[MIS19-05] Unveiling the underground cultural heritage of Yokohama, Japan – the contribution of geosciences
キーワード：Taya Caves, Rock art, Soft porous rock, Stone decay, Environmental survey
In the outskirts of Yokohama (Kanagawa, Japan) lies an underground wonder known as Taya Caves, a complex network of subterranean halls and galleries, decorated with hundreds of stunning rock-cut reliefs, excavated by Shingon Buddhist monks in the 13–19th c. The caves were dedicated to ascetic training and rituals, and later on became a pilgrimage destination. Multidisciplinary studies, aimed at exploring, preserving, and promoting this site of historical importance, began only in the very last years, and the preliminary results were introduced during the JpGU Meeting 2019. Here, the contribution of geosciences is presented, providing the first comprehensive information about the properties and decay of the rock of Taya Caves, and the relevant microenvironmental setting. Taya stone is a very soft and porous siltstone, which suffers of diverse decay processes, the most significant being salt weathering – associated with crust and efflorescence formation – and slake deterioration. The most crucial factor is the constant interaction with water, related to percolating rainfall, rising damp, and the extremely high relative humidity inside the caves. That regulates the stability of rock-forming minerals and weathering phases, provokes dissolution and hydration phenomena, brings in pollutants from the nearby soils and bodies of water, and produces microstructural damage. The preservation of a semi-natural site like Taya Caves and of the artifacts enshrined therein is very problematic to achieve, but many of the most critical points to address in the future conservation may be inferred from the results of this study.