1) The understratum of the soil contains important minerals.

2) The understratum of the lake is rich in natural gas.

3) Archaeologists discovered ancient ruins in the understratum of the city.

4) The understratum of the building's foundation needed reinforcement.

5) The understratum of the ocean floor is home to diverse marine life.

6) Geological studies revealed the composition of the understratum in the region.

7) Miners extracted valuable ores from the understratum of the mountain.

8) The understratum of the forest floor is teeming with organisms.

9) Engineers examined the stability of the understratum before construction.

10) Excavations uncovered artifacts buried deep in the understratum of the archaeological site.