model of straton

例句：

1. 1.The geologist is analyzing the stratum to determine its age.
   地质学家正在分析地层以确定其年龄。
2. 2.The stratum beneath the city was once covered in water.
   城市下方的地层曾经被水覆盖。
3. 3.The stratum of sediments is crucial for understanding the history of the region.
   沉积物层对于理解该地区的历史至关重要。