3.3.8

Waterfalls & Gorges

Test yourself

Waterfalls and Gorges

When a river flows over hard rock that overlays softer rock, a waterfall can form. Gorges are formed when waterfalls retreat over time.

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Stage 1

  • The less resistant (softer) rock begins to erode because of abrasion and hydraulic action.
  • A step or notch forms in the softer rock, creating a river rapid.
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Stage 2

  • Over time, the softer rock gets more eroded. This leaves the hard rock sticking out above the soft rock.
  • The height of the drop increases as the water pounds the less resistant rock at the base. Eventually a waterfall forms.
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Stage 3

  • The less resistant rock starts to be eroded underneath the hard rock. This process is called undercutting.
  • The overhanging harder rock collapses because there is nothing underneath it to support it.
  • The hard rock crumbles into the base and the abrasion between the hard rock and soft rock base creates a plunge pool.
  • Hydraulic action keeps undercutting behind the waterfall.
  • If the process repeats over a long time, a gorge may form.
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Jump to other topics

1The Challenge of Natural Hazards

1.1Natural Hazards

1.2Tectonic Hazards

1.3Weather Hazards

1.4Climate Change

2The Living World

3Physical Landscapes in the UK

3.1The UK Physical Landscape

3.2Coastal Landscapes in the UK

3.3River Landscapes in the UK

3.4Glacial Landscapes in the UK

4Urban Issues & Challenges

5The Changing Economic World

6The Challenge of Resource Management

6.1Resource Management

6.2Food

6.3Water

6.4Energy

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