Cookies and milk double as hands-on activity materials for teaching children about the process of beach erosion, which is especially useful for kids who aren’t near a body of water to observe this natural phenomenon out in the real world. Put protective coverings down on the table and surrounding floor surfaces to minimize messes and make clean-up easy afterward. Experiment with different cookie types to represent a variety of beach terrains.
Simulate the erosion of a sandy beach in a deep, rectangular baking dish with finely ground soft cookie crumbs and a cup or two of milk. Pack the cookie crumbs into half of the baking dish, about 1/2-inch deep. Pour the milk into the dish from the opposite end, just until the liquid meats the cookie "beach." Instruct your child to push the dish back and forth across the table to create waves, or use an electric mixer on the lowest setting and insert it into the far end of the dish opposite the beach to simulate ocean movement. Encourage your child to observe what happens to the cookie shoreline as the waves continue to thrash against it.
Repeat the activity with larger, broken-up hard cookie pieces to simulate a rocky beach erosion. Encourage your child to compare and contrast the two activities. Ask guided questions, such as “Which beach eroded faster?” and “What happened to the rocky beach that was different from the sandy one?”
Repeat the setup for a sandy, rocky or mixed terrain beach activity (combining fine and coarse cookie crumbs and pieces to create a mixed terrain beach) and add a barrier to help your child perceive the effects of bulkheads, seawalls and other retaining wall barriers. Once the beach element is assembled, create stacked rows of hard chocolate, butterscotch or caramel candies at the shoreline to create a barrier. Pour the milk into the baking dish and have your child push the pan back and forth to create the waves. Observe how the candy barrier helps protect the shoreline, and take notice of the additional time it takes the milk to begin to erode the cookie beach.
Recycle clean, edible materials after you finish the erosion activities. Make a cookies and milk trifle treat by layering the softened cookie crumbs and pieces with whipped cream in a deep trifle dish. Garnish the treat with broken up candy pieces. Add the milk to ice cream and blend for a milkshake dessert.