Mechanical/physical weathering

• mechanical weathering occurs when exposed rocks are physically broken down into smaller pieces called regolith
• mechanical weathering takes place on areas of weakness in rock
• mechanical weathering mainly takes place in areas of extremes of temperature such as deserts and mountains
• There are two main types of mechanical weathering:

  • Freeze-thaw action
  • Exfoliation
• Freeze-thaw action can also be called frost shattering
• Freeze-thaw action is the most common type of mechanical weathering
• Freeze-thaw action is common in upland areas as where there is a plentiful supply of precipitation and temperatures fluctuate above and below freezing
• Water fills the cracks during the day when the temperature is warm
• What is physical weathering?

  Breaking down of rocks into smaller particles
• What is regolith?

  Smaller particles resulting from weathering
• Where does physical weathering generally occur?

  Areas with little vegetation and extreme climates
• What are the main types of physical weathering?

  Freeze-thaw action and exfoliation
• What is freeze-thaw action also known as?

  Frost action
• In what type of areas does freeze-thaw action commonly occur?

  Mountainous areas with frequent temperature changes
• What conditions are necessary for freeze-thaw action to occur?

  Frequent temperature changes and rainfall
• How does freeze-thaw action lead to rock breakdown?

  Water freezes, expands, and widens cracks
• What happens to the water during freeze-thaw cycles?

  It freezes and expands, then melts
• What is the term for weathered rock that moves down slope?

  Mass movement
• What is weathered rock known as?

  Scree or talus
• Where can evidence of scree slopes be seen?

  Croagh Patrick and The Sugarloaf
• What is exfoliation also known as?

  Onion weathering
• In which regions does exfoliation occur?

  Regions with large diurnal temperature ranges
• What temperature can desert rocks reach during the day?

  50 C
• What happens to rocks at night in deserts?

  They cool and contract
• How does the process of exfoliation weaken rocks?

  Expansion and contraction cause outer layers to shatter
• What collects at the base of rocks due to exfoliation?

  Broken layers forming scree
• What is the significance of regolith in weathering processes?

  It represents the product of weathering
• How does vegetation cover affect physical weathering?

  Less vegetation increases physical weathering rates
• What specific conditions favor freeze-thaw action?

  Frequent temperature changes and rainfall
• How do temperature fluctuations impact rock integrity?

  They cause expansion and contraction, weakening rocks
• What role does gravity play in mass movement of weathered materials?

  It causes regolith to move down slope
• What are the characteristics of scree and talus?

  They are accumulations of weathered rock
• Where can evidence of physical weathering be observed geographically?

  In mountainous regions and deserts
• What is the process of exfoliation?

  Peeling away of rock layers
• How does diurnal temperature range influence exfoliation?

  It causes expansion and contraction of rocks
• What physical changes do rocks undergo during temperature fluctuations?

  They expand when heated and contract when cooled