What 2 layers make up the topsoil?

1
What 2 layers make up the topsoil?
2
Horizon O and horizon A make up topsoil.
3
What layer is made up of partly weathered rock?
4
Horizon C is composed of partly weathered rock.
5
How does material move from horizon A to horizon
B?
6
The process of leaching moves material from
horizon A to horizon B.
7
What do horizon A and horizon B have in common?
8
Both horizon A and horizon B have decayed organic
material called humus.
9
Where does the material in horizon C come from?
10
The partly weathered rock in horizon C comes from
unweathered parent rock.
11
What is the composition of horizon O?
12
Horizon O is composed of leaf litter and other
organic matieral.
13
In what horizon is there very little organic
material?
14
Horizon C had very little organic material.
15
What is the composition of horizon R?
16
Horizon R is composed of unweathered parent
material.
17
How are horizon A and horizon C different?
18
Horizon A is rich in organic material and horizon
C has very little organic mateial.
19
Why do plants grow well in horizon A?
20
Plants grow well in horizon A because it is rich
in organic material and nutrients.