To explain a landform, link four steps: the cause, the process, the change to the ground and the feature that results. The steps must be in order.
This lesson is part of physical geography. The same chain works for tectonic, river and coastal features.
What is the four-step chain?
- Cause: what sets the process off, such as a hard rock layer lying over a soft one.
- Process: what the water, wave or movement does, such as undercutting.
- Change: what happens to the ground as a result, such as the rock above being left unsupported.
- Feature: what is left behind, such as a gorge.
Worked example: an original waterfall
An original river flows over a band of hard rock that lies above a band of soft rock. Explain how a waterfall and gorge form.
- The river crosses a hard rock layer above a soft layer, so the two resist erosion at different rates.
- Water falls over the edge and swirls at the base, which wears away the soft rock faster, forming a plunge pool.
- The hard rock above is undercut and left as an overhang, which is unsupported and eventually collapses.
- Each collapse moves the waterfall upstream, so a steep-sided gorge is left behind it.
The chain explains the gorge as a result of the waterfall moving, not as a separate event.
The mistake: the answer that stops at the name
A common slip is to write “a waterfall forms where the river falls over hard rock”. The sentence is true, but it stops at step 1, and it does not say how the feature changes.
| Weak answer | Strong answer |
|---|---|
| “Hard rock makes a waterfall.” | “The soft rock below is eroded faster, so the hard rock is undercut and collapses.” |
| “A gorge is a steep valley.” | “The waterfall retreats upstream as the overhang collapses, leaving a gorge.” |
| Names the landform only | Names the cause, process, change and feature |
A second slip is to put the steps in the wrong order, for example writing the plunge pool before the undercutting. Use “so”, “which” and “then” to keep the order honest.
Check yourself
An original river bends, with a steep bank on the outside and a gentle sandy slope on the inside. Explain how the two features form using the four-step chain.
Answer
- Cause: at a bend, the fastest water is pushed towards the outside.
- Process: the fast water erodes the outer bank, while slow water on the inside can no longer carry its load.
- Change: the outer bank is cut back and steepens, and sand is dropped on the inside.
- Feature: a steep river cliff on the outside and a gently sloping slip-off slope on the inside.
What to study next
Learn to work backwards from the feature to the process in connecting processes with observed features. Then try the physical geography practice set.
If you want a teacher to check your explanations step by step, see online one-to-one Geography tuition.