Weathering vs Erosion
Weathering is the breakdown of rock into smaller pieces or dissolved material in place. Erosion is the removal and transport of that material by water, wind, ice or gravity. Weathering makes the pieces; erosion carries them away; deposition drops them somewhere else.
Last reviewed on 2026-10-03.
Quick Comparison
| Aspect | Weathering | Erosion |
|---|---|---|
| What happens | Rock is broken down or chemically altered | Broken material is picked up and moved |
| Does material move? | No (stays in place) | Yes |
| Main agents | Temperature changes, water, ice, oxygen, acids, plants and animals | Running water, waves, wind, glaciers, gravity |
| Types | Mechanical (physical), chemical, biological | Water, wind, glacial, coastal, gravity (mass wasting) |
| Result | Sediment, soil, rounded or crumbling rock | Valleys, canyons, beaches, sand dunes, deltas |
| Example | Frost cracking a boulder | A river carrying sand to the sea |
Key Differences
1. Weathering: Breaking Rock Down
Mechanical (physical) weathering breaks rock into smaller pieces without changing its chemistry. Frost wedging is the classic example: water seeps into cracks, expands by about 9% as it freezes, and pries the rock apart. Other forms include exfoliation (sheets peeling off as overlying rock is removed), salt crystal growth, and repeated heating and cooling.
Chemical weathering changes the minerals themselves. Rainwater containing dissolved carbon dioxide is a weak acid that dissolves limestone (forming caves and sinkholes); oxygen rusts iron-bearing minerals (giving many soils their red colour); and feldspar in granite slowly turns into clay. Biological weathering comes from living things — tree roots widening cracks, lichens releasing acids, burrowing animals.
2. Erosion: Moving the Pieces
Erosion begins when an agent picks material up. Rivers carry sand and silt and cut valleys; waves erode coastlines into cliffs and arches; wind lifts fine particles in dry regions; glaciers scrape and carry rock, carving U-shaped valleys and fjords; and gravity moves material downslope in landslides, rockfalls and soil creep (often called mass wasting).
The Grand Canyon is mainly a product of erosion by the Colorado River and its tributaries over millions of years, helped by weathering of the canyon walls.
3. Order and Overlap
Weathering usually comes first: rock must be loosened or broken before it can be carried. But the two processes run at the same time and reinforce each other — erosion exposes fresh rock to weathering, and weathering supplies new material for erosion.
Some processes blur the line. Abrasion, when sand carried by wind or water grinds against rock, is a form of mechanical weathering caused by an agent of erosion. Textbooks may list it under either heading.
4. Deposition and the Rock Cycle
When an eroding agent slows down — a river entering the sea, wind dropping behind a dune — it deposits its load. Layers of deposited sediment can be compacted and cemented into sedimentary rock, completing a key step of the rock cycle. See igneous vs sedimentary vs metamorphic rock.
Examples
Weathering examples
- Frost wedging splitting boulders in the mountains
- Limestone dissolving to form caves
- Rust-coloured soil from oxidised iron minerals
- Tree roots cracking pavements and rock
- Old gravestones with blurred lettering
Erosion examples
- Rivers carving valleys and canyons
- Waves forming sea cliffs and arches
- Wind building sand dunes
- Glaciers carving U-shaped valleys and fjords
- Landslides and rockfalls on steep slopes
Frequently Asked Questions
What is the main difference between weathering and erosion?
Weathering breaks rock down where it is; erosion moves the broken material to another place. If the material stays put, it is weathering. If it is carried away, it is erosion.
Which comes first, weathering or erosion?
Usually weathering, because rock has to be broken or loosened before it can be transported. In practice both act at the same time, and erosion keeps exposing fresh rock to weathering.
What are the agents of erosion?
Running water (the most important on land), ocean waves and currents, wind, glacial ice and gravity.
Is a landslide weathering or erosion?
Erosion. A landslide moves material downhill under gravity, a type of erosion often called mass wasting. Weathering may have weakened the slope beforehand.
What is deposition?
Deposition is the dropping of sediment when the agent carrying it (water, wind or ice) loses energy. It follows erosion and builds features like deltas, beaches and sand dunes.