Drop a steel ball onto a dish of sand. The ball becomes partially buried and a crater forms.
Bury the end of the hose in the sand using the plastic strip attached to the end of the hose, and smooth out the sand. Using lung power, blow in a blast of air and notice the crater that forms.
A generation ago there was a debate among geologists and astronomers as to the origin of lunar and terrestrial craters. This demonstration illustrates two ways in which craters can form.