hydrosphere

• solution


  acids in the water react with soluble bedrock
• abrasion


  the force of the water throws bedload against the banks causing a scouring action
• attrition


  load is thrown against other particles in the water causing it to become smaller and rounder
• hydraulic action


  when water compresses air into the riverbank causing materials to be dislodged
• formation of a v-shaped valley

  • rivers begin high up in the mountains so they flow quickly downhill eroding the landscape vertically
  • the river cuts a deep notch in the landscape using hydraulic action
  • abrasion occurs
  • attrition occurs
  • as the river erodes downwards the sides of the valley are exposed to freeze-thaw weathering which loosens the rock and steepens the valley
  • the river transports the rock downstream and the channel becomes wider and deeper creating a v-shaped valley with interlocking spurs
• formation of a waterfall

  • differential erosion takes place over bands of more and less resistant rock, the softer rock is more easily eroded by hydraulic action and abrasion
  • the softer rock is undercut causing an overhang of the hard rock
  • overtime the hard rock becomes unsupported and colla[ses due to gravity into the plunge pool
  • attrition occurs here when the rocks in the plunge pool hit off each other
  • eventually the waterfall retreats upstream
• formation of a meander

  • in a straight river channel water twists and turns around obstructions such as boulders
  • this creates riffles and pools. this results in areas of slower and faster water movement
  • rivers flow faster on the outside bend increasing the erosive power to form river cliffs, eroded through hydraulic action, abrasion and solution
  • helicoidal flow moves material from the outside bend to the next inside bend
  • water moves slowly on the inside bend and water deposits load, creating a river beach
  • continuous erosion and deposition overtime creates a meander
• formation of an oxbow lake

  • a river meanders laterally across the valley
  • fast flowing water erodes the outside bends using hydraulic action, undercutting to form river cliffs
  • outside bend is further eroded by solution and abrasion
  • the river flows slowest on the inside bend leading to deposition
  • meanders become more pronounced over time and the continual erosion and deposition narrows the neck of the meander
  • during a flood, rivers have more energy and cut through the neck of the meander, the river then takes the shortest path
  • the meander is abandoned and the oxbow lake dries up eventually