Pediment
Topic: Landforms and their Evolution: Rivers, Groundwater, Glaciers, Waves and Wind · NCERT: Class 11, Ch 6 "Landforms and their Evolution"
Meaning
A pediment is a gently sloping floor of rock at the foot of desert mountains. It may be bare, or it may have a thin cover of loose rock and sand. Two things cut it: lateral erosion by streams (water cutting sideways) and sheet floods (wide, shallow flows of water after heavy rain). As the mountain front wears back while keeping its steepness, the pediment grows at the mountain's expense. Pediments show that running water shapes deserts as well as wind.
Example
The desert mountains of Arizona in the south-western USA have wide rocky pediments at their feet. These slope gently away from the steep mountain fronts.
Don't confuse with
- Alluvial fan: a cone of loose sediment dropped by a stream. A pediment is a surface cut into solid rock (erosional), not a pile of sediment (depositional).
- Pediplain: the large, low plain formed when many pediments join together.
Related concepts
- Aeolian processes
- Deflation
- Wind abrasion
- Sheet flood
- Erg, reg and hamada
- Parallel retreat of slopes
- Pediplain
- Inselberg
- Playa
- Deflation hollow