This activity should be done after the students have already learned that sedimentary rocks take hundreds of thousands of years to form in nature. They will need a paper cup or clean, empty milk carton, sediments such as sand and clay, plaster and water. If desired, have them add "fossils" such as twigs and leaves. Fill the cup halfway with sediments. Mix the plaster according to the manufacturer instructions, fill the cup the rest of the way with plaster and stir. After the "rocks" dry, allow students to explore them.
Each student will need a clear plastic bottle, sand, pebbles, clay and water. Mix the sediments (sand, etc.) in the bottle, and then pour in the water. For the first few days, allow the students to observe what is happening to the items inside the bottle. After this, take the lids off the bottles and allow the water to evaporate. Once there is no moisture inside the bottles, allow the students to cut away the plastic and observe the "rocks" they have made.
For this activity, the students will need a paper cup or clean milk carton, cement mix, sand and water. Pour the sand into the carton or cup and add enough water to saturate the sand. Add three teaspoons of cement mix to the wet sand and stir thoroughly. Wait for the mixture to dry completely before allowing the students to cut away the paper and explore the "rocks" they have made.
Sedimentary rocks are created when sediments such as sand and clay are pressed together over the course of hundreds of centuries. Igneous rocks are formed when magma pushes from the core of the Earth to the surface, cools and crystallizes. Metamorphic rock once was either sedimentary or metamorphic rock, but was exposed to extreme heat and pressure under the Earth's surface for many years until its structure changed completely and it became a completely different rock form.