Geography- paper 1

• Sedimentary Rocks:

  • Have layers and may have fossils in them
  • E.g. chalk and sandstone
  • Formed by layers of sediment building up over time and compressed underneath rivers/oceans
• Igneous Rocks:

  • May have crystals, are normally rough and non-porous
  • E.g. basalt and granite
  • Formed by volcanic eruptions. They are magma that has cooled
• Metamorphic Rocks:

  • Are hard and smooth
  • E.g. schists and slates
  • Formed from igneous or sedimentary rocks that have been compressed under heat and pressure over millions of years
• Physical Processes in Upland Areas:

  • Freeze-thaw (mechanical) weathering in upland areas like Dartmoor has led to igneous intrusions
  • Glaciers in the last ice age moved slowly downhill eroding U-shaped valleys in the Lake District
  • Vertical (downwards) erosion by rivers created v-shaped valleys
  • Metamorphic rocks found in upland areas e.g. Scotland
  • Igneous rocks found in upland areas e.g. Scotland and igneous intrusions in SW England (Dartmoor)
• Physical Processes in Lowland Areas:

  • Sedimentary rocks found in lowland areas e.g. SE England
  • The Giants Causeway formed 60m years ago when Pangaea broke up, creating hexagon shapes from lava cooling
  • Igneous intrusions (called Tors) formed when volcanic rock cooled inside the earth and weathering eroded the rock around it
  • The Grampian Mountains formed by convergent plates 490m years ago, with oceanic crust melting and rising up forming volcanoes
  • East Anglia is flat and formed of sedimentary rock because rivers from upland areas deposited layers of sediment here over time
• River Physical Processes:

  • Weathering is the wearing away of rock in one place, including chemical weathering from small amounts of acid in rain
  • Erosion is the wearing away of rock by moving water, involving abrasion, hydraulic action, attrition, and solution
  • Mass Movement is the movement of sediment downhill due to gravity, including sliding and slumping
• Human Activities on the UK Landscape:

  • Farming clears trees leading to an artificial landscape/mono-culture
  • Deforestation of deciduous forests has led to soil erosion
  • Roads cut across the landscape connecting settlements, increasing impermeable surfaces and flood risk
• Transport:

  • Rock slides off a slip plane
  • Steep slopes get saturated with water and collapse in a rotational movement
  • Traction involves large boulders rolled along river bed
  • Saltation includes small stones bounced along river bed
  • Suspension carries tiny particles in river flow
  • Solution dissolves rock carried by water
• Deposition:

  • Sediment being dropped by water with the same appearance
• Upper Course of River Severn:

  • Narrow and shallow
  • Steep valley sides
  • Low velocity (speed) and low discharge
  • Larger sediment size
• Lower Course of River Severn:

  • Wide and deep
  • Flat valley and floodplain/levees
  • High velocity and discharge
  • Smaller sediment size due to erosion from upper to lower course
• Impact of weather & climate on River processes:

  • Increase the rate of river erosion with higher discharge and more energy for hydraulic action
  • Droughts reduce the rate of erosion with lower discharge and less energy to erode the river channel
• Interlocking Spurs and V-shaped Valleys (EROSION):

  • Vertical erosion like abrasion due to low discharge and steep gradient for downward erosion
• Rivers – upper to lower course:

  • Discharge increases with more tributaries adding water
  • Sediment size decreases due to attrition making sediments smaller
  • Velocity increases with less friction in the lower course for faster flow
• Waterfalls and Gorges (EROSION):

  • Weathering like biological on exposed valley sides
  • Abrasion leading to overhang formation and collapse due to gravity
  • Mass movement like slumping from steep slope and weathered material in v-shaped valley
• Interlocking spurs:

  • Form in the upper course where energy is low
  • River erodes soft rock and winds around hard rock spurs
• Floodplains and Levees (DEPOSITION):

  • Waterfall retreats upstream forming a steep gorge
  • Hard rock overlays soft rock along river channel
  • Soft rock erodes more quickly forming a plunge pool below
  • Plunge pool continues to erode from hydraulic action and abrasion
• Meanders and Ox-Bow Lakes (EROSION and DEPOSITION):

  • River floods in lower course during high discharge
  • Heaviest sediment deposited first forming natural levees
  • Smaller sediment deposited further from the channel
  • Floodplain forms over years with layers of silt/sediment and meandering rivers
• Meander and ox- bow lake

  • Fastest water erodes outside of meander (river cliff) and deposition occurs on the inside (point bar)
  • Meander becomes more wiggly with tighter bends forming a 'swan's neck meander'
  • High discharge leads to erosion of a new channel across the meander neck
  • Old channel becomes an ox-bow lake as deposition seals each end, potentially drying out and filling up with soil