1. Unit 3E
The Changing Earth

2. 5. Soil

3. Soil is made of rocks that slowly break down into tiny bits
Vocabulary
soil
Made of broken bits of rock mixed with air, water, and humus

4. These bits of broken rock mix with air, water, and humus to form soil
Vocabulary
humus
The remains of dead plants and animals found in soil

5. One inch of soil takes hundreds or thousands of years to form
Soil forms slowly
One inch of soil takes hundreds or thousands of years to form

6. There are many different kinds of soils
Sandy soil
Silty soil
Clay soil
Loamy Soil
Peaty Soil
Chalky Soil
That is because different areas have rocks made of different minerals

7. Each kind of rock makes a certain type of soil
Feldspar makes sand

8. Vocabulary
sand
A kind of soil made of feldsar which is the biggest grain of any kind of soil

9. When quartz is broken down, it makes silt
Vocabulary
silt
Soil made when quartz is broken down into tiny grains

10. Silt grains are tiny but they can be seen

11. Micas and other minerals break down to make clay
Vocabulary
clay
Soil made of mica and other minerals and has tiny grains that can only be seen with a microscope

12. Soil often has two layers
The layers are the topsoil and the subsoil

13. Vocabulary
topsoil
The uppermost layer of soil which has rock particles, humus, and minerals

14. The topsoil is usually the richest part of the soil
In this layer, dissolved minerals and nutrients from the humus make it possible for plants to grow

15. A layer of soil made of larger rocks that have been broken down
Vocabulary
subsoil
A layer of soil made of larger rocks that have been broken down

16. Solid rock called bedrock is under the layers of soil
Vocabulary
bedrock
Solid rock under layers of soil

17. Erosion from wind and water carry away tons of soil each year

18. The water soaks into the ground instead of washing away soil
One way that farmers protect soil is by planting rows of crops around a slope
The water soaks into the ground instead of washing away soil

19. People also put grass and plants in places where the soil is bare
Plants help to hold the soil

20. Wind and water will not be able to move the soil so easily