1. The stories rocks tell

2. Starter
Can you draw a labelled diagram of the Earth?

3. The Earth’s Interior
How do we know what the Earth’s interior looks like if we can’t actually get down there and look at it?
How can we check what each part is made from?
In pairs discuss your ideas.
Be ready to share!

4. The Earth’s interior… The crust?
We can analyse samples of the rocks to work out their composition, by drilling bore holes.
The mantle?
Volcanoes often bring up molten material from the mantle that we can analyse.
The time taken for seismic waves to travel through the Earth allow us to measure it’s thickness.
The core?
We can only guess at it’s structure and compare it to iron meteorites that were formed at a similar time!

5. The stories rocks tell Objectives At the end of this lesson you......
must be able to state the way rocks are dated
should be able to describe how scientists explore Earth’s history

6. Timescales on Earth
We know that the Earth was formed 5000 million years ago. That’s a really long time ago.
How does it compare to how fast mountain belts were formed or earthquakes last?
It is important when we are talking about the Earth and the processes that happen on Earth that we can compare them.

7. Timescales on Earth What does it mean to compare timescales?
As an example could you tell me what would take the longest to happen...
Dinosaurs lived on Earth
Mountains were formed
Glaciers melting after the ice age
What about these?
Driving to Scotland
Cleaning your teeth
Making dinner

8. Work to do... Complete worksheet p1_02_01 fast and slow changes.
Worksheet answers
Event
Timescale
earthquake
day
mudslide
volcano eruption
months
volcanic island appearing
years
erosion
decades
retreat of glacier
hundreds of years
formation of English Channel
thousands of years
fossilisation
two million years
formation of fold mountains
several million years

9. The stories rocks tell
Mountains and rocks take millions of years to form and change. The Earth’s surface is constantly changing. Most of these changes happen so slowly though that people can’t see it happening.
We need other evidence to show how the Earth has changed over the last 5000 million years.

10. The stories rocks tell
People were not curious about the history of Earth until about 200 years ago. They became curious because they found clamshells and marine fossils at the top of mountains and wondered how they got there!
James Hutton was a farmer who made journeys around the UK studying rock formations and collected specimens.
He learned to read the rocks!

11. The stories rocks tell 1785 he came up with the idea that….
‘Processes such as erosion and deposition of sediment slowly take place. Over enormous periods of time they add up to huge changes in the Earth’s surface. Heating inside the Earth changes the rocks and lifts them up. The Earth has a history……it was not created all at once!’
Over the next few lesson’s we will
learn that he was right and see the
evidence.

12. The stories rocks tell
Most people thought he was crazy. They believed the Earth had been created exactly as they saw it and that it had never changed and never would.
How do you know that this is not true?
It took another century and another scientist for Hutton’s idea to really become accepted.
Let’s see what Hutton discovered....

13. Dating rocks… Which rocks are older the red ones or the white ones?
Deeper rocks are older.
The oldest rocks are laid down first. Younger rocks appear on top of older rocks.

14. Dating rocks…
Which rocks are older the ones with the dinosaur fossils, shelled animal fossil or single cell organism fossils?
Fossils are time markers.
Many species lived at particular times and then became extinct.

15. Dating rocks…
Complete worksheet p1_02_03 phone layers

16. Dating rocks…
Which rocks are older the grey stripy ones or the lighter grey column?
Cross cutting features show age.
If one rock cuts another then it is younger. The older rock gets eroded away and then replaced.
4 levels of coloured sand demo

17. Which rock is the oldest?

18. Work to do…
Complete worksheet p1_02_04 to test your skills of rock dating
1st cut out the diagram and stick it in your books. Label the four stages it took to create the rock layers in the picture.
2nd answer the questions in your books using full sentences.

20. Worksheet p1_02_04
Hutton read a story in the rocks. He could imagine the enormous time it took for the lower sedimentary layers to form. These layers had tilted, and the upper section had eroded away. More and more time passed. Then new layers were deposited on top of the older rocks.

21. Plenary
Complete worksheet p1_02_02 to see what you have learnt this lesson.

22. Worksheet answers
Activity 2 (Standard demand)
Q1 New rocks forming: image A volcano (igneous); images C, D basin fills with layers of sediment (sedimentary).
Rocks breaking down: images C, D – mountains and basin edges eroding
Q2 Students’ own sentences about erosion, transportation and sedimentation
Q3 There needs to be further mountain building.
Activity 3 (High demand)
Q1 Fossil comparisons – easy to compare samples; does not give a true age, cannot be used for older rocks.
Comparing rock samples – reasonably easy to use; does not give a true age.
Radioactive dating – very accurate; requires specific elements to be present.
Q2 Radioactive dating of the oldest rock samples, including single crystals; assuming that Earth is approximately the same age as the Moon and meteorites.
Q3 The Earth cannot be younger than its oldest rocks but we may still find older rocks; rocks are recycled on Earth so the oldest rocks may not be in an accessible form.
Q4 Radioactive dating gives an accurate age and can date much older rocks than the other methods.