heaves

• what are heaves?

  • involve movement of upper layer of surface material on a slope generated because of its own weight, through repeated wetting and drying or alternate freezing and thawing
  • can operate readily even on gentle slopes of 5 degrees
• what is the speed that heaves move at?

  • extremely slow and occur at surface layers of regolith
  • rate of 1-10mm per year and are the result of individual particles moving downslope
• Causes of heaves


  1. Alternate wetting and drying

  2. Freeze thaw cycles in high altitudes in the tropics
• Alternate wetting and drying

  Moisture increases volume and weight of the soil during rainfall causing expansion. Soil contracts during dry season and moves downslope under gravity
• Freeze thaw cycles in high altitudes in the tropics

  Freezing of soil -> Presence of ice crystals increases the volume of soil. As soil expands, particles are lifted at right angles to the slope. When ground thaws and soil contracts, particles fall back vertically under influence of gravity
• Water freezes within grains or rocks during winter


  Volume of grain/rock expands displacing the particle upwards
• Ground thaws during summer

  Melting of frozen water and sudden decrease in weight -> Momentum of particles causes it to move horizontally downslope
• what are the 2 types of heaves?

  • soil creep
  • solifluction
• how are the types of heaves distinguished?

  by amount of water content and rate of movement
• what is the speed of soil creep?

  slow movement usually unnoticed and continues for a very long time
• what are the materials involved in soil creep?

  clay soils > moist clay deforms slowly under gravity
• evidence of soil creep

  • bending of soil/ rock layers
  • accumulation of soil on the upslope side of fences
  • curved trees and tilted poles
• location of soil creep

  tropical rainforest esp if thick weathered layer is present
• speed of solifluction


  slightly faster rate of 5cm-1m per year
• evidence of solifluction

  • solifluction lobes
  • if soil creep and solifluction occur in same area, forms soil terracettes
• location of solifluction

  • common in periglacial areas where groundwater is permanently frozen (permafrost) -> thawing of permafrost brings high moisture content -> inability of meltwater to percolate downward to impermeable permafrost layer, upper zone of soil becomes completely saturated, large areas of regolith flow slowly downslope