Waterfall formation

• What causes differential erosion between two adjacent rock types?

  Different properties of the rock types
• Where do waterfalls typically form?

  Where more resistant rock overlies less resistant rock
• What happens to the rock types as water flows over them?

  They are eroded at different rates
• What is hydraulic action in the context of waterfall formation?

  It erodes the less resistant rock, creating an undercut
• What is created at the base of a waterfall due to erosion?

  A plunge pool
• What happens to the overhang of more resistant rock over time?

  It collapses due to lack of support from below
• What happens to the eroded material that falls to the plunge pool?

  It is broken up by attrition
• What is attrition in the context of waterfall erosion?

  It is the process of breaking up eroded material
• What happens to the broken material after attrition?

  It is either deposited or carried away by the river
• What is the sequence of processes that occur at a waterfall?

  • Undercutting of less resistant rock
  • Formation of a plunge pool
  • Creation of an overhang of more resistant rock
  • Collapse of the overhang
  • Erosion and attrition of fallen material
  • Movement of the waterfall upstream, forming a gorge
• How does the process of undercutting, overhanging, and collapse affect the location of a waterfall over time?

  It moves the waterfall upstream, leaving a steep-sided gorge