Upload
trinhtruc
View
219
Download
6
Embed Size (px)
Citation preview
9/3/2014 MindTap - Cengage Learning
http://ng.cengage.com/static/nb/ui/index.html?nbId=49852&nbNodeId=9252906#!&parentId=9252912 1/55
Chapter 5: Geologic Resources Chapter Contents
Book Title: Earth
Printed By: Kevin Murray ([email protected])
© 2015, 2011 Cengage Learning, Cengage Learning
5
Geologic Resources
Chapter Introduction
5-1 Mineral Resources
5-2 Ore and Ore Deposits
5-2a Magmatic Processes
5-2b Hydrothermal Processes
5-2c Sedimentary Processes
5-2d Weathering Processes
5-3 Mineral Reserves vs. Mineral Resources
5-3a The Geopolitics of Metal Resources
5-4 Mines and Mining
5-5 Energy Resources: Coal, Petroleum, and Natural Gas
5-5a Coal
5-5b Petroleum
5-5c Natural Gas
5-6 Unconventional Petroleum and Gas Reservoirs
5-6a Coal Bed Methane
5-6b Tar Sands
5-6c Oil Shale
5-7 Energy Resources: Nuclear Fuels and Reactors
5-8 Energy Resources: Renewable Energy
5-8a Solar Energy
5-8b Wind Energy
5-8c Geothermal Energy
5-8d Hydroelectric Energy
5-8e Biomass Energy
9/3/2014 MindTap - Cengage Learning
http://ng.cengage.com/static/nb/ui/index.html?nbId=49852&nbNodeId=9252906#!&parentId=9252912 2/55
5-8f The Future of Renewable Energy Resources
5-9 Conservation as an Alternative Energy Resource
5-9a Technical Solutions
5-9b Social Solutions
5-10 Energy for the st Century
Chapter Review
Key Terms
Chapter Review
Review Questions
Chapter 5: Geologic Resources Chapter Introduction
Book Title: Earth
Printed By: Kevin Murray ([email protected])
© 2015, 2011 Cengage Learning, Cengage Learning
Chapter Introduction
The Maersk Developer, a semisubmersible deepwater drilling platform on its
maiden voyage from Singapore. This platform is capable of drilling in water depths
of kilometers and is currently deployed in the Gulf of Mexico.
9/3/2014 MindTap - Cengage Learning
http://ng.cengage.com/static/nb/ui/index.html?nbId=49852&nbNodeId=9252906#!&parentId=9252912 3/55
COURTESY OF MAERSK DRILLING
Fertile soil, level plains, easy passage across the mountains, coal, iron, and other metals
imbedded in the rocks, and a stimulating climate, all shower their blessings upon man.
Ellsworth Huntington
Since humanlike creatures emerged to million years ago, our use of geologic resources
has become increasingly sophisticated. Early hominids used sticks and rocks as simple
weapons and tools. Later prehistoric people used flint and obsidian to make more-effective
weapons and tools, and they used natural pigments to create elegant art on cave walls.
About 8000 BCE (Before Common Era), people learned to shape and fire clay to make
pottery. Archaeologists have found copper ornaments in Turkey dating from 6500 BCE;
years later, Mesopotamian farmers used copper farm implements. Today, geologic
resources provide iron for steel, silicon for making computer chips, and gasoline that
powers most cars.
9/3/2014 MindTap - Cengage Learning
http://ng.cengage.com/static/nb/ui/index.html?nbId=49852&nbNodeId=9252906#!&parentId=9252912 4/55
We use two types of geologic resources: mineral resources (Economically valuable
geological materials including both metal ore and nonmetallic minerals.) and energy
resources (Geologic resources—including petroleum, coal, natural gas, and nuclear fuels—
used for heat, light, work, and communication) Mineral resources include all useful rocks
and minerals. As we will see in the sections that follow, many mineral resources are
naturally concentrated by processes that involve interactions among rock of the geosphere,
atmospheric gases, and water from the hydrosphere. Humans have mined and refined
these resources further to create the industrial world that has altered our planet. The
primary energy resources of the early st century are coal, petroleum, and natural gas—
all formed from the decayed remains of prehistoric plants and animals that have been
altered by Earth systems processes.
Chapter 5: Geologic Resources: 5-1 Mineral Resources
Book Title: Earth
Printed By: Kevin Murray ([email protected])
© 2015, 2011 Cengage Learning, Cengage Learning
5-1 Mineral Resources
Mineral resources include both metal ore and nonmetallic minerals. Recall from Chapter 2
that ore is rock sufficiently enriched in one or more minerals to be mined profitably.
Geologists usually use the term to refer to metallic mineral deposits, and it is commonly
accompanied by the name of the metal—for example, iron ore or silver ore.
Nonmetallic mineral resources (Economically useful rocks or minerals that are not
metals; examples include salt, building stone, sand, and gravel) refers to the useful rocks or
minerals that are not metals—such as salt, building stone, sand, and gravel. When we think
about “striking it rich” from mining, we usually think of gold. However, despite the recent
historically high price of gold, more money was made in the United States in the year 2010
from mining and selling sand, gravel, and crushed stone ($ billion in estimated
revenue) than from gold ($ billion in estimated revenue). Sand and gravel are mined
from stream and glacial deposits, sand dunes, and beaches, whereas crushed stone is
quarried from nonweathered igneous, metamorphic, or sedimentary bedrock. These
nonmetallic resources are mixed with portland cement—a material produced by heating a
mixture of crushed limestone and clay—to make concrete. Reinforced with steel, concrete is
used to build roads, bridges, and buildings. Thus, reinforced concrete is one of the basic
building materials of the modern world. In addition, many buildings are faced with stone—
usually granite or limestone. Marble, slate, sandstone, and other rocks used for building are
also mined from quarries cut into bedrock (Figure 5.1).
Figure 5.1
A quarryman in China splits a large granite block with a sledgehammer. After he
splits the rock, the circular saws in the background will cut it into thin slabs for
floors and walls.
9/3/2014 MindTap - Cengage Learning
http://ng.cengage.com/static/nb/ui/index.html?nbId=49852&nbNodeId=9252906#!&parentId=9252912 5/55
COURTESY OF GRAHAM R. THOMPSON/JONATHAN TURK
There are many important metals and other elements that are fundamental parts of our
lives and of the industries that produce a range of products in daily use. Some of these
metals are familiar to us, such as iron, lead, copper, aluminum, silver, and gold. Others are
less well known, such as molybdenum (rifle barrels), tungsten (lightbulb filaments), and
borax (soaps, antiseptics).
All mineral resources are nonrenewable: we use them up at a much faster rate than
natural processes create them, although many can be recycled.
Chapter 5: Geologic Resources: 5-2 Ore and Ore Deposits
Book Title: Earth
Printed By: Kevin Murray ([email protected])
© 2015, 2011 Cengage Learning, Cengage Learning
5-2 Ore and Ore Deposits
If you pick up any rock and send it to a laboratory for analysis, the report will probably
show that the rock contains measurable amounts of iron, gold, silver, aluminum, and other
valuable metals. However, the concentrations of these metals are so low in most rocks that
the extraction cost would be much greater than the income gained by selling the refined
metals. In certain locations, however, natural geologic processes have enriched metals
many times above their normal concentrations. Table 5.1 shows that the concentration of a
metal in ore may exceed its average abundance in ordinary rock by a factor—called the
enrichment factor—of more than .
Table 5.1
Comparison of Concentrations of Specific Elements in Earth’s Crust with
9/3/2014 MindTap - Cengage Learning
http://ng.cengage.com/static/nb/ui/index.html?nbId=49852&nbNodeId=9252906#!&parentId=9252912 6/55
Concentrations Needed to Operate a Commercial Mine
Element Natural
Concentration
in Crust (% by
Weight)
Concentration
Required to Operate a
Commercial Mine (%
by Weight)
Enrichment Factor
Aluminum to to
Iron to
Copper to to
Nickel
Zinc
Uranium
Lead
Gold
Mercury
© Cengage Learning
Successful exploration for new ore deposits requires an understanding of the processes that
concentrate metals to form ore. For example, platinum concentrates in certain types of
igneous rocks. Therefore, if you were exploring for platinum, you would focus on those
rocks rather than on sandstone or limestone.
With the exception of magmatic processes, which occur deep within the crust, the natural
processes that concentrate ore minerals all involve interactions of rocks and minerals of the
geosphere with water from the hydrosphere. The more common ore-forming processes are
described below.
Chapter 5: Geologic Resources: 5-2a Magmatic Processes
Book Title: Earth
Printed By: Kevin Murray ([email protected])
© 2015, 2011 Cengage Learning, Cengage Learning
5-2a Magmatic Processes
9/3/2014 MindTap - Cengage Learning
http://ng.cengage.com/static/nb/ui/index.html?nbId=49852&nbNodeId=9252906#!&parentId=9252912 7/55
Magmatic processes (Geologic processes that form ore deposits as liquid magma solidifies
into igneous rock.) form mineral deposits as liquid magma solidifies to form an igneous
rock. These processes create metal ores as well as some gems and nonmetallic mineral
deposits including sulfur deposits and building stone.
