Teacher sheet · Ages 10–11 · about 45–50 minutes
The rock cycle
Lesson page: echoesof.science/school/rocks/ages-10-11/ · Pupil worksheet: echoesof.science/school/rocks/ages-10-11/print/
Learning aims
- Describe how igneous, sedimentary and metamorphic rocks form.
- Link cooling rate to crystal size.
- Explain weathering, erosion, deposition, compaction and cementation.
- Describe the rock cycle.
- Plan and carry out a fair test.
Lesson plan
| Time | Activity |
|---|---|
| 5 min | Starter: show granite, sandstone and marble. How could they have formed? |
| 10 min | Read the text; build the rock-cycle diagram on the board together. |
| 15 min | Sugar-cube river (fair test). |
| 5 min | Play Which kind of rock? |
| 10 min | Quiz and discussion. |
Materials for the experiment
- 12 sugar cubes per group
- 3 identical plastic jars with lids
- A stopwatch or a counter
- A sieve or tea strainer
- A sheet of dark paper
- A magnifying glass
Safety: Use plastic jars, not glass. Hold the lids on firmly. Do not eat the sugar. Wipe up spilt sugar so nobody slips.
Common misconceptions
| Pupils may think… | Actually… |
|---|---|
| Metamorphic rocks are melted rocks. | Metamorphic rocks change through heat and pressure without melting; melted rock that cools makes igneous rock. |
| Weathering and erosion are the same thing. | Weathering breaks rock where it is; erosion moves the pieces. |
| The rock cycle happens in a few years. | It takes millions of years. |
Worksheet answers
- Three boxes joined by arrows, for example igneous → (weathering, erosion, deposition, compaction) → sedimentary → (heat and pressure) → metamorphic → (melting and cooling) → igneous.
- More shakes wore away more corners and made more powder; fair: same number of cubes, same jars, same shaking strength, only the number of shakes changed.
- Granite cooled slowly underground, so its crystals had time to grow large; basalt cooled quickly from lava, so its crystals are small.
- Weathering breaks or wears rock while it stays in place; erosion moves the broken pieces away.
Quiz answers
- Lava cools quickly at the surface. What size are the crystals in the rock? Small. Fast cooling leaves little time for crystals to grow.[1]
- What does limestone change into when it is heated and squeezed deep underground? Marble. Metamorphosed limestone becomes marble.[1]
- What is erosion? Moving rock pieces by water, wind, ice or gravity. Erosion moves rock fragments from one place to another.[2]
- What squeezes layers of sediment together? The weight of the layers above. This is called compaction.[4]
- Why can freezing water break a rock? Ice expands and pushes the crack apart. Water expands when it freezes.[3]
- In a pile of sedimentary rock layers, which layer is usually the oldest? The bottom layer. Each layer is younger than the one beneath it.[4]
Going further
Make a sediment jar: shake gravel, sand and soil in a jar of water and let it settle overnight. Draw the layers. Which settled first?
Sources used in this lesson
- [1] Rocks and minerals (British Geological Survey (BGS)): reliability High
- [2] Geological processes (British Geological Survey (BGS)): reliability High
- [3] Weathering (British Geological Survey (BGS)): reliability High
- [4] The Rock Cycle (Physical Geography and Natural Disasters, section 3.5) (R. Adam Dastrup, open textbook (Salt Lake Community College Pressbooks)): reliability Medium-high
- [5] Chapter 5: The Rock Cycle (Investigating the Earth: Exercises for Physical Geology) (D. Hauptvogel, V. Sisson and M. Comas, open lab textbook (University of Houston Libraries Pressbooks)): reliability Medium-high
Full list with links and a note on each source's reliability: echoesof.science/school/rocks/sources/
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