soils!!! - gomezFOSmccaskey

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Transcript soils!!! - gomezFOSmccaskey

As rocks weather, they combine
with organic material to form soil.
• What is soil and how is it created
• What video clip: Geography Principles: Soil and
Vegetation : soil formation
• Soil - combination of mineral and organic
matter, water, and air
• It is that portion of the regolith (weathered
rock and mineral) that supports the growth
of plants
Components in soil
that support plant growth
• Factors controlling soil formation
• Parent material
– parent material is the underlying bedrock composition affects soil types
• Factors controlling soil formation
• Time
– Soils get better developed (Thicker, with
greater differences between layers)
with more time
• Climate
– Biggest control on soil formation
–Key factors are temperature and
• Factors controlling soil formation
• Plants and animals
– Organisms influence soil properties
– Also furnish organic matter to the
soil (especially plants)
Soil Profile
• The soil profile
• Soil forming processes operate from
the surface downward
• Vertical differences are called
horizons – zones or layers of soil
An idealized
soil profile
with horizons
• The soil profile
– O horizon: Organic layers or decaying plant and animal
– A horizon: Mineral horizon mixed with humus (dark
decayed organic matter)
– E horizon: Mineral horizon with less organic matter and
certain minerals leak down
– B horizon: Mineral horizon in which materials that have
leaked from above begin to accumulate
– C horizon: unweathered geologic material (sediment;
some bedrock) with little sign of soil forming processes
– R horizon: Hard, completely unweathered parent material
(bedrock); needs blasting or heavy machinery to dig
Mnemonic: Only Active Educators Become Champions Really
Remember the different horizons
Animal Activity
Soluble Minerals
Soluble Minerals
Crushed Rock
Earth’s surface processes
• Erosion – the physical removal of
material by mobile agents like water,
wind, ice, or gravity
Soil Erosion
• Soil erosion
• Recycling of Earth materials
• Natural rates of soil erosion depend on
–Soil characteristics
–Type of vegetation
Where Does Our
Eroded Soil Go?
• Soil erosion
• In many regions the rate of
soil erosion is significantly
greater than the rate of soil
• Farmers now level fields
with lasers to slow loss of
• Terraces
Soil makes up the outermost layer of our planet.
Topsoil is the most productive soil layer.
Soil has varying amounts of organic matter (living and dead organisms),
minerals, and nutrients.
Five tons of topsoil spread over an acre is only as thick as a dime.
Natural processes can take more than 500 years to form one inch of topsoil.
Soil scientists have identified over 70,000 kinds of soil in the United States.
Soil is formed from rocks and decaying plants and animals.
An average soil sample is 45 percent minerals, 25 percent water, 25
percent air, and five percent organic matter.
Different-sized mineral particles, such as sand, silt, and clay, give soil its
Fungi and bacteria help break down organic matter in the soil.
Plant roots and lichens break up rocks which become part of new soil.
Roots loosen the soil, allowing oxygen to penetrate. This benefits animals
living in the soil.
Roots hold soil together and help prevent erosion.
Five to 10 tons of animal life can live in an acre of soil.
Earthworms digest organic matter, recycle nutrients, and make the surface
soil richer.