Some large bodies of plutonic igneous rock, particularly those of mafic (high in magnesium
and iron) composition, solidify in layers (Figure 5.2). Each layer contains different minerals
and is of a different chemical composition than adjacent layers. Some of the layers may
contain rich ore deposits. The layering can develop by at least two processes:
1. Cooling magma does not solidify all at once. Instead, higher-temperature minerals
crystallize first, and lower-temperature minerals form later as the magma cools and
the temperature drops. Most minerals are denser than magma. Consequently, early-
formed crystals may sink to the bottom of a magma chamber in a process called
crystal settling (A process in which the crystals that solidify first from a cooling
magma settle to the bottom of the magma chamber because the minerals are more
dense than magma; the ultimate result is a layered body of igneous rock, each layer
containing different minerals.) . In some instances, ore minerals crystallize with
other early-formed minerals and accumulate in layers near the bottom of a pluton.
2. Some large bodies of mafic magma crystallize from the bottom upward. Thus, early-
formed ore minerals become concentrated near the base of the pluton.
Figure 5.2
An outcrop of layered mafic igneous rock from the Bushveld intrusion in South
Africa. The dark layers are made of chromite crystals that settled to the bottom of
the magma chamber more rapidly than the lower-density feldspar, making up the
lighter-colored layers. The layering itself is interpreted to reflect multiple injections
of magma into the magma chamber.
9/3/2014 MindTap - Cengage Learning
http://ng.cengage.com/static/nb/ui/index.html?nbId=49852&nbNodeId=9252906#!&parentId=9252912 8/55
PHOTOGRAPH COURTESY OF JOHN DILLES
The largest ore deposits found in layered mafic plutons are the rich chromium and
platinum reserves of South Africa’s Bushveld intrusion. The pluton is about by
kilometers in area—roughly the size of the state of Maine—and about kilometers thick.
The Bushveld deposits contain more than billion tons of chromium and more than
billion grams of platinum, the greatest reserves in any known deposit on Earth. The
platinum alone is worth over $ billion at 2013 prices.
Chapter 5: Geologic Resources: 5-2b Hydrothermal Processes
Book Title: Earth
Printed By: Kevin Murray ([email protected])
© 2015, 2011 Cengage Learning, Cengage Learning
5-2b Hydrothermal Processes
Hydrothermal processes (Geologic processes in which hot water or steam dissolves
metals and minerals from rocks or magma; the solutions then seep through cracks before
cooling, to create ore deposits.) —hydro for “water” and thermal for “heat,” involving
interactions between hot water or steam and rocks or minerals—are probably responsible
for the formation of more ore deposits, and a larger total quantity of ore, than all other
processes combined. To form a hydrothermal ore deposit, hot water dissolves metals from
rock or magma. The metal-bearing solutions then seep through cracks or through
permeable rock, where they precipitate to form an ore deposit.
9/3/2014 MindTap - Cengage Learning
http://ng.cengage.com/static/nb/ui/index.html?nbId=49852&nbNodeId=9252906#!&parentId=9252912 9/55
Although water by itself is capable of dissolving minerals, most hydrothermal waters also
contain dissolved salts. The presence of the salts greatly increases the water’s ability to
dissolve minerals. Therefore, hot, salty, hydrothermal water is a very powerful solvent,
capable of dissolving and transporting metals.
Hydrothermal water comes from three sources—granitic magma, groundwater, and the
oceans:
1. Granitic magma contains more dissolved water than solid granite rock. Thus, the
magma gives off hydrothermal water as it solidifies. Because many ore metals do not
fit neatly into the crystal structure of silicate minerals that form from a cooling
granitic magma, these elements become concentrated in the hydrothermal waters.
2. Groundwater can seep into Earth’s crust, where it is heated and forms a
hydrothermal solution. The solution circulates through rock in the crust and dissolves
ore metals, which later precipitate in concentrated form elsewhere. This scenario is
common in volcanic areas where hot rock or magma heat groundwater at shallow
depths.
3. In the oceans, hot, young basalt at a mid-oceanic ridge heats seawater as it seeps into
cracks in the seafloor.
Refer again to Table 5.1, which shows that tiny amounts of all metals are found in average
rocks of the Earth’s crust. For example, gold makes up percent of the crust,
while copper makes up percent and lead percent. Although the metals are
present in very low concentrations in country rock, hydrothermal solutions percolate
through vast volumes of rock, dissolving or scavenging (The process by which
hydrothermal fluids sweep through large volumes of country rock and dissolve low
concentrations of metals, concentrating them elsewhere as an ore deposit.) the metals and
carrying them in solution. Where they encounter changes in temperature, pressure, or
chemical environment, the solutions then can deposit the metals to form a local ore deposit,
(Figure 5.3).
Figure 5.3
Hot water scavenges metals from crystallizing igneous rock and the country rock
that surrounds it. The hydrothermal water then deposits metallic minerals in ore-
rich veins that fill fractures in bedrock. It also deposits low-grade disseminated
metal ore in large volumes of rock surrounding the veins.
9/3/2014 MindTap - Cengage Learning
http://ng.cengage.com/static/nb/ui/index.html?nbId=49852&nbNodeId=9252906#!&parentId=9252912 10/55
© Cengage Learning
A hydrothermal vein deposit (A rich, sheetlike mineral deposit that forms when
economically-valuable minerals precipitate from hot water solutions along a fault or other
fracture.) forms when dissolved metals precipitate in a fracture in rock. Ore veins range
from less than a millimeter to several meters in width. A single vein can yield several
million dollars worth of gold or silver. The same hydrothermal solutions may also soak into
pores in country rock near the vein to create a large but much less concentrated
disseminated ore deposit (A large, low-grade hydrothermal deposit in which metal-
bearing minerals are widely scattered throughout a rock body; not as concentrated as a
hydrothermal vein.) . Because they commonly form from the same solutions, rich ore veins
and disseminated deposits are often found together. The history of many mining districts is
one in which early miners dug shafts and tunnels to follow the rich veins. After the veins
were exhausted, later miners used huge power shovels to extract low-grade ore from
disseminated deposits surrounding the veins.
In volcanically active regions of the seafloor, near a mid-ocean ridge and submarine
volcanoes, seawater circulates through the hot, fractured oceanic crust. The hot seawater
dissolves metals from the rocks and then, as it rises through the upper layers of oceanic
crust, cools and precipitates the metals to form submarine hydrothermal ore deposits
(Ore deposits that form when hot seawater dissolves metals from seafloor rocks and then,
as it rises through the upper layers of oceanic crust, cools and precipitates the metals.) .
The metal-bearing solutions can be seen today as jets of black water, called black smokers
(A jet of black water spouting from a fracture or vent in the seafloor, commonly near a
mid-oceanic ridge. The black color is caused by precipitation of fine-grained metal sulfide
minerals as the hydrothermal solutions cool on contact with seawater.) , spouting from
9/3/2014 MindTap - Cengage Learning
http://ng.cengage.com/static/nb/ui/index.html?nbId=49852&nbNodeId=9252906#!&parentId=9252912 11/55
fractures and vents in the Mid-Oceanic Ridge. The black color is caused by precipitation of
fine-grained metal sulfide minerals as the solutions cool upon contact with seawater. The
precipitating metals accumulate as chimneylike structures near the hot-water vent. Rich
ore deposits form in such environments, but the cost to operate machinery in such great
water depths is prohibitive.
Chapter 5: Geologic Resources: 5-2c Sedimentary Processes
Book Title: Earth
Printed By: Kevin Murray ([email protected])
© 2015, 2011 Cengage Learning, Cengage Learning
5-2c Sedimentary Processes
Placer Deposits
Gold is denser than any other mineral. Therefore, if you swirl a mixture of water, gold dust,
and sand in a gold pan, the gold sinks to the bottom fastest. Differential settling also occurs
in nature. Many streams carry silt, sand, and gravel with an uncommon small grain of
gold. The gold settles fastest when the current slows down. Over years, currents agitate the
sediment and the dense gold works its way into cracks and crevices in the streambed. Thus,
grains of gold concentrate in gravel as well as in cracks and potholes eroded into the
bedrock of the streambed, forming a placer deposit (A surface mineral deposit formed
along stream beds, beneath waterfalls, or on beaches when water currents slow down and
deposit high-density minerals.) (Figure 5.4). The prospectors who rushed to California in the
Gold Rush of 1849, for example, mined placer deposits in conglomerate of Eocene age there.
Figure 5.4
Placer deposits form where water currents slow down and deposit high-density
minerals.
9/3/2014 MindTap - Cengage Learning
http://ng.cengage.com/static/nb/ui/index.html?nbId=49852&nbNodeId=9252906#!&parentId=9252912 12/55
© Cengage Learning
Precipitates
Groundwater dissolves minerals as it seeps through soil and bedrock. In most
environments, groundwater eventually flows into streams and then to the sea. Some of the
dissolved ions, such as sodium and chloride, make seawater salty. In deserts, however,
playa lakes develop with no outlet to the ocean. Water flows into the lakes but can escape
only by evaporation. As the water evaporates, the dissolved salts concentrate until they
precipitate to form evaporite deposits (see Chapter 3). The composition of the salt and
specific salt minerals that form depend on the composition of dissolved ions transported to
the basin, which in turn depend upon the bedrock in the region. Evaporite deposits in desert
9/3/2014 MindTap - Cengage Learning
http://ng.cengage.com/static/nb/ui/index.html?nbId=49852&nbNodeId=9252906#!&parentId=9252912 13/55
lakes include sodium chloride (table salt), borax, sodium sulfate, and sodium carbonate.
These salts are used in the production of paper, soap, and medicines and for the tanning of
leather.
Several times during the past million years, shallow seas covered large regions of North
America and all other continents. At times, those seas were so weakly connected to the open
oceans that water did not circulate freely between seas and the oceans. Consequently,
evaporation concentrated the dissolved salts until they precipitated as marine evaporites.
