硬质地层

例句：

1. 1. The geologists are analyzing the rock layers in the area.
   地质学家正在分析该地区的岩石层。
2. 2. The construction crew is working on the excavation of the hard rock stratum.
   施工队正在挖掘坚硬的岩石层。
3. 3. The engineers were discussing the potential risks associated with mining the hard rock stratum.
   工程师们正在讨论开采坚硬岩石层可能带来的风险。