Geology: Soils

Earth SciencePrairie School

Chapter 14.3 and 14.4

Earth SciencePrairie School

Chapter 14.3 and 14.4

Erosion and Weathering: REVIEW Erosion and Weathering: REVIEW Erosion: process by which material is dissolved,

loosened or worn away from one part of the

earth’s surface and deposited in other places.

Erosion: process by which material is dissolved, loosened or worn away from one part of the

earth’s surface and deposited in other places. Mechanical weathering: Large rock mass is

broken into smaller fragments of the original material. Ex. Frost wedging, plant/human interactions

Mechanical weathering: Large rock mass is broken into smaller fragments of the original material. Ex. Frost wedging, plant/human interactions

Chemical weathering: one or more chemical reactions decompose a mass of rock usually reaction with O2, CO2, and water.

Chemical weathering: one or more chemical reactions decompose a mass of rock usually reaction with O2, CO2, and water.

Minerals and Rocks REVIEW Minerals and Rocks REVIEW Mineral (diamond, bauxite): element or

inorganic compound that occurs naturally and is solid.

Mineral (diamond, bauxite): element or inorganic compound that occurs naturally and is solid.

Rock Types: Rocks are any material that make up a large, natural, continuous part of the earth’s crust. May contain one or more minerals.

Rock Types: Rocks are any material that make up a large, natural, continuous part of the earth’s crust. May contain one or more minerals.

Igneous (granite, lava)Igneous (granite, lava)

Sedimentary (limestone, sandstone)Sedimentary (limestone, sandstone)

Metamorphic (marble, slate)Metamorphic (marble, slate)

Soils: Formation Soils: FormationSoil: a complex mixture of eroded rock mineral

nutrients, decaying organic matter, water, air and billions of living organisms, mostly of the microscopic decomposers.

Soil Composition: Characteristics of the soil depend on the characteristics of the “parent rock” it is formed from. The soil forms distinct layers over time, creating a soil profile.

Soil: a complex mixture of eroded rock mineral nutrients, decaying organic matter, water, air and billions of living organisms, mostly of the microscopic decomposers.

Soil Composition: Characteristics of the soil depend on the characteristics of the “parent rock” it is formed from. The soil forms distinct layers over time, creating a soil profile.

Soils: Formation Soils: FormationSoil horizons: mature soil is arranged in a

series of zones called soil horizons. Each has a very distinct texture and composition that varies with different types of soils.

Soil horizons: mature soil is arranged in a series of zones called soil horizons. Each has a very distinct texture and composition that varies with different types of soils.

Soil profile: cross sectional view of the horizons in a soil. Most mature soils have at least 3 horizons of the possible horizons.

OABC Layers

Soil profile: cross sectional view of the horizons in a soil. Most mature soils have at least 3 horizons of the possible horizons.

OABC Layers

Soils: Formation Soils: Formation Soil Horizon O: Surface litter layer, consists mostly of

freshly fallen and partially decomposed leaves, twigs, animal waste, fungi and other organic materials.

Soil horizon A: Topsoil layer, a porous mixture of partially decomposed organic matter called humus. Animals that live in the soil inhabit this layer. Usually darker and looser than deeper layers. A fertile soil will have a thick topsoil with lots of humus.

Soil Horizon O: Surface litter layer, consists mostly of freshly fallen and partially decomposed leaves, twigs, animal waste, fungi and other organic materials.

Soil horizon A: Topsoil layer, a porous mixture of partially decomposed organic matter called humus. Animals that live in the soil inhabit this layer. Usually darker and looser than deeper layers. A fertile soil will have a thick topsoil with lots of humus.

B and C horizons: inorganic matter and broken-down rock. Layer C is partially weathered bedrock.

B and C horizons: inorganic matter and broken-down rock. Layer C is partially weathered bedrock.

O HorizonOrganic

A horizonTopsoil

B horizonSubsoil

C horizonParent

material

Mature soil

RegolithRegolith

BedrockBedrock

Immature soil

Soil Properties

Infiltration: When water percolates downward through the soil through the pores.

Infiltration: When water percolates downward through the soil through the pores.

Leaching: During the percolation the water dissolves various soil components in the upper layers and carries them to the lower layers.

