Chapter Two

Soil Origin and Development

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.

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

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

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.

Rocks and MineralsSedimentary 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

Rocks and Minerals

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

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.

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.

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

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.

The Soil Profile

Soil does change over time today Scientist have classified them into four areasThey are:– Addition– Losses– Translocations– Transformations

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

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.

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.

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.

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.

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.

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.

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

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.

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.

Horizons

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

chemicals and organic matter.

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

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

Horizons

The R Horizon-– is the underlying bedrock such as the limestone,

sandstone, and or granite.