Make Mud Bricks: Add a small amount of water to different kinds of dirt and dirt with sticks or leaves. Pack in to a brick mold or some sand toys. Let them dry in the sun for a day or two. Make some predictions about which bricks will be the strongest? How could you test your idea? Unmold them and test your ideas.
What is in the dirt? Put dirt in a kitchen strainer and pour water thru it. What happens? What stays and what goes thru? Now put a coffee filter in the strainer and do the same thing. What is left behind now?
Erosion: Make a mountain of dirt and slowly pour water over it. What happens? Make your mountain again. What would happen if you poured water quickly or in a different place?
Growing: Do a dirt scavenger hunt in your yard. Gather up some pots and put different kinds of dirt in to each pot. Then put in a seed or plant and see which soil is best for growing plants.
Eat Dirt: Make chocolate pudding and sprinkle the top with crushed chocolate cookies or chocolate graham crackers. Add some gummy worms and you have dirt for lunch!