Year 8 Science · Unit 3 · Lesson 26

Soil Formation

Challenge Worksheet

Name
Date
Class

Learning Goals

Warm Up

Because… chain

Fill in the five missing effects to complete the dryland salinity cause-and-effect chain. Each step leads to the next.

Native deep-rooted trees and shrubs are cleared for farming across southern Australia
→
Rainwater is no longer used by deep-rooted trees, so it drains into the ground
→
The rising water table reaches layers of soil where salt has been stored for millions of years
→
Salty groundwater continues rising toward the surface due to capillary action
→
White salt crystals form on the soil surface as water evaporates
→

Overall outcome for Australian agriculture:

Go Deeper

Evaluate the claim

Someone claims...

"Soil is just dirt, farmers can always buy fertiliser from the shop to replace any nutrients that are lost. There's no reason to worry too much about protecting soil because you can just add back what the crops take out. Soil degradation is not really a crisis."

(a) What part of this claim is partially supported by science? (Hint: fertilisers do replace some things, what exactly?)

Challenge 2 marks

(b) What important things about soil can fertiliser NOT replace? Use evidence from the lesson about soil structure, time, and living organisms.

Challenge 3 marks

(c) Using the fact that it takes approximately 1,000 years to form 1 cm of topsoil, explain why soil should be treated as a non-renewable resource on human timescales. What does this mean for how we farm?

Challenge 3 marks

Wrap Up

In one sentence, what was the main idea of this lesson?

HSCScience · Year 8 Science · Unit 3 · Lesson 26 · Challenge Worksheet