Unloading
Also called: Pressure release, Dilation · Topic: Geomorphic Processes: Weathering, Mass Movement, Erosion and Soil Formation · NCERT: Class 11, Ch 5 "Geomorphic Processes"
Meaning
Unloading, also called pressure release or dilation, is a type of physical weathering. Rock that forms deep underground is squeezed by the weight of the rock above it. When erosion removes that upper rock, the pressure drops. The buried rock then expands upwards. It cracks into curved sheets that run parallel to the land surface. These sheets later peel off and leave smooth, rounded exfoliation domes.
Example
The granite hills around Ramanagara, near Bengaluru in Karnataka, show curved sheets of rock. These formed when overlying rock was worn away and the granite expanded.
Don't confuse with
- Exfoliation: it is the result (sheets peeling off). Unloading is one of the processes that causes it.
Related concepts
- Physical weathering
- Thermal expansion and contraction
- Frost weathering
- Salt weathering
- Biological weathering