APES soil

Erosion

The movement of broken down rocks/soils

Weathering

the process of breaking down rocks/soils

Mechanical Weathering

takes place when rocks are broken down without any change in the chemical nature of the rocks (ie physical weathering)

frost wedging

occurs when water freezes in rock fractures. as the water freezes, it expands, putting pressure on the sides of the crack, enlarging it until the rock breaks apart.

thermal heating and cooling

weaken rock by causing it to disintegrate

exfoliation

as underlying rock layers are exposed, there is less pressure on them and they expand. this causes the rigid layers to crack and sections to slide off.

abrasion

moving sediments or rock sections can break off pieces from a rock surface they strike

plants and roots

can work their ways into rock crevices called joints. as they grow, roots create pressure on the sides of the crack, enlarging it until the rock breaks apart.

Chemical Weathering

reactions break down the bonds holding rocks together. It is common especially where there is a lot of water

Natural Erosion

Wind, Water, Glaciers

Human Erosion

Industrial agriculture, (Excessive Over tilling), Overgrazing, Deforestation

Erosion Effects

1. pollution and sedimentation in streams and rivers,

2. clogging waterways

3. causing declines in fish and other species.

4. worsen flooding.

Factors affecting soil formation

1. climate

2. organisms

3. relief

4. parent material

5. time

Soil

A complex mixture of inorganic minerals, decaying organic matter, water, air, and living organisms.

O horizon

the organic horizon at the surface of many soils composed of organic detritus in various stages of decomposition - contains hummus

A Horizon

frequently the top layer of soil a zone of organic matter and minerals that have been mixed together- also known as topsoil

E horizon

A zone of leaching or eluviation found in some acidic soils under the O horizon or less often the A horizon

B horizon

a soil horizon composed primarily of mineral material with very little organic matter

C horizon

the least weathered soil horizon which always occurs beneath the B horizon and is similar to the parent material

Humus

the most fully decomposed organic matter in the lowest section of the O horizon

Optimal range for phosphorus:

• 30-50 ppm (for farming)

Optimal range for nitrogen:

• 40 ppm (for farming)

Optimal range for potassium:

• 100-250 ppm (depending on soil texture and organic content)

Porosity:

a measure of the open spaces within soil

Permeability

a measure of how well water passes through the sample

cation exchange capacity

the ability of a particular soil to absorb and release cations

parent material

the underlying rock material from which the inorganic components of soil are derived