Columnar Joints Research Articles

Reappraising columnar joints in different rock types and settings

Columnar joints comprise a network of opening-mode fractures that divide material into prismatic columns. They are known in several materials and rock types, including basalt, mud, sandstone, and starch. In all types, the resultant prismatic columns have a similar geometry, facilitating a comparison of columnar joints in different materials and processes such as cooling and drying. In this study, we provide a unique example of columnar joints in low-grade meta-chalks that are the product of spontaneous combustion metamorphism of organic-rich chalks in the “Mottled Zone Complex”, Israel. Although the geometry of the prismatic columns observed in these rocks resembles those seen in basalts, our approximate calculations, based on thermal expansion and temperature difference, show that contraction due to cooling is two orders of magnitude less than the measured contraction. Moreover, the cooling effect should be much more significant in high-grade (ca. 550–900 °C) rather than in low-grade (ca. 200 °C) rocks, but only the latter contain prismatic columns. The prismatic columns are restricted to a discrete stratigraphic level between 1 and 10 meters above a chert and phosphorite unit. We suggest that burning of organic matter in the protolith results in mass and volume losses, and is the principal process that leads to contraction. Changes in texture and pore-structure (recrystallization) accompany the contraction resulting in the rearrangement of the protolith into columnar meta-chalk. This intriguing example of columnar joints in meta-chalk indicates that the geometric similarity of prismatic columns should not serve as the sole argument for their formation during cooling.

Disclosing the temperature of columnar jointing in lavas

Columnar joints form by cracking during cooling-induced contraction of lava, allowing hydrothermal fluid circulation. A lack of direct observations of their formation has led to ambiguity about the temperature window of jointing and its impact on fluid flow. Here we develop a novel thermo-mechanical experiment to disclose the temperature of columnar jointing in lavas. Using basalts from Eyjafjallajökull volcano (Iceland) we show that contraction during cooling induces stress build-up below the solidus temperature (980 °C), resulting in localised macroscopic failure between 890 and 840 °C. This temperature window for incipient columnar jointing is supported by modelling informed by mechanical testing and thermal expansivity measurements. We demonstrate that columnar jointing takes place well within the solid state of volcanic rocks, and is followed by a nonlinear increase in system permeability of <9 orders of magnitude during cooling. Columnar jointing may promote advective cooling in magmatic-hydrothermal environments and fluid loss during geothermal drilling and thermal stimulation.

Basaltic Dyke with Specific Volcanogenic Structures and Its Geomorphic Evolution: Unique Geoheritage of the Faroe Islands (North Atlantic Ocean)

Volcanic landforms resulting from Cenozoic volcanism represent the most peculiar features of global geodiversity and provide eminent narratives for geoeducation. Among them, however, relict volcanic forms and site-specific landforms in remote areas have received less attention. In this paper, we provide the first description of unique volcanogenic features (hereinafter referred to as pseudo-hieroglyphs) developed on a summit rock wall at the Sandfelli ridge near the village of Gjogv in the N Eysturoy Island (Faroe Islands). The geomorphic evolution of the ridge and rock wall during the Quaternary is described and detailed petrographic analyses of the volcanogenic features are provided. Based on observed petrographical features, we interpret the pseudo-hieroglyphs to probably represent unique examples of chaotic horizontal columnar jointing. Following the geomorphological and petrographic examination of the study site, we analyse current Faroese legislation aiming at nature conservation and use this case to discuss broader implications of geoheritage conservation and geotourism in distant regions.

Integration of remote sensing, geochemical and field data in the Qena-Safaga shear zone: Implications for structural evolution of the Eastern Desert, Egypt

The Qena-Safaga shear zone (QSSZ) represents a significant structural characteristic in the Eastern Desert of Egypt. Remote Sensing, field and geochemical data were utilized in the present study. The results revealed that the QSSZ dominated by metamorphic complex (MC) that intruded by syn-tectonic granitoids. The low angle thrust fault brings calc-alkaline metavolcanics to overlie MC and its association. Subsequently, the area is dissected by strike-slip faults and the small elongated basins of Hammamat sediments of Precambrian were accumulated. The MC intruded by late-to post-tectonic granites (LPG) and Dokhan Volcanics which comprise felsic varieties forming distinctive columnar joints. Remote sensing analysis and field data revealed that major sub-vertical conspicuous strike-slip faults (SSF) including sinistral NW-SE and dextral ca. E-W shaped the study area. Various shear zones that accompanying the SSF are running NW-SE, NE-SW, E-W, N-S and ENE-WSW. The obtained shear sense presented a multiphase of deformation on each trend. i.e., the predominant NW-SE strike-slip fault trend started with sinistral displacement and is reactivated during later events to be right (dextral) strike slip cutting with dextral displacement the E-W trending faults; while NE-SW movements are cut by both the N-S and NNW - SSE trends. Remote sensing data revealed that the NW-SE direction that dominated the area is associated with hydrothermal alteration processes. This allowed modifying the major and trace elements of the highly deformed rocks that showed depletion in SiO2 and enrichments in Fe2O3, MnO, Al2O3, TiO2, Na2O, K2O, Cu, Zn and Pb contents. The geochemical signatures of major and trace elements revealed two types of granites including I-type calc-alkaline granites (late-to post-tectonic) that formed during an extensional regime. However, syn-tectonic granitoids are related to subduction-related environment.

