[M-IS19] Conservation of geoparks, natural geosites, and cultural heritage: weathering and damage assessment

[MIS19-04] Study on groundwater quality inside of the Taya cavern

*小口 千明¹、安 素賢¹、田村 裕彦² (1.埼玉大学大学院理工学研究科、2.田谷の洞窟保存実行委員会)

キーワード：田谷の洞窟、地下水

The Taya Cave, located in the precincts of Josenji Temple, is registered as one of the region historical properties by Yokohama city. This cave originated from the Kamakura period (13th Century). The Buddhist priests excavated and enlarged it to be about 570 m length and 3 floors. There are 11 dome-shaped spaces with various sizes inside, as well as there are more than 300 bas-reliefs engraving Buddhist murals on the walls and ceilings. However, at present, deterioration and weathering have progressed inside the cave in Taya. Salt precipitation, cracks and peeling are observed. In the present study, the geological properties, local environment and the groundwater quality were analyzed for the purpose of salt origin from the viewpoint of water-rock interaction. The results revealed that the temperature inside the cave is kept almost constant, while the humidity varies depending on the location inside the cave because of seasonal changes such as rainfall. The quality of the groundwater in the cave was also affected by seasonal changes which are shown by time-lag, and by location inside of the cave broadly reflecting the difference in depth of from the earth surface.