soil gnats

The critical entrainment velocity curve suggests that particles below a certain size are just as resistant to entrainment as particles with larger sizes and masses (Figure 2). Fine silt and clay particles tend to have higher resistance to entrainment because of the strong cohesive bonds between particles. These forces are far stronger than the forces of friction and gravity. 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) Entrainment Forces Particle weight, size, shape, surface configuration, and medium type are the main factors that determine which of these processes operate. Erosion is defined as the removal of soil, sediment, regolith, and rock fragments from the landscape. Most landscapes show obvious evidence of erosion. Erosion is responsible for the creation of hills and valleys. It removes sediments from areas that were once glaciated, shapes the shorelines of lakes and coastlines, and transports material downslope from elevated sites. In order for erosion to occur, three processes must take place: detachment, entrainment and transport. Erosion also requires a medium to move material. Wind, water, and ice are the environmental media primarily responsible for erosion. Finally, the process of erosion stops when the transported particles fall out of the transporting medium and settle on a surface. This process is called deposition. Figure 1 illustrates an area of Death Valley, California where the effects of erosion and deposition can be easily seen. Introduction

* 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. Erosion can be seen as a sequence of three events: detachment, entrainment, and transport. These three processes are often closely related and sometimes not easy distinguished between each other. A single particle may undergo detachment, entrainment, and transport many times. Deposition * 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. Erosion can be seen as a sequence of three events: detachment, entrainment, and transport. These three processes are often closely related and sometimes not easy distinguished between each other. A single particle may undergo detachment, entrainment, and transport many times. * Abrasion: the excavation of surface particles by material carried by the erosion agent. 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.