Erosion and deposition — Geography, 11–13 years
Learn how moving water, wind and ice wear land away and build it somewhere else. Geography, 11–13 years.
Land can move
Erosion is the wearing away and carrying off of rock or soil by water, wind, ice or gravity. Deposition happens when that moving material is dropped in a new place. Together, these processes slowly reshape slopes, river valleys, beaches and coastlines.
Why do geographers study it?
People noticed that the same river could cut into land in one place and leave mud or sand in another. Explaining both parts was better than treating each landform as a separate mystery. It also helped people understand why fields disappear, harbours fill with silt and coasts change.
A river bend
Picture a river bend. Water travels fastest along the outside bank, so it strikes and erodes that bank; the inside has slower water, so sand is deposited there. Over many years, the outside may become a steep cliff while the inside grows into a shallow beach.
Erosion is not only breaking
A reasonable mistake is to call every cracked or broken rock erosion. Cracking is often weathering, which breaks material in place; erosion also involves moving it away. The distinction matters because a rock can weather on a hillside for years without its pieces travelling anywhere.
Why it matters today
Engineers study erosion before building roads, bridges or houses near rivers and cliffs. They may plant vegetation, add rocks or change drainage to slow soil loss. These measures reduce risk, but they do not stop natural erosion everywhere or forever.
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