Thermal expansion and contraction
Also called: Insolation weathering · Topic: Geomorphic Processes: Weathering, Mass Movement, Erosion and Soil Formation · NCERT: Class 11, Ch 5 "Geomorphic Processes"
Meaning
This is a type of physical weathering, also called insolation weathering. Rock heats up by day and expands, then cools at night and shrinks. Rock is a poor conductor of heat, so the outer layer changes much more than the inside. This creates stress between the surface and the core. Repeated many times, the stress causes fatigue, flaking and granular disintegration (rock breaking into separate grains). It matters most in hot deserts, where the gap between day and night temperatures is large. It also helps form tors, which are piles of rounded boulders.
Example
Around Jaisalmer in the Thar Desert, Rajasthan, sun-baked rocks flake and break down into loose grains.
Don't confuse with
- Frost weathering: it breaks rock through ice expanding in cracks, not through the rock itself heating and cooling.