As a result, weathered materials are normally more susceptible than unaltered rock to the forces of detachment. In the implosion of the bubble, a micro-jet of water is created that travels with high speeds and great pressure producing extreme stress on a very small area of a surface. Cavitation only occurs when water has a very high velocity, and therefore its effects in nature are limited to phenomenon like high waterfalls. The amount of force exerted by a raindrop in a function of the terminal velocity and mass of the raindrop. The effectiveness of this process is related to the velocity of the moving particles, their mass, and their concentration at the eroding surface.
Abrasion is very active in glaciers where the particles are firmly held by ice.
Abrasion can also occur from the particles held in the erosional mediums of wind and water. Entrainment Entrainment is the process of particle lifting by the agent of erosion. In many circumstances, it is hard to distinguish between entrainment and detachment. There are several forces that provide particles with a resistance to this process. The most important force is frictional resistance.