Relict Upland Landscapes & Glacial Processes (Edexcel GCSE Geography A)

Weathering & Mass Movement

• Glaciated landscapes are still being changed by weathering and mass movement

Weathering

• Freeze-thaw weathering happens when rocks contain cracks and temperatures regularly dip below the freezing point

• Any water in the cracks will freeze as the temperature drops and expand as it freezes, exerting pressure on the crack

• Repeated freezing and thawing of water will eventually break the rock apart

The process of freeze-thaw weathering

Mass movement

• Mass movement is the downhill movement of material under the influence of gravity

• Mass movement includes rockfalls and soil movement

Rock falls

• This is the fast movement of rocks from the steep glaciated slopes to the valley floor

• Falls happen as a result of freeze-thaw action

  • This loosen the rocks, makes them unstable and causes them to collapse

Soil movement

• Soil movement happens slowly as a result of gravity

• It occurs when:

  • Soil particles are saturated 

  • The soil structure is weakened by frost action

  • The ground below (often still frozen) acts as a slip plane

Slide 

• A movement of material 'en masse', which remains together, until hitting the bottom of a slope

UK Weather & Climate & Impact on Relict Upland Landscape

• The UK has a temperate climate

• This means there are warm summers and cold, wet winters

Seasonal variations

• Colder winters lead to temperatures below 0 °C, particularly in upland areas

  • This increases freeze-thaw weathering

  • Which leads to rockfalls and slides

• High rainfall levels, particularly in autumn and winter in upland areas 

  • Leads to an increase in landslides and soil movement

Diurnal variations

• Diurnal temperature variations will increase freeze-thaw weathering in a 24-hour period

• The decrease in temperatures overnight, particularly during winter, may also lead to an increase in freeze-thaw weathering