Periodically, new seawater from the open ocean would replenish the shallow seas,
providing a new supply of salt. Thick marine evaporite beds, formed in this way, underlie
nearly percent of North America. Table salt, gypsum (used to manufacture plaster and
sheetrock), and potassium salts (used in fertilizer) are mined extensively from these
deposits.
Most of the world’s supply of iron is mined from sedimentary rocks called banded iron
formations (Iron-rich sedimentary rocks composed of alternating iron-rich and silica-rich
layers; source of most of the world’s supply of iron.) , which are deposits composed of
alternating iron-rich and silica-rich layers (Figure 5.7). These iron-rich rocks precipitated
from the seas between and billion years ago, as a result of rising atmospheric
oxygen concentrations.
Figure 5.7
Banded iron formations from Michigan. The iron is concentrated as iron oxide in
the metallic gray layers; the red layers are chert.
COPYRIGHT AND PHOTOGRAPH BY DR. PARVINDER S. SETHI
9/3/2014 MindTap - Cengage Learning
http://ng.cengage.com/static/nb/ui/index.html?nbId=49852&nbNodeId=9252906#!&parentId=9252912 14/55
Chapter 5: Geologic Resources: 5-2d W eathering Processes
Book Title: Earth
Printed By: Kevin Murray ([email protected])
© 2015, 2011 Cengage Learning, Cengage Learning
5-2d Weathering Processes
In environments with high rainfall, the abundant water dissolves and removes most of the
soluble ions from soil and rock near Earth’s surface. This process leaves the relatively
insoluble ions in the soil to form residual ore deposits (A mineral deposit formed from
relatively insoluble ions left in the soil near Earth’s surface after most of the soluble ions
were dissolved and removed by abundant water.) . Both aluminum and iron have very low
solubilities in water. Bauxite (A gray, yellow, or reddish-brown rock, composed of a
mixture of aluminum oxides and hydroxides, that formed as a residual deposit; the
principle source of aluminum.) , the principal source of aluminum, forms as a residual
deposit, and in some instances iron also concentrates enough to become ore. Most bauxite
deposits form in warm and rainy tropical or subtropical environments where chemical
weathering occurs rapidly. Thus, bauxite ores are common in Jamaica, Cuba, Guinea,
Australia, and parts of the southeastern United States (Figure 5.8).
Figure 5.8
This spheroidal texture is typical of bauxite, which is aluminum ore formed as a
residual soil deposit by intense tropical weathering of aluminum-rich rocks. This
bauxite is from northern Queensland in Australia. The pencil tip is pointing to
concentric layering within a spheroid that has been broken.
COPYRIGHT AND PHOTOGRAPH BY MARC S. HENDRIX
9/3/2014 MindTap - Cengage Learning
http://ng.cengage.com/static/nb/ui/index.html?nbId=49852&nbNodeId=9252906#!&parentId=9252912 15/55
Box 5.1
DiggingDeeper
Manganese Nodules
A rich source of strategically important metals rests on the deep-ocean floor
Much of the Pacific Ocean floor is covered with golf ball– to bowling ball–sized
manganese nodules (A potato-shaped rock found on the ocean floor and rich in
manganese and other metals precipitated from seawater through
biomineralization) (Figures 5.5 and 5.6). A typical nodule contains to percent
manganese, percent iron, about percent each of copper and nickel, and lesser
percentages of other metals such as cobalt, zinc, and lead. At least different
elements have been reported from manganese nodules, several of which are metals
with significant commercial and military applications. The metals are probably
introduced into seawater by volcanic activity at mid-oceanic ridges, perhaps by
black smokers. Certain specialized bacteria and algae on the seafloor are able to
precipitate or biomineralize (The process by which living organisms produce
minerals.) the metals, effectively forming a nodule seed that continues to grow as
more metals are added to its outer layers.
Figure 5.5
Manganese nodules cover large portions of the seafloor. These are from the
central North Pacific Ocean at a depth of meters.
9/3/2014 MindTap - Cengage Learning
http://ng.cengage.com/static/nb/ui/index.html?nbId=49852&nbNodeId=9252906#!&parentId=9252912 16/55
K.L. SMITH JR (MBARI) AND S.E. BEAULIEU (WHOI)
Figure 5.6
Close-up of a manganese nodule from the South Pacific Ocean Penny for
scale.
COPYRIGHT AND PHOTOGRAPH BY MARC S. HENDRIX
Hundreds of billions of tons of manganese nodules lie on the seafloor, with the
densest accumulations occurring in the Pacific Ocean. Most nodules occur at depths
of around kilometers, although some occur in water over kilometers deep and
some have been reported at less than kilometers.
9/3/2014 MindTap - Cengage Learning
http://ng.cengage.com/static/nb/ui/index.html?nbId=49852&nbNodeId=9252906#!&parentId=9252912 17/55
Since the 1970s, large-scale mining of the nodules has been discussed, although it
has never been undertaken because the costs of recovering the nodules from these
depths is prohibitive. However, the economics of mining nodules from the seafloor
is changing because of recent increases in most metals prices and the strategic
importance of the so-called rare earth elements that occur in manganese nodules.
Rare earth elements are a suite of different metals that are used in an ever-
increasing array of high-tech equipment, including lasers, fiber optics, computer
disk drives and memory chips, rechargeable batteries, X-ray tubes, certain
superconductors, and liquid crystal displays.
Because of their chemical properties, rare earth elements do not commonly
concentrate in ore bodies, are expensive to refine, and create environmental
problems when they are mined. Over the past years, mining of rare earth
elements has largely shifted to China because of lower labor costs and less
restrictive environmental regulations. As a result, China now controls the vast
majority of rare earth element production, with some estimates as high as
percent.
In 2010, China temporarily halted exports of rare earth elements to Japan.
Although the embargo was short-lived, it set off political alarms around the world.
U.S. Secretary of State Hillary Rodham Clinton called the move a “wake up call,”
because it underscored the vulnerability of the U.S. economy to disruptions in the
supply of rare earth elements.
Among the alternatives to diversifying the source of rare earth elements is large-
scale mining of manganese nodules from the deep seafloor. As a result, detailed
maps of the distribution of manganese nodules are now being rapidly developed, as
are various systems for recovering nodules profitably from the deep seafloor. One
can imagine robotic undersea video cameras locating the nodules and giant
vacuums sucking them up and lifting them to a ship. But, because the seafloor is a
difficult environment in which to operate complex machinery and the
environmental consequences of such large-scale mining are not well understood,
the question as to when the profitable harvest of manganese nodules will begin
remains unanswered.
Chapter 5: Geologic Resources: 5-3 Mineral Reserves vs. Mineral Resources
Book Title: Earth
Printed By: Kevin Murray ([email protected])
© 2015, 2011 Cengage Learning, Cengage Learning
5-3 Mineral Reserves vs. Mineral Resources
Mineral reserves (A term to describe the known supply of ore in the ground; can be used
on a local, national, or global scale.) are the known amount of ore in the ground that can
be mined profitably. Reserves represent a working inventory of an economically extractable
mineral commodity in a particular mine or on a national or global scale. Mineral
resources, described at the beginning of this chapter, are all occurrences of a mineral
9/3/2014 MindTap - Cengage Learning
http://ng.cengage.com/static/nb/ui/index.html?nbId=49852&nbNodeId=9252906#!&parentId=9252912 18/55
commodity, including those only surmised to exist, that have present or anticipated future
value.
Mining depletes mineral reserves by decreasing the amount of ore remaining in the ground,
but reserves may also increase in two ways. First, geologists may discover new mineral
deposits, thereby adding to the known amount of ore. Second, subeconomic mineral deposits
—those in which the metal is not sufficiently concentrated to be mined at a profit—can
become profitable if the price of that metal increases or if improvements in mining or
refining technology reduce extraction costs.
For example, in 1970, world copper resources, including all identified and undiscovered
sources, were estimated at billion metric tons. World reserves of copper—that portion of
copper resources that could be profitably extracted—were estimated at only million
metric tons. Between 1970 and 2010, however, improved mining techniques and rising
copper prices resulted in the production of about million metric tons of copper, nearly
percent more than the 1970 global reserve estimate. Moreover, these factors and the
discovery of new copper deposits have caused the 2010 global estimated reserve to be
million metric tons, more than double the 1970 estimate despite the past years of mining
and production.
Chapter 5: Geologic Resources: 5-3a The Geopolitics of Metal Resources
Book Title: Earth
Printed By: Kevin Murray ([email protected])
© 2015, 2011 Cengage Learning, Cengage Learning
5-3a The Geopolitics of Metal Resources
Earth’s mineral resources are unevenly distributed, and no single nation is self-sufficient in
all minerals. Moreover, as technology evolves, the value of mineral and energy resources
can change drastically. For example, salt was once used as currency. It drove the
establishment of trade routes, caused armed conflicts between the Vatican and its subjects
in Perugia (part of modern Italy) in 1540, and was at the source of a -year-long armed
struggle along the Texas-Mexican border in the 1860s and s. The discovery of large salt
deposits and development of refrigeration since then has significantly reduced the strategic
value of salt. Similarly, the discovery and refinement of large petroleum reserves has
eliminated the strategic value of whale oil.