Petrological Study on Basaltic Rocks of the Daljeon-ri Columnar Joint and the Noeseongsan Noerok Site in Pohang, Korea

Petrological Study on Basaltic Rocks of the Daljeon-ri Columnar Joint and the Noeseongsan Noerok Site in Pohang, Korea

Thermal shock response via weakly coupled peridynamic thermo-mechanics

A 3D peridynamic formulation of the thermo-mechanical problem allows to efficiently simulate the occurrence and propagation of cracks due to extreme thermal loading. The model is weakly coupled since no internal heat generation due to material deformation and damage is accounted for. As such, it is suitable to simulate low strain rate phenomena. Since the typical time scales of the mechanical and thermal systems may differ of several orders of magnitude, using a multirate explicit integration technique is suggested by the nature of the problem itself. Finally, the proposed formulation is used to model the thermal shock behavior of thin and thick slabs, in order to observe respectively a 2D ordered set of parallel cracks and a 3D honeycomb crack pattern addressed as columnar jointing.

경주 동해안권의 해양과학자원과 문화자원 융합을 통한 문무대왕 재조명 및 경주지역 해양교육관광 활성화 방안

The eastern coast of Gyeongju has a variety of resource of marine history such as the submerged tomb of King Munmu, Gamunsa Temple, Songdaemal Lighthouse and columnar joints at the beach area. In addition, Gyeongju eastern coast region is remarkable coastal upwelling area in Korea, where subsurface cold water with much nutrient is induced to surface layer due to its bottom topography and wind. This paper explore the multidisciplinary characteristics through the fusion of marine science and marine culture resources in the eastern coast of Gyeongju, and its applications to marin education tourism in Gyeongju. Firstly, it is necessary to focus the value of the Gyeongju eastern coast area as a center for marine territory education of East Sea using the historical resources. Secondly, it is also required to find storytelling that combines with the scientific results such as upwelling, advection of ocean currents toward the Dokdo and variation of sea level. Finally, in order to revitalize marine education tourism of Gyeongju it is necessary to actively connect with neighboring marine resources and Silla culture area.

Fracture mechanics criterion of time-dependent crack initiation from interface free-edge in adhesively bonded butt joints

The time-dependent crack initiation from the interface free-edge of adhesively bonded axisymmetric columnar butt joints (epoxy/SUS, edge shape: 90°/90°) was investigated in detail. With the change of applied stress level, σn, the butt joints exhibited crack initiation life, tC, that varied about four orders of seconds (102–106 s). Such a clear time-dependent life property was then studied in terms of the fracture mechanics. The near-edge stress/strain field at the crack initiation was numerically evaluated with the finite element method (FEM) by applying the time-hardening creep law to the epoxy resin. It was found that the critical asymptotic stress field along the interface represented by the combination of two parameters, λσcr (creep stress singularity index) and Kσcr (creep stress intensity factor), satisfies a unique relation irrespective of (σn, tC) sets. The same tendency was also confirmed when the near-edge total strain field parameters were employed. These results indicate that the K-λ criterion, originally developed for static fracture problems, still holds its validity in the time domain.

