What is weathering?
Quick answer
Weathering is the process by which rocks are broken down at or near Earth’s surface, by water, ice, temperature changes, chemicals and living things. It happens in place, without the rock being carried away. There are three main types: physical, chemical and biological weathering.
The three types of weathering
| Type | How it works | Example |
|---|---|---|
| Physical (mechanical) | Rock is broken into smaller pieces without changing what it’s made of | Frost wedging: water freezes in cracks, expands by about 9% and splits the rock |
| Chemical | Minerals in the rock react and change | Rain containing carbon dioxide dissolves limestone; iron-rich rocks rust |
| Biological | Living things break rocks down | Tree roots widen cracks; lichens release acids; burrowing animals |
Physical weathering is strongest in cold or desert climates with big temperature swings. Chemical weathering is fastest in warm, wet places.
Weathering vs erosion
| Weathering | Erosion | |
|---|---|---|
| What happens | Rock breaks down | Broken pieces are moved |
| Moves material? | No | Yes, by water, wind, ice or gravity |
Weathering and erosion often work together. For example, frost breaks rock on a mountain, and a river then carries the pieces downstream.
Everyday examples
- Potholes in roads, widened by freezing water
- Old gravestones with worn, unreadable letters
- Caves carved through limestone by slightly acidic water
- Soil, which forms partly from weathered rock mixed with organic matter
Famous landscapes shaped by weathering
- Utah’s Arches National Park
- Turkey’s Cappadocia, with its “fairy chimneys” of soft volcanic rock
- The rounded granite tors of Dartmoor, England
Over millions of years, weathering helps recycle rocks and shape continents that once formed Pangaea. Freezing water is key; see what temperature water freezes at.
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