Historically, five nations—the United States, Russia, South Africa, Canada, and Australia—
have supplied most of the mineral resources used by modern societies. However, today,
China is the world’s leading producer of many mineral resources, including aluminum,
gold, iron, lead, phosphate rock (used mainly for fertilizer), tin, tungsten and zinc. China is
also the world’s leading exporter of several mineral resources, including antimony, barite
(used in drilling muds), graphite, tungsten, and rare earth metals critical to defense and
other high-tech industries.
Although it is the lead producer and exporter of many mineral resources, China is also the
world’s largest consumer of many mineral commodities and has embarked on a strategic
policy of purchasing the rights to many large mineral deposits around the world. Today,
China’s domestic supply and demand for various mineral commodities is high enough to
9/3/2014 MindTap - Cengage Learning
http://ng.cengage.com/static/nb/ui/index.html?nbId=49852&nbNodeId=9252906#!&parentId=9252912 19/55
directly affect the world mineral markets.
Many other nations have few mineral resources. For example, Japan has almost no metal
or fuel reserves; despite its modern economy and high productivity, it relies entirely on
imports for metals and fuel.
Currently, the United States depends on dozens of other countries for the majority of its
mineral consumption. In 2010, the United States was percent dependent on imports for
as many as different mineral commodities, because we have no geologic supply of our
own. Many of these commodities are important in the high-tech, communications, and
defense industries. Examples include yttrium, essential for microwave communications
equipment; cobalt, a critical metal alloy; and vanadium, essential for the manufacture of
supercomputers. The U.S. dependence on many mineral and metal imports has caused
some politicians to seek the establishment of a strategic reserve of these commodities.
Chapter 5: Geologic Resources: 5-4 Mines and Mining
Book Title: Earth
Printed By: Kevin Murray ([email protected])
© 2015, 2011 Cengage Learning, Cengage Learning
5-4 Mines and Mining
Miners extract both ore and coal (described in the following section) from underground
mines and surface mines. A large underground mine (A mine consisting of subterranean
passages that commonly follow ore veins or coal seams.) may consist of tens of kilometers
of interconnected passages that commonly follow ore veins or coal seams (Figure 5.9). The
lowest levels may be several kilometers deep. In contrast, a surface mine (A hole excavated
into Earth’s surface for the purpose of recovering mineral or fuel resources.) is a hole
excavated into Earth’s surface. The largest human-created excavation on Earth is the open-
pit copper mine at Bingham Canyon, Utah (Figure 5.10). It is kilometers in diameter and
kilometers deep and can be seen with the unaided eye from space. Since its beginning in
1873, the mine has produced about million tons of copper, along with significant
amounts of gold, silver, and molybdenum. Most modern coal mining is done by large power
shovels that extract coal from huge surface mines (Figure 5.11).
Figure 5.9
Machinery extracts coal from an underground coal mine.
9/3/2014 MindTap - Cengage Learning
http://ng.cengage.com/static/nb/ui/index.html?nbId=49852&nbNodeId=9252906#!&parentId=9252912 20/55
Cultura Creative (RF)/Alamy
Figure 5.10
The Bingham Canyon, Utah, open-pit copper mine is the largest human-created
excavation on Earth. It is over kilometers in diameter and kilometer deep.
AGRICULTURAL STABILIZATION AND CONSERVATION SERVICE/USDA
Figure 5.11
Lignite (brown coal) being mined in Germany as a source of power.
9/3/2014 MindTap - Cengage Learning
http://ng.cengage.com/static/nb/ui/index.html?nbId=49852&nbNodeId=9252906#!&parentId=9252912 21/55
MIK LAV/ SHUTTERSTOCK.COM
In the United States, the Surface Mining Control and Reclamation Act of 1977 requires
mining companies to restore mined land so that it can be used for the same purposes for
which it was used before mining began. In addition, a tax is levied to make it possible to
reclaim land that was mined before the law was enacted. Enforcement and compliance of
environmental laws waxes and wanes with the political climate in Washington. Yet
environmental awareness has increased dramatically over the past generation, and,
overall, mining operations pollute much less today than they did years ago. One of the
big challenges for the future is to clean up old mines that were operated under lax or
nonexistent environmental regulations of the past. In the United States, more than
unrestored coal and metal surface mines cover an area of about square kilometers,
almost as large as the state of Virginia. This figure does not include abandoned sand and
gravel mines and rock quarries.
Although underground mines do not directly disturb the land surface, some abandoned
mines collapse, and occasionally buildings have sunken into the resulting holes (Figure
5.12). Over hectares ( million acres) of land in central Appalachia have settled into
underground coal mine shafts.
Figure 5.12
This house tilted and broke in half as it sank into an abandoned underground coal
mine.
9/3/2014 MindTap - Cengage Learning
http://ng.cengage.com/static/nb/ui/index.html?nbId=49852&nbNodeId=9252906#!&parentId=9252912 22/55
CHUCK MEYERS/U.S. DEPT. OF THE INTERIOR
Mining of both metal ores and coal also creates huge piles of waste rock—rock that must be
removed to get at the ore or coal or that is left over after the refining of the ore. If the
waste piles are not treated properly, rain erodes the loose rock and leaches toxic elements
such as arsenic, sulfur, and heavy metals from the piles, choking the streams with sediment
and polluting both stream water and groundwater.
Chapter 5: Geologic Resources: 5-5 Energy Resources: Coal, Petroleum, and Natural Gas
Book Title: Earth
Printed By: Kevin Murray ([email protected])
© 2015, 2011 Cengage Learning, Cengage Learning
5-5 Energy Resources: Coal, Petroleum, and Natural Gas
Coal, petroleum, and natural gas are called fossil fuels (Energy resources including
petroleum, coal, and natural gas, which formed from the partially decayed remains of
plants and animals; they are nonrenewable and unrecyclable.) because they formed from
the remains of plants and animals. Fossil fuels are not only nonrenewable, but also
unrecyclable. When a lump of coal or a liter of oil (petroleum) is burned, the energy
dissipates and is, for all practical purposes, lost. Thus, our fossil fuel supply inexorably
diminishes.
Chapter 5: Geologic Resources: 5-5a Coal
Book Title: Earth
9/3/2014 MindTap - Cengage Learning
http://ng.cengage.com/static/nb/ui/index.html?nbId=49852&nbNodeId=9252906#!&parentId=9252912 23/55
Printed By: Kevin Murray ([email protected])
© 2015, 2011 Cengage Learning, Cengage Learning
5-5a Coal
Coal (Figure 5.13) is a sedimentary rock made mostly of organic carbon—enough that the
rock will burn without refining. Coal-fired electric generating plants burn about percent
of the coal consumed in the United States and produce slightly less than percent of the
nation’s electricity. Although it is easily mined and abundant in many parts of the world,
coal emits air pollutants that can be removed only with expensive control devices. Mercury,
in particular, is released into the atmosphere mainly through coal-fired power plants.
Despite these drawbacks, coal is an abundant resource, with widespread availability
projected to last beyond the st century.
Figure 5.13
Anthracite is a hard, compact variety of coal with the highest carbon count and
lowest level of impurities of all coals.
ABUTYRIN/ SHUTTERSTOCK.COM
In North America, large quantities of coal formed during the Carboniferous Period,
between and million years ago, and later in Cretaceous and Paleocene times, when
warm, humid swamps covered broad areas of low-lying land. When plants die in forests
and grasslands, organisms consume some of the plant litter, and chemical reactions with
oxygen and water decompose the remainder. As a result, little organic matter accumulates,
except in the topsoil. In some swamps and bogs, however, plants grow and die so rapidly
that newly fallen vegetation quickly buries older plant remains. The new layers prevent
atmospheric oxygen from penetrating into the deeper layers, and decomposition stops
before it is complete, leaving brown, partially decayed plant matter called peat.
9/3/2014 MindTap - Cengage Learning
http://ng.cengage.com/static/nb/ui/index.html?nbId=49852&nbNodeId=9252906#!&parentId=9252912 24/55
Plant matter is composed mainly of carbon, hydrogen, and oxygen and contains large
amounts of water. During burial, rising pressure expels the water and chemical reactions
release most of the hydrogen and oxygen. As a result, the proportion of carbon increases
until coal forms (Figure 5.14). The grade of coal and the heat that can be recovered by
burning coal can vary considerably depending on the carbon content (Table 5.2).
Figure 5.14
Peat, lignite, and coal form as organic litter accumulates rapidly in a swamp and
does not undergo complete decay. With subsequent burial, the organic litter
compacts, expels water, and transforms to peat. With further burial and the
addition of heat, peat will transform to lignite, then bituminous coal, and finally
anthracite.
Source: Cite Stephen Greb, the Kentucky Geological Survey at The University of Kentucky.
Table 5.2
Classification of Coal by Grade, Heat Value, and Carbon Content
Type Color Water
(%)
Other Volatiles
and
Noncombustible
Compounds (%)
Carbon
(%)
Heat
Value
(BTU/lb)
Peat Brown –
Lignite Dark brown
Bituminous
(soft coal)
Black – – –
9/3/2014 MindTap - Cengage Learning
http://ng.cengage.com/static/nb/ui/index.html?nbId=49852&nbNodeId=9252906#!&parentId=9252912 25/55
Anthracite
(hard coal)
Black
© Cengage Learning
Chapter 5: Geologic Resources: 5-5b Petroleum
Book Title: Earth
Printed By: Kevin Murray ([email protected])
© 2015, 2011 Cengage Learning, Cengage Learning
5-5b Petroleum
The word petroleum (A complex liquid mixture of hydrocarbons, formed from decayed
plant and animal matter, that can be extracted from sedimentary strata and refined to
produce propane, gasoline, and other fuels. Also called crude oil or simply oil.) comes from
the Latin for “rock oil” or “oil from the earth.” Some natural oil seeps in Asia were used at
least as long ago as Alexander the Great, and oil wells in China were hand dug with bamboo
poles in 347 CE. In North America, the first commercial oil well was drilled in Titusville,
Pennsylvania, in 1859, ushering in a new energy age. Crude oil, as it is called when pumped
from the ground, is made up of thousands of different chemical compounds and ranges
widely in consistency and color. Some petroleums are brown, waxy substances that are
solid at room temperature but liquid at higher temperatures that exist within the Earth’s
crust. Some petroleums are yellowish or nearly clear liquids that resemble refined gasoline.
