alluvial layer

例句：

1. 1. The alluvial layer is rich in minerals and can be used for building materials.
   冲积层富含矿物质，可用于建筑材料。
2. 2. The alluvial deposits are evidence of the long-term erosion and deposition processes.
   冲积沉积物是长期侵蚀和沉积过程的证据。
3. 3. The alluvial plain is a flat area where rivers flow into the sea, often with sediment deposited.
   冲积平原是河流流入海洋的平坦区域，通常有沉积物堆积。