earth’s resources chapter 4. energy and mineral resources renewable – replenished over fairly...
TRANSCRIPT
Earth’s Resources
Chapter 4
Energy and Mineral Resources
• Renewable – replenished over fairly short time spans (months, years, decades)– Plants, animals, natural
fibers trees, water, wind, sun
• Nonrenewable – takes millions of years to form and accumulate– Coal, oil, natural gas,
iron, copper, uranium, gold
Fossil Fuels
• Any hydrocarbon that may be used as a source of energy
– Coal, oil, natural gas1. Coal – forms when heat and pressure transform
plant material over millions of years. a. Stages:
i. Peatii. Ligniteiii. Bituminous coaliv. anthracite
Coal Continued
b. Uses:a. Power plantsb. Enormous
reserves
c. Disadvantagesa. Surface mining -
scars landb. Underground
mining - dangerous
c. Burning – produces sulfuric acid
Coal in the United States
Petroleum and Natural Gas
• Form from remains of plants and animals that were buried in ancient seas
• Steps:1. Large # of plants & animals buried in ocean-floor
sediments2. Continual sediment build-up causes organic
remains to transform into petroleum and natural gas
3. Oil and gas move into nearby rock beds4. Less dense than water – so migrate upwards
through water-filled spaces
Petroleum and Natural Gas
5. Oil trap – structure that allows large amounts of fluid to accumulate– Anticline –
uparched series of sedimentary rock layers
Tar Sands
• Tar sands – mixtures of clay and sand combined with water and black tar– Can be refined into oil– Disadvantages:
• Causes huge land disturbance
• Requires large amounts of water
• Contaminated water and sediment accumulate in toxic disposal ponds
Oil Shale• Oil Shale – rock that
contains waxy mixture of hydrocarbons called kerogen
• Processes:1. Can be mined and heated
to vaporize kerogen2. Vapor processed to remove
impurities
– Disadvantages:– Heat energy 1/8 that of
crude oil– More expensive to mine,
process, and dispose of
Formation of Mineral Deposits
• Ore – useful metallic mineral that can be mined at a profit– Natural
concentration of many minerals is small
Mineral Resources and Igneous Processes
• Igneous Processes produce deposits of:– Gold– Silver– Copper– Mercury– Lead– Platinum– Nickel
Hydrothermal Solutions
• Most form from hot, metal-rich fluids left during late stages of movement and cooling of magma
• Examples:– Gold deposits in
Homestake Mine, South Dakota
– Lead, zinc, silver ores in Idaho
Placer Deposits
• Formed when eroded heavy minerals settle quickly from moving water while less dense particles remain suspended and continue to move– Common sites: inside
bends of streams, cracks, depressions
– Sparked California gold rush
Nonmetallic Mineral Resources
• All are used for specific chemical elements or compounds
• Divided into two broad groups:– Building materials
• Crushed stone, sand, and gravel)
– Industrial minerals• Limestone• Not nearly as abundant• Require considerable processing before use
Alternate Energy Sources
• Solar Energy• Nuclear Energy• Wind Energy• Hydroelectric Energy• Geothermal Energy• Tidal Power
Solar Energy
• Direct use of the sun’s rays to supply heat or electricity– Two advantages
• “fuel” is free• Non-polluting
– Draw-backs• Equipment and
installation is not free• Supplemental energy is
needed on cloudy days, in winter, and at night
– Example: Solar collector• Passive or active
Nuclear Energy
• Fuel for nuclear plants comes from radioactive materials that release energy through nuclear fission:
1. Heavy atoms bombarded with neutrons;2. split into smaller nuclei and emit neutrons and heat
energy3. Produces a chain reaction
– Energy drives steam turbines that turn electrical generator
Nuclear Energy• Obstacles:
1. Cost of building safe facilities2. Hazards associated with disposal of nuclear wastes3. Possibility of a serious accident could allow radioactive
materials to ascape– Three Mile Island; 1979
– Substantial damage to reactor; little harm to public
– Chernobyl; 1986 – Reactor out of control; 10 days to put out fire– High levels of radioactive material as far as Norway
Wind Energy• Estimate – all winds of N.
and S. Dakota could provide 80% electrical energy in U.S.
• Wind turbines used to collect wind energy– Experiments by U.S.
Department of Energy since 1980
– Altamont Pass near San Fransisco
• Next 50-60 years: 5-10% of country’s demand
• Needs:– technical advances– Noise pollution– Cost of land
Hydroelectric Power
• Drives turbines that produce electricity• Produce about 5% of the country’s electricity• Dams – allow for controlled flow of water
– Water held in a reservoir behind a dam is a form of stored energy that can be released through the dam to produce electric power
• Disadvantages:– Sediment is deposited behind dam and builds up –
eventually fills reservoir– Availability of suitable sites
Geothermal Energy
• Harnessed by tapping natural underground reservoirs of steam and hot water– Used directly for heating
and to turn turbines to generate electric power
– First one in U.S. built in 1960
– Disadvantages• Clean, but not
inexhaustible• Cannot be recharged
Tidal Power
• Harnessed by constructing a dam across mouth of a bay or estuary in coastal areas with a large tidal range
• Strong in-and-out flow that results drives turbines and electric generators
• Is not economical if tidal range is too big or too small
Renewable Energy
• Some of the renewable energies we will look at:– Biomass– Wind– Hydroelectric– Solar– Geothermal
• Which is the most advantageous???...