Most are rather thick and dark colored. Once recovered from a well, crude oil is refined to
produce propane, gasoline, heating oil, and other fuels (Figure 5.15). Petroleum also is used
to manufacture plastics, nylon, and other useful materials.
Figure 5.15
An oil refinery converts crude oil into useful products such as gasoline.
9/3/2014 MindTap - Cengage Learning
http://ng.cengage.com/static/nb/ui/index.html?nbId=49852&nbNodeId=9252906#!&parentId=9252912 26/55
COPYRIGHT AND PHOTOGRAPH BY MARC S. HENDRIX
Formation of Petroleum
Petroleum forms from the accumulation of large quantities of organic matter in muddy
sediment deposited in swamps, lakes, and marine waters. Most of the organic matter comes
from algae, plant remains, and bacteria. Over millions of years, younger sediment buries
this organic-rich mud to depths of a few kilometers, where rising temperature and pressure
convert the mud to shale. At the same time, the elevated temperature and pressure cause
the organic matter to convert to a solid organic substance called kerogen (The waxy, solid
organic material in oil shales that yields oil when the shale is heated; the precursor of liquid
petroleum.) . At temperatures ranging from to about , the kerogen breaks
down chemically, liberating small organic molecules. These organic molecules form
petroleum.
The shale or other sedimentary rock from which oil originally forms is called the
petroleum source rock (The shale or other sedimentary rock from which oil or natural
gas originates.) . With time, some of the organic molecules in the source rock are expelled
as liquid petroleum that seeps into the pore spaces in adjacent rock layers. Because
petroleum is less dense than water in the pore spaces, the petroleum rises towards the
surface through the network of pores in the rock. If it is not trapped along the way, the oil
will migrate all the way to the surface, forming a natural oil seep. The La Brea Tar Pits in
downtown Los Angeles is perhaps the most famous example of a natural oil seep. Between
and years ago, over years ago species of organisms became trapped in tar
formed from the La Brea oil seeps, died, and were preserved.
In many circumstances, migrating petroleum will not reach the surface but rather will
become trapped in a conventional petroleum reservoir (A porous, permeable
sedimentary rock that is saturated with trapped oil.) . A conventional reservoir consists of
9/3/2014 MindTap - Cengage Learning
http://ng.cengage.com/static/nb/ui/index.html?nbId=49852&nbNodeId=9252906#!&parentId=9252912 27/55
oil-saturated porous rock that is like an oil-soaked sponge (Figure 5.16). It is not an
underground pool or lake of oil. Many conventional reservoirs form when the rising oil is
trapped by an overlying layer of impermeable rock—that is, rock through which liquids do
not pass quickly because the pore spaces are too small or are otherwise big enough but not
interconnected, as with the isolated holes in Swiss cheese.
Figure 5.16
(A) Organic-rich mud accumulates in swamps, lakes, and some parts of the ocean
where low oxygen conditions prevent it from decaying quickly. (B) Younger
sediment buries the organic-rich mud. Rising temperature and pressure converts
the mud to shale, and the organic matter in it to kerogen. (C) With continued heat,
the kerogen breaks down, liberating petroleum that migrates out of the organic-
rich source rock and into adjacent layers. Once there, the petroleum rises towards
the surface until it is trapped. In this illustration, the oil is trapped where it
encounters an impermeable cap rock in the crest of a dome-like fold in the rock
layers.
9/3/2014 MindTap - Cengage Learning
http://ng.cengage.com/static/nb/ui/index.html?nbId=49852&nbNodeId=9252906#!&parentId=9252912 28/55
© Cengage Learning 2015
To extract petroleum from a conventional reservoir, an oil company drills a well into it.
After the hole has been bored, the expensive drill rig is removed and replaced by a smaller
rig that sets pipe in the borehole and perforates the pipe adjacent to oil-bearing layers so
that the oil can flow from the rock into the pipe. Following, a pump jack (The above-
ground portion of a reciprocating piston pump on an oil well.) is installed to draw the
petroleum up the pipe (Figure 5.17). Fifty years ago, many conventional reservoirs lay near
the surface and oil was easily pumped from shallow wells. But these reserves have been
largely depleted, causing many modern oil companies to seek deeper reservoir targets,
sometimes below the seafloor in water up to kilometers deep.
Figure 5.17
A pump jack extracts oil from a conventional reservoir in Alberta, Canada. This
pump jack is situated in a field of canola, a plant used to make biofuel (see
9/3/2014 MindTap - Cengage Learning
http://ng.cengage.com/static/nb/ui/index.html?nbId=49852&nbNodeId=9252906#!&parentId=9252912 29/55
“Biomass Energy” in Section 5-8).
KARL NAUNDORF/ SHUTTERSTOCK.COM
Primary recovery techniques utilize the pressure in a conventional reservoir to push oil into
the wellbore. As oil is removed, however, this pressure decreases to the point at which the
remaining oil cannot be drawn into the well bore. On average more than half of the oil in a
reservoir is too viscous to be pumped to the surface by conventional techniques and is left
behind when the oil field has “gone dry.” Additional oil can be extracted by secondary and
tertiary recovery techniques (Methods of extracting oil or natural gas by artificially
augmenting the reservoir energy or fluid composition, as by injection of water, pressurized
gas, solvents, or other fluids.) involving the injection of water, detergent, pressurized gas, or
other fluids into the reservoir. Secondary methods are employed first, and when those are
exhausted, tertiary methods are used. In one simple secondary process, water is pumped
into one well, called the “injection well.” The pressurized water floods the reservoir, driving
oil to nearby wells, where both the water and oil are extracted. At the surface, the water is
separated from the oil and reused, while the oil is sent to the refinery. One tertiary process
pumps detergent into the reservoir. The detergent dissolves the remaining oil and carries it
to an adjacent well, where the petroleum is then recovered and the detergent recycled.
Because an oil well location occupies only a few hundred square meters of land, most cause
relatively little environmental damage. However, oil companies are now extracting
petroleum from fragile environments such as the ocean floor and the Arctic tundra. To
obtain oil from the seafloor, engineers build platforms on pilings driven into the ocean floor
and mount drill rigs on these steel islands or use a drilling platform that floats but
maintains its position through powerful stabilizing motors controlled by a precise GPS
system (Figure 5.18).
9/3/2014 MindTap - Cengage Learning
http://ng.cengage.com/static/nb/ui/index.html?nbId=49852&nbNodeId=9252906#!&parentId=9252912 30/55
Figure 5.18
An offshore oil-drilling platform extracts oil from below the seafloor.
PHOTOBANK.KIEV.UA/ SHUTTERSTOCK.COM
Despite great care, accidents occur during the drilling and extraction of oil. In 2010, the
largest accidental marine oil spill in the history of the petroleum industry took place in the
Gulf of Mexico when a blowout occurred on the seafloor below the Deepwater Horizon oil
platform. The seafloor blowout caused an explosion on the drilling platform that killed
workers and injured others. For three months, oil gushed uncontrollably from the
seafloor before the well was finally capped and declared dead. By then, however, an
estimated million barrels of oil had been released into the environment. The oil spread
throughout much of the Gulf of Mexico, poisoning marine life and disrupting marine and
coastal ecosystems.
Chapter 5: Geologic Resources: 5-5c Natural Gas
Book Title: Earth
Printed By: Kevin Murray ([email protected])
© 2015, 2011 Cengage Learning, Cengage Learning
5-5c Natural Gas
Natural gas (A mixture of naturally occurring light hydrocarbons composed mainly of
methane, , that is used for home heating and cooking and to fuel large electric
9/3/2014 MindTap - Cengage Learning
http://ng.cengage.com/static/nb/ui/index.html?nbId=49852&nbNodeId=9252906#!&parentId=9252912 31/55
generation plants.) is an energy resource that forms in source rock or an oil reservoir when
crude oil is heated above during burial and causes the organic molecules to break
down to methane, , an organic molecule consisting of a single carbon atom bonded to
four hydrogen atoms. Many conventional petroleum reservoirs contain a layer of oil-
saturated rock, with a layer of gas-saturated rock above the heavier liquid petroleum. Other
conventional reservoirs are saturated only by gas.
Natural gas is used without refining for home heating and cooking and for fueling large
electrical generating plants. Because natural gas contains few impurities, it releases little
sulfur or other pollutants when it burns, although, as with all fossil fuels, combustion of
natural gas releases carbon dioxide, a greenhouse gas. This fuel has a higher net energy
yield, produces fewer pollutants, and is less expensive to produce than petroleum. At
current consumption rates, global natural gas supplies are projected to last between and
years.
