Definitions for "Alluvial fan"
Keywords:  canyon, valley, fan, semiarid, arid
A triangular deposit of sediment left by a stream that has lost velocity upon entering a broad, relatively flat valley.
(3) a low, outspread, relatively flat to gently sloping mass of loose rock material deposited by a stream where it flows from a narrow mountain valley onto a plain or broad valley.
The mass of sediment deposited in a cone shape where a stream widens or there is a sharp decrease in gradient.