Activity 01
Model Building: Waterfall Retreat
Pairs layer clay, sand, and pebbles in trays to mimic caprock over softer beds. They pour measured water volumes repeatedly, recording undercutting depth and plunge pool growth after each trial. Groups sketch cross-sections before and after to note gorge formation.
Explain the sequence of events leading to the formation of a waterfall and gorge.
Facilitation TipDuring Model Building: Waterfall Retreat, circulate to ensure groups measure caprock thickness and soft-rock height before each trial so retreat distances can be compared across classes.
What to look forProvide students with a diagram of a waterfall cross-section showing caprock and softer rock. Ask them to label the key erosional processes (hydraulic action, abrasion) at work and briefly explain how the waterfall forms and retreats.