geography

• Weathering

  The process by which rocks are broken down into small particles OR the breakdown of rock into smaller pieces through exposure to wind, water, heat, and cold
• Exfoliation

  1. Thermal expansion

  2. Contraction

  3. Cracks

  4. Layers of rock peel off as expansion alternates with contraction
• Thermal expansion

  The breaking down of rocks due to expansion and contraction of rocks as a result of extreme range of temperatures
• Salt wedging

  Occurs when salts crystallize out of solution as water evaporates. As the salt crystals grow, they apply pressure to the surrounding rock weakening it, until it eventually cracks and breaks down.
• Abrasion

  The breaking down and wearing away of rock material by the mechanical action of other rocks
• Agents of physical weathering that can cause abrasion

  • Moving water
  • Wind
  • Gravity
• Hydration

  A process where mineral structure in the rock forms a weak bond with water which causes the mineral grains to expand, creating stress which causes the disintegration of the rock
• Oxidation

  A chemical reaction between some minerals in rocks and the oxygen in the air, changing iron minerals in rocks from a light grey colour to a brown-red colour
• Solution

  A process by which rock is dissolved in water, most commonly occurring on rocks containing carbonates such as limestone, but may also affect rocks with large amount of halite, or rock salt
• Biological weathering

  The disintegration (breaking down) or decay of rocks and minerals caused by chemical or physical agents of organisms
• Biological weathering characteristics

  • Organic activity from lichen and algae
  • Rock disintegration by plant growth
  • Burrowing and tunneling organisms
  • Secretion of acids
• Organic activity from lichen and algae

  Organisms such as lichen and algae often live on bare rock and extract minerals from the rock by iron-exchange mechanisms, leaching minerals from the rock causing it to weaken and breakdown
• Rock disintegration by plant growth

  Plant roots penetrate into cracks and crevices of rocks and cause the rock to split or break into smaller particles through mechanical weathering
• Burrowing and tunneling organisms

  Animals may burrow or tunnel into rocks or cracks in rocks and cause the rock to break down and disintegrate
• Secretion of acids

  Some organisms, such as snails, barnacles, or limpets, attach themselves to rocks and secrete acids that chemically dissolve the rock surface
• types of weathering

  • physical or mechanical weathering
  • chemical weathering
  • biological weathering
• physical or mechanical weathering

  the breakdown of rocks into smaller fragments by natural physical forces without changing its chemical form.
• examples of physical weathering

  • freeze thaw
  • exfoliation
  • thermal expansion
  • salt wedging
  • abrasion
• freeze thaw

  happens when water is collected in the cracks of the rock

  day: during the day the water melts which then releases the pressure of the rocks and contracts, the rock starts to breakdown.

  night: the water freezes during the night which causes the rock to expand because of the prressure of the ice.
• exfoliation

  exfoliation is when the high temperature causes the rrock to expand because of the heat. (this only happens during the day)

  when it is night, the rock starts to contract because of the loss of heat.

  (this constant action causes the rocks outer layer to peel off)
• impacts of human activities on weathering

  • buring of fossil fuels/pollution makes air to be acidic, which leads to acid rain, that eats away at some softer rocks.
  • removal of vegetation led to the decrease in chemical and biological weathering.
  • use of dynamites to blast large rocks (along the mountain side to build roads)
  • diggings of tunnels for mining opperations/quarries used for construction
  • use of nitrogen fertilizers
• deposition

  the laying down of sediments carried by water, wind and ice.
• erosion

  the wearing away of a rock and other depsits on the Earths surface due to water, wind and water.
• Three courses of a river

  • upper course
  • middle course
  • lower course
• where erosion and depostion can be found

  • upper course - vertical erosion
  • middle course - lateral erosion
  • lower course - depostion
• meander

  a bend in the river channel. located in the lower course and also in the middle course.
• the 2 slopes in a meander

  cutt - off slope

  slip - off slope
• cutt-off slope characteristics

  • located on the outside part of meander
  • erosion
  • deep
  • fast moving water
• slip-off slope characteristics

  • located on the inside part of the meander
  • deposition
  • slow moving water
  • shallow
• Oxbow lake definition

  A lake that is formed from a meander after cutting off from the main stream
• Oxbow lake

  • They occur in the lower course
  • They occur in a meander neck
  • There is erosion on the outside
  • There is deposition on the inside both processes result in the meander neck becoming narrower
  • After some time the meander neck will be cut-off from the mainstream to form an oxbox lake
• A dried up oxbow lake becomes a meander scar
• Floodplain definition

  The flat land that is found on the banks of a river
• Floodplain

  • It is found on the middle course and lower course
  • Occurring due to deposition
• Uses of Floodplains

  • Soil is fertile good for crop farming
  • Next to a river, easy access for water for crop farming
  • Flat, good for farming and settlement
• Braided Stream definition

  Forms when a river deposits it's load and blocks it's own path and is forced to Split into smaller channels
• Braided Stream


  • The water is moving slow
  • The build up of sediment causes the smaller channels that will be built after sand islands (distributaries)
• Natural Levees definition

  Naturally raised banks of a river
• Natural Levees


  • It raises the level of the river higher (flooding)
• Waterfall definition

  Found in the upper course, form from erosion where there is a hard rock and soft rock