This document discusses soil composition and formation. It defines key soil terms like soil profile, parent material, soil horizons, and topsoil. The document explains that soil is made from weathered rock and organic material and is affected by factors like climate, time, topography, and parent material. It describes the differences between residual and transported soils and lists typical components found in the A, B, and C horizons of a soil profile. Rainfall is also discussed as affecting whether a region supports grassland or forest soils.

1. Weathering, Soil, and Erosion
12.2 Soil

2. Know
✤ soil ✤ soil profile
✤ parent material ✤ soil horizon
✤ residual soil ✤ topsoil
✤ transported soils ✤ subsoil

3. Understand
✤ Soil is made of weathered rock and organic material.
✤ Climate and other factors affect the composition of soils.

4. Do
✤ Explain how soil forms.
✤ Describe soil composition and the factors that affect it.

5. A-horizon
Residual Transported (topsoil)
soil soil B-horizon C-horizon
Parent Profile of
material mature soils
Soil
Arctic Type Desert
Temperate Tropical

7. Name four factors that affect soil
composition.
✤ Time; parent material; topography; climate

9. 12.2 #1. Describe the difference between a
residual soil and a transported soil.
✤ 12.2 #1. Residual soils form from the
bedrock beneath it. Transported soil forms
from parent material that originated in a
different location.

10. #2. Sketch a soil profile and
label A-, B-, and C- horizons.
Describe what you are likely
to find in each horizon.
✤ #2. A-horizon- is likely to
contain humus and sand.
✤ B-horizon is likely to contain
iron oxides, clay and soluble
minerals such as calcium
and magnesium.
✤ C-horizon- is likely to
contain slightly weathered
parent material.

12. #3. What rock materials are found in
soil?
✤ #3. Sand, silt, and clay

14. #4. How does the amount of rainfall appear to affect
whether a soil is a grassland or a forest soil? Explain your
thinking.
✤ #4. It takes more rain to support a forest than
it does to support grassland, thus, forest soil
exists where there is more rain.

15. #5. How do you think the type of soil found in a
particular region might affect the lives of people in
the region?
✤ #5. The type of soil affects how easily
crops can be grown and thus how
large a population can be supported
by local food growth.