SoilsSoilsEarth’s Changing Earth’s Changing
SurfaceSurface
ReviewReview
Weathering – breaks down rockWeathering – breaks down rock– MechanicalMechanical– Chemical Chemical
Erosion – removes the rock particlesErosion – removes the rock particles
What is soil?What is soil?
The loose, weathered material on The loose, weathered material on Earth’s surface in which plants can Earth’s surface in which plants can grow.grow.
SoilSoil
Bedrock - the solid layers of rock Bedrock - the solid layers of rock beneath soil. beneath soil.
Soil CompositionSoil Composition
Mixture of rock particles, minerals, Mixture of rock particles, minerals, decayed organic material, water, and decayed organic material, water, and airair
Humus – decayed organic material in Humus – decayed organic material in soil soil
SoilSoil
Fertility of Soil – measures how well Fertility of Soil – measures how well the soil supports plan growth. the soil supports plan growth. – Rich in humus has high fertility Rich in humus has high fertility
Why does fertility of soil matter?Why does fertility of soil matter?
Soil TextureSoil Texture
What does soil feel like? What does soil feel like? Sand feels coarse and grainySand feels coarse and grainy Clay feels smooth and silkyClay feels smooth and silky
Soil texture depends on the size of Soil texture depends on the size of soil particles. soil particles.
Soil Particle sizeSoil Particle size
ClayClay SiltSilt Sand Sand GravelGravel
Less than Less than 1/256 mm1/256 mm
Less than Less than 1/16 mm1/16 mm
Less than Less than 2 mm2 mm
2 mm and 2 mm and largerlarger
LoamLoam
Soil that is made up of about equal Soil that is made up of about equal parts of clay, sand, and silt is called parts of clay, sand, and silt is called loam. loam.
Soil FormationSoil Formation
Forms as rock is broken down by Forms as rock is broken down by weathering and mixes with other weathering and mixes with other materials on the surface.materials on the surface.
Soil FormationSoil Formation
Soil HorizonsSoil Horizons– A layer of soil that differs in color and A layer of soil that differs in color and
texture from the layers above or below texture from the layers above or below it. it.
Soil Horizons Soil Horizons
A HorizonA Horizon
Topsoil – a crumbly, dark brown soil Topsoil – a crumbly, dark brown soil that is a mixture of humus, clay, and that is a mixture of humus, clay, and other minerals.other minerals.
Develops as plants add organic Develops as plants add organic material to soil and plants weather material to soil and plants weather rock.rock.
B HorizonB Horizon
Subsoil – clay and other particles Subsoil – clay and other particles washed down from the A horizon, but washed down from the A horizon, but little humus. little humus.
Soil TypesSoil Types
Thousands of different types of soil in Thousands of different types of soil in U.S. aloneU.S. alone
Classified based on climate, plants, Classified based on climate, plants, and soil composition. and soil composition.
Living Organisms in SoilLiving Organisms in Soil
Some soil organisms make humusSome soil organisms make humus Some soil organisms mix the soil and Some soil organisms mix the soil and
make spaces in it for air and water. make spaces in it for air and water.