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I. Earth’s Resources

I. Earth’s Resources. Nonrenewable Energy Renewable Energy Conservation. I. Energy Resources. A. Nonrenewable Fossil Fuels. B. Renewable Energy. Can be replenished over fairly short time spans; months , years, or decades Energy from flowing water, wind, and the sun.

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I. Earth’s Resources

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  1. I. Earth’s Resources • Nonrenewable Energy • Renewable Energy • Conservation

  2. I. Energy Resources A. Nonrenewable Fossil Fuels B. Renewable Energy Can be replenished over fairly short time spans; months, years, or decades Energy from flowing water, wind, and the sun • Takes thousands (Catastrophism)/millions (Uniformitarianism) of years to form and accumulate • Coal, oil, and natural gas

  3. Because of a rising standard of living, the rate of energy resource use has climbed faster than the population growth(which also increases the demand for resources).

  4. A. Fossil Fuels1. Coalforms when heat and pressure transform plant material. 4 stages of development

  5. CoalFacts • As coal develops from peat to bituminous, it becomes harder and releases moreheat when burned. • Power plantsprimarily use (>70% of mined) coal to generate electricity.

  6. CoalProblems • Surface miningscars the land • Underground mininghazards of collapsing roofs and gas explosions • Burning coal pollutes the air; sulfur dioxide (SO2) sulfuric acid (H2SO4) precipitation (rain)

  7. 2. Petroleum (Oil) and Natural Gas formthe remains of plants and animals that were buried in ancient seas. • Ocean-floor sediments protects remains from oxidation and decay. Chemical reactions slowly transform organic remains into liquid and gaseous hydrocarbons (methane CH4, propane C3H8, butane C4H10, octane C8H18) which are gradually squeezed from compacting mud layers, moving into nearby permeable sandstone beds. Less dense than water, oil and natural gas migrate upward to reach the surface.

  8. An oil trap (impermeable cap rock-anticline) keeps oil and gas from escaping from reservoir rock. c. When a drill punctures the cap rock, pressure is released, and a pump lifts petroleum out of the hole.

  9. B. Renewable Energy • Solarenergy is the direct use of the sun’s rays to supply heat or electricity (it’s free and non-polluting). • Passive solar collectors; south-facing windows • Active solar collectors; large roof-mounted devices (blacked boxes covered w/glass or plastic) Collected heat is transferred to needed areas by circulating air or liquids through piping. • Photovoltaic cells

  10. 2. Nuclear fuel comes from radioactive materials that release energy through nuclear fission. • The nuclei of heavy atoms such as uranium-235 (stable as lead-206) are bombarded w/neutrons, splitting into smaller nuclei, emitting heat energy and neutrons (an uncontrolled chain reaction could lead to an atomic explosion). • In a nuclear power plant, neutron-absorbing control rods are moved into and out of the reactor. Heat energy drives steam turbines that turn electrical generators.

  11. 3. Wind energy has been used for centuries to power sailing ships and windmills for grinding grains. • In 1980, following the “energy crisis” brought about by the oil embargo, the U.S. Dept. of Energy set up experimental wind farms in mountain passes (Altamont pass near San Francisco) w/strong, steady wind. • Obstacles include noise pollution, and the cost of large tracts of land in populated areas.

  12. 4. Hydroelectric Power-the energy of falling water drives turbines that produce electricity • For centuries, the mechanical energy that waterwheels produce has powered mills and other machinery. • The water held in a reservoir behind a dam is a form of stored (potential) energy that can be released. Dams allow for a controlled water flow. • Rivers deposit sediment behind the dam, which eventually fills the reservoir (finite lifetime). • The availability of suitable sites w/significant height and a high rate of flow is an important limiting factor.

  13. 5. Geothermal (clean) energy is harnessed by tapping natural underground reservoirs of steam and hot water. • Reservoirs occur where subsurface temperatures are high due to recent volcanic activity. • The 1st commercial geothermal power plant in the U.S. was built in 1960 at The Geysers, an important source of electrical power for San Francisco and Oakland. • Volcanically heated reservoirs cannot often be recharged after being pumped.

  14. 6. Tidalpower-energy production from the ocean • Beginning in the 12th century, tides drove water wheels that powered gristmills and sawmills. • Tidal power is harnessed by constructing a dam across the mouth of a narrow enclosed bay or estuary in coastal areas w/a large(8 meter) tidal range.

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