Thermal expansion and contraction shapes rocks dramatically. This process, also called exfoliation or onion-skin weathering, breaks down rocks without any chemicals.
Sunlight heats the rock surface intensely during the day. The outer layer expands quickly as temperatures rise. At night, the rock cools rapidly. The outer layer contracts and shrinks back.
These repeated heating and cooling cycles create stress. The rock surface cracks slowly over time. Thin sheets or layers peel away like onion skins.
Deserts and hot, dry regions see this process most often. Daytime temperatures swing wildly between extremes. Granite and other hard rocks show classic onion-skin patterns.
First, the outer shell loosens and flakes off. Then, a new layer becomes exposed and starts the cycle again. Eventually, rounded boulders form from once angular rocks.
Exfoliation speeds up in places with no vegetation cover. Bare rock faces absorb heat directly from the sun. Moisture sometimes joins in and widens the cracks further.
This weathering carves stunning landscapes. Think of exfoliated domes in Yosemite National Park. Large curved sheets lie scattered at the base of cliffs.
Overall, thermal expansion and contraction works quietly but powerfully. It reshapes Earth’s surface over thousands of years. Nature uses simple temperature changes to sculpt massive rocks into smooth, rounded forms.