speed camera imaging

Sedimentation process of ashfall during a Vulcanian eruption as revealed by high-temporal-resolution grain size analysis and high-speed camera imaging

Phreatic eruptions at crater lakes: occurrence statistics and probabilistic hazard forecast

Reconstruction of the 2014 eruption sequence of Ontake Volcano from recorded images and interviews

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