地学雑誌
総説
岩石の物理的風化
─実験・観測・自然現象のリンク─
松岡 憲知藁谷 哲也若狭 幸
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ジャーナル フリー

126 巻 (2017) 3 号 p. 369-405

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 Physical rock weathering has been studied through laboratory experiments, field observations, and numerical modeling, but linking these approaches and applying the results to weathering features in the field are often problematic. We review recent progress in three weathering processes—frost shattering, thermal fracturing, and lightning strikes—and explore better approaches to linking weathering processes and products. New visual and sensor technologies have led to great advances in field monitoring of weathering of fractured bedrock and resulting rockfalls in cold mountains. Laboratory simulations successfully produce fractures resulting from segregational freezing in various intact rocks. Modelling approaches illustrate the long-term evolution of periglacial slopes well, but improvements are required to apply laboratory-derived criteria to frost weathering. The efficacy of thermal weathering, which has long been under debate, is now partly supported by laboratory and field evidence that cracking takes place when wild fires or artificial explosions lead to thermal shock. Rock fracturing due to strong radiation is also reevaluated from the presence of large cooling/warming rates and meridian cracks in rocks exposed to arid environments. Linking laboratory simulations and natural features, however, needs further field-based observations of thermal fracturing. Irregular fractures formed in boulders are often attributed to lightning strikes, despite rarely being witnessed. Artificial lightning in the laboratory produces radial cracks, marking the first step toward interpreting irregular fractures in the bedrock that are unlikely to originate from other weathering processes. Identifying the origins of fractured rocks in the field requires distinguishing between fracture patterns derived from these weathering processes.

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© 2017 公益社団法人 東京地学協会
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