Waterfall

• Differential erosion takes place over bands of more and less resistant rock/where harder rock is overlaying softer rock/bands of hard/soft rock
• Differential erosion


  Erosion that takes place at different rates depending on the resistance of the rock
• Softer rock is more easily eroded
• Undercutting


  Causes an overhang of the hard rock
• Over time the hard rock is unsupported and collapses due to gravity into the plunge pool
• Attrition


  Rocks in the plunge pool hit off each other, eroding further
• The waterfall retreats upstream