Which geomorphic feature is defined as a broad, gently sloping expanse of rock debris extending outward from the foot of a mountain slope, especially in a desert?

Which geomorphic feature is defined as a broad, gently sloping expanse of rock debris extending outward from the foot of a mountain slope, especially in a desert?

• A. Bajada
• B. Pediment
• C. Alluvial fan
• D. Mesa

Answer: (B)

A pediment is a broad, gently sloping surface at the base of a mountain, formed over time by weathering and erosion of the bedrock and the removal of debris by water and wind. In desert settings this surface extends outward from the mountain front as a relatively continuous, smooth incline, often capped by a thin veneer of rock rubble. This differs from an alluvial fan or bajada, which are depositional features built from sediment that has washed down from the mountains and spread out into cone- or apron-shaped accumulations; and from a mesa, which is a flat-topped hill or high plateau with steep sides. So the described broad, debris-covered slope extending outward from the mountain base in a desert best matches a pediment.

A pediment is a broad, gently sloping surface at the base of a mountain, formed over time by weathering and erosion of the bedrock and the removal of debris by water and wind. In desert settings this surface extends outward from the mountain front as a relatively continuous, smooth incline, often capped by a thin veneer of rock rubble. This differs from an alluvial fan or bajada, which are depositional features built from sediment that has washed down from the mountains and spread out into cone- or apron-shaped accumulations; and from a mesa, which is a flat-topped hill or high plateau with steep sides. So the described broad, debris-covered slope extending outward from the mountain base in a desert best matches a pediment.