The Rock Cycle - Weathering
Geography: KS3, topic 7.1.4
The Rock Cycle - Weathering
Rocks do not stay the same forever; they are constantly changing and being affected by conditions on planet earth as part of the rock cycle.
Weathering
- Weathering is the wearing away of rocks.
- There are three types of weathering that wear away rocks over time.
- Weathering happens ‘in situ’- it happens to the rocks where they are.
- This is different to erosion which happens because rocks move past each other or collide with each other.
Biological weathering
- Biological weathering is caused by plants and animals.
- It is the action of plants and animals that wear away rocks.
- For example, rabbits burrow into cracks in rocks. This makes the crack bigger and splits the rock apart (eventually).
Chemical weathering
- Chemical weathering is caused because of the slightly acidic rainwater that falls onto rocks.
- When rainwater reacts with certain minerals in the rocks, it causes the rock to wear away - weathering.
- Chemical weathering affects some rocks more than others.
- Limestone and chalk are particularly affected.
Physical weathering
- Physical weathering is caused by the wind, rain or waves.
- It is also caused from changes in temperature. This is freeze-thaw weathering.
- Freeze-thaw weathering is one example of physical weathering.
Freeze-thaw weathering
- Water expands when it freezes. When water fills cracks in rocks, if it then freezes, it expands, putting pressure on the rock. The water will then melt, but it has put pressure on the rock. Eventually, this process of freezing and thawing will wear down rock. This is called freeze-thaw weathering.
Test yourself on The Rock Cycle - Weathering
Freeze-thaw weathering is an example of which kind of weathering?