What type of topographical feature is described as a flat area made up of sediment deposited by a lake?

A flat area formed by sediment deposited by a lake is referred to as a lake plain. Lake plains typically develop as lakes experience periods of sedimentation where materials such as silt, clay, and fine sands accumulate on the lakebed and eventually spill out onto the edges of the lake. The sediments settle and create a relatively flat landscape surrounding the lake, which can extend for significant distances depending on the size and duration of the lake's existence.

The term “lake plain” specifically identifies this type of geomorphological feature, differentiating it from other landforms created by different processes and environments. While outwash plains are formed by sediments transported by glacial meltwaters, stream terraces arise from the lateral erosion of rivers and alluvial fans are found at the base of mountains where sediment spreads out from a stream. Each of these landforms arises from distinct geological processes that set them apart from a lake plain.