Chapter 5: Geologic Resources: 5-6 Unconventional Petroleum and Gas Reservoirs
Book Title: Earth
Printed By: Kevin Murray ([email protected])
© 2015, 2011 Cengage Learning, Cengage Learning
5-6 Unconventional Petroleum and Gas Reservoirs
Today, roughly percent of energy used in the United States comes from petroleum, coal,
and natural gas, which traditionally have been the cheapest fuels. However, the price of
crude petroleum is subject to very large swings. For example, in inflation-adjusted 2011
dollars, crude oil rose from a low of $ in 1998 to a high of $ in 2008 before crashing
to $ per barrel that same year. Less than years later, in 2011, the price again had
climbed to more than $ per barrel. As of this writing (September, 2013), the price of
crude oil remains over $ per barrel.
In the past, many alternative forms of energy have been more expensive to develop than
coal or oil and gas produced from conventional reservoirs. However, the cost of producing
these alternative forms of energy has been decreasing, while the cost of producing
traditional fuels has been increasing. As a result, a major restructuring of the global energy
economy presently is underway. Many fuel sources that were uneconomical even a year
ago are now economic, particularly given the development of new technologies.
Among the biggest of the new changes in the energy economy is the production of oil and
gas from unconventional reservoir (A sedimentary rock that is capable of producing oil
with the application of special techniques, such as hydraulic fracturing.) . For example,
over the past few years in the United States, much of the exploration for oil and natural gas
has shifted towards the direct drilling of organic-rich petroleum source rocks. Previously,
these organic-rich shales were not drilled and produced directly because they are relatively
impermeable, and neither liquid hydrocarbons nor natural gas could migrate from the
rock into the wellbore quickly enough for production to be economic. Today, however,
technologic advances allow drilling rig operators to drill vertically down to near the top of
the source rock layer, then curve the wellbore degrees so that it passes horizontally
within it. After drilling a horizontal borehole for up to kilometers within the source rock
9/3/2014 MindTap - Cengage Learning
http://ng.cengage.com/static/nb/ui/index.html?nbId=49852&nbNodeId=9252906#!&parentId=9252912 32/55
layer, the drill is removed from the borehole and the source rock is hydraulic fracturing
(The process of fracturing an unconventional reservoir—usually an organic-rich shale—by
forcing large volumes of pressurized fluid into it.) , or “fracked,” by forcing large volumes
of water mixed with sand down the borehole. The water pressure fractures the source rock,
while the sand is forced into the newly created fractures, propping them open. The network
of sand-filled fractures creates a permeable system of pores that allows the petroleum in the
source rock to migrate to the wellbore, where it is pumped to the surface.
Today, many organic-rich shale units in the United States, including the Marcellus Shale in
New York and Pennsylvania, the Eagleford and Barnett Shales in Texas, and the Bakken
Shale in Montana and North Dakota are developed by direct horizontal drilling and
hydraulic fracturing. Moreover, according to the U.S. Geological Survey, roughly half of the
industrial-grade sand that is quarried in the United States today is used for hydraulic
fracturing process, providing some indication of the magnitude of this recent shift in
exploration techniques.
Chapter 5: Geologic Resources: 5-6a Coal Bed Methane
Book Title: Earth
Printed By: Kevin Murray ([email protected])
© 2015, 2011 Cengage Learning, Cengage Learning
5-6a Coal Bed Methane
Although most commercial natural gas is produced from conventional reservoirs or
through direct drilling and hydraulic fracturing of source rocks, about percent of
current U.S. gas production comes from coal seams. There, natural Earth heat and
microbial activity slowly convert buried coal to coal bed methane (Methane that is
chemically bonded to coal. The methane can be recovered by removing the groundwater
from a coal bed, which decreases the pressure and allows the methane to separate from the
coal as a gas.) , methane that is chemically bonded to coal. Coal bed methane reserves in the
United States are estimated to be more than trillion cubic feet (Tcf), roughly a -year
supply at current rates of consumption.
Most coal beds have a high capacity to store water in small voids in the coal itself. As
natural processes convert coal to methane, the gas dissolves in the groundwater within the
coal. There, the gas is kept in solution by the pressure of overlying groundwater. Natural
gas companies drill thousands of wells into the coal beds and pump the groundwater to the
surface, decreasing the pressure on the water remaining in the coal bed. The decreased
pressure allows the methane to separate from the water. It is then piped to the surface,
where it is compressed and sent to market.
Because they store so much water, coal beds are important groundwater reservoirs for
farmers and ranchers, especially in the arid and semiarid western United States, where
extensive coal bed methane development is now occurring. However, coal bed methane
development has two serious impacts on regional agriculture and ecosystems. The
extraction of so much water from the coal beds has depleted essential aquifers and lowered
the water table over large areas. Secondly, coal bed water is commonly salty. After it is
pumped to the surface, the salt water can poison streams and soils, rendering them useless
for agriculture and wildlife. State and federal regulations on water extraction and disposal
9/3/2014 MindTap - Cengage Learning
http://ng.cengage.com/static/nb/ui/index.html?nbId=49852&nbNodeId=9252906#!&parentId=9252912 33/55
methods attempt to minimize these impacts.
Chapter 5: Geologic Resources: 5-6b Tar Sands
Book Title: Earth
Printed By: Kevin Murray ([email protected])
© 2015, 2011 Cengage Learning, Cengage Learning
5-6b Tar Sands
In some regions, large sand deposits called tar sands (Sand deposits saturated with heavy
oil and an oil-like substance called bitumen.) are permeated with heavy oil and bitumen (A
thick, sticky, oil-like substance that permeates tar sands and can be converted to crude oil.) ,
a sticky, tar-like hydrocarbon. Crude oil can be obtained from both substances, but these
are too thick to be pumped and therefore require other methods of extraction.
The richest tar sands exist in Alberta (Canada), Utah, and Venezuela. In Alberta alone, tar
sands contain an estimated trillion barrels of petroleum, roughly years of U.S.
consumption at the 2010 rate. About percent of this fuel is shallow enough to be surface
mined. Tar sands are dug up and heated with steam to make the heavy oil and bitumen
fluid enough to separate from the sand. The oil and bitumen are then treated chemically
and heated to convert them to crude oil. At present, several companies mine the Alberta tar
sands profitably. Once those reserves are depleted, a portion of the deeper deposits,
comprising the remaining percent of the reserve, can be extracted using subsurface
techniques similar to those discussed for secondary and tertiary recovery.
Despite its great size, much controversy has surrounded the development of the Alberta tar
sands, because the refinement process uses water in very large volumes, which is then
expensive to clean prior to being released back into the environment. This controversy has
spilled over into the United States, where a major debate is ongoing regarding the
construction of the Keystone XL Pipeline that would connect the Alberta Tar Sands, the
currently booming oil fields in eastern Montana and western North Dakota, and refineries
on the Gulf Coast.
Chapter 5: Geologic Resources: 5-6c Oil Shale
Book Title: Earth
Printed By: Kevin Murray ([email protected])
© 2015, 2011 Cengage Learning, Cengage Learning
5-6c Oil Shale
In many parts of the world, including the United States, large quantities of organic-rich
shale exist that have not been heated enough to break down the kerogen contained in the
rock, to form petroleum. Such rock is called oil shale (A kerogen-bearing shale or fine-
grained limestone that yields liquid or gaseous hydrocarbons when heated.) (Figure 5.19). If
oil shale is mined, mixed with water, and then heated, the kerogen converts to petroleum.
In the United States, shale deposits contain the energy equivalent of up to six trillion barrels
of petroleum, enough to fuel the nation for more than years at the 2010 consumption
rate. However, with currently available technology, more energy is required to mine and
convert the kerogen in oil shale to petroleum than is generated by burning the oil, so it will
9/3/2014 MindTap - Cengage Learning
http://ng.cengage.com/static/nb/ui/index.html?nbId=49852&nbNodeId=9252906#!&parentId=9252912 34/55
be necessary for a combination of world oil price increases and technological advances in
oil shale recovery techniques to make oil shale a viable source of energy in the future.
Figure 5.19
Oil shale is an organic-rich, fine-grained sedimentary rock containing significant
amounts of kerogen. This sample is from the Eocene Green River Formation near
Rock Springs, Wyoming. Penny for scale.
COPYRIGHT AND PHOTOGRAPH BY MARC S. HENDRIX
Water consumption also is a serious problem in oil shale development. Approximately two
barrels of water are needed to produce each barrel of oil from shale. Oil shale occurs most
abundantly in the semiarid western United States. In this region, scarce water is also needed
for agriculture, domestic use, and industry.
Chapter 5: Geologic Resources: 5-7 Energy Resources: Nuclear Fuels and Reactors
Book Title: Earth
Printed By: Kevin Murray ([email protected])
© 2015, 2011 Cengage Learning, Cengage Learning
5-7 Energy Resources: Nuclear Fuels and Reactors
Nuclear fuels (Radioactive isotopes, such as those of uranium, used to generate electricity
in nuclear reactors.) are radioactive isotopes that produce heat through nuclear reactions;
the heat is used, in turn, to generate electricity in nuclear reactors. Uranium is the most
commonly used nuclear fuel. These energy resources, like mineral resources, are
nonrenewable, although uranium is abundant.
Every step in the mining, processing, and use of nuclear fuel produces radioactive wastes.
The mine waste discarded during mining is radioactive. Enrichment of the ore produces
additional radioactive waste. When a uranium nucleus undergoes fission in a reactor, it
splits into two useless radioactive nuclei that must be discarded. After several months in a
reactor, the concentration of useful uranium in the fuel rods drops until the fuel pellets are
9/3/2014 MindTap - Cengage Learning
http://ng.cengage.com/static/nb/ui/index.html?nbId=49852&nbNodeId=9252906#!&parentId=9252912 35/55
no longer viable. In some countries, these pellets are reprocessed to recover useful uranium
fuel, but in the United States this process is not economical, so the pellets are discarded as
radioactive waste.
