All lessons › Challenge: Rock cycle detectives › Lesson 2
Australian primary science · Years 5–6 (challenge) · Lesson 2 of 3
How long is a long time?
Inquiry question: Which Earth processes take minutes, and which take millions of years?
Marked no materials needed
Using a model
What students learn
Some rock-cycle processes are fast (a lava flow cooling) but most are extremely slow (layers building up, rocks wearing away, mountains rising). A scale timeline helps us picture times far longer than a human life.
Success criteria
- I can sort Earth processes from fastest to slowest.
- I can use a scale to place events on a timeline.
- I can explain why we can’t watch most of the rock cycle happen.
Preparation and materials
Before this lesson: Students know the three rock types (lesson 1) and fast and slow changes to Earth’s surface (Changing Earth and sky).
- iPads with Bottlebrush Education open (nothing else needed) — 13 (one per pair)
- Projector or big screen — 1
Teacher setup
- Open Earth & space › Play › Fast or slow? on your screen to demonstrate.
- Check the iPads are charged and set to Your year › Years 5–6.
Safety and adaptations
Follow school science and equipment risk assessment procedures for the materials used.
Review your school policies and curriculum requirements before teaching.
How to investigate
The lesson sequence should leave pupils with evidence to interpret, not only an activity to finish.
- Pairs play Fast or slow? to warm up.
- Sort the events in the data table from fastest to slowest.
- Make a scale timeline of Earth’s history (45 cm = 4.5 billion years) and mark the long-ago events.
- Calculate: at about 2 cm a year, how far would the Twelve Apostles cliffs retreat in 100 years? In 10 000 years?
- Answer the puzzle: is the coast changing quickly or slowly? Use both kinds of evidence.
Teacher modelling prompt
Draw a 45 cm line on the board. Think aloud: “If this whole line is the 4.5 billion years since Earth formed, each 1 cm stands for 100 million years. Uluru’s sandstone started forming more than 500 million years ago: that’s about 5 cm from today’s end. People have only been around for a tiny fraction of the last millimetre.”
Record and explain evidence
Recording question: Which Earth processes take minutes, and which take millions of years?
| Event or process | How long it takes | Fast or slow? | Place on my timeline (cm from today) |
|---|---|---|---|
| ________________ | ________________ | ________________ | ________________ |
Example recording headings; record actual observations, including inconclusive results.
Discussion prompt
Can both be partly right? Use both pieces of evidence.
Provided example or reference data
Earth timescales (rounded estimates)
| Event or process | About how long or how long ago |
|---|---|
| Earth forms | about 4.5 billion years ago |
| Sediments that became Uluru’s rock were laid down | more than 500 million years ago |
| Dinosaurs die out | about 66 million years ago |
| Limestone of the Twelve Apostles forms from sea-creature shells | about 10–20 million years ago |
| Volcanoes erupt in western Victoria | within the last 40 000 years or so |
| A lava flow cools and hardens on top | hours to days |
| One of the Twelve Apostles collapses | seconds, in July 2005 |
| Waves wear back the Twelve Apostles cliffs | about 2 cm per year (estimate) |
Check the data source in the teacher lesson. Illustrative or fictional data are not measurements collected by your class.
Check understanding
What should pupils know? Give one rock-cycle process that is fast and one that is very slow.
Explain with evidence: Why can’t a geologist watch a sedimentary rock form from start to finish?
Apply the idea: A council plans a car park 10 m from the edge of a cliff that wears back about 2 cm a year. Is that safe for 100 years? Show your working.
Teacher answer guidance and saved classroom work are available through the main lesson experience where supported.