Take two different colored crayons and shave them down with a knife. Pretend that the crayons are igneous rocks that are being broken down by weather. If you are worried about the children cutting themselves, use a cheese grater or a pencil sharpener. Mix the colored crayon shavings and set them on top of aluminum foil. The aluminum foil should be doubled lined. The website Think Quest recommends your crayon shavings pile be 6 cm by 6 cm and 1 to 2 cm thick. Push on the pile so that the shavings stick together. You have now created sedimentary rocks.
Most elementary students are familiar with the water cycle, but they might not know that rocks also go through a cycle. The rock cycle begins with an igneous rock. The igneous rock goes through a change and turns into a sedimentary rock. Later, the sedimentary rock goes through a change and turns into a metamorphic rock. The cycle is then repeated when the metamorphic rock begins to change and ends up as an igneous or sedimentary rock. Teachers can demonstrate this change through experiments.
Sedimentary Rock Experiment
Metamorphic Rock Experiment
Take your sedimentary rock shavings and fold all four sides of the aluminum foil over them. Explain that, as more sedimentary rocks lie on top of each other, they cause more pressure. This leads to the sedimentary rocks changing into metamorphic rock. You can see this change by experimenting with pressure. Lightly hammer over your packet of sedimentary crayon shavings. Do this for about 30 seconds. Unwrap the foil to reveal the new metamorphic rock. Notice how the shavings have bonded together to form a stronger rock.
Igneous Rock Experiment
Explain to the students that when metamorphic rock is heated it changes into igneous rock. You can perform yet another experiment to demonstrate this change. Wrap the metamorphic rock back up in the aluminum foil and hold it over a candle flame. Use tongs to hold the aluminum foil packet over the flame and not your hands or you will get burned. Do this for 60 seconds. Wait for the packet to cool, and open it to reveal your new igneous rock. This igneous rock will look smooth, just like the crayon you started with. You will even be able to write with it. If you shave the igneous rock, you can begin the rock cycle all over again.
Rock Candy Experiment
The rock cycle can also include an experiment on the forming of new rocks, which is referred to as reformation. A chemical reaction is what causes new rocks to form, and this can be witnessed by creating homemade rock candy. Bring 2 cups of water to a boil and add 4 cups of sugar to it. Stir until the sugar is dissolved. Once the water appears clear, remove it from the stove and pour the contents into a glass jar. Tie a piece of string to the middle of a pencil. Add a paper clip to the other end of the string. Dip the string into the jar and then lay it on a sheet of wax paper for two days. Keep your jar of sugar water covered with wax paper. After the two days are up, set the string back in the sugar water and let it hang there. This is done by placing the pencil across the top of the jar. Wait seven days and return to find the rocks formed on the piece of string.
- Photo Credit rocks image by Richard Hodgkins from Fotolia.com
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