Rock pillars shaped by columnar joints in granite at <scp>Mt. Mizugaki, Central Japan</scp>

Chigira, Masahiro

doi:10.1111/iar.12424

Cited by 5 publications

(13 citation statements)

References 30 publications

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“…The average flight height was 130 m. Ground control points were not used because of the steep topography, so the onboard GPS was used instead. This choice did not affect the crucial results of this paper, as has been confirmed by Chigira (2021) for the Mt. Mizugaki Survey.…”

Section: Methodssupporting

confidence: 64%

“…Such a sequence has been inferred in the granite of Mt. Mizugaki to the northeast of the Kofu basin (Chigira, 2021), where NNW–SSE‐trending joints were also developed, and rock slabs in between were separated into rock columns. The direction NNW–SSE is approximately parallel to the trend of Itoigawa–Shizuoka Tectonic Line, but there is no available explanation.…”

Section: Discussionmentioning

confidence: 80%

“…Kinpu is close to Mt. Mizugaki, which has rock towers shaped by columnar joints of granite (Chigira, 2021). Mt.…”

Section: Geologic Settingmentioning

confidence: 99%

“…The granitoid of the obelisk and its surrounding area is medium-to coarse-grained hornblende-biotite granodiorite (Figure 4b), sometimes with megacrysts of potassium feldspar (Figure 4a). The granitoid of the obelisk is jointed but not microsheeted, while the granitoid below the obelisk along the trails has several mm to cm thick microsheets with 30 -50 dips (Chigira, 2001(Chigira, , 2021) (Figures 2b,c and 5). Granitoid in some areas around the obelisk is relatively weathered to decomposed granite, which is disintegrated to grus (Figure 1a; Durgin, 1977).…”

Section: Lithology and Weathering Of Granitoidmentioning

confidence: 99%

“…Such a new approach using UAVs has suggested that primary joints of granitic pluton are not always orthogonal and sometimes not perpendicular to each other. For example, Chigira (2021) studied granite rock towers based on UAV observations and photogrammetric processing; the study found that those towers are shaped by columnar joints, which are much larger and more irregularly shaped than those of volcanic rocks such as basalt. Cross‐sections of the rock columns exhibited irregularly shaped trigonal to pentagonal and rarely consistent square or rectangle.…”

Section: Introductionmentioning

confidence: 99%

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An obelisk‐shaped granitoid tower at Mt. Jizogadake in the Southern Alps of Japan: A 3‐D morphological study

Chigira

2022

Island Arc

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Well‐developed tors and associated boulder fields are present in exposed granitoid pluton, but their geomorphological origins have not been fully addressed. Although the tor‐like features are commonly attributed to the orthogonal joint system along which weathering proceeds and the weathering materials are removed, the majority of previous studies lack three‐dimensional (3‐D) morphological observations. One of the well‐known granitoid rock towers in Japan, namely, the obelisk at Mt. Jizogadake in the Japanese Southern Alps, was investigated using unmanned air vehicles (UAVs). A 3‐D observation of the granitoid obelisk found that it is shaped by columnar joints with an undulation along a long axis and irregularly shaped cross‐sections. Because of these features and intersection angles between the rock columns and exposure surfaces, the obelisk exhibits a peculiar morphology appearing as a heap of rock blocks when observed from the ground. The columnar jointing might have occurred in a marginal zone of the granitoid pluton due to faster cooling rates. The 3‐D observations also confirmed the columnar joints formation was predated by high‐angle, planar joints. The columnar joints divide the rock mass between those planar joints. This may imply that the high‐angle joints would have formed probably during cooling under the presence of tectonic and thermal stresses.

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Section: Methodssupporting

confidence: 64%

Section: Discussionmentioning

confidence: 80%

“…Kinpu is close to Mt. Mizugaki, which has rock towers shaped by columnar joints of granite (Chigira, 2021). Mt.…”

Section: Geologic Settingmentioning

confidence: 99%

Section: Lithology and Weathering Of Granitoidmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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An obelisk‐shaped granitoid tower at Mt. Jizogadake in the Southern Alps of Japan: A 3‐D morphological study

Chigira

2022

Island Arc

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A precise modeling method of three‐dimensional discrete fracture network based on rectangular joint model

Kang,

Fu,

Sheng

et al. 2024

Num Anal Meth Geomechanics

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As the weak structure and main seepage channel of rock mass, the discrete fracture network (DFN) has a significant influence on the physical and mechanical properties of rock mass. In this paper, based on the rectangular joint model, two algorithms are proposed to realize the precise modeling of the DFN in any polyhedron. First, the equivalence of DFN modeling with the rectangular joint model and the elliptical joint model is theoretically deduced. On this basis, the chain splicing algorithm suitable for the rectangular joint model is proposed, which can generate the DFN model according to the actual distribution of joint spacing, trace, and bridge length. Aiming at the concave boundary in the model domain, the segmentation‐stitching operation is put forward, and the continuity of the joint when passing through the interface is ensured. Finally, the effectiveness of the above algorithm is verified by several simple cases, and the relationship between the size of the geometrical representative elementary volume (REV) and discontinuity parameters is discussed. The results show that when the mean values of the joint distribution parameters are the same, even if the distribution rules are different, the number of joints generated in the same spatial region is approximately equal. The size of the geometrical REV is independent of the spacing and bridge length and is approximately three to five times the mean of the trace. The relevant algorithms and conclusions in this paper can be used as the basis for subsequent rock mass stability analysis and seepage calculation.

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Granite rock towers shaped by mesh‐like joint sets, which formed in the shallower portion of a granite body during cooling at depth

Chigira

Kato²

2023

Island Arc

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Granite is fractured according to the stress state during the cooling stage, providing predispositions for later topographic evolution. This study clarified that triangular mesh‐like joints can be made during granite cooling and that they can become the structural causes for the formation of rock towers and corestones on the ground. Tengu rock, which consists of rock towers and granite corestones in Hiroshima, was investigated using an unmanned air vehicle. The rock towers were shaped by high‐angle mesh‐like joints, which were likely made during the cooling of the granite and are dominated by three joint sets. All the joint sets have sharp planar surfaces, which suggests that they are brittle fractures. One joint set is cut by the other two joint sets, frequently accompanies aplite and quartz veins and is developed in the whole exposed granite; this set likely formed first during cooling and then was penetrated by aplite from depth. The other two joint sets are high‐angle conjugate joint sets, are limited to the shallower portion of the granite pluton and do not extend deeper, which strongly suggests that they formed in a rapidly cooled shallower portion of the pluton, probably near its roof. These three joint sets form rock columns with parallelogram cross‐sections, in which incipient corestones were made. Subsurface weathering along the joints and subsequent exhumation of the weathering products formed the present rock towers and corestones only in the shallower portion of the granite.

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Rock pillars shaped by columnar joints in granite at Mt. Mizugaki, Central Japan

Cited by 5 publications

References 30 publications

An obelisk‐shaped granitoid tower at Mt. Jizogadake in the Southern Alps of Japan: A 3‐D morphological study

An obelisk‐shaped granitoid tower at Mt. Jizogadake in the Southern Alps of Japan: A 3‐D morphological study

A precise modeling method of three‐dimensional discrete fracture network based on rectangular joint model

Granite rock towers shaped by mesh‐like joint sets, which formed in the shallower portion of a granite body during cooling at depth

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