Extensive, gently sloping plain of unconsolidated rock debris resting against the foot of a mountain front in a semi-arid environment. Typically it is made of a number of coalescing alluvial fans laid down by ephemeral streams as their gradients lessen on leaving the mountain zone. Material is also supplied by the weathering of the mountain front. Alternatively, it may comprise the alluvial accumulation on the lower part of a pediment.
Subjects: Earth Sciences and Geography.