In the early 1970s, the nuclear industry in the United States was growing rapidly, and
many energy experts predicted that nuclear energy would dominate the generation of the
country’s electric energy. These predictions have not been realized. Four factors have led to
the decline of the nuclear power industry:
1. Construction of new reactors in the United States has become so costly, in part
because of increased regulation, that electricity generated by nuclear power is more
expensive than that generated by coal-fired power plants.
2. After major accidents at Three Mile Island in the United States (1979), Chernobyl in
Ukraine (1986), and Fukushima Daiichi in Japan (2011), many people have become
concerned about safety.
3. Serious concerns remain about the safe disposal of nuclear wastes.
4. The demand for electricity has risen less than expected during the past three decades.
After the 1979 Three Mile Island nuclear accident (Figure 5.20), many plans for the
construction of new nuclear power plants were cancelled or suspended, and for years no
permits were issued for the construction of new reactors by the U.S. Nuclear Regulatory
Commission. Finally, in 2012 the Commission approved permits for four new reactors, two
at an existing nuclear power plant in Georgia and two at an existing plant in South
Carolina. Currently, the Commission is reviewing applications for new reactors at eight
existing nuclear power plants and two new locations.
Figure 5.20
The nuclear power plant at Three Mile Island in central Pennsylvania. The two
cooling towers and smaller dome-covered reactor (partly hidden from view) on the
left were permanently shut down following the 1979 accident. The reactor and
cooling towers on the right continue to operate.
9/3/2014 MindTap - Cengage Learning
http://ng.cengage.com/static/nb/ui/index.html?nbId=49852&nbNodeId=9252906#!&parentId=9252912 36/55
DOBRESUM/ SHUTTERSTOCK.COM
Elsewhere in the world, nuclear power production has risen rapidly, and the International
Atomic Energy Agency in 2010 predicted a global increase of gigawatts, or percent
more capacity, by 2020. The agency additionally predicted that worldwide, by 2020, roughly
percent of electricity would come from nuclear generation. Much of this new growth is
anticipated to be in Asia. Thus, although policymakers in the United States have largely been
reconsidering the role of nuclear power as an energy source, the overall capacity for
nuclear-generated power worldwide is likely to increase.
Chapter 5: Geologic Resources: 5-8 Energy Resources: Renewable Energy
Book Title: Earth
Printed By: Kevin Murray ([email protected])
© 2015, 2011 Cengage Learning, Cengage Learning
5-8 Energy Resources: Renewable Energy
Solar, wind, geothermal, hydroelectric, and wood and other biomass fuels are renewable—
natural processes replenish them as we use them. Although the amount of energy produced
today by renewable sources is small compared to that provided by fossil and nuclear fuels,
renewable resources have the potential to supply all of our energy needs. As the prices of
conventional fossil fuels have risen along with worldwide energy demand, some renewables
have become economical. Except for biomass fuels, renewable energy sources emit no
carbon dioxide and therefore do not contribute to global warming.
Chapter 5: Geologic Resources: 5-8a Solar Energy
Book Title: Earth
Printed By: Kevin Murray ([email protected])
© 2015, 2011 Cengage Learning, Cengage Learning
9/3/2014 MindTap - Cengage Learning
http://ng.cengage.com/static/nb/ui/index.html?nbId=49852&nbNodeId=9252906#!&parentId=9252912 37/55
5-8a Solar Energy
Current technologies allow us to use solar energy in three ways: passive solar heating,
active solar heating, and electricity production by solar cells.
A passive solar house is built to absorb and store the Sun’s heat directly. In active solar
heating systems, solar thermal collectors absorb the Sun’s energy and use it to heat water.
Pumps then circulate the hot water through radiators to heat a building, or the inhabitants
use the hot water directly for washing and bathing.
A solar cell (A device that produces electricity directly from sunlight; also sometimes called
a photovoltaic (PV) cell.) , or photovoltaic (PV) cell, produces electricity directly from
sunlight. A modern solar cell is a semiconductor, a device that can conduct electrical
current under some conditions but not others. Sunlight energizes electrons in the
semiconductor, producing an electric current.
Figure 5.21 shows an installation of solar panels. Although solar power still accounts for
less than percent of world energy demand, solar energy is our most abundant resource,
and PV cell production is the fastest-growing segment of the energy industry. Photovoltaic
arrays are now competitive with electricity costs during peak demand times in many desert
areas, especially those installed for single-family units. PVs are also cost-effective for
electricity needs far from existing power lines.
Figure 5.21
A Solar Farm in Germany.
9/3/2014 MindTap - Cengage Learning
http://ng.cengage.com/static/nb/ui/index.html?nbId=49852&nbNodeId=9252906#!&parentId=9252912 38/55
ANYAIVANOVA/ SHUTTERSTOCK.COM
Chapter 5: Geologic Resources: 5-8b W ind Energy
Book Title: Earth
Printed By: Kevin Murray ([email protected])
© 2015, 2011 Cengage Learning, Cengage Learning
5-8b Wind Energy
In the United States, wind energy grew percent—a ten-fold increase—in the decade
between 2001 and 2011, and now accounts for about percent of the country’s total
electricity production. The total U.S. capacity for wind-generated electricity is the second
largest in the world at about gigawatts, enough to supply electricity to about million
average U.S. households. China’s capacity at gigawatts is highest in the world, and the
average household electricity use there is much lower, so many more average households
are served by China’s wind-generated electricity than in the United States.
Wind energy production is growing rapidly because construction of wind generators is
cheaper than building new fossil fuel–fired power plants. Wind energy is also clean and
virtually limitless. Gigantic wind farms now generate electricity in Texas, California, and
other states, and wind farms are now commonplace in many parts of Europe and
elsewhere (Figure 5.22). In the United States, a huge, untapped potential for wind
generation exists in several midwestern and western states, where winds blow strongly and
almost continuously. The main drawbacks to wind energy include its inconsistency, the
conspicuous nature of the wind turbines (which some people view as unsightly), the death
of birds and bats that collide with the turbine blades, and the noise generated by the blades.
Figure 5.22
Wind turbines generate electricity in Hesse, Germany.
ANKIRO/SHUTTERSTOCK.COM
9/3/2014 MindTap - Cengage Learning
http://ng.cengage.com/static/nb/ui/index.html?nbId=49852&nbNodeId=9252906#!&parentId=9252912 39/55
Chapter 5: Geologic Resources: 5-8c Geothermal Energy
Book Title: Earth
Printed By: Kevin Murray ([email protected])
© 2015, 2011 Cengage Learning, Cengage Learning
5-8c Geothermal Energy
Energy extracted from Earth’s internal heat is called geothermal energy (Figure 5.23).
Geothermal plants typically collect underground steam from geysers, volcanoes, and hot
springs and use the steam to spin turbines, which generate electricity. Naturally hot
groundwater also can be pumped to the surface to generate electricity, or it can be used
directly to heat homes and other buildings. Alternatively, cool surface water can be pumped
deep into the ground, to be heated by subterranean rock, and then circulated to the surface
for use. The United States is the largest producer of geothermal electricity in the world, with
a production capacity of just over gigawatts.
Figure 5.23
The Wairakei geothermal power plant in New Zealand.
N.MINTON/ SHUTTERSTOCK.COM
In the United States, most geothermal plants are located in the western states, because the
region is more tectonically active and the geothermal gradient is higher. We will learn
about tectonics in Chapter 6. The oldest, and also presently the largest, steam-driven
geothermal plant in the United States is located at The Geysers, about miles north of San
Francisco. That plant alone is capable of generating gigawatts of electricity, enough for
about average U.S. households.
9/3/2014 MindTap - Cengage Learning
http://ng.cengage.com/static/nb/ui/index.html?nbId=49852&nbNodeId=9252906#!&parentId=9252912 40/55
Relative to other renewables such as wind and solar, geothermal energy can be used
hours a day, days a week, so it has a larger capacity factor (A measure of the actual to
total potential output of an energy source over a period of time) —a measure of the amount
of the actual output of energy to the total possible output over some period of time. Because
the wind does not blow all the time and the Sun does not shine all the time, these energy
sources have a lower capacity factor.
Chapter 5: Geologic Resources: 5-8d Hydroelectric Energy
Book Title: Earth
Printed By: Kevin Murray ([email protected])
© 2015, 2011 Cengage Learning, Cengage Learning
5-8d Hydroelectric Energy
If a river is dammed, the energy of water dropping downward through the dam can be
harnessed to turn turbines that produce electricity. Hydroelectric generators supply
roughly percent of the world’s electricity. In the United States, about percent of our
electricity comes from hydroelectric power.
Although hydroelectricity is renewable, it is entirely dependent on adequate runoff, and
recent climate change has caused many of the large reservoirs in the western United States
to be drawn down significantly. Inadequate runoff lowers the capacity factor of
hydroelectric generating facilities. In addition, the construction of dams and formation of
reservoirs destroys wildlife habitats, agricultural land, towns, and migratory fish
populations. For example, the dams on the Columbia River and its tributaries are largely
responsible for the demise of salmon populations in the Pacific Northwest. Undammed wild
rivers and their canyons are prized for their aesthetic and recreational value. Large dams
also are expensive to build, and few suitable sites remain.
