alluvium
/əˈljuːvɪəm/noun
mass noun
- a deposit of clay, silt, and sand left by flowing flood water in a river valley or delta, typically producing fertile soil（尤指产生肥沃土壤的）冲积层, 淤积层。
词源
mid 17th cent.: Latin， neuter of alluvius 'washed against'， from ad- 'towards' + luere 'to wash'.