Arches, stacks and caves

• What causes cracks at the base of the headland to become exposed?

  Hydraulic action
• How does hydraulic action affect cracks in the headland?

  It pressurizes air, forcing the crack to widen
• What is the effect of wave refraction on wave direction?

  It distorts the wave direction
• What happens to the cave as a result of destructive waves?

  It deepens the cave
• What forms when an arch collapses under its own weight?

  A pillar of rock called a stack
• Which coastal feature is an example of a stack?

  Old Harry along the Dorset coast
• What eventually happens to the exposed stack?

  It collapses to form a stump
• How is the broken material from the stack further affected?

  It is eroded through attrition and transported away
• What are wave-cut notches?

  Widened cracks that develop over time
• What processes deepen wave-cut notches to form caves?

  Further processes of abrasion and hydraulic action
• What weathering processes further widen cracks?

  Salt crystallization and wet and dry weathering
• How does wave refraction affect the headland?

  It affects all three sides of the headland
• What can happen if two caves are aligned?

  Waves may cut through to form an arch
• What happens to the base of the arch due to wave-cut notches?

  It widens the base of the arch
• What continues to weaken the stack from above?

  Sub-aerial processes
• What is exposed by tall breakers associated with destructive waves?

  Vertical joints
• How can joints be weathered from above?

  Through carbonation in limestone
• What may form as a result of weathering in joints?

  Blowholes
• What are the processes involved in the formation of caves, arches, and stacks?

  • Cracks exposed by hydraulic action
  • Wave refraction deepens caves
  • Arches collapse to form stacks
  • Stacks erode to form stumps
• What are the stages of coastal erosion leading to the formation of coastal landforms?

  1. Cracks widen through hydraulic action
  2. Wave-cut notches develop into caves
  3. Caves may form arches if aligned
  4. Arches collapse into stacks
  5. Stacks erode into stumps
• What are the effects of weathering and wave action on coastal features?

  • Weathering widens cracks
  • Hydraulic action deepens caves
  • Wave refraction affects headland
  • Erosion creates wave-cut notches