Explain the formation of a waterfall 12 marks

A waterfall is an erosional landform, which occurs where there is a layer of hard rock on top of a layer of softer rock. Erosional processes such as hydraulic action and abrasion occur as the river flows downstream, however differential erosion takes place as the softer rock erodes faster.

Explanation:

Waterfalls often form in the upper stages of a river where it flows over different bands of rock. It erodes soft rock more quickly than hard rock and this may lead to the creation of a waterfall.

Formation of a waterfall:

▪︎The soft rock erodes more quickly, undercutting the hard rock.

▪︎The hard rock is left overhanging and because it isn’t supported, it eventually collapses.

▪︎The fallen rocks crash into the plunge pool. They swirl around, causing more erosion.

▪︎Over time, this process is repeated and the waterfall moves upstream.

▪︎A steep-sided gorge is formed as the waterfall retreats.

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