Earth Systems and Resources Chapter 8

A.Earth ’ s resources were determined when the planet formed B.Minerals and elements are unevenly distributed around the globe I. General Info

C.Earth’s Layers 1. Core - the innermost zone of the planet made of nickel and iron 2. Mantle – above the core containing magma that slowly circulates in convection cells 3. Crust - the outermost layer of the planet

A.Rock cycle recycles scarce minerals and elements by constantly forming and destroying rock 1.Rock, the substance of the lithosphere, is composed of one of more minerals 2. Minerals - solid chemical substances with uniform (often crystalline) structures that form under specific conditions and pressures (e.g. pyrite, graphite, halite (NaCl), silver) II.Minerals and Elements

B.Formation of Rocks and Minerals 1. Igneous rocks a. Form directly from magma 1) Intrusive igneous - within Earth as magma cools 2) Extrusive igneous - when magma cools above Earth (ex. volcano that ejects magma out will form this ) b. Two types: 1) Basaltic rock – dark-colored; contains minerals high in concentrations of iron, magnesium, and calcium; oceanic plate crust 2) Granitic rock – lighter-colored; contains minerals high in concentrations of silicon, aluminum, potassium, and calcium; continental plate crust 3) Both types weather to form fertile soil

2. Sedimentary rocks- form when sediment such as mud, sands, or gravels are compressed by overlying sediments. 3. Metamorphic rocks- form when sedimentary, igneous or other metamorphic rocks are subjected to high temperatures and pressures

A. General Info 1. Soil is a mix of geologic and organic components 2. Medium for plant growth 3. Serves as a filter for water 4. Provides habitat for many living organisms a. Contributes greatly to biodiversity b. Soil organisms recycle organic matter 5. Serves as a filter for pollutants III.Soil

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1.Factors that determine the formation of soil: a. Parent material - the rock material from which soil is derived 1)Ex. Quartz sand gives rise to nutrient poor soil found along the Atlantic coast b. Climate - type influences soil formation 1)Soil does not develop well in below freezing temps because decomposition and water movement are slow 2)Tundra vs. rainforest B.The Formation of Soil

c. Topography - the surface and slope 1)Erosion vs. accumulation d. Organisms - plants and animals can affect soil formation 1)Remove nutrients, excrete organic acids, mix soil, etc. e. Time - the amount of time a soil has spent developing can determine soil properties

C.Soil Horizons and Properties 1.As soils form, they develop characteristic layers called horizons : a.O horizon- (organic layer) composed of the leaves, needles, twigs and animal bodies on the surface. b.A horizon- (topsoil) the zone of organic material and minerals mixed together. c.B horizon- (subsoil) composed primarily of mineral material with very little organic matter d.C horizon- (parent material) the least weathered horizon and is similar to the parent material.

2.Physical Properties of Soil a. Texture is determined by the percentage of sand, silt and clay the soil contains.

b. Porosity - how quickly the soil drains (depends on its texture) 1)Best agricultural soils are a mixture of all 3 2)Promotes balanced water drainage and retention 3)How will pollutants move through different soil types?

3.Chemical Properties of Soil a.Clay particles contribute the most because they are negatively charge and attract cations b. Cation exchange capacity (CEC) - the ability of a soil to adsorb and release cations (positively charged mineral ions) c.Soils with high CEC are desirable in agriculture d. Soil acids are generally detrimental to plant nutrition, while soil bases promote plant growth (except for Na) i.Soil bases- calcium, magnesium, potassium and sodium ii.Soil Acids- aluminum and hydrogen iii. Base saturation - the proportion of soil bases to soil acids e.All important determinants of ecosystem productivity

4.Biological Properties of Soil a.Fungi, bacteria, and protozoans account for 80-90% of biological activity in soil (detritivores ) b.Rodents, earthworms, snails, slugs, etc also contribute

D.Soil Degradation and Erosion 1.Centuries of overuse for agriculture, forestry, and other human activities has led to signification soil degradation a.Loss of some of all of soil’s ability to support plant growth 2.Major causes: a.Soil erosion (topsoil is removed) caused by intensive agricultural use and irrigation b.Compaction of soil by machines, humans, or livestock

A. General Info 1. Four elements constitute 88% of the Earth’s crust – O, Si, Al, Fe a. Average concentration of each element is called crustal abundance III.Mineral Resources

2.Ores a.Concentrated accumulations of minerals b.Economically valuable 3.Metals a.Elements that conduct electricity and heat b.Copper, nickel, aluminum, gold, etc. 4.Formed by variety of geologic processes 5.Found in small, highly concentrated amounts in “veins” or large, low concentrations called disseminated deposits 6.Global supply is unevenly distributed 7.Known quantity that can be economically recovered is a reserve

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B.Mining (two types) 1. Surface mining - removing minerals that are close to Earth ’ s surface a.Strip mining- removing strips of soil and rock to expose ore. b.Open pit mining- the creation of a large pit or hole in the ground that is visible from the surface. c.Mountain top removal- removing the entire top of a mountain with explosives. d.Placer mining- looking for metals and stones in river sediments. 2. Subsurface mining - mining for resources that are 100 m below Earth ’ s surface (e.g. coal, diamonds, gold, etc.)

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C. Mining Safety and the Environment 1.Variety of environmental impacts and human health consequences 2.Requires construction of roads = soil erosion, and waterway and habitat degradation 3.All types of mining produce tailings (unwanted waste material) that is often toxic

D. Mining Legislation 1.Early legislation promoted economic growth 2.Mining Law of 1872 allowed individuals and companies to recover ores or fuels from federal land a.Written to encourage development and settlement of US West b.Few environmental protection provisions 3.Surface Mining Control and Reclamation Act of 1977 a.Mandates that land be minimally disturbed and reclaimed afterwards 4.Clean Air Act, Clean Water Act, and Superfund Act