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Environmental Science AP - Chapter 20 Study Guide


  1. Environmental impacts of extracting, processing, and using mineral resources

    The 1872 mining law allows a person or corporation to acquire ownershp of any public land not classified as either wilderness or a park by "patenting" it as follows.

    The mining law can be reformed by:

  2. soil horizons
    Horizontal zones that make up a particular mature soil. Each horizon has a distinct texture and composition that varies with different types of soil.
    O horizon (surface-litter layer)
    freshly fallen and partially decomposed organic material
    A horizon (topsoil layer)
    porous mixture of partially decomposed organic matter (humus) and some loose inorganic particles. Usually darker and looser than deeper layers. Most plant roots don't extend beyond this layer.
    B horizon (subsoil)
    varying mixtures of sand, silt, clay, and gravel
    C horizon (parent material)
    mostly broken down rock; rests on unweathered parent rock called bedrock

    Common Soil Profiles

    Desert Soil

    hot, dry climate

    1. closely packed pebbles, boulders
    2. weak humus-mineral mixture
    3. dry, brown to reddish-brown with variable accumulations of clay, calcium carbonate, and soluble salts
    4. deposits from eroded uplands

    Grassland Soil

    semiarid climate

    1. alkaline, dark, and rich in humus
    2. clay, calcium compounds

    Tropical Rain Forest Soil

    humid, tropical climate

    1. acidic, light-colored humus
    2. iron and aluminum compounds mixed with clay

    Deciduous Forest Soil

    humid, mild climate

    1. forest litter and leaf mold
    2. humus-mineral mixture
    3. light, grayish-brown, silt loam
    4. dark brown firm clay
    5. glacial deposits

    Coniferous Forest Soil

    humid, cold climate

    1. acid litter and humus
    2. light-colored and acidic topsoil
    3. humus and iron and alumium compounds
  3. loam
    Soil containing a mixture of clay, sand, silt, and humus. good for growing most crops.
    sandy soil
    Soil containing notably more sand. Sandy soils are easy to work, but water flows rapidly through them.
    clay soil
    Soil with very small, easily compacted particles; form large, dense clumps when wet. Clay soils are more porous and hold water better than sandy soils, but have low permeability (small pores).
    Fine soil particles
    soil porosity
    Percentage of space in rock or soil occupied by voids whether the voids are isolated or connected.
    soil permeability
    Rate at which water and air move from upper to lower soil layers.
    Soil Texture Nutrient-Holding Capacity Water-Infiltration Capacity Water-Holding Capacity Aeration Workability
    Clay Good Poor Good Poor Poor
    Silt Medium Medium Medium Medium Medium
    Sand Poor Good Poor Good Good
    Loam Medium Medium Medium Medium Medium

    A high or low ph affects the plants' ability to take up nutrients. Humus helps retain water and water-soluble nutrients, which can be taken up by plant roots.

  4. Wind and, more commonly, water erode the soil, often pouring it into waterways. The loss of topsoil results in less fertile land and the eroded sediment, the largest source of water pollution, clogs the waterways. The water becomes cloudy, fish die, and flood risk increases. If soil erodes faster than it is formed, it becomes a nonrewable resource. Annual erosion rates for farmlands around the world are 7-100 times the natural renewal rate. We are losing 7% of our topsoil each decade; this has slowly disastrous effects on agriculture. In the US, the Dust Bowl years spurred government action to promote soil conservation. However, while this has improved the situation somewhat, it's still dire: we have lost large percentages of our topsoil over the years, and are losing vast amounts each year.

    People are not aware of soil erosion because it is such a gradual process.

  5. desertification
    Conversion of rangeland, rain-fed cropland, or irrigated cropland to desertlike land, with a drop in agricultural productivity of 10% or more. It is usually caused by a combination of overgrazing, soil erosion, prolonged drought, and climate change.