Materials From The Earth – Part VI – Sedimentary Rocks & Fossils

Lesson Objectives – by the end of this lesson you will:

1. understand how sediments get stuck together to form sedimentary rocks
2. understand how sandstone and limestone are formed
3. know that fossils are the shapes of dead organisms preserved in sedimentary rocks

 

There are 3 tasks for today’s lesson, you will complete them all in a circus, one at a time.

Task 1 – Sand & Sandstone

This is an investigation and writing task.

You will have a tray of damp sand, do the following things, observe what happens and write down your findings:

1. Observe the sand with a hand lens. What structure does the sand have?

2. Take a handful of sand and squeeze it as hard as you can.  What happens?

3. Carefully examine the squeezed sand. What has happened to it?

4. Can you see a shiny coating on the grains of sand?  These are mineral deposits that were dissolved in the water and are left behind when the water is squeezed out. Eventually these mineral deposits would cement the grains of sand together.  What would happen to the grains of sand if they were stuck together?

5. We can experiment with different types of cement by mixing sand with a) plaster of paris, b) clay – see what happens to pellets of sand mixed with different cement.

6. Take a look at your pet rock – is it a sedimentary rock, how big are the grains?

 

Task 2 – Different Sedimentary Rocks

 

This is an internet research task.

There are many different types of sedimentary rocks, you are going to do some research about some of them. Draw the table below in your books and use the The Geological Society website for schools to help fill in the information.   Does any of this information help you identify your pet rock?

 

Task 3. How are fossils formed?

 

This is a research, writing and drawing task.

1. Watch this video, about how dinosaur fossils are formed in sedimentary rocks.

2. Explain in your own words how mold and cast fossils are formed.

3. Using your understanding of how igneous and sedimentary rocks are formed, can you explain why don’t we find fossils in igneous rocks?

4. What type of rock is your pet rock? Does your pet rock contain a fossil? How do you know? Could it contain a fossil?

5. Take a look at some of the fossils we have in class. Draw a sketch of your favorite fossil.

6. Extension – do some research on your favourite fossil – what animal is it? How long ago did it live?   Some ammonites (see picture above) lived 100 million years ago, that is older than the dinosaurs!