August 2008 Soil Origin and Development Original by Nancy Williams Modified by Georgia Agricultural Education Curriculum Office July, 2002.

August 2008

Soil Origin and Development

Original by Nancy Williams

Modified by Georgia Agricultural Education Curriculum Office

July, 2002

August 2008

Soil Body

• Terms to know:– Pedon is a section of soil extending from the

surface to the depth of the root penetration of the deepest rooted plants.

– Polypedon a collection of pedons that are much the same.

– Weathering it is where weather, plants are the major agents responsible for forming soil from rock.

August 2008

Soil Body

• Physical Weathering-– refers to the effects of such climatic factors

as Temperature, water, and wind. One of the most important is frost wedging.

– Chemical Weathering- changes the chemical makeup of rock and breaks it down.

– Hydrolysis- water reacts with minerals to produce new and softer compounds

August 2008

Rocks and Minerals

• Igneous Rock:– it is the basic material of the

earth’s crust. It is created by the cooling and solidification of molten materials from deep in the earth.

– Sedimentary Rock• Forms when loose

materials like mud or sand are deposited by water, wind, and other agents

August 2008

Rocks and Minerals

• Metamorphic Rock:– This is where igneous and sedimentary rocks

are subjected to great heat and pressure so they change to metamorphic rock.

August 2008

Rocks and Minerals• Sedimentary rock-

• Is like limestone or sandstone,formed by deposition of materials in water or by wind. Note: fresh mud and sand that will someday be sedimentary rock.

• Igneous rock-

• like basalt,formed from molten rock as in volcano. Most of the earth’s crust is igneous rock overlain by sedimentary rock

August 2008

Rocks and Minerals

• Metamorphic rock- has been altered by heat, pressure or chemical action. Examples are limestone becomes marble and sandstone becomes quartzite.

August 2008

Rocks and Minerals

• What is Residual Soil-– this is soil formed right from bedrock. They

are actually less common than soils of parent material carried from elsewhere by wind, water, ice and or gravity.

– They form very slowly as the rock must be weathered first.

August 2008

Rocks and Minerals

• Glacial Ice- – Carried parent materials all over the northern

part of the North America during the four separate periods of glaciations

– What is glacial drift?• It is the melting and the shrunk between the

glacial periods and transported materials remained in deposits. This is how we got the most beautiful landscapes in the United States.

August 2008

Rocks and Minerals

• What is Glacial Till-– It is the melting process where some debris

simply dropped in place to form deposits.

Eolian is where the wind will carry and leave soil somewhere else.

Alluvial Soils- are soils whose parent materials were carried and deposited in moving fresh water to form sediments

August 2008

Rocks and Minerals

• Colluvium- – this is where the soil

will slide down or roll down a slope. This is scattered in hilly and mountainous areas

– Some examples are: Avalanches, mudslides, and landslides.

August 2008

The Soil Profile

• Soil does change over time today Scientist have classified them into four areas

• They are:– Addition– Losses– Translocations– Transformations

August 2008

The Soil Profile

• What is Additions?– It is materials such as fallen leaves windblown

dust or chemicals from air pollution may be added to the soil

August 2008

The Soil Profile

• What is Losses?– It is materials that may be lost from the soil

as a result of deep leaching or erosion from the surface.

August 2008

The Soil Profile

• What is Translocation?– It is materials that may be moved within the

soil as with leaching deeper into the soil or being carried upward with evaporating water.

August 2008

The Soil Profile

• What is Transformation?– It is the materials that may be altered in the

soil, for example organic matter decay weathering of the minerals to smaller particles or chemical reactions.

August 2008

The Soil Profile

• Each of these processes will occur at different depths of the soil.

• For example:– Organic Matter will be at the top or the near

the surface of the soil.

August 2008

The Soil Profile

• What is a horizon?– They are the layers

of the different types of soil and the different depths that the layers will be located at.

August 2008

The Soil Profile

• What is a soil profile?– It is the vertical section through the soil and

extending into the unwreathered parent materials and exposing all the horizons.

August 2008

Master Horizons

• What is the Master Horizons?– The are A, B and C horizons are known as the

master horizons. They are a part of a system for naming soil horizons in which each layer is identified by a code O, A, E, B, C and R

August 2008

Horizons

• The O Horizon-– Is the organic layer made of wholly or partially

decayed plant material and animal debris . You can normally find this layer in a forest with fallen leaves, branches and other debris.

August 2008

Horizons

• The A Horizon-– It is usually called the topsoil by most farmers.

This is where the organic matter accumulates over time. This layer is very prone to leaching and losing iron and other minerals. The A horizon provides the best environment for the growth of plant roots, microorganisms and other life.

August 2008

Horizons

• The E Horizon-– This is the zone of the greatest leaching of

clay, chemicals and organic matter.

August 2008

Horizons

• The B Horizon-– This is also called the subsoil is often called

the zone of accumulation where chemicals leached out of the A horizon

August 2008

Horizons

• The C Horizon-– lacks the properties of the A and B horizon.

It is the soil layer that is less touched by soil forming processes and is usually the parent material soil

August 2008

Horizons

• The R Horizon-– Is the underlying bedrock such as the

limestone, sandstone, and or granite.