humus soil

Raindrop impact: the force of a raindrop falling onto a soil or weathered rock surface is often sufficient to break weaker particle bonds. The amount of force exerted by a raindrop is a function of the terminal velocity and mass of the raindrop. Figure 1: The following image was created from DEMs (Digital Elevation Model) for the following 1:24,000 scale topographic quadrangles: Telescope Peak, Hanaupah Canyon, and Badwater, California. (Source: PhysicalGeography.net) Transport * Cavitation: intense erosion due to the surface collapse of air bubbles found in rapid flows of water. 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. * Solution is a transport mechanism that occurs only in aqueous environments. Solution involves the eroded material being dissolved and carried along in water as individual ions.

Entrainment Forces Detachment * Solution is a transport mechanism that occurs only in aqueous environments. Solution involves the eroded material being dissolved and carried along in water as individual ions. Figure 2 shows a graph that describes the relationship between stream flow velocity and particle erosion, transport, and deposition. The curved line labeled "erosion velocity" describes the velocity required to entrain particles from the stream's bed and banks. The erosion velocity curve is drawn as a thick line because the erosion particles tends to be influenced by a variety of factors that changes from stream to stream. Also, note that the entrainment of silt and clay needs greater velocities then larger sand particles. This situation occurs because silt and clay have the ability to form cohesive bounds between particles. Because of the bonding, greater flow velocities are required to break the bonds and move these particles. The graph also indicates that the transport of particles requires lower flow velocities then erosion. This is especially true of silt and clay particles. Finally, the line labeled "settling velocity" shows at what velocity certain sized particles fall out of transport and are deposited.