Earth Scie(Mass wasting)

• Water has the ability to change the angle of repose.
• Addition of water from rainfall or snowmelt adds weight to the slope.
• Water can reduce friction along a sliding surface.
• Expansive and hydrocompacting soils, contain a high proportion of smectite or montmorillonite which expand when wet and shrink when they dry out.
• Sensitive soils, clays in some soils rearrange themselves after dissolution of salts in the pore spaces.
• Clay minerals line up with one another and the pore space is reduced.
• Quick clays, water-saturated clays that spontaneously liquefy when disturbed.
• Weak materials and structures, become slippage surfaces if weight is added or support is removed.
• Slope failures, sudden failure of the slope resulting in transport of debris downhill by rolling, sliding, and slumping.
• Slump, type of slide wherein downward rotation of rock or regolith occurs along a curved surface.
• Rock fall and debris fall, free falling of dislodged bodies of rocks or a mixture of rock, regolith, and soil in the case of debris fall.
• Rock slide and debris slide, involves the rapid displacement of masses of rock or debris along an inclined surface.
• Sediment flow, materials flow downhill mixed with water or air.
• Slurry and granular flows are further subdivided based on the velocity at which flow occurs.
• Slurry flow, water-saturated flow which contains 20-40% water.
• Above 40% water content, slurry flows grade into streams.
• Solifluction, common wherever water cannot escape from the saturated surface layer by infiltrating to deeper levels; creates distinctive features: lobes and sheets of debris.
• Debris flow, results from heavy rains causing soil and regolith to be saturated with water; commonly have a tongue-like front.
• Debris flows composed mostly of volcanic materials on the flanks of volcanoes are called lahars.
• Mud flow, highly fluid, high velocity mixture of sediment and water; can start as a muddy stream that becomes a moving dam of mud and rubble.
• Granular flow, containing low amounts of water, 0-20% water, exhibits fluid-like behavior by mixing with air.
• Creep, the slowest type of mass wasting, requires several years of gradual movement to have a pronounced effect on the slope.
• Creep occurs when regolith alternately expands and contracts in response to freezing and thawing, wetting and drying, or warming and cooling.
• Earth flow, involving fine-grained material such as clay and silt, is usually associated with heavy rains or snowmelt and tends to be narrow tongue-like features that begin at a scarp or cliff.
• Grain flow, which forms in dry or nearly dry granular sediment with air filling the pore spaces such as sand flowing down the dune face, is a type of mass wasting.
• Debris avalanche, a very high velocity flow involving huge masses of falling rocks and debris that break up and pulverize on impact, often occurs in very steep mountain ranges.
• Some studies suggest that high velocities in debris avalanches result from air trapped under the rock mass creating a cushion of air that reduces friction.
• Subaqueous mass movement occurs on slopes in the ocean basins.
• Subaqueous mass movement may occur as a result of an earthquake or due to an over-accumulation of sediment on slope or submarine canyon.
• Submarine slumps are similar to slumps on land.
• Submarine debris flow is similar to debris flows on land.
• Turbidity current is when sediment moves as a turbulent cloud.
• Shocks and vibrations, earthquakes and minor shocks such as those produced by heavy trucks on the road, man-made explosions can cause slope modification.
• Undercutting is due to streams eroding banks or surf action undercutting a slope.
• Changes in hydrologic characteristics, heavy rains lead to water-saturated regolith increasing its weight, reducing grain to grain contact and angle of repose, can cause changes in slope strength.
• Changes in slope strength can be caused by weathering weakening the rock and leading to slope failure; vegetation holds soil in place and slows the influx of water; tree roots strengthen slope by holding the ground together.
• Volcanic eruptions, which produce shocks, may produce large volumes of water from melting of glaciers during eruption, resulting in mudflows and debris flows.