Rock Cycle “Crayon” Lab Activity
Procedures
BACKGROUND:
Geologists classify rocks into three different categories based
upon how they are formed. These rock categories are called
igneous, metamorphic, and sedimentary. All of these rock
categories have been formed by the different geologic processes
of the rock cycle. Over long periods of time any rock type could
change into another rock type under the correct conditions.
OBJECTIVE:
Students will be able to demonstrate how the processes of the
rock cycle lead to the the formation of igneous, sedimentary, and
metamorphic rock.
SAFETY:
MATERIALS:
Crayons
Steel file
Paper Towel
Aluminum Foil
Aluminum Pie Tins
Goggles
Hot Plate
PROCEDURES:
PART A: WEATHERING
In the natural world, rocks are broken down by the forces of
nature. This is called weathering. In this simulation the crayons
represent rock material, and the file represents mechanical
weathering agents (such as water, wind, ice, and heat) that
cause rocks to break down into smaller pieces called sediment.
1. While using goggles, use a file to weather your rock by
shaving your crayon into small pieces. Collect the shavings
on a paper towel. Be as neat as you can!
2. Use your iPad camera to take a “close up” photograph of
your lab partner’s hands while they perform the process of
weathering the rock/crayon. In turn, they should also take a
photograph of your hands while performing the process.
PART B: EROSION and DEPOSITION
In nature, once the sediment has been created, it is moved to a
new location by the forces of erosion which includes water, wind,
ice, and gravity. The sediment is then dropped into a new
location. This is called deposition. Here you will act as the
erosive and depositional forces.
3. Using a square of aluminum foil, each lab partner, in
turn, should place their rock fragments in a neat pile in the
center of the foil. In doing this, you are eroding (moving)
and depositing (leaving behind) the sediments in a new
location.
4. Use your iPad camera to take a photograph of your
deposited sediment.
PART C: SEDIMENTARY ROCK
This part of the simulation requires you to understand the
compaction and cementation process that forms some types of
sedimentary rock. Spaces between the fragments are reduced in
size by compaction (pushed together) and “glued together” by
the process of cementation. Cements include minerals and
substances such as calcite, silica, and iron oxide (rust). This
simulation will not add cementing agents. It will only simulate
compaction. The compaction process occurs as sediment layers
are continually covered by new layers of sediment. The lower
layers become compacted by the weight of the new layers above.
5. Carefully fold the foil over and enclose the loose layers of
crayon shavings inside the aluminum foil.
6. Place the foil packet in between your hand and a table
and compact the packet and sediment inside. Add pressure
as best as you can but remember that too much pressure
will turn it into “metamorphic rock.”
7. Use your iPad camera to take a photograph of your newly
created clastic sedimentary rock. Note: If your sediment did
not compact into a solid rock, you may need to perform step
6 again with slightly more pressure.
8. ANSWER the analysis questions for Parts A-C.
PART D: METAMORPHIC ROCK
As the pressure deep within the Earth increases, the temperature
increases as well. 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 over-riding rock.
9. Rewrap the loosely compacted sedimentary rock-type
crayon shavings in the aluminum foil. Arrange the
aluminum foil crayon packets neatly together with all lab
groups from the class. Carefully pile all of the textbooks on
top of the aluminum foil packets and leave them under
pressure overnight.
10. Unwrap the foil packet and remove your newly formed
metamorphic rock. Use your iPad camera to take a
photograph of it.
11. Answer the analysis questions for Part D.
PART E: IGNEOUS ROCK
Igneous rocks form deep within the Earth. They originate in
magma chambers embedded in solid rock. These rocks are either
extrusive or intrusive. Extrusive igneous rocks form when lava
exits the Earth and cools on its surface. Intrusive igneous rocks
are the result of magma cooling within Earth’s interior.
12. Put your crayon metamorphic rock in a small aluminum
pie tin and bring it to your teacher. Your teacher will heat
the metamorphic rock in an aluminum pan over a hot
plate. Observe what is happening from a safe distance.
USE EXTREME CAUTION. You must wear GOGGLES!
13. Have the teacher pour the melted “magma” into your
assigned container. Let cool.
14. Use your iPad camera to take a photograph of the newly
formed igneous rock.
15. Answer the analysis questions for Part E.