What defines the geological feature known as a kame?

A kame is specifically defined as a conical hill that is formed from material deposited by glaciers. As glaciers advance and retreat, they can pick up and transport sediments. When the glacier melts, it leaves behind these materials in a hill-like mound. This distinguishing feature of kames is the result of the glacial activity and the characteristics of the sedimentary deposits, which tend to accumulate in a conical shape due to the flow of meltwater and the gravitational settling of sediments.

Other geological features mentioned in the options differ fundamentally from kames. Flat areas formed from river sediment are known as floodplains or deltas, while flat depressions created by melting glaciers are referred to as kettles. Smooth ridges formed by glacial action are called moraines. Each of these features has unique origins and characteristics, setting them apart from the conical hills specifically termed kames.