Soil Formation

Soil Formation and Earth’s Structure

Soil Formation

What is the first step in soil formation?

The weathering of rocks

Mosses and lichens are called pioneer organisms because they are the first organisms to grow on rocks

What is the second step in soil formation?

the addition of humus (decaying organic matter)

Multiple Choice

One component of soil is decayed plant and animal remains, but the major component of soil is - 

• Fossil Fuels
• Weathered rocks
• Iron ore
• Salt water

Multiple Choice

Plants and animals become part of soil when they -- 

• Die and Decay
• Produce offspring
• Grow and Develop
• Take in nutrients

Multiple Choice

Soil is composed of all of these natural materials EXCEPT

• weathered rock
• plant matter
• plastic substances
• animal remains

Soil Profile- Draw this!(SS)

A soil profile is a cross section of soil.

There are three major soil horizons – A, B, and C.

Horizon A

top & darkest layer (high concentration of organic matter - humus)

Top soil

Horizon B

subsoil enriched with clay minerals leached from the topsoil.

Horizon C

bottom layer (weathered rock)

Parent Rock

Multiple Choice

What is the name of Horizon 1?

• Subsoil 
• Topsoil
• Bedrock 
• Parent Rock

Multiple Choice

What is the name of Horizon 2?

• Subsoil 
• Topsoil
• Bedrock 
• Parent Rock

Multiple Choice

What is the name of Horizon 3?

• Subsoil 
• Topsoil
• Bedrock 
• Parent Rock

Factors Affecting Soil Profiles

Topography (slope) of the land – Soils on slopes tend to be thinner soils in flat areas like valleys or plains are thicker

Age – older soils are thicker because they have had more time to develop.

Climate

Distribution of Soil Types

Soil Textures

Particles of soil are classified by size.

The particles of soil are clay, silt, & sand.

What determines a soil’s texture?

The relative proportions of these particles.

The texture of a soil affects its capacity to absorb and retain water & support plant growth.

Soil Texture Triangle

Multiple Choice

What are loam, clay loam, silt loam, and clay?

• Soil particle sizes

• Soil Textures

• Soil pH

• Soil composition

Multiple Choice

What does the size of the soil particles determine?

• pH

• mineral composition

• texture

• horizon posiition