The Evolution Process and its Characteristics in the Hachijojima Volcanic Group, Izu-Bonin Arc.

Suga, Kayoko

doi:10.4116/jaqua.37.59

Cited by 6 publications

(7 citation statements)

References 6 publications

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“…The topology shows severe dissection of the Mihara-yama volcano to the extent that the original edi ce has been severely modi ed (cf., Isshiki 1959;Sugihara 1998;Suga 1998). Whereas this erosional dissection destroys the original edi ce shape (Fig.…”

Section: Morphological and Volcanic Geological Surveymentioning

confidence: 96%

“…Although dissection of the Mihara-yama volcano is extensive (Fig. 1E), previous studies on this volcano (Isshiki 1959;Tsukui et al 1991Tsukui et al , 1993Suga 1994Suga , 1998Suga et al 1997;Sugihara, 1998) were based primarily on aerial photo interpretation. The geological map by Sugihara and Shimada (1998) for the younger Hachijo-Fuji volcano appears to be inconsistent with eld relationships recorded by detailed geologic mapping of the outcrops.…”

Section: Regional Setting and Backgroundmentioning

confidence: 99%

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4D volcanic geology of Hachijo-jima islet, Izu-Bonin arc

Osozawa

Ito

Nakazato

et al. 2021

International Geology Review

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This study provides geological, geochemical, and chronological insight into the evolution of the Hachijojima volcanoes of the Izu Bonin arc. The regional Ata-Torihama tephra (Ata-Th; 0.24 Ma) and Kikai-Tozurahara tephra (K-Tz; 0.095 Ma) from Kyushu are intercalated within the voluminous proximal volcanic products. Our study combines detailed geologic mapping, tephrochronology, U-Pb zircon dating, and published drill core data from NEDO (1993) to evaluate the time transgressive 3-dimensional (thus 4dimensional) structure of the dissected Mihara-yama volcano, the older of the two volcanoes on Hachijojima. The volcanic succession comprises terrestrial volcanic basement, marine volcaniclastic rocks, and terrestrial tuff intercalated with tholeiitic basalt and the regional calc-alkaline tephra layers. The undissected Hachijo-Fuji stratovolcano (tholeiitic basalt) overlies marine volcaniclastics abutting the northwestern paleo sea cliffs of Mihara-yama. Newly-described folding and normal faulting of the marine and overlying terrestrial volcaniclastic rocks suggests NW-SE shortening that may be associated with the collision of the Izu-Bonin arc with the Honshu arc. The proto Hachijo-jima volcano emerged above the sea > 0.24 Ma, and this date can be applied as a molecular biological calibration date for organisms on this island. HighlightThe erosionally-dissected Mihara-yama volcano was built on 2.1 Ma altered volcanic basement. Deposition of volcanic strata over this basement buttress unconformity began in submarine conditions at < 1.8 Ma, followed by subaerial pyroclastic ows and a tholeiitic-lava ow from 0.24 Ma onward.Emergence of the Mihara-yama volcano above sea level was > 0.24 Ma.The Ata-Torihama tephra (Ata-Th; 0.24 Ma; U-Pb age < 0.46 Ma) and Kikai-Tozurahara tephra (K-Tz; 0.095 Ma; U-Pb age < 0.24 Ma) from giant calderas of Ata and Kikai of Kyushu (calc-alkaline) are intercalated in the terrestrial scoriaceous-pumice tuffs derived from the Mihara-yama volcano (tholeiite). Previous correlations to the Aira-Tn tephra (Aira-Tanzawa; AT; 0.0275 Ma) are not viable.Adjacent to the northwestern paleo sea cliff of this old volcano, a shallow marine basin was formed at < 0.26 Ma. Subaerial scoria and tuff cones were also formed as small-scale lateral volcanoes.Tholeiitic lava ows built the subaerial Hachijo-Fuji stratovolcano over the shallow marine basin, and two major volcanoes were connected to form a single Hachijo-jima island.The island deformed by NNW-SSE shortening, re ecting the Izu-Bonin collision toward the central Japan arc.

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Section: Morphological and Volcanic Geological Surveymentioning

confidence: 96%

Section: Regional Setting and Backgroundmentioning

confidence: 99%

4D volcanic geology of Hachijo-jima islet, Izu-Bonin arc

Osozawa

Ito

Nakazato

et al. 2021

International Geology Review

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“…The Hachijo-jima Island is the largest volcanic island in the Izu-Bonin arc, with the island located on the volcanic front of the central Izu arc (e.g., Taylor, 1992;Tamura et al, 2005;Ishizuka et al, 2008). The Hachijo-jima volcanic group (Isshiki, 1963;Suga, 1998) consists of three Quaternary volcanoes: Hachijokojima, Nishiyama, and Higashiyama volcanoes, which run from west to east (Fig. 1).…”

