Rivers Mind-Map

Rivers Mind-Map

1. Features

   • Source = Beginning of a river
   • Course of River = Route taken towards the sea
   • Tributary = Smaller river/stream that joins a larger river
   • Confluence = Where a tributary joins a river
   • Mouth = Where a river enters the sea
   • Estuary = Part of a river mouth that's tidal
   • River Basin = Area of land drained by a river
   • Watershed = High ground separating river basins
   • Erosion (n) = Gradual wearing away of land

2. 3 Stages of a River

   • Upper/Youthful Stage
     • Valley has narrow floor and steep sides
     • Small amount of water but very fast
     • Most energy used to erode
     • Features: V-shaped valley, waterfalls, interlocking spurs, potholes
       • V-Shaped Valley
         • Get name from shape
         • Landscape eroded in shape of a V
         • Vertical Erosion occurs. River cuts into river bed, making it deeper. Creates a narrow, deep valley
         • Mechanical weathering & mass movement
         • e.g. River Liffey
       • Interlocking Spurs
         • River meets areas of hard rock
           • Cannot erode these so instead flows around them while eroding downstream
         • Zigzag course
         • e.g. River Moy
       • Waterfalls
         • Rivers flow over areas of hard & soft rock
           • River erodes the soft rock but can't erode the hard rock
             • Falling water erodes deeper into the bed, creating a Plunge Pool
         • e.g. Iquazu Falls
           • One of the widest waterfalls in the world (1.5 miles across)
           • On the border between Argentina & Brazil
           • 13 million litres of water spill over per second
           • Found towards the end of its river
   • Middle/Mature Stage
     • Valley has wider floor and sides are more gently sloping
     • River starts slowing & deposits some materials
     • Features: Wide river valley, meanders, flood plains
       • Meanders
         • Bends/curves along the river
         • Formed by erosion and deposition
           • Erosion occurs on one side while deposition occurs on the other
         • e.g. River Shannon
   • Lower/Old Stage
     • Valley has flat floor and gentle sides
     • Carrying lots of sand & silt
     • Moving over flat land so moving slowly
     • Lots of deposition
       • Creates many features/landforms
         • Features: Ox-bow lakes, levees, deltas
           • Ox-Bow Lakes
             • Horseshoe shaped lake found beside a river
             • Formed when continued erosion and deposition create very pronounced meanders
               • Eventually the river cuts through the neck of the meander
                 • Deposition then occurs which separates the ox-bow lake from the river

3. Erosion Processes

   • Hydraulic Action = Force of moving water wears away banks and bed of river
   • Abrasion = Small stones carried by river wear away at banks and bed of river
   • Attrition = Small stones wear down as they hit each other
   • Solution = Rocks and soil are dissolved by acid in water

4. Erosion Ability

   • Speed of river (steeper = faster)
   • Volume (more water = increased ability to carry material)

5. Transporting Material

   • All rivers carry material
     • e.g. sand, stones
     • River's Load = All material
     • River Transportation = River moves its load
       • Traction = Large stones rolled along river bed
       • Saltation = Small stones bounced along river bed
       • Suspension = Light material (sand, silt, etc.) is carried (floating) in river
       • Solution = Dissolved materials are carried by river

6. River Deposition

   • Deposits materials when:
     • River slows (flatter land)
     • Volume decreases (e.g. drought)
     • River reaches sea