Parallel retreat of slopes
Also called: Backwasting · Topic: Landforms and their Evolution: Rivers, Groundwater, Glaciers, Waves and Wind · NCERT: Class 11, Ch 6 "Landforms and their Evolution"
Meaning
Parallel retreat of slopes is a way desert mountains wear away. The steep slope and the free face (the bare rock wall at the top of the slope) move backward, but they keep the same angle. As the mountain front moves back, a gently sloping rocky floor called a pediment grows at its foot. In the end only a small leftover hill remains, called an inselberg. The idea explains how deserts are worn down into wide, flat plains.
Example
Uluru in central Australia is an inselberg. It is the leftover of a much bigger upland that was worn back slowly, with the land around it turned into a low plain.
Don't confuse with
- Slope decline (Davis's cycle of erosion): here slopes get gentler over time as the land wears down to a peneplain ("almost a plain"). In parallel retreat, slopes keep their steepness and move backward instead.
Related concepts
- Aeolian processes
- Deflation
- Wind abrasion
- Sheet flood
- Erg, reg and hamada
- Pediment
- Pediplain
- Inselberg
- Playa
- Deflation hollow