Answer:This activity explores the various filter media available. Once water is dirty or polluted, it can be very complicated to clean. Many steps may be necessary to filter dirty water! The rocks and sand formed by erosion perform a very important function: they help to clean our water supply. Sand and gravel make good water filters because they form permeable layers. When the sand particles are next to one another, there are tiny spaces between them. Water can pass slowly through these tiny spaces and some of the dirt particles get trapped. The smaller the particles, the smaller the spaces will be in the layer and the smaller the dirt particles that can be trapped.
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