Weathering
Geography: Edexcel IGCSE, topic 1.2.1
What are the 3 Types of Weathering?
Weathering describes the natural processes that break down rocks. There are 3 main types of weathering - mechanical weathering and chemical weathering.
Mechanical weathering
- The chemical composition of rock stays the same in mechanical weathering (also called physical weathering).
- The main type of mechanical weathering that affects coastlines is freeze-thaw weathering. This happens in colder weather conditions when water fills a crack in a rock and freezes.
- Water expands when it freezes causing the crack to get wider and deeper.
- When the ice melts, there is now a larger crack that fills with water and then freezes again.
- This process of freezing and melting (known as thawing) can cause significant erosion on coastlines over time.
Chemical weathering
- In chemical weathering, the chemical composition of rock changes.
- When the climate is warm and wet, carbon dioxide can dissolve in rain to create a 'carbonic acid'.
- The carbonic acid in rainfall hits rocks and dissolves the parts of the rock made of calcium carbonate.
- This also breaks down rock.
Biological weathering
- In biological weathering, living things (organisms) break down rock.
- Plant roots can biologically weather a rock by pushing cracks apart.
Test yourself on Weathering
Which of the following is not a type of weathering process?
What is the main type of mechanical weathering affecting coasts?
If the conditions are warm and wet, which kind of weathering is most likely to take place?
Freeze-Thaw Weathering