Waterfalls and Gorges - Edexcel GCSE Geography

Key Terms

• Waterfall
• Hard Rock: Example - Winstone
• Soft Rock: Example - Limestone
• Erosion Types:
  • Hydraulic Action
  • Abrasion
  • Solution
• Plunge Pool
• Overhang
• Unsupported Rock Fall
• Gorge

Waterfalls

Basic Structure

• Occur in the course of a river
• Consist of two layers of rock:
  • Hard rock on top
  • Soft rock on bottom

Diagram Guidelines

• Use a pencil for diagrams
• Avoid using a ruler; real-life rock faces aren't straight

Process

1. Erosion of Soft Rock:
   • Soft rock erodes faster than hard rock through solution, hydraulic action, and abrasion.
   • Sediment from erosion is washed downstream, creating a plunge pool.
   • Water, debris, and rock swirl in the plunge pool, increasing its size through abrasion.
2. Formation of Overhang:
   • As the plunge pool enlarges, the overhang becomes unsupported.
   • Rock fall occurs when overhang collapses, a type of mass movement.
   • Collapsed hard rock contributes to upstream retreat of the waterfall.
   • Cycle repeats: the area of rock fall becomes the gorge.
3. Gorge Formation:
   • The gorge forms between valley walls following the retreat of the waterfall.
   • Eroded hard rock is carried downstream as larger particles.

Named Example: High Force (River Tees)

• Location: Teesdale, County Durham
• Hard Rock: Winstone
• Soft Rock: Limestone
• Limestone eroded away by solution, resulting in waterfall dynamics.

Exam Tips

• Be prepared to apply knowledge to diagrams or pictures.
• Identify soft rock, hard rock, and main waterfall in images.
• Note conditions like high rainfall contributing to additional water flow.
• Annotate diagrams thoroughly to demonstrate understanding.