A Pediplain is an extensive, nearly level landscape found in arid or semi-arid regions. It is formed by the gradual retreat of mountain slopes and the joining together (coalescence) of several pediments (gently sloping rock-cut surfaces at the foot of mountains). This concept was popularized by geomorphologist L.C. King as an alternative to the humid “peneplain.” ANSWER: (B) Coalescence of pediments in arid and semi-arid regions.
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In dry climates, the primary mechanism of landscape evolution is “scarp retreat.” As the steep slopes of mountains erode backward, they leave behind a gentle, rocky slope called a pediment. When several of these pediments join together over a vast area, they form a Pediplain. Unlike peneplains, which are associated with vertical down-cutting by rivers in humid climates, pediplains are the result of lateral erosion in dry regions. These plains often feature isolated, resistant hills called Inselbergs that rise sharply from the flat surface, creating the characteristic topography of parts of Africa and Australia.