Crayon rock cycle
Crayon rock cycle Field(s) of Science: Biology Concepts: sedimentary, metamorphic and igneous rocks, rock cycle Grade: 4 Duration: 40-‐50 minutes Materials Needed: ● Crayons (with paper wrapper peeled off): at least two different colors of wax crayons per group, at least half of a crayon per student ● Pencils sharpeners with big opening ● Water + container to refill water ● 2 side burners with frying pans ● Aluminum Foil pieces to create little boats ● Wax paper ● Popsicle sticks ● Paper towel to clean up ● Poster of the Rock Cycle Context Define the concepts Sedimentary rocks: formed when sediments (small pieces of rock) are compacted and cemented together (lithified) Metamorphic rocks: formed when rocks undergo heat and pressure Igneous rocks: formed from the cooling and crystallization of magma and lava Weathering: the wearing /breaking down of rocks by wind, water, sand, and chemicals Erosion: the movement of sediments produced after weathering Deposition: when sediments are dropped off in a new location after erosion Intro questions for the classroom
Q: How can we create rocks in the classroom? Crayons have the ability to be ground into small particles (weathered), heated, cooled and compressed just like rocks. In nature, the forces of nature break down rocks. Q: Why are we using crayons and not real rocks to demonstrate the rock cycle? Actual rocks take MILLIONS of years to go through the rock cycle! We would not be able to do this in the classroom! In fact, the oldest known rocks on the surface of the earth are 3.8 billion years old (found in Greenland). Q: Identify some weathering agents (natural ways to weather a rock). Wind, sun, ice, rain. In this simulation we will “weather” our crayons with the sharpener, our popsicle sticks and our hands. 1 Version date: May 2016
Prepare ahead in the classroom: ● Crayons (with paper wrapper peeled off): at least two different colors of wax crayons per group, at least half of a crayon per student ● Preheat water in frying pans to ensure that water is warm for crayon melting ● Cut pieces of wax paper for students to sharpen/collect their crayon sediments on AND to keep their desks clean. ● Cut pieces of foil that students will use to create “boats” to float their crayon shavings in Doing the Activity! Part One: Make a Sedimentary rock 1. Have students split into pairs for this activity. 2. Have each group pick up: 1 or 2 crayon pieces per person (different colour than their partner), 1 sharpener per person, 1 foil piece, 1 wax paper piece, 1 popsicle stick 3. Have each student make small “sediments” out of their crayons by sharpening the crayons in the sharpeners. Collect the crayon shavings on the wax paper. 4. Once rock fragments have been created, they are usually moved (eroded) by some force of nature like gravity and dropped in a new location (deposition). Here you will act as a depositional force. Each partner, in turn, should move (erode) and lay down (deposit) the rock fragments in a neat pile in the center of the foil boat. Set each new pile on top of the previous ones. 5. Press down on this pile (with finger or popsicle stick, and wax paper between the crayon and the pushing force to avoid sticking) to allow the particles to stick together. This part of the simulation requires you to understand the cementation process. Spaces between the fragments are reduced in size by pressure (compaction) and filled in with cementing agents (cementation). This simulation will not add cementing agents. It will only simulate compaction. The compaction process occurs as new layers of sediments continually cover sediment layers. The lower layers become compacted by the weight of the new layers above. 6. Your crayon sediments are now sedimentary crayons. Note that you can still distinctly see each layer of coloured crayon, as below. Sedimentary rock has distinguishable layers of rock as well. 2 Version date: May 2016
Part Two: Make a Metamorphic Rock 7. As rocks are pushed deeper into the Earth’s crust, pressure and temperature increases (Think: there is more rock on top of this rock, pushing it harder and bringing it closer to the HOT core of the Earth). Metamorphic rock may become contorted in appearance and actually flow like a plastic material in response to the heat and pressure that is caused by the overlying rocks. 8. Float your foil “boat” filled with sedimentary rock on hot water. 9. Watch as the heat from the water transfers to the foil and to the crayons. The crayons should start to melt. Remove your foil boat IMMEDIATELY after the crayon starts to melt. 10. Bring your boat back to your desk and let your crayons cool without touching them. 11. The partially melted and cooled crayons are now equivalent to metamorphic crayons. Note that you can still see layers of sediment, but the heat has compacted the sediment even further.
Part Three: Make an Igneous rock
12. Igneous rock forms deep within the earth. It originates in magma chambers embedded in solid rock. Bring your foil boat filled with metamorphic rock back to the hot water. Float the boat, and watch as the heat from the water transfers to the foil and to the crayons. The crayons should start to melt. Stir with the popsicle stick to bring any stray sediment down to the melted mixture. 13. Allow the crayons to melt until a smooth liquid forms: you are making magma!!! 14. Carefully remove molten crayon wax and let cool. Your totally melted and cooled crayons are now equivalent to igneous crayons. Note that individual crayon 3 Version date: May 2016
colours/pieces (“sediment”) are no longer visible and the crayon rock is one homogeneous piece of rock.
Part Four: Continue through the rock cycle as a class 15. Explain: What is a cycle? A series of events REPEATED in the same order. In the case of the rock cycle, igneous rock held in one’s hands today may become part of a sedimentary or metamorphic rock in the distant future. Very little rock on the surface of the earth has remained fixed in its original rock type. The Earth recycles all rock through the rock cycle! Most rocks have undergone several iterations of the rock cycle. 16. Have each group break off a piece of their “metamorphic crayon”. They have now made sedimentary rock out of their igneous rock. 17. Combine pieces from each group into one tin foil boat and repeat the above process, Making these sedimentary pieces into a metamorphic rock and then an igneous rock. (You can do all of this and have the class watch and walk through everything with you). 18. Explain that you, as a class, have now taken your crayons through TWO cycles of the crayon rock cycle. 19. Explain that this cycle could continue infinitely with more pieces of “sedimentary crayon” made in the class, other classrooms, other schools, etc. What's Happening? Use your simulated “rocks” to help you describe the following rock types: • What is a sedimentary rock? Formed when sediments (small pieces of rock) are compacted and cemented together (lithified)
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• What processes must occur to produce a sedimentary rock? Compaction and cementation • What is a metamorphic rock? Formed when rocks undergo heat and pressure • What is an igneous rock? Formed from the cooling and crystallization of magma and lava • What processes must occur to produce an igneous rock? Cooling, crystallization • What is the difference between an extrusive and intrusive igneous rock? Igneous rocks form by the cooling/crystallization of magma. If this happens INSIDE the Earth, they are called intrusive rocks. If this happens at the surface of the Earth, they are called extrusive rocks.
How to Restock the kit? Replace: ● Crayons ● Aluminum foil Please ensure everything is back in the kit, clean and dry.
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