Leaching: During the percolation the water dissolves various soil components in the upper layers and carries them to the lower layers.

Soil Properties

Texture: the relative amounts and types of mineral particles. (clay, silt, sand, and gravel)

Loams: are a roughly equal mixture of all the above.

Texture: the relative amounts and types of mineral particles. (clay, silt, sand, and gravel)

Loams: are a roughly equal mixture of all the above.

Structure: ways soil particles are organized and clumped together.

Structure: ways soil particles are organized and clumped together.

Soil Properties

Porosity: determined by soil texture, it measures the volume of pores or spaces per volume of soil and the average distances between those spaces.

Porosity: determined by soil texture, it measures the volume of pores or spaces per volume of soil and the average distances between those spaces.

pH: Measures alkalinity or acidity of soil and influences the uptake of nutrients by plants. To correct soil that is too acidic, add lime. When too alkaline add sulfur.

pH: Measures alkalinity or acidity of soil and influences the uptake of nutrients by plants. To correct soil that is too acidic, add lime. When too alkaline add sulfur.

Permeability: the rate at which water an d air move from upper to lower soil layers. Influenced by the average size of the pores and the soil structure.

Permeability: the rate at which water an d air move from upper to lower soil layers. Influenced by the average size of the pores and the soil structure.

Soil Profiles for Different Biomes

Climate determines the weathering processes and because of this soil formation.

1.Tropical Soils: lots of rain and high temperatures lead to chemical weathering, developing thick soils rapidly. Contain iron and aluminum, which do not dissolve easily. Lots of leaching of top soil from heavy rains lead to thin A horizon.

Form Thick, Infertile Soils

Soil Profiles for Different Biomes

2. Temperate Soils: Where there is some rainfall and temperatures range from hot to cold, there is both mechanical and physical weathering. These areas have the thickest A horizon. Form Thick, Fertile Soil

3. Desert/Arctic Soils: Little hummus in soil, as it is too cold to sustain life. There is also a very thin layer of mostly regolith from mechanical weathering.Form Thin Soil

Water Water

High permeability Low permeability

Soil and Topography

The shape of the land has an impact on soil formation. Because water washes away much of the topsoil on a slope, the most fertile soil will be at the bottom of the slope.

Lack on vegetation on slopes leads to a low production of organic matter, which forms humus. A flat area, with good drainage, provides the best service for fertile layers of soil.

Homework: Read over Chapter 14.3 by tomorrow

Answer Questions 1-9 for the Section 3 ReviewDUE MONDAY

Vocabulary Quiz Tuesday

Soils: ErosionSoils: Erosion

Sheet erosion: occurs when water moves down a slope or across a field in a wide flow and peels off fairly uniform sheets or layers of soil.

Sheet erosion: occurs when water moves down a slope or across a field in a wide flow and peels off fairly uniform sheets or layers of soil.

Rill erosion: occurs when surface water forms fast-flowing rivulets that cut small channels in the soil.

Rill erosion: occurs when surface water forms fast-flowing rivulets that cut small channels in the soil.

Gully erosion: when rivulets of fast-flowing water join together and with each succeeding rain cut the channels wider.

Gully erosion: when rivulets of fast-flowing water join together and with each succeeding rain cut the channels wider. See Fig. 10-18 p. 217See Fig. 10-18 p. 217

How Serious Is the Problem of Soil Erosion?

Causes loss of soil organic matter and vital plant nutrients

Reduced ability to store water for use by crops

Increased use of costly fertilizer to maintain soil fertility

Increased water runoff on eroded mountain slopes that can flood agricultural land and dwellings in the valleys below

Increased buildup of soil sediment in waterways and coastal areas that reduce fish production and harms other aquatic life

Increased input of sediment into reservoirs

Global Soil Erosion

Areas of serious concern

Areas of some concern

Stable or nonvegetative areasFig. 10-19 p. 218

Soil Erosion in the U.S.Erosion in the U.S. has been a major concern for years as

the farmers plowed over the fields every year at harvest and left it bare for a long period of time allowing it to be eroded mainly by wind.

