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OPENING
http://studyjams.scholastic.com/study
jams/jams/science/rocks-minerals-
landforms/soil.htm
The Ground Beneath Our Feet
Soil Formation
• Soil
• How does soil form?
• Loose weathered material on Earth’s surface where plants can grow
• Soil forms as rock is broken down by weathering and mixes with other materials
What Makes Up Healthy Soil?
• Mineral fragments, humus, air, water, and living things
–Plant roots, Insects, Worms
• Humus–Organic Material
–Can support the growth of vegetation
• Parent rock– source of mineral fragments in the soil
• What is Humus?
• What is a parent rock?
–Organic Material that can support the growth of vegetation
– source of mineral fragments in the soil
Left Side Right Side
Soil Formation
• Soil starts out as rock
• The surface rocks break 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 Texture
The soil’s quality is based on the proportions of soil particles.
Soil texture affects
–Consistency:
• soil’s ability to be broken up.
–Infiltration:
• ability of water to move through soil.
• What is soil Consistency ?
• What is a soil Infiltration ?
soil’s ability to be broken up
ability of water to move through soil
Left Side Right Side
Sizes of Weathered Rock That Make Up Soil
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
Review Questions
• Which particle is the biggest one that goes in soil?
– A. Clay
– B. Silt
– C. Quartz
– D. Sand
Review Questions
• Which particle is the biggest one that goes in soil?
– A. Clay
– B. Silt
– C. Quartz
– D. Sand
Review Questions
• What is loam?
– A. Loam is the perfect combination of sand, silt, and clay.
– B. Loam is the combination of 30% sand, 40% mud, and 30% clay.
– C. Loam is located on in horizon B.
– D. Loam is the particle quality of any soil.
Review Questions
• What is loam?
– A. Loam is the perfect combination of sand, silt, and clay.
– B. Loam is the combination of 30% sand, 40% mud, and 30% clay.
– C. Loam is located on in horizon B.
– D. Loam is the particle quality of any soil.
What is a Soil horizon?
• OLitter from dead plants and animals
• A– Topsoil
• E– Zone of intense leaching.
• B– Collects dissolved substances
from upper horizons• C
– Weathered bedrock• R
– Bedrock
• Bedrock • Solid layer of rock beneath the soil
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
Soil pH
• Have you ever seen this?
• Why does this happen?
• What creates CO2?
Soil pH
• Carbonic acid and Humic acid changed the pH of the soil to be more acidic.
• Carbonic acid
– come from Carbon Dioxide.
• Humic acid
– various organic acids produced from humus.
Tropical Climate
• Very rich humus.
• Very little topsoil
–Leeching of nutrients from topsoil to horizon B and C.
–Plants demand a lot of nutrients.
• Soil in Tropical Climate?
• Very rich humus
• Very little topsoil
Left Side Right Side
Desert Climate
• Deserts get less than 25 cm rain a year.
• Slow rate of weathering = Slow rate of soil formation.
• Due to no water, salt gathers in the ground.
• Salt is toxic to plants!
• What is the problem with soil in Desert Climate?
• Due to no water, salt gathers in the ground.
• Salt is toxic to plants!
Left Side Right Side
Temperate Climate
• Lots of weathering = lots of fertile soil
• Most productive soil in the world.
• Most of Continental USA has a temperate climate.
• Soil in Temperate Climate?
• Lots of weathering = lots of fertile soil
• Most productive soil in the world.
Left Side Right Side
Arctic Climate
• Very cold desert = Slow rate of soil formation.
• Low amount of humus due to cold temperatures.
• Cold temperatures
slow down
decomposition.
• Soil in Arctic Climate?
• Very cold desert = Slow rate of soil formation.
• Low amount of humus due to cold temperatures
Left Side Right Side
Review Questions
• What acids can change the pH of the soil?
–A. Humic acid and Hydrochloric acid
–B. Carbonic acid and Humic acid
–C. Carbonic acid and water
–D. Water and citric acid
Review Questions
• What acids can change the pH of the soil?
–A. Humic acid and Hydrochloric acid
–B. Carbonic acid and Humic acid
–C. Carbonic acid and water
–D. Water and citric acid
Review Questions
• Which climate is called the “breadbasket of the world”?
–A. Tropical
–B. Desert
–C. Temperate
–D. Arctic
Review Questions
• Which climate has very little, but fertile topsoil?
–A. Tropical
–B. Desert
–C. Temperate
–D. Arctic
Review Questions
• Which climate is called the “breadbasket of the world”?
–A. Tropical
–B. Desert
–C. Temperate
–D. Arctic
Review Questions
• Which climate has very little, but fertile topsoil?
–A. Tropical
–B. Desert
–C. Temperate
–D. Arctic
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