Alluvium is loose earth which sits on top of consolidated sediment (~ rock). It usually consists of loose gravel and clay.
Where people live, it is usually covered with "made ground". That is what we call pavements, buildings, and roads. They are the most obvious examples of made ground.
There is a discussion about what other sediment deposits should be included under the term "alluvium".
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- ↑ Miller, Bradley A.; Juilleret, Jérôme 2020. The colluvium and alluvium problem: historical review and current state of definitions. Earth-Science Reviews 209: 103316. 
- ↑ Chisholm, Hugh, ed. 1911. Alluvium. Encyclopædia Britannica (11th ed). Cambridge University Press