falls

• what are falls?

  • when a mass of materials breaks away from slopes with near vertical or vertical profiles
  • most common on steepest slopes of 70-90 degrees
  • materials may fall from a considerable height esp from the more resistant, high rock faces
• causes of falls

  • rock being well-jointed and/or subjected to freeze-thaw or pressure release encourage the formation of joints
  • triggered by seismic action shaking the ground, river undercutting the case of rock faces -> reduce stability
• types of falls

  • rock fall: when a single mass or several pieces of rock fall
  • debris fall: when falling mass is made up of a mixture of material from boulders to fine particles
• evidence of falls

  • rocks may break into large angular fragments at base of the slope -> accumulation known as talus or scree
  • talus slope forms at base and may develop a concave or straight shape
  • talus slope can have an angle of repose up to 45%
  • as the talus pile slips and slides, adjusting to the weight of overlying rocks, the pile extend outwards
• location of falls

  • common at high altitudes in the tropics-> favourable conditions due to glaciation
  • retreat of glaciers due to warming throughout holocene -> release of pressure as ice masses were removed from lower altitude areas creating joints along which fracturing of rocks may take place
  • likely where steep coastal cliffs with resistant rocks, fast consistently flowing waters are present to undercut slopes