Formation of a waterfall

Question 1

1) Waterfalls occur where …

Answer 1

a band of hard rock (e.g granite) overlies a softer rock like sandstone.

Question 2

2) Erosion processes such as hydraulic action, TMT

Answer 2

the force of the water forces air into cracks in the rocks, breaking them apart.

Abrasion also occurs, TMT this is where the river rubs stones that are being transported against the bed of a river, thereby breaking it down. The processes dominate.

Question 3

3) The softer rock is eroded quicker than the harder rock TMT

Answer 3

it is gradually washed away downstream.

Question 4

4) This creates a plunge pool, where water is swilled around TMT

Answer 4

potholing can occur here + any rocks + debris swept in to the plunge pool by the river will be swirled round + rub against the bed + banks of the plunge pool (called corrosion) TMT it will be deepened further.

Question 5

5) Over time, the softer rock is eroded further, creating an overhang of hard rock TMT

Answer 5

this overhang is unstable as the rock is unsupported.

Question 6

6) Eventually, this hard rock collapses because it is unsupported and TMT

Answer 6

the waterfall moves back upstream.

Question 7

7) This creates gorges, which are steep sided, deep river valleys. TMT

Answer 7

this process will repeat continually with the location of the waterfall moving back upstream.