Chapter 16- Soils and Environment Flashcards
(50 cards)
- solid Earth material that has been altered by physical, chemical,and biological processes such that it can
support rooted plant life. (Soil Scientists) - solid Earth material that can be removed without blasting. (Engineers)
- is produced by weathering, a term that encompasses a variety of chemical, physical, and biological
processes acting to break down rocks and minerals.
SOIL
Soil Categories
This is the material resulting from the in situ weathering of the Parent Rock
Residual Soil
Soil Categories
Eroded rock particles that are transported by water, wind, or glacier and then modified in their new deposition location form
Transported Soil
Soil formation depends on:
● Climate
● Topography
● Parent material
● Maturity
● Biological processes
vertical and horizontal movements of the materials in a soil system create a distinct layering, parallel to the surface. The layers are called zones or soil horizons.
Soil Profile
mostly organic materials. The color of the horizon is often dark brown or black.
O Horizon
composed of both mineral and organic materials. The color is often light black to brown.
A Horizon
composed of light-colored materials resulting from leaching of clay, calcium, magnesium, and iron to lower horizons.
E Horizon
enriched in clay, iron oxides, silica, carbonate, or other material leached from overlying horizons. Horizon is known as the zone of accumulation.
B Horizon
composed of partially altered (weathered) parent material; rock is shown here but the material could also be alluvial in nature, such as river gravels in other environments. The horizon may
be stained red with iron oxides.
C Horizon
unweathered (unaltered) parent material.
R Horizon
Soil color may be an important indicator of how well a soil drains
- soils are well aerated, creating excellent oxidizing conditions; for example, in a well-aerated soil, iron produces soil with a
red color. - soils are wet, and these soils tend to have a yellow color
This distinction is important because poorly drained soils are associated with
environmental problems, such as lower slope stability and an inability to be
utilized as a disposal medium for household sewage systems.
Well-Drained
Poorly Drained
● Clay particles: Diameter less than 0.004 mm (0.0002 in)
● Silt particles: Diameter ranges from 0.004 to 0.063 mm (0.0002 to 0.003 in)
● Sand particles: Diameter ranges from 0.063 to 2.0 mm (0.003 to 0.08 in)
● Particles larger than 2.0 mm (0.08in.): Classified as gravel, cobbles, or boulders, depending on particle size.
Soil particles often cling together in aggregates called _______
Peds
Type of Peds
1-10mm
Horizon A
Can Also be found in B and C Horizon
Granular
Type of Peds
5-50mm
Horizon B
Are designated as angular or subangular
Blocky
Type of Peds
10-100mm
Horizon B
If columns have rounded tops, structure is called a columnar
Prismatic
Type of Peds
1-10mm
Horizon E
May also occur in Horizon B
Platy
A soil may be considered a complex ecosystem in which many types of living things convert soil nutrients into
forms that plants can use.
True
Is the ability of soil to provide essential nutrients (N, P, K) for plant growth. It can be improved with fertilizers and organic matter
Soil Fertility
developed on some floodplains and glacial deposits
Naturally Fertile Soils
developed on leached bedrock or loose deposits.
Low Fertility Soils
Factors reducing fertility:
erosion, flooding, pesticides
all pore spaces are completely filled with water.
Saturated Soil