For these reasons, the United States is unlikely to increase its production of hydroelectric
energy. In fact, many historic dams—including some with hydroelectric power–generating
capabilities—are being removed.
Chapter 5: Geologic Resources: 5-8e Biomass Energy
Book Title: Earth
Printed By: Kevin Murray ([email protected])
© 2015, 2011 Cengage Learning, Cengage Learning
5-8e Biomass Energy
Biomass (plant based) fuels provide many sources of energy. The burning of wood as a
source of heat is familiar to all of us. Today, wood and agricultural products also are
burned for the generation of steam and electricity at the industrial level. Additionally,
biomass from oil-rich plants such as canola is converted to liquid form for use as a
transportation fuel. Much research currently is being directed towards the production of
liquid fuels and other chemicals from biomass.
Biomass energy can be produced domestically in most countries, thereby creating local jobs
and reducing foreign oil imports. However, production of biofuels is not always a net
9/3/2014 MindTap - Cengage Learning
http://ng.cengage.com/static/nb/ui/index.html?nbId=49852&nbNodeId=9252906#!&parentId=9252912 41/55
energy gain; in some cases, more energy is used in the production and processing of these
fuels than can be extracted from them. In addition, burning of biomass produces carbon
dioxide, a greenhouse gas, and releases particulates and other pollutants into the
atmosphere.
Chapter 5: Geologic Resources: 5-8f The Future of Renewable Energy Resources
Book Title: Earth
Printed By: Kevin Murray ([email protected])
© 2015, 2011 Cengage Learning, Cengage Learning
5-8f The Future of Renewable Energy Resources
Aside from biofuels, none of the renewable resources discussed here can be used directly to
power cars and trucks. Several methods are available, however, to convert these energy
sources for use in transportation.
Perhaps the easiest way to use electricity to transport people and goods is the old-fashioned
electric train. Electric streetcars, commuter trains, and subways have been used for
decades. If we build more electric mass transit systems, and if people use them, we could
shift away from our dependence on the internal-combustion engine and on petroleum.
Eventually, the required electricity consumption could be supplied by renewable energy
sources.
Another solution is the electric car. Battery-only and gasoline-electric hybrid cars have seen
a recent increase in popularity and availability. If that trend continues, perhaps we can
further reduce the cost of and dependence on petroleum.
Energy planners also envision a hydrogen economy (An energy economy in which
hydrogen is used as a fuel.) , using a process in which elemental hydrogen is used as fuel. A
necessary part of this process is an electrochemical device called a fuel cell (An
electrochemical energy-conversion device that produces electricity from an external supply
of fuel, such as hydrogen.) , which uses the chemical energy of hydrogen to produce
electricity cleanly and efficiently, with water and heat as by-products. One type of fuel cell
separates hydrogen’s negatively charged electron from the hydrogen nucleus, which then
consists of a single positively charged proton. The electrons, in turn, combine with oxygen,
which then reacts with the hydrogen proton to form water and heat energy. In other types
of fuel cells, the electrons travel through an electrical circuit to reach the other side of the
cell, thereby producing an electrical current. Fuel cells can provide energy for systems as
large as a power station and as small as a laptop computer. They can also power cars,
trucks, trains, and other vehicles. Because they emit only water vapor, fuel cells release no
pollutants that create smog and cause health problems. However, fuel cells require a
reservoir of hydrogen, an extremely flammable gas, and there currently exists little
infrastructure for the refilling of fuel cells with hydrogen.
Chapter 5: Geologic Resources: 5-9 Conservation as an Alternative Energy Resource
Book Title: Earth
Printed By: Kevin Murray ([email protected])
© 2015, 2011 Cengage Learning, Cengage Learning
9/3/2014 MindTap - Cengage Learning
http://ng.cengage.com/static/nb/ui/index.html?nbId=49852&nbNodeId=9252906#!&parentId=9252912 42/55
5-9 Conservation as an Alternative Energy Resource
The single quickest and most effective way to decrease energy consumption and to prolong
the availability of fossil fuels is to conserve energy (see Figure 5.24). Policies to improve
energy efficiency are more cost-effective than building new power plants. Such policies help
to reduce air pollution and dependence on oil imports while saving money for consumers
and industry.
Figure 5.24
The end-use efficiencies of common energy-consuming systems. Home heating
represents the only energy-consumption system that is even remotely efficient—
and even there, percent is wasted. Energy to produce incandescent lighting is
percent wasted; automobile transportation energy is percent wasted.
© Cengage Learning
Energy conservation has helped to produced dramatic results in the United States, where
expenditures for energy as a percentage of gross domestic product (GDP) fell from about
percent of GDP in 1980 to about percent of GDP in 2000. Higher global energy prices
since 2000 have caused expenditures for energy to rise again, to over percent of GDP,
despite the fact that the amount of energy used per person in the United States has fallen by
about percent over the same time period. Clearly, conservation is a critical component of
9/3/2014 MindTap - Cengage Learning
http://ng.cengage.com/static/nb/ui/index.html?nbId=49852&nbNodeId=9252906#!&parentId=9252912 43/55
keeping the total expenditure for energy in the country from continuing to rise. Some
energy experts have suggested that if people in industrialized nations use more efficient
equipment and develop more efficient habits, these nations could conserve as much as half
of the energy they consume.
Energy use in the United States falls under three categories: buildings, industry, and
transportation. Two types of conservation strategies can be applied in each of those
categories. Technical solutions involve switching to more efficient implements. Social
solutions involve decisions to use existing energy systems more efficiently.
Chapter 5: Geologic Resources: 5-9a Technical Solutions
Book Title: Earth
Printed By: Kevin Murray ([email protected])
© 2015, 2011 Cengage Learning, Cengage Learning
5-9a Technical Solutions
Buildings
In 2010, residential and commercial buildings consumed about percent of all the energy
produced in the United States. Most of that energy was used for heating, air-conditioning,
and lighting.
Significant energy savings are possible in all aspects of energy consumption in buildings. As
one example, lighting accounts for about percent of the average U.S. home’s electricity
bill. Because incandescent lighting is about percent inefficient in energy consumption,
savings in that area alone are potentially great. A fluorescent bulb consumes one-fourth as
much energy as a comparable incandescent bulb and can last times longer. In addition,
new solid-state technology promises further advances in energy-efficient lighting. For
example, light-emitting diodes (LED) are lights that are illuminated by the movement of
electrons through a semiconductor (Figure 5.25). There is no filament as with incandescent
lights, and LEDs release almost no heat, so they are much more efficient, last much longer,
and use far less energy. Today, LEDs are used to in clock radios, jumbo TVs, and many
other applications. According to the U.S. Department of Energy, widespread switching to
LED lighting technologies over the next years could save the equivalent annual electrical
output of years by large electrical power plants.
Figure 5.25
A bank of light-emitting diodes (LEDs).
9/3/2014 MindTap - Cengage Learning
http://ng.cengage.com/static/nb/ui/index.html?nbId=49852&nbNodeId=9252906#!&parentId=9252912 44/55
IGOR STEPOVIK/SHUTTERSTOCK.COM
Industry
Industry consumes about percent of the energy used in the United States. In general,
conservation practices are cost-effective, and many companies are taking advantage of the
fact that saving energy is profitable, although industry still wastes great amounts of energy.
For example, about two-thirds of the electricity consumed by industry drives electric
motors for machinery and tools. Most motors are inefficient because they run only at full
speed and are slowed by brakes to operate at the proper speeds to perform their tasks. This
approach is like driving your car with the gas pedal pressed to the floor and controlling
your speed with the brakes. Replacing older electric motors with variable-speed motors
would save vast amounts of electricity, but such replacement has been slow.
Transportation
About percent of all energy, more than percent of the oil usage in the United States,
and one-third of the nation’s carbon emissions are consumed transporting people and
goods.
The efficiency of standard gasoline-powered auto and truck engines is about percent
(Figure 5.24). Thus, we can save much energy by using more-efficient cars and trucks. Over
the past few decades, automobile manufacturers have offered vehicles with increasingly
efficient internal-combustion engines. Other avenues that auto companies are exploring
9/3/2014 MindTap - Cengage Learning
http://ng.cengage.com/static/nb/ui/index.html?nbId=49852&nbNodeId=9252906#!&parentId=9252912 45/55
include electricity and hydrogen power.
A hybrid car uses a small, fuel-efficient gasoline engine combined with an electric motor
that assists the engine when accelerating. Hybrids consume less gas and produce less
pollution per mile than conventional gasoline engines. Current models of hybrid cars
achieve fuel efficiencies ranging from (traffic/highway) to miles per gallon,
depending on make and model, and they produce as much as percent fewer harmful
emissions than a comparable gasoline engine. Using hybrids and other energy-efficient
vehicles, American motorists could achieve a percent or greater increase in fuel
economy, the equivalent of about one-third of current oil imports.
Chapter 5: Geologic Resources: 5-9b Social Solutions
Book Title: Earth
Printed By: Kevin Murray ([email protected])
© 2015, 2011 Cengage Learning, Cengage Learning
5-9b Social Solutions
Social solutions involve altering human behavior to conserve energy. Energy-conserving
actions can be used in buildings, in industry, and in transportation. Some result in
inconvenience to individuals. For example, if you choose to carpool rather than drive your
own car, you save fuel but inconvenience yourself by coordinating your schedule with your
carpool companions. High-mileage cars are on the market, but they will make an impact
only if people make the social decision to use them. People argue that this social decision
comes at a cost because light vehicles make the driver and passengers more vulnerable in
case of an