Chapter 21 - Soils

Question 1

What is the composition of soil?

Answer 1

45% mineral particles 
25% air 
25% water
5% plant remains (humus)
?% micro-organisms (not visible to human eye)

Question 2

How are soils formed?

Answer 2

Denudation (weathering and erosion) breaks down rock into loose material. This material works with climate, vegetation and human activities to produce soils

Question 3

What is a soil profile?

Answer 3

A vertical section of the soil from the surface downwards.
(Draw and label)
-A horizon, most of the soils plant litter occur
here
- the B horizon, less humus lighter in colour more stony texture
- C horizon, consists of bedrock

Question 4

What Is leaching?

Answer 4

The movement of water through the soil

Question 5

How does leaching damage soil?

Answer 5

Water dissolves minerals,humus and plant nutrients on the upper parts of the soil.
Then it washes these plant nutrients down beyond the reach of many plant roots. This deprives plants of the many nutrients they need

Question 6

What are tropical red soils?

Answer 6

These soils are found in regions that have tropical or equalatorial climates.

Question 7

How are tropical red soils formed?

Answer 7

They are formed from so much chemical weathering. This chemical weathering happens because:

• high amount of rainfall
• high temperatures speed up chemical reactions. Also help break down iron into iron oxide
• rotting vegetation
• rapid leaching

Question 8

What is soil?

Answer 8

A thin layer of loose material on the surface of the land.