This is a hands-on investigation to support the Next Generation Science Standard (NGGS) ESS2. It fits nicely into a unit about erosion and weathering and does a great job of showing how water changes the shape of the land. It can easily be adapted to show how wind changes land too. I had my students work on this lab in partners but it could be done in small groups as well with children taking turns being sprayers and timers. I used a small plastic bin and built a mountain out of dirt from my yard. I made sure it had a mixture of rocks, soil and sand in it so my students could see how the sand and soil was moved to the bottom of the mountain by the water/rain. Also, it showed how the rocks were left exposed at the top of the mountain. We also measured the height of our mountain at the beginning and after each trial and then graphed our height at the end of the experiment to show the change. My students had lots of fun doing this investigation and I'm sure yours will too.