Weathering - Breaks it down.
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Physical Weathering
- Moving water breaks up rock on beaches to form sand. - Water seeps into crevices in rock. When it freezes, the ice cracks the rock. - Wind carries small particles such as sand. The sand smooths away surface rock, just like sandpaper smooths wood. Physical Weathering changes, aka mechanical 
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Chemical Weathering
Chemicals in the environment break it down. |
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Oxygenation (rust) occurs when the oxygen combines with moisture causing a reaction called iron oxide breaking it down.
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CO2 combines with the water in the rock forming carbonic acid. This acid reacts to minerals in the rock to break it down. This is how most caves are formed.
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Acid/rain pollution breaks down rock. This is why old tombstones and statues look like they are dissolving.
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Biological Weathering
Living things such as animals, insects, plants & people break down the rock.
Plants root's grow into the crevice of a rock and expand causing the rock to split. This includes the pioneer species, lichen and moss.
People cut rocks to build things like roads, dams and buildings. This makes the surface area of a rock larger and speed up erosion.
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Animals, insects and worms dig or borrow into a rock. This will widen the crack.
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