Weathering and erosion — Earth science, 14–17 years
Rocks can break apart where they are, then their pieces can be carried elsewhere. These two processes help turn solid landscapes into soils, valleys and sediments.
Breaking, then moving
Weathering breaks or changes rock where it is, through water, ice, temperature changes, chemicals or living things. Erosion is the removal and transport of that material by running water, wind, ice or gravity. A cliff may weather without its pieces travelling far.
Why landscapes change
The problem is explaining how high mountains become lower and how loose material reaches a river, coast or basin. Without separating weathering from erosion, it is easy to imagine that rock simply “wears away” in one step. The distinction reveals both the breakdown and the journey.
A pebble’s route
A crack in a mountain fills with water. The water freezes and expands, widening the crack: this is weathering. A storm then washes a loosened fragment into a stream; the stream carries it downhill, where collisions make it rounder. That movement and wearing are erosion.
Not every break is erosion
People often call every cracked or crumbling rock “erosion”. That is reasonable because both processes make a landscape look worn. The key question is whether the material moved: breaking in place is weathering; being carried away is erosion. The same piece can experience both in sequence.
Coasts, roads and soil
Engineers consider these processes when building roads, bridges or houses near slopes and coasts. Farmers depend on weathered rock becoming soil, while conservation workers try to reduce the loss of fertile soil. Waves and rivers can reshape land, but not every visible change needs human control.
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