Shaking Things Up!

Why do rocks on a beach have rounded edges, while many of the rocks in your schoolyard have jagged edges? By doing the experiment below, you and your family members can see how rough rocks can turn into smooth stones!


A girl shaking a jar. Three jars are labled a, b, c.


Start by separating the stones into three equal piles, and put each pile on a sheet of paper. Label the sheets of paper A, B, and C. Put masking tape on each can and each jar, and label them A, B, and C. Fill Can A halfway with water and put the stones from Pile A into it. Do the same with the stones for Can B and Can C. Let the stones sit overnight in the water. The next day, shake Can A hard about 100 times. Remove the stones from Can A and pour the water into Jar A. Then write down what you see in Can A and Jar A. Next, hold Can B in both hands and shake it hard, about 100 times. Do this each day for 10 days until Can B has been shaken 1,000 times. Then remove the stones from Can B and pour the water into Jar B. Write down what you see. Do not shake Can C. Remove the stones from Can C and pour the water into Jar C. Write down what you see.


Which stones had rounder edges? Which jars had more sediment? How does this activity model what happens to stones on a beach?