paper 1 geography

• Erosion


  The process of wearing away of the earth's surface by natural forces
• Transportation


  The movement of eroded material
• Deposition


  When a river drops the material it is carrying
• Four Processes of Erosion


  1. Hydraulic action

  2. Abrasion

  3. Attrition

  4. Solution
• Hydraulic action


  The force of the river water colliding with rocks breaks rock particles away from the river channel
• Abrasion


  Eroded rocks picked up by the river scrape and rub against the channel, wearing it away
• Attrition

  Eroded rocks picked up by the river crash into each other and break into smaller fragments
• Solution


  River water dissolves some types of rock, e.g. chalk and limestone
• How material is transported


  • Traction
  • Saltation
  • Suspension
  • Solution
• Traction


  Large particles like boulders are pushed along the river bed by the force of the water
• Saltation


  Pebble-sized particles are bounced along the river bed by the force of the water
• Suspension


  Small particles like silt and clay are carried along by the water
• Solution


  Soluble materials (e.g. limestone) dissolve in the water and are carried along
• Waterfalls


  • Form where a river flows over an area of hard rock followed by an area of softer rock
  • The softer rock is eroded more than the hard rock, creating a 'step' in the river
  • As water flows over the step it erodes more and more of the softer rock
  • A steep drop is eventually created, which is called a waterfall
• Gorges


  • The hard rock is eventually undercut by erosion and collapses
  • The collapsed rocks are swirled around at the foot of the waterfall where they erode the softer rock by abrasion
  • Over time, more undercutting causes more collapses and the waterfall retreats, leaving behind a steep-sided gorge
• Meanders


  • Rivers develop large bends called meanders in their middle and lower courses
  • The current is faster on the outside of the bend because the river channel is deeper
  • More erosion takes place on the outside of the bend, forming river cliffs
  • The current is slower on the inside of the bend because the river channel is shallower
  • Eroded material is deposited on the inside of the bend, forming slip-off slopes
• Formation of Ox-Bow Lakes


  1. Erosion causes the outside bends to get closer

  2. Until there's only a small bit of land left between the bends (called the neck)

  3. The river breaks through this land, usually during a flood

  4. Deposition eventually cuts off the meander, forming an ox-bow lake
• Levees


  • Natural embankments (raised banks) along the edges of a river channel
  • During a flood, eroded material is deposited over the whole flood plain
  • The heaviest material is deposited closest to the river channel, because it gets dropped first when the river slows down and loses energy
  • Over time, the deposited material builds up, creating levees along the edges of the channel
• Estuary


  Tidal area where the river meets the sea
• Erosion, Transportation and Deposition


  1. Erode material

  2. Transport it

  3. Deposit it further downstream
• Four Processes of Erosion


  • Hydraulic action
  • Abrasion
  • Attrition
  • Solution
• Hydraulic action


  The force of the river water colliding with rocks breaks rock particles away from the river channel
• Abrasion


  Eroded rocks picked up by the river scrape and rub against the channel, wearing it away. Most erosion happens by abrasion
• Erosion is dominant in the upper course. The faster a river's flowing the more erosion happens
• Attrition


  Eroded rocks picked up by the river crash into each other and break into smaller fragments. Their edges also get rounded off as they rub together. The further material travels, the more it is eroded-attrition causes particle size to decrease from a river's source to its mouth
• Solution


  River water dissolves some types of rock, e.g. chalk and limestone
• How material is transported


  • Traction
  • Saltation
  • Suspension
  • Solution
• Traction


  Large particles like boulders are pushed along the river bed by the force of the water
• Saltation


  Pebble-sized particles are bounced along the river bed by the force of the water
• Suspension


  Small particles like silt and clay are carried along by the water
• Solution


  Soluble materials (e.g. limestone) dissolve in the water and are carried along
• Deposition is when a river drops the material it is carrying
• Deposition occurs when a river loses velocity and energy
• Reasons why rivers slow down and deposit material

  • Permition
• Waterfalls


  • Form where a river flows over an area of hard rock followed by an area of softer rock
  • The softer rock is eroded more than the hard rock, creating a 'step' in the river
  • As water flows over the step it erodes more and more of the softer rock
  • A steep drop is eventually created, which is called a waterfall
  • The hard rock is eventually undercut by erosion. It becomes unsupported and collapses
  • The collapsed rocks are swirled around at the foot of the waterfall where they erode the softer rock by abrasion
  • Over time, more undercutting causes more collapses. The waterfall retreats, leaving behind a steep-sided gorge
• Waterfall


  • High Force waterfall on the River Tees, County Durham
• Meanders


  • Rivers develop large bends called meanders in their middle and lower courses, in areas where the channel has both shallow and deep sections
  • The current is faster on the outside of the bend because the river channel is deeper (there's less friction to slow the water down)
  • So more erosion takes place on the outside of the bend, forming river cliffs
  • The current is slower on the inside of the bend because the river channel is shallower (there's more friction)
  • So eroded material is deposited on the inside of the bend, forming slip-off slopes
• Thalweg


  The line of deepest water and fastest flow in a river channel
• Ox-Bow Lakes


  • Formed from meanders when erosion causes the outside bands to get closer
  • The river breaks through this land, usually during a flood
  • Deposition eventually cuts off the meander, forming an ox-bow lake
• Ox-Bow Lakes


  • The River Calder has formed several ox-bow lakes near Castleford, West Yorkshire