1. Rocks Weathering and Soil Components
6th Grade Science

2. Weathering and Erosion
Weathering is the process that breaks down rock and other substances at Earth’s surface.
Heat, cold, water, and ice all contribute to weathering.
The forces of weathering break rock into smaller pieces.

3. Weathering and Erosion
Erosion is the removal of rock particles by wind, water, ice, or gravity
Weathering and Erosion work together continuously to wear down and carry away the rocks at Earth’s surface

4. What is soil?
Soil is the loose, weathered material on Earth’s surface n which plants can grow.
Soil is a mixture of rock particles, minerals, decayed organic material, and air.

5. What is soil?
Broken down dead plants
animals
Including
rocks

6. Soil Horizon Horizon is a side profile of the layers of soil
Soil is usually divided into 3 main layers (A, B, & C), but will also include the layers above and below for a total of 5 layers.

7. Soil Horizons Diagram Dark brown/black Reddish brown (clay)
Yellowish brown
Solid rock

8. O Horizon: Litter Not really a layer of soil
It’s on top of the first layer of soil
Contains grass, plants, and animals

9. A Horizon: Topsoil 1st layer of soil
Darkest layer of soil (dark brown or black)
Contains humus (organic matter), plant roots, small animals, water, and nutrients for plant growth
The darker the soil, the more nutrients it contains

10. B Horizon: Subsoil 2nd layer of soil Lighter in color (reddish brown)
Fewer nutrients and water
Limited plant growth

11. C Horizon: Parent Material
3rd layer of soil
Lightest in color (yellowish brown/gray)
No nutrients, animals, or plant growth
Contains weathered rock and sediment

12. R Horizon: Bedrock Below the last layer of soil Solid Rock
Has not been weathered or broken down yet
No soil in this layer

13. Living Organisms in Soil
Some soil organisms make humus, the material that makes soil fertile. Other soil organisms mix the soil and make spaces in it for air and water.
Plants: Contribute most to soil humus—supply organic remains, also form the litter

14. Living Organisms cont.
Microorganisms: Break down the remains of dead organisms and mix it with the soil
Animals: Break up hard compacted soil and mix humus through it. They add nitrogen and organic material to the soil.