Hydration reaction characteristics of CaO from various local limestone samples as Chemical heat pump/storage materials

The reaction characteristics, including hydration reaction rate and performance over repeated reaction cycles, of CaO extracted from different local limestone samples in Japan were examined to identify the optimal material to be used in chemical heat storage and pumps. The factors influencing the chemical reaction, including the chemical composition, crystal grain structure, collapse due to hydration/dehydration reactions of CaO/Ca(OH)2, specific surface area, and mean pore diameter, were compared and discussed. Based on the results, it was observed that CaO derived from limestone from Hiroshima, previously utilized by our research group, and Kawara CaO with a high purity exhibit similar reaction characteristics. Garou CaO, which has more impurities than that in the others tested, exhibits a lower initial hydration reaction rate and conversion change than those of Hiroshima/Okayama and Kawara CaO due to the presence of magnesium in Garou CaO as dolomite, which initially fills the pores. However, it was shown that Garou CaO can be used as a practical material for chemical heat storage and pumps with relatively high strength and reactivity compared with the other limestone samples because of its columnar joint texture and larger pore size following activation by four water vapor reaction cycles.

Basaltic ring structures of the Serra Geral Formation at the southern Triângulo Mineiro, Água Vermelha region, Brazil

The Serra Geral Formation constitutes a continental magmatic province on the southern part of South America within the Paraná basin. Basaltic magmatism of the Serra Geral Formation occurred as extrusions at around 134.5 to 131.5My ago. The formation is part of the Paraná-Etendeka large igneous province, spanning South America and southwestern Africa. The main extrusion mechanism was probably through fissures related to extensional regime during the breakup of Gondwana in the Cretaceous. Basaltic ring structures (BRS) with tens of meters of diameter, cropping out downstream of Grande river at Água Vermelha hydroelectric dam in southern Triângulo Mineiro region, enable the study of the mechanism of extrusion. The origin of the BRS has been subject to differing interpretations in the past, either collapsed lava flows or central conduits. Detailed geological mapping at 1:1000 scale, stratigraphic, petrographic and gravimetric analysis of the most well preserved of the BRS, with a 200m diameter, has enabled the description of thirteen different basalt lava flows, along with single a central lava lake and a ring dyke structure. The central flow, interpreted as a preserved lava lake, comprises vesicle- and amygdale-rich basalt, spatter, ropy and degassing structures. The most basal of the thirteen lava flows has massive basalt containing geodes filled with quartz. Above, the lava flows show massive basalt with vertical columnar jointing where is possible to identify the top and bottom of each individual flow, with gentle dips towards the perimeter of the structure. A prominent ring dyke dipping towards the lava lake presents horizontal columnar jointing and cuts the basal and central flows. The gravimetric analysis shows a weak negative Bouguer anomaly on the center of the BRS. The proposed model describes the volcanism of the region in three main steps: (1) fissure flow occurs with lava input; (2) this lava cools and crystallizes cementing most of the fissures, promoting the formation of localized central conduits; and (3) the presence of dissolved gas in lava produces ring and radial fractures around the solidified lava lake. The magma uses some of the ring fissures to ascend and the following lava flows assume the ring shape of the dyke vent. Thus, the BRS in Água Vermelha region can be interpreted as remnants of central conduits representing the late stage magmatism of the Serra Geral Formation.

Basaltic ignimbrites in monogenetic volcanism: the example of La Garrotxa volcanic field

Ignimbrites are pyroclastic density current deposits common in explosive volcanism involving intermediate and silicic magmas and in less abundance in eruptions of basaltic central and shield volcanoes. However, they are not widely described in association with monogenetic volcanism, where typical products include lava flows, scoria and lapilli fall deposits, as well as various kinds of pyroclastic density current deposits and explosion breccias. In La Garrotxa basaltic monogenetic volcanic field, part of the Neogene-Quaternary European rift system located in the northeast of the Iberian Peninsula, we have identified a particular group of pyroclastic density current deposits that show similar textural characteristics to silicic ignimbrites, indicating an overlap in transport and depositional processes. These deposits can be clearly distinguished from other pyroclastic density current deposits generated during phreatomagmatic phases that typically correspond to thinly laminated units with planar-to-cross-bedded stratification. The monogenetic ignimbrite deposits correspond to a few meters to several tens of meters thick units rich in lithic- and lapilli scoria fragments, with an abundant ash matrix, and internally massive structure, emplaced along valleys and gullies, with run-out distances up to 6 km and individual volumes ranging from 106 to 1.5 × 107 m3. The presence of flattened scoria and columnar jointing in some of these deposits suggests relatively high emplacement temperatures, coinciding with available paleomagnetic data that suggests an emplacement temperature around 450–500 °C. In this work, we describe the main characteristics of these pyroclastic deposits that were generated by a number of phreatomagmatic episodes. Comparison with similar deposits from silicic eruptions and previous examples of ignimbrites associated with basaltic volcanism allows us to classify them as ‘basaltic ignimbrites’. The recognition in monogenetic volcanism of such pyroclastic products, which may extend several kilometres from source, has an important consequence for hazard assessment in these volcanic fields, which previously have been considered to present only minor hazards and risks.

