Erosion and deposition — Earth science, 11–13 years
Moving water, wind, ice and gravity can wear rock away and carry its pieces elsewhere. The same forces can then drop the material, building new landforms such as beaches, dunes and river deltas.
Rock on the move
Erosion is the wearing away and transport of rock or soil. Deposition happens when the moving material is dropped because the water, wind or ice loses energy. Together, these processes can lower one place while slowly building another.
Why does the landscape change?
A cliff, riverbank or field can look permanent during one afternoon, yet change over years or centuries. Scientists needed to explain where the missing soil and sand went. Erosion and deposition connect the source, the journey and the new resting place of sediment.
Following a river pebble
After heavy rain, a river flows faster and has more energy. It breaks a 5-centimetre piece from a bank, carries it downstream and rounds its edges as it bumps along. Where the river widens and slows, the pebble may be deposited with sand and gravel.
Erosion is not only breaking
It is easy to call every crack or weathered patch erosion, because both can make rock smaller. Weathering breaks or changes rock in place; erosion includes the removal and movement of that material. A stone crumbling on the ground is weathering until water or wind carries the pieces away.
Rivers, farms and coasts
These processes matter when a river undercuts a road, when fertile soil blows from a field, or when a beach loses sand. Plant roots, terraces and carefully placed barriers can slow erosion, but they cannot stop every natural change. Understanding the movement helps people plan without pretending to control it completely.
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