Weathering: how rock breaks down without moving
Geography · Key Stage 2 · The School
Breaking down, not moving away
WEATHERING breaks rock down where it sits. It does not carry the rock anywhere. That is the key difference from erosion. Erosion moves rock. Weathering just breaks it. Both work slowly, over many years.
Three ways rock breaks down
FROST weathering happens when water freezes in a crack. Ice takes up more space than water. It pushes the crack wider. This happens again and again. Eventually the rock splits. PLANT weathering happens when roots grow into cracks. The roots get thicker. They force the crack apart. CHEMICAL weathering happens when rain slowly dissolves some rocks. Limestone is worn away like this over many years. Old gravestones show this clearly, their letters slowly fading.
Why the difference matters
Weathering breaks rock apart on the spot. Erosion then carries the broken pieces away. The two usually work together. Weathering makes the small pieces. Erosion moves them somewhere else. One without the other tells only half the story. Both together explain most of what shapes a landscape.
A small crack sits in a rock on a hillside. Rain fills the crack with water. Night comes and the temperature drops. The water freezes solid. Ice takes up more room than water did. The crack is pushed slightly wider. Day comes and the ice melts again. More water fills the wider crack. This happens night after night, all winter. By spring the crack has split the rock in two. No wind or river moved anything. The rock simply broke apart where it stood. The two halves are now ready for erosion to carry them away.