Insights into statistical structural characteristics and deformation properties of columnar jointed basalts: field investigation in the Baihetan Dam base, China

The columnar jointed basalt (CJB) in the left-bank dam foundation of the Baihetan hydropower station, China, is a special jointed rock mass with a columnar cylinder structure. A field investigation revealed three types of joints developing in the CJB: (1) columnar joints, (2) internal steeply dipping joints (ISDJ), and (3) internal gently dipping joints (IGDJ). A uniform distribution survey lines method (UDSLM) is proposed to describe quantitatively the spatial structural features of CJB exposed in limited outcrops. The visible spacing of internal joints in CJB is found to evolve; joint spacing decreases with increased degrees of weathering, disturbance, and time after unloading excavation. Combined with the actual structure, the formation mechanism of CJB is discussed from the structure of a single column to the whole rock mass, based on the contraction hypothesis. A columnar joint tensor, which is closely related to the CJB deformation characteristics, is established for describing the complex columnar joint network in the three-dimensional space based on the measurement data with the UDSLM. In addition, the structural characteristics of intact columns were exposed through dismantling cuboid specimens of 0.5 m edge lengths and 1.0 m height, verifying the rationality of the UDSLM and the evaluation of structural characteristics of CJB in the Baihetan dam foundation. This in situ study presents an in-depth understanding of CJB structure and provides meaningful guidance for excavation and supporting reinforcement for the CJB exposed on the Chinese Baihetan dam foundation.

P2-11 アナログ実験による曲がった柱状節理の形態の再現(ポスターセッション)

P2-11 アナログ実験による曲がった柱状節理の形態の再現(ポスターセッション)

A Study of Columnar Joint in Goheung, Jeollanam-do, Korea

A Study of Columnar Joint in Goheung, Jeollanam-do, Korea

Anisotropic characteristic of irregular columnar-jointed rock mass based on physical model test

Columnar joint is a special geological structure with self-organized joint network which separates the rock into an assemblage of blocks. The mechanic characteristics of irregular columnar-jointed rock mass (ICJRM) are dependent not only on the intact rock material but also on unique types of columnar joints. In effort to understand the anisotropic mechanic characteristics of ICJRM by the inherent anisotropic nature of the jointed structure, we conducted a series of uniaxial compression tests. Experiments were performed on an artificial ICJRM of 50 mm in diameter and 100 mm high. The “intact material” consisted of cement mortar and the columnar joints of photosensitive resins. The columnar joint in the specimen was made into six different orientations: 0°, 30°, 45°, 60°, 75°, and 90°, respectively, so observe the deformation behavior and failure modes of ICJRM with different various angles between the loading orientation and columnar joint were observed. Based on the analysis of the test results, the uniaxial compression strength and elastic modulus of ICJRM showed strong anisotropic behavior along with a special “U” shape in response to the angle between the loading orientation and columnar joint. Furthermore, the failure modes of ICJRM was observed.

무등산국립공원 입석대 주상절리대에 대한 물리역학적 특성

무등산국립공원 입석대 주상절리대에 대한 물리역학적 특성

Anisotropic mechanical behaviors of columnar jointed basalt under compression

Columnar jointed basalt is a typical type of jointed rock mass formed by the combined cutting effect of primary joints and aphanitic fissures and exhibits highly anisotropic mechanical behaviors in terms of strength and deformation modulus. In order to understand the anisotropic mechanical properties of columnar jointed basalt, a series of laboratory tests and numerical simulations were carried out. Firstly, a mixture of water, river sand, and gypsum was prepared to model the columnar jointed basalt. A series of uniaxial compression tests were then conducted according to the different cooling times and prefabricated dip angles (α = 0°–90°). The model test results reveal that the strength and deformation modulus of columnar jointed basalt are obviously affected by the primary joint angles, and the deformation modulus and the peak strength of columnar jointed basalt under uniaxial compression are correlated with the dip angles of primary joints by a U-shaped curve. The deformation modulus and the peak strength reach the minimum when the joint angle is in the range of 60°–75°. A multi-jointed softening constitutive model was the established based on the results of model tests. The 3DEC software was adopted to simulate the uniaxial compression tests. The simulation results are in agreement with the test results, demonstrating the rationality of the numerical method proposed in this paper. Lastly, the triaxial compression tests on columnar joints under different confining pressures were modeled. The modeling results indicate that, with the presence of confining pressure, the similar material exhibits different mechanical properties, such as elastic–plastic and elastic–brittle behaviors, under different primary joint angles. The primary joints are the predominant factor affecting the anisotropy of the similar material. By comparing the normalized indexes, it is found that increasing confining pressure can effectively reduce the effect of columnar joints on the anisotropy of mechanical properties of rock masses.

