Soil Formation

Soil Formation

Open Ended

What do you think is soil made of?

It is the organic material on the surface of the earth.

It is the medium of growing terrestrial plants.

​Living things, temperature, rain, and parent materials interact to produce soil.

Soil

Soil is formed slowly as rock erodes into tiny fragments.

Organic matter decays and mixes with inorganic materials to produce soil.

Soil Formation

Factors that Affect Soil Formation

Warmer climates speed up chemical reactions and the formation of soil.

Soil in warm regions have more silt and clay.

Many communities in warm areas have farming as their primary source of livelihood.

Climate

Plants' roots protect the soil from erosion.

They help the soil retain moisture.

Fungi, bacteria, insects, earthworms and burrowing animals help in decomposition and aerate the soil.

Organisms

Multiple Choice

What could be true about the formation of soil in cold climates?

• Snow covers the soil and plants just die.

• There is no soil and plants cannot grow.

• It takes longer to form because the cold slows down chemical reactions.

Soil carries the properties of its parent material.

Ex. Soil from limestone is rich in calcium.

Ex. Soil that come from rocks will have the same color and texture.

Parent Material

Soils takes many years to form.

Over time, organic matter is added to soil.

As it gets buried, the soil may change to another type.

Time

If the slopes are steep, water will run down faster and erode the soil.

The nutrients will be deposited at the foot of the slopes.

Slopes that are mostly exposed in dry sunlight get dried out.

Slope of the Land

Layers of Soil

Topsoil. Seeds take root here. It is made of humus and minerals.

It has a lot of organic matter and microorganisms.

A Horizon

The top, organic layer is made of leaf litter and humus (decomposed organic matter)

O Horizon

Layers of Soil

Subsoil. It contains clay and mineral deposits that comes from the layer above.

B Horizon

Eluviation or leached layer.

Made of mostly sand and silt. Eluviated means the nutrients have been lost to water.

E Horizon

Layers of Soil

Bedrock. The unweathered parent material of the soil. It solid rock.

R Horizon

Regolith. It is made of broken-up bedrock. Plant roots do not reach this layer.

C Horizon

Layers of Soil