Special issue “Towards forecasting phreatic eruptions: examples from Hakone volcano and some global equivalents”

Mannen, Kazutaka; Roman, Diana C.; Leonard, Graham S.; Prejean, S. G.; Nakagawa, Mitsuhiro

doi:10.1186/s40623-019-1068-9

Cited by 8 publications

(5 citation statements)

References 28 publications

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“…Phreatic eruptions do not expel juvenile magma and are typically small in scale. For "wet volcanoes" they can be the dominant type of volcanic eruption that sometimes causes hazardous damage (e.g., Caudron et al, 2015;Yamaoka et al, 2016;Mannen et al, 2019). Although understanding the mechanism and forecast of phreatic eruptions are still challenging, previous studies have shown that various processes in magma-hydrothermal systems, such as rapid pressurization of fluids due to contact between groundwater and hot rocks, increased release of magmatic gases, rapid vaporization of superheated water due to decompression, and sealing by precipitation of hydrothermal minerals, play an important role in triggering this type of eruption (e.g., Hedenquist and Henley, 1985;Barberi et al, 1992;Mastin, 1995;Browne and Lawless, 2001;Stix and de Moor, 2018;Ohba et al, 2019a).…”

Section: Introductionmentioning

confidence: 99%

Groundwater Interacting at Depth With Hot Plastic Magma Triggers Phreatic Eruptions at Yugama Crater Lake of Kusatsu-Shirane Volcano (Japan)

2021

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Interpreting the triggering mechanisms for phreatic eruptions is a key to improving the hazard assessment of crater lakes. Yugama Crater Lake at Kusatsu-Shirane volcano, Japan, is the site of frequent phreatic eruptions with the recent eruptions in 1982–83, 1989, and 1996, as well as volcanic unrest, including earthquake swarms in 2014 and 2018. To understand the magma–hydrothermal interaction beneath Yugama Crater Lake, we analyzed lake waters from November 2005 to May 2021. From 2005 to 2012, Cl and SO4 concentrations decreased slowly, suggesting the development of a self-sealing zone surrounding the crystallizing magma. We focused on Ca, Al, and Si concentrations as representatives of the breach and dissolution of minerals comprising the self-sealing zone and the Mg/Cl ratio as an indicator for enhanced interaction between groundwater and hot plastic rock within the self-sealing zone. In 2006–2007, the Ca, Al, Si concentrations and the Mg/Cl ratio increased. No Cl and SO4 increase during this period suggests the self-sealing zone was leached by deep circulating groundwater rather than by magmatic fluids injection. After the 2014 earthquakes, Ca, Al, and Si increased again but were associated with a significant Cl increase and a pH decrease. We believe that the HCl-rich magmatic fluids breached the self-sealing zone, leading to fluids injection from the crystallizing magma to the Yugama crater. During this period, the Mg/Cl ratio did not increase, meaning that magmatic fluids ascending from the breached area of the self-sealing zone inhibited deep intrusion of groundwater into the hot plastic rock region. In 2018, magmatic fluids ascended through the self-sealing zone again with less intensity than in 2014. All eruptions since 1982 have been accompanied by a Mg/Cl ratio increase and a Cl decrease, whereas, when a significant HCl input occurs, as in 2014, no eruptions and no Mg/Cl ratio increase occurred. This demonstrates that the groundwater–hot plastic rock interaction, rather than the magmatic fluids input, played an essential role in triggering phreatic eruptions; i.e., phreatic eruptions can potentially occur without clear signs of fresh magma intrusions.

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Section: Introductionmentioning

confidence: 99%

Groundwater Interacting at Depth With Hot Plastic Magma Triggers Phreatic Eruptions at Yugama Crater Lake of Kusatsu-Shirane Volcano (Japan)

2021

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“…Irrespective of the presence of shallow magma, flashed water contains enough energy to efficiently fragment rock and violently eject material upwards and laterally (Montanaro et al., 2016a; Morgan et al., 2009). Often impulsive and short‐lived relative to magmatic eruptions, they are still deadly due to their sudden onsets, and the generation of violent blasts (Breard et al., 2014; Hurst et al., 2014; Kaneko et al., 2016; Mannen et al., 2019). For instance, the unheralded 2014 Ontake eruption in Japan (Yamamoto, 2014), and the 2019 Whakaari (White Island) eruption in New Zealand (Kennedy et al., 2020) resulted in ∼100 combined fatalities.…”

