短语词组短語covered rock separation strata 覆巖離層rock -strata-structure 巖石地層搆造和地質事件overlying rock strata 上覆巖層rock strata movement 巖層移動key rock strata 關鍵層rock strata support 巖層支護clastic rock strata 碎屑巖地層 返回 rock strata