Spheroidal weathering of granite porphyry with well‐developed columnar joints by oxidation, iron precipitation, and rindlet exfoliation

AbstractSpheroidal weathering, one of the important rock weathering styles, has been attributed to chemical weathering by the water from joint surfaces, and mechanical aspects of the weathering have not been well addressed. We made an investigation on spheroidal weathering of Miocene granite porphyry with well‐developed columnar joints and found that this spheroidal weathering proceeds through chemical processes and accompanying mechanical processes. The investigation of the textures, physical properties, mineralogy, and chemistry of the porphyry revealed the presence of a brown band on the surface margins of corestones, representing the oxidation of pyrite and chlorite, and the precipitation of iron hydroxides, and the consequent generation of micro‐cracks within the band. During weathering, oxidation progresses inwards from joints that surround the rindlets, including both high‐angle columnar and low‐angle planar joints, and causes rounding of the unweathered interior portion of the rock. Microscopic observations of the brown band embedded with fluorescent resin show that pores are first filled with iron hydroxides, and that micro‐cracks then form parallel to the oxidation front in the outer portion of the brown band. Iron hydroxide precipitation increases the P‐wave velocity in the brown band, while micro‐crack formation decreases the tensile strength of the rock. Where the brown band has thickened to ~6 cm, the micro‐cracks are connected to one another to create continuous cracks, which separate the rindlets from the corestone. Micro‐crack formation parallel to the corestone surface may be attributed to compressive stresses generated by small amounts of volumetric expansion due to the precipitation of iron hydroxides in the brown band. Earth surface is under oxidizing environments so that precipitation of iron hydroxides commonly occurs; the spheroidal weathering in this paper is a typical example of the combination of chemical and mechanical processes under such environments. Copyright © 2016 John Wiley &amp; Sons, Ltd.

Scale selection in columnar jointing: Insights from experiments on cooling stearic acid and numerical simulations

AbstractMany natural fracture systems are characterized by a single length scale, which is the distance between neighboring fractures. Examples are mud cracks and columnar jointing. In columnar jointing the origin of this scale has been a long‐standing issue. Here we present a comprehensive study of columnar jointing based on experiments on cooling stearic acids, numerical simulations using both discrete and finite element methods and basic analytical calculations. We show that the diameter of columnar joints is a nontrivial function of the material properties and the cooling conditions of the system. We determine the shape of this function analytically and show that it is in agreement with the experiments and the numerical simulations.

Engineering geological classification of the structural planes for hydroelectric projects in Emeishan Basalts

The scale and characteristics of rock mass are important indexes of the rock mass structural plane classification. This paper firstly analyzes the spatial distribution characteristics, the structural plane types (original structural plane, tectonic structural plane and hypergenic structural plane) and the associated features of the Emeishan basalts and then studies the classification schemes of the built hydropower structure planes of different rock areas (the east district, the central district and the west district) in the Emeishan basalt distribution area, Southwest China. Based on the analysis and comparison of the scale and the engineering geological characteristics of the typical structure planes in the basalt hydroelectric Stations, the types of structural planes are used in the first order classification. The secondary order classification is made by considering the impact factors of rock mass quality, e.g., the state of the structural planes, infilling, joint opening, extending length, the grade of weathering and strength. The engineering geological classification for Emeishan basalt is proposed. Because there are no evidences of a large structure presenting in study area, the first-order (I) controlling structural planes do not appear in the classification, there only appear II, III, IVand Vgrade structural planes influencing the rock-mass quality. According to the different rock-block types in bedding fault zone, the second-grade (II) structural planes consisted of bedding fault zone is further classified into II1, II2 and II3. The third-grade (III) structural planes constructed by intraformational faulted zones are not subdivided. According to the different characteristics of intrusion, alteration and weathering unloading structural planes, the IVgrade structure plane is divided into IV1, IV2 and IV3. According to the development characteristics of joints and fractures, the Vgrade structure plane is divided into fracture V1 and columnar joint V2. In all, the structural planes are classified into four groups with nine subsets. The research proposes the engineering geological classification of the structural plane for the hydropower project in the Emishan basalts, and the result of the study has a potential application in similar regions.