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River processes

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  • 1. River Processes Aim: To understand the different types of erosion in a river To know and understand the different features of the upper course of a river
  • 2. A river is split into 3 stages
  • 3. Types of erosion • Erosion and Transportation
  • 4. Types of erosion • Erosion and Transportation
  • 5. The four main forms of river erosion • Hydraulic action - the force of the river against the banks can cause air to be trapped in cracks and crevices. The pressure weakens the banks and gradually wears it away. • Abrasion - rocks carried along by the river wear down the river bed and banks. • Attrition - rocks being carried by the river smash together and break into smaller, smoother and rounder particles. • Solution - soluble particles are dissolved into the river
  • 6. Transportation
  • 7. Transportation
  • 8. The four different river transport processes • Solution - minerals are dissolved in the water and carried along in solution. • Suspension - fine light material is carried along in the water. • Saltation - small pebbles and stones are bounced along the river bed. • Traction - large boulders and rocks are rolled along the river bed Rivers need energy to transport material, and levels of energy change as the river moves from source to mouth. • When energy levels are very high, large rocks and boulders can be transported. Energy levels are usually higher near a river's source, when its course is steep and its valley narrow. Energy levels rise even higher in times of flood. • When energy levels are low, only small particles can be transported (if any). Energy levels are lowest when velocity drops as a river enters a lake or sea (at the mouth).
  • 9. Label your photos with the answers to the following questions How steep are the slopes? How wide is the channel? What is the bed load like? What are these? Where has most of the erosion happened here? How fast is the water moving?
  • 10. Upper-course river features include: steep-sided V-shaped valleys, interlocking spurs, rapids, Waterfalls gorges. These are all features formed by EROSION!
  • 11. Spurs…..
  • 12. V-shaped valley
  • 13. Rapids…….
  • 14. Waterfalls….
  • 15. Gorges….
  • 16. Formation of Waterfalls and Gorges Using the above sequence to help you, write a short paragraph to explain how waterfalls form. Use the following words somewhere in your answer: Hard Rock Soft Rock Undercutting Plunge pool Erosion
  • 17. V-shape valley formation – write these out in the correct order in which a V-shape valley is formed • This vertical erosion deepens the valley, making the sides steeper and exposed. • As the small stream flows downhill steeply, the bedload will erode downwards and scrape away the bottom of the chanel (vertical erosion) • Over time, weathering and gravity wear away the steep valley sides, forcing material into the stream, which it uses to cut the valley deeper. • A small stream will naturally follow small depressions in the landscape.
  • 18. V-shape valley formation – CORRECT ORDER • A small stream will naturally follow small depressions in the landscape. • As the small stream flows downhill steeply, the bedload will erode downwards and scrape away the bottom of the chanel (vertical erosion) • This vertical erosion deepens the valley, making the sides steeper and exposed. • Over time, weathering and gravity wear away the steep valley sides, forcing material into the stream, which it uses to cut the valley deeper.
  • 19. 4,3,2,1, upper course • Name 5 river upper course features • Give the names of 4 types of river erosion • Name the 3 courses of a river long profile • Name 1 upper-course feature that you are confident in explaining to someone else.

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