Transcript Powerpoint Presentation Physical Geology, 10/e

Lecture Outlines
Physical Geology, 10/e
Plummer, McGeary &
Carlson
Geologic Resources
Physical Geology 10/e, Chapter 21
Steve Kadel, Glendale Community College
Geologic Resources and
Earth’s Systems
• Geologic resources are valuable materials of geologic
origin that can be extracted from the Earth
– Many geologic resources originate in the hydrosphere
• Petroleum and coal come from organisms that lived and died in water
• Halite (salt) and other evaporite minerals come from dry lake beds
– Weathering interactions between geosphere, atmosphere and
hydrosphere produce metal oxide ores
– Humans (biosphere) interact directly with the geosphere, the
hydrosphere, and the atmosphere when extracting and
utilizing resources
– Even water, when found beneath the Earth’s surface, is a
geologic resource (renewable)
Types of Geologic Resources
• Geologic resources can be grouped into three
major categories:
– Energy resources - petroleum (oil and natural
gas), coal, uranium, geothermal resources
– Metals - iron, copper, aluminum, lead, zinc,
gold, silver, platinum, etc.
– Non-metallic resources - sand and gravel,
limestone, building stone, salt, sulfur, gems,
gypsum, phosphates, etc.
• Groundwater is included in this category
Resources and Reserves
• Resources - the total amount of
a valuable geologic material in
all deposits, discovered and
undiscovered
• Reserves - discovered deposits
of geologic resources that can
be extracted economically and
legally under present conditions
– The short-term supply of a
geologic materials
Energy Resources
• Fossil fuels (oil, natural gas, and coal)
account for nearly 90% of U.S. energy
• Petroleum - oil and natural gas - occurs in oil
pools (valuable underground accumulations)
• Occurrence of oil pools requires:
– A source rock (rich in organic matter)
– A reservoir rock in which it can be stored and
transmitted (e.g., sandstone)
– An oil trap (set of conditions holding rock in
reservoir rock and preventing migration)
– Deep enough burial (and sufficient time) to
“cook” the oil and gas out of the organic matter
Oil traps
Petroleum Recovery
• Oil fields are regions underlain
by one or more oil pools
– Largest in U.S. are in Texas and Alaska
• Oil and natural gas are removed from
the ground through wells that are
drilled down into a reservoir rock
within a trap
• Negative environmental effects
resulting directly or indirectly from oil
recovery and transport include oil
spills, brine contamination of surface
water, and ground subsidence
Petroleum Reserves
• At current rate of use, worldwide oil
reserves should last about 35 to 40 years,
and natural gas reserves somewhat longer
• As petroleum prices rise, alternate
petroleum sources, such as heavy
crude, oil shale and oil sand, will
be increasingly exploited
– Heavy crude is dense, viscous petroleum
– Oil shale is a black or brown shale with a
high solid organic matter content from which
oil can be extracted by distillation
– Oil sands (or tar sands) are asphalt-cemented
sand or sandstone deposits
Coal
• Coal is a sedimentary rock that
forms from the compaction of
plant material that has not
completely decayed
– Forms from shallow burial and
compaction of peat
– Occurs in beds ranging from a few
centimeters to thirty meters thick
– Primary use in U.S. is for
generating electricity
Coal
• Four varieties of coal are lignite, subbituminous, bituminous, and anthracite
– Lignite (brown coal) is soft and crumbly
– Sub-bituminous and bituminous coal (soft coal)
are black and dusty; burn with a smoky flame
• Often strip-mined
– Anthracite (hard coal) is shiny and dust-free;
burns with a smokeless flame; low-level
metamorphic rock
• Burning of high-sulfur coal can produce
acid rain; strip mines can scar landscape
• U.S. has coal reserves than could last
for centuries
Other Energy Resources
• The metal uranium is used to power nuclear power generators
– Typically found in association with organic matter in sedimentary rocks
– Accounts for 10% of U.S. energy production
– Leaves radioactive waste as by-product
• Hydroelectric power provides about 4% of the energy needs of
the United States
– Renewable and non-polluting
• Geothermal power provides about 0.2% of U.S. energy needs, but
could be greatly expanded with new techniques
• Other renewable and non-polluting sources include wave/current
power, solar power, wind power, and hydrogen fuel cells
– As fossil fuel supplies dwindle, these sources will become more important
Metals and Ores
• Metal ores are naturally occurring
materials that can be profitably mined
• Whether or not a mineral deposit is
considered an ore depends on its
chemical composition, percentage of
extractable metal, and the current
market value of the metal
• Metallic ore deposits can originate by
crystal settling in igneous intrusions,
from hydrothermal fluids cooling in
pores and factures, by chemical
precipitation in surface or groundwater,
or by river sedimentation (placers)
Mining and Metals
• Mining can be carried out on Earth’s
surface (strip mines, open-pit mines,
and placer mines) or underground
– Metals mined using these techniques
include iron, copper, aluminum, lead,
zinc, silver, gold and many others
• With care, negative environmental
effects of mining, including unsightly
tailings piles, surface scars, land
subsidence, and acid mine drainage
can be minimized
Non-metallic Resources
• Non-metallic resources are those that
are not mined to extract a metal or as a
source of energy
– Such resources are used for construction
materials (sand, gravel, limestone, and
gypsum), agriculture (phosphate, nitrate
and potassium compounds), industrial uses
(rock salt, sulfur, asbestos), gemstones
(diamonds, rubies), and for manufacture of
household and business products (glass
sand, fluorite, diatomite, graphite)
• If it can’t be grown, it must be mined
End of Chapter 21