8. Weathering By day By night Over time 2. Freeze-thaw in action
Scree
By day water collects in cracks in the rock.
At night the water freezes and expands.
Repeated freeze-thaw action causes the rock to shatter, and it falls to the bottom of the slope as scree.
Being creative
Partially fill a plastic bottle with water and mark the height of the water in the bottle with a permanent marker. Place the plastic bottle into the freezer overnight to allow the water to freeze. Note how much the water has expanded when you remove the bottle the next day.
To see the process of weathering and freeze-thaw in action, go to YouTube and search for ‘Weathering and erosion – freeze-thaw weathering (Lammas Science)’ (1:20).
1. What is the name of the broken material you see here in the photo?
2. Where would you expect to find it as a result of freeze- thaw action: at the top or bottom of mountains?
Question Time
1. What is denudation? 2. Describe the difference between weathering and erosion. 3. Name the three types of weathering. 4. What is mechanical weathering? 5. Using a labelled diagram/s, explain freeze-thaw action.