What happens when a crust is disturbed?
Now, one of the major things I've been interested in over the past couple of decades is the effect of disturbance on these crusts. There are lots of things that will disrupt the crust. Trampling disturbance is one of the major forms of disturbance. This can come from grazing animals. Many of the lands in Utah and Nevada and other arid areas belong to the federal government, and government agencies such as the Bureau of Land Management lease the land out to ranchers who put cattle on it. Thus, cattle are a major source of disturbance. They walk over the crusts and destroy them if their densities are too large. But vehicles are also a problem: off-road vehicles, tanks in some of the military bases, mountain bikes, and even hikers can cause disturbance. Range fire is also an important disturbance in some areas, particularly the cooler deserts, which will carry a range fire. This can actually be much more damaging. I'll show you some evidence of this later on, but fire is much less common than trampling disturbance.