Section: Geologymentioning

confidence: 99%

“…A d v a n c e P u b l i c a t i o n A r t i c l e ed at~10-13 ka (e.g., Nakano et al, 1991Nakano et al, , 1997Ishizuka et al, 2008;Saito et al, 2019), based on the tephra chronology of the Higashiyama volcano (Hayakawa, 1990;Tsukui et al, 1991;Sugihara, 1998). According to Suga (1998), the volcanic activity of the Nishiyama volcano can be divided into the following stages: the pre-caldera forming (13-4 ka), the Kando-yama tuff cone forming (Kando-yama surge deposit), the syn-caldera forming (buried caldera at the Nishiyama mountainside), and the post-caldera forming stages (the formation of the main stratovolcano and the scoria cones at the southern foot of the Nishiyama volcano). In this study, we focus on the lava flows at the pre-to post-caldera stages.…”

Section: Geologymentioning

confidence: 99%

Anorthosites in Nishiyama volcanic products from the Hachijo–jima island, Izu–Bonin arc: The direct evidence for ‘plagioclase control’ in shallow magma reservoir

Aizawa

Saito²,

Imura

et al. 2020

Journal of Mineralogical and Petrological Sciences

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The Nishiyama volcano is a Quaternary stratovolcano consisting of the northwestern part of the Hachijo-jima island, located in a volcanic front of the Izu-Bonin arc. The Holocene activity of the Nishiyama volcano began at~10-13 ka and has mainly produced basaltic lava flows and scoria fall deposits. While gabbroic and doleritic enclaves are generally found in scoriaceous pyroclasts, we discovered anorthositic enclaves in the lava flows.Here, we report the petrographical and petrological characteristics of the anorthositic enclaves. In the basaltic lava flows, the amount of plagioclase phenocrysts positively correlated with the whole-rock content of Al 2 O 3 , CaO, and Sr with these elements preferentially contained in the feldspar. In addition, an ideal anorthite content obtained from the whole-rock chemistry of the basaltic lava flows (An 88 ) was largely consistent with the measured anorthite content obtained from anorthosite (An 84 ). These results suggest that the plagioclase fractionation and/or accumulation controls the whole-rock chemical composition of basaltic lava flows and that the accumulated plagioclases represent part of anorthositic enclaves. Anorthosite was divided into three types of textures: 1) Comb texture, 2) adcumulate texture, and 3) radial texture. These textures (from the comb texture to the radial texture) reflected the change in the undercooling state of the magma. Based on the petrography of the anorthosite and lava flows, the plagioclase was in a liquidus phase in the Nishiyama basaltic magma. Additionally, the anorthosite was formed by the effects of adiabatic ascent and the degassing of near-H 2 O-saturated magma at the shallow magma reservoir (~5 km in depth) beneath the Nishiyama volcano.

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“…The island is mainly composed of Holocene volcanic rocks (Geological Survey of Japan, AIST (ed.) ), and volcanos have been active here during the past 140,000 years (Suga ). At the study site on the northwest coast, there is a 5 m high cliff which is composed of basaltic rock.…”

Section: Application To Boulder Transport At Hachijo Islandmentioning

confidence: 99%

Modeling boulder transport by coastal waves on cliff topography: Case study at Hachijo Island, Japan

Watanabe

Goto

Imamura

et al. 2019

Earth Surf Processes Landf

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Clifftop coastal boulders transported by storm waves or tsunamis have been reported around the world. Although numerical calculation of boulder transport is a strong tool for the identification of tsunami or storm boulders, and for estimation of the wave size emplacing boulders, models which can reasonably solve boulder transport from below a cliff or from a cliff‐edge onto a cliff‐top do not yet exist. In this study, we developed a new numerical formulation for cliff‐top deposition of boulders from the cliff edge or below the cliff, with validation from laboratory tests. We then applied the model using storm and tsunami wave forcing to simulate the observed boulder deposits at the northwest coast of Hachijo Island, Japan. Using the model, the actual distribution of boulders was explained well using a reasonable storm wave height without assumption of anomalously high‐water level by storm surge. Results show that boulder transport from the cliff edge or under the cliff onto the cliff‐top was possible from a tsunami with periods of 5~10 min or storm waves with no storm surge. However, the actual distribution of boulders on the cliff was explained only by storm waves, but not by tsunami. Therefore, the boulders distributed at this site are likely of storm wave origin. Our developed model for the boulder transport calculation can be useful for identifying a boulder's origin and can reasonably calculate cliff‐top deposition of boulders by tsunami and storm waves. © 2019 John Wiley & Sons, Ltd. © 2019 John Wiley & Sons, Ltd.

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The Evolution Process and its Characteristics in the Hachijojima Volcanic Group, Izu-Bonin Arc.

Cited by 6 publications

References 6 publications

4D volcanic geology of Hachijo-jima islet, Izu-Bonin arc

4D volcanic geology of Hachijo-jima islet, Izu-Bonin arc

Anorthosites in Nishiyama volcanic products from the Hachijo–jima island, Izu–Bonin arc: The direct evidence for ‘plagioclase control’ in shallow magma reservoir

Modeling boulder transport by coastal waves on cliff topography: Case study at Hachijo Island, Japan

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