* Physical weathering breaks down rocks and minerals into smaller pieces without changing their chemical composition.
* Chemical weathering alters the chemical composition of rocks and minerals, leading to their breakdown.
How thermal expansion works:
1. Temperature changes: Rocks and minerals expand when heated and contract when cooled.
2. Differential expansion: Different minerals within a rock expand and contract at different rates. This creates stress within the rock.
3. Fracturing: Over time, repeated cycles of heating and cooling can cause the rock to crack and break apart.
Examples of thermal expansion weathering:
* Exfoliation: Large sheets of rock peel away from a mountain due to temperature fluctuations.
* Frost wedging: Water seeps into cracks in rocks, freezes, expands, and widens the cracks.
* Desert varnish: The alternating heating and cooling of desert rocks can cause the formation of a dark, shiny coating.
Key takeaway: Thermal expansion is a physical process that uses temperature changes to break down rocks. It doesn't involve any chemical reactions.