Since the great Dust Bowl of the 1930’s, caused by a severe drought and over-plowing for years, the development of the Soil Conservation Service ahs made the prevention of soil erosion their top priority. (now known as the National Resources Conservation Service)

EvaporationTranspiration

Evaporation

Waterlogging

Less permeableclay layerFig. 10-22 p. 221Fig. 10-22 p. 221

Waterlogging: Large amounts of irrigation water are used to leach salts deeper into the soil. However many times the soil doesn’t have good drainage and there is an accumulation of water as the water table rises. The roots get enveloped in water and lower their productivity and killing them after prolonged exposure.

Waterlogging: Large amounts of irrigation water are used to leach salts deeper into the soil. However many times the soil doesn’t have good drainage and there is an accumulation of water as the water table rises. The roots get enveloped in water and lower their productivity and killing them after prolonged exposure.

Solutions: Soil ConservationSolutions: Soil Conservation

Conventional-tillage: Soil is plowed in the fall and left bare through winter and early spring and vulnerable to erosion

Conventional-tillage: Soil is plowed in the fall and left bare through winter and early spring and vulnerable to erosion

Conservation tillage: disturb soil as little as

possible while planting crops. Minimum tillage and no-till farming allow for the land to remain with crops residues and cover vegetation without disturbing the topsoil.

Conservation tillage: disturb soil as little as

possible while planting crops. Minimum tillage and no-till farming allow for the land to remain with crops residues and cover vegetation without disturbing the topsoil.

Soil Conservation: reducing soil erosion and restoring soil fertility. Most often done by keeping the soil covered.

Soil Conservation: reducing soil erosion and restoring soil fertility. Most often done by keeping the soil covered.

Solutions: Soil ConservationSolutions: Soil Conservation

Cropping methods: various cropping methods are used to reduce erosion, largely by working with the land and protecting the removal of topsoil. Include: terracing, contour planting, strip cropping, alley cropping, windbreaks, and gully reclamation.

Cropping methods: various cropping methods are used to reduce erosion, largely by working with the land and protecting the removal of topsoil. Include: terracing, contour planting, strip cropping, alley cropping, windbreaks, and gully reclamation.

Land Classification: classify the land to identify whether it is suitable for cultivation.

Land Classification: classify the land to identify whether it is suitable for cultivation.

Slide 32Slide 32Slide 32Slide 32Slide 32Slide 32Slide 32Slide 32Slide 32Terracing

Figure 10-26aPage 224

Slide 33Slide 33Slide 33Slide 33Slide 33Slide 33Slide 33Slide 33Slide 33

Contour planting and strip cropping Figure 10-26bPage 224

Slide 34Slide 34Slide 34Slide 34Slide 34Slide 34Slide 34Slide 34Slide 34

Alley cropping Figure 10-26cPage 224

Slide 35Slide 35Slide 35Slide 35Slide 35Slide 35Slide 35Slide 35Slide 35

Windbreaks

Figure 10-26dPage 224

Additional Soil Conservation Cropping Methods

Soil Restoration Organic fertilizer: plant and animal waste Organic fertilizer: plant and animal waste

Animal manure: from cow, goat ,chicken, horses, etc.

Animal manure: from cow, goat ,chicken, horses, etc.

Green manure: from plant wastes Green manure: from plant wastes

Spores: spores that attach to roots to help absorb nutrients

Spores: spores that attach to roots to help absorb nutrients

Crop rotation: rotate crops that deplete soil with those that conserve and add nutrients to the soil

Crop rotation: rotate crops that deplete soil with those that conserve and add nutrients to the soil

Compost: sweet dark brown humus like material rich in organic matter.

Compost: sweet dark brown humus like material rich in organic matter.

Commercial inorganic fertilizer : contain nitrogen, phosphorous and potassium. They may contain trace amounts of other required nutrients.

Commercial inorganic fertilizer : contain nitrogen, phosphorous and potassium. They may contain trace amounts of other required nutrients.

Easily transported, stored and applied. Used extensively worldwide.

Problems: •They don’t add humus to the soil•Reduce soil organic matter and ability to hold water•Lowers oxygen content and ability to take up nutrients•Not all nutrients needed are included•Lots of energy needed for production, transport and application•Increase global warming by release of N2O