Point release avalanches, or loose snow slides, begin at one point on a slope and get progressively wider as they proceed down the slope.  A fundamental characteristic that must be present for this type of avalanche to occur is a surface layer of cohesionless, or nearly cohesionless, snow (University of Colorado IBS 1975; Fredston and Fesler 1994).  An initially small amount of snow begins to move downward when the force of gravity is greater than the forces of cohesion at a particular angle or when debris from above starts the snow in a downward direction and there is not enough friction or resistance to sliding and rolling.  Because there is little to no cohesion and the surface layer, the initially small amount of snow is able to dislodge other snow particles below it and increase in cumulative size as it moves downhill.  The avalanche increases in horizontal width because snow particles are dislodged laterally, as well.  While a surface snow layer that never becomes cohesive is obviously vulnerable to this process, these avalanches often occur when external forces, such as sun and rain, weaken bonding in this layer until cohesion is little enough that some snow breaks free (Graydon and Hanson 1997).  The angle of the snow slope ultimately determines at what point cohesionless snow will be able to break free, and varies for the type of snow on that slope. This critical angle at which the snow will begin to slide is called the angle of repose (Daffern 1983).  The following diagram shows general breakpoints for this angle of repose.  The technical descriptions of the snow types is not important for this immediate discussion, and can be read about in more detail in Daffern's publication (1983).  The important point is that extremely cohesionless snow, such as slush, will begin to slide even on the most gradual of slopes, and greater angles are required for progressively more cohesive forms of snow to break free, with well sintered grains being the most cohesive.
  
    While many point release slides remain small and relatively harmless, others can be extremely dangerous if they are just forceful enough to dislodge a human from a safe perch or cliff, or if the magnitude of the slide is enough to include a human in the accumulation of snow which can lead to a burial of the person when it stops.  A couple basic laws of physics will determine the magnitude of these slides.  The vertical height of the starting point will determine how much kinetic energy can be gained when it is converted from potential energy, and the accumulation of mass affects both the potential energy available and the momentum, which is crucial at the point of contact with a human.

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