Section: Introductionmentioning

confidence: 99%

Host Rock Variability Powers the Diversity of Steam‐Driven Eruptions

Montanaro

Cronin

Scheu

et al. 2021

Geophysical Research Letters

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Steam-driven, phreatic and hydrothermal eruptions are a common explosive phenomenon in volcanic and geothermal systems (Browne & Lawless, 2001; Stix & Moor, 2018). In active volcanic terrains, phreatic eruptions may be triggered by the sudden arrival of extra fluid (gas, waters or brines) interacting with heat from intruding magma (Browne & Lawless, 2001; Stix & Moor, 2018). In geothermal settings, hydrothermal eruptions may be triggered by depressurization and steam-flashing of trapped hot pressurized fluids, released by earthquakes, landslides, or other localized natural hydrological disturbances (Browne & Lawless, 2001; Mastin, 1995; Thiéry & Mercury, 2009). Moreover, in both active volcanic and geothermal settings, hydrothermal alteration and mineral sealing can promote high local overpressures and thus more readily an explosive destabilization (Mayer et al, 2015, 2016; Scolamacchia & Cronin, 2016). Irrespective of the presence of shallow magma, flashed water contains enough energy to efficiently fragment rock and violently eject material upwards and laterally (Montanaro et al., 2016a; Morgan et al., 2009). Often impulsive and shortlived relative to magmatic eruptions, they are still deadly due to their sudden onsets, and the generation of violent blasts (

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“…A phreatic eruption results from the vaporization of fluids located at shallow depths beneath a volcano. Such vaporization is often triggered by the intrusion of magmatic fluid, which is sometimes detectable in well-monitored volcanoes (Yamaoka et al 2016;Mannen et al 2019). However, in many cases, there are long time lags between an intrusion of the magmatic fluid and the subsequent phreatic eruption (Stix and De Moor 2018).…”

Section: Introductionmentioning

confidence: 99%

Source constraints for the 2015 phreatic eruption of Hakone volcano, Japan, based on geological analysis and resistivity structure

Mannen

Tanada

Jomori³

et al. 2019

Earth Planets Space

Self Cite

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On June 29, 2015, a small phreatic eruption occurred in the most intensively steaming area of Hakone volcano, Japan. A previous magnetotelluric survey for the whole volcano revealed that the eruption center area (ECA) was located near the apex of a bell-shaped conductive body (resistivity < 10 Ωm) beneath the volcano. We performed local, high-resolution magnetotelluric surveys focusing on the ECA before and after the eruption. The results from these, combined with our geological analysis of samples obtained from a steam well (500 m deep) in the ECA, revealed that the conductive body contained smectite. Beneath the ECA, however, the conductive body intercalated a very local resistive body located at a depth of approximately 150 m. This resistive body is considered a vapor pocket. For the 2 months prior to eruption, a highly localized uplift of the ECA had been observed via satellite InSAR. The calculated depth of the inflation source was coincident with that of the vapor pocket, implying that enhanced vapor flux during the precursory unrest increased the porosity and vapor content in the vapor pocket. In fact, our magnetotelluric survey indicated that the vapor pocket became inflated after the eruption. The layer overlaying the vapor pocket was characterized by the formation of various altered minerals, and mineral precipitation within the veins and cracks in the layer was considered to have formed a self-sealing zone. From the mineral assemblage, we conclude that the product of the 2015 eruption originated from the self-sealing zone. The 2015 eruption is thus considered a rupture of the vapor pocket only 150 m below the surface. Even though the eruption appeared to have been triggered by the formation of a considerably deeper crack, as implied by the ground deformation, no geothermal fluid or rocks from significantly deeper than 150 m were erupted.

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Special issue “Towards forecasting phreatic eruptions: examples from Hakone volcano and some global equivalents”

Abstract: which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.

Cited by 8 publications

References 28 publications

Groundwater Interacting at Depth With Hot Plastic Magma Triggers Phreatic Eruptions at Yugama Crater Lake of Kusatsu-Shirane Volcano (Japan)

Groundwater Interacting at Depth With Hot Plastic Magma Triggers Phreatic Eruptions at Yugama Crater Lake of Kusatsu-Shirane Volcano (Japan)

Host Rock Variability Powers the Diversity of Steam‐Driven Eruptions

Source constraints for the 2015 phreatic eruption of Hakone volcano, Japan, based on geological analysis and resistivity structure

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