The Ground Beneath Our Feet
S6E5h. Describe soil as consisting of weathered rocks and
decomposed organic material.
What Makes Up Healthy Soil?
• Mineral fragments, humus, air, water, and living things such as– Plant roots, Insects, Worms
• Humus– Organic Material– Forms from decayed plant and animal material – Can support the growth of vegetation
• Parent rock– The source of mineral fragments in the soil
Soil Formation
• Soil starts out as rock
• The surface rock breaks down into smaller pieces and is mixed with organic matter.
• Over time this creates a thin layer of soil.
• Decaying matter makes the soil thick and rich
Soil Formation Video
• http://nroc.mpls.k12.mn.us/Environmental%20Science/course%20files/multimedia/lesson17/animations/2c_soil_formation.html
Soil Particles
Different Types of Soil• Every soil type is a
mixture of sand, silt, clay.
• The right mixture is called loam.
• Loam = • 40% sand• 40 % silt• 20 % clay
Soil Profile
• The vertical display of soil horizons.
• Each soil profile is different from another.
• http://courses.soil.ncsu.edu/resources/soil_classification_genesis/soil_formation/soil_transform.swf
What is a Soil horizon?• O- Litter from dead plants &
animals• A– Topsoil
• E– Zone of intense leaching.
• B– Collects dissolved
substances from upper horizons (sub soil)
• C– Weathered bedrock
• R– Bedrock
Review Questions
1. Which particle is the biggest one that goes in soil?
– A. Clay
– B. Silt
– C. Quartz
– D. Sand
Review Questions
2. Horizon C is made mostly of
– A. Humus
– B. Organic Material
– C. Bedrock
– D. Weathered Rock
O
C
B
A
Review Questions
3. What is loam?
– A. Loam is the perfect mixture of 40 % sand, 40% silt, and 20 % clay.
– B. Loam is the combination of 30% sand, 40% mud, and 30% clay.
– C. Loam is located in horizon B.
– D. Loam is the particle quality of any soil.
Review Questions
4. What is missing from this profile?
– A. Humus
– B. Organic Material
– C. Bedrock
– D. Weathered Rock
O
C
B
A
Review Questions
5. How does soil start?
- A. A large rock is weathered
- B. Bits & pieces of rocks are cemented together
- C. Decaying matter is compacted together
- D. None of the above
Review Questions
1. Which particle is the biggest one that goes in soil?– A. Clay
– B. Silt
– C. Quartz
–D. Sand
Review Questions
2. Horizon C is made mostly of
– A. Humus
– B. Organic Material
– C. Bedrock
–D. Weathered Rock
O
C
B
A
Review Questions
3. What is loam?
– A. Loam is the perfect mixture of 40% sand, 40%silt, and 20% clay.
– B. Loam is the combination of 30% sand, 40% mud, and 30% clay.
– C. Loam is located in horizon B.
– D. Loam is the particle quality of any soil.
Review Questions
4. What is missing from this profile?
– A. Humus
– B. Organic Material
– C. Bedrock
– D. Weathered Rock
O
C
B
A
Review Questions
5. How does soil start?
- A. A large rock is weathered
- B. Bits & pieces of rocks are cemented together
- C. Decaying matter is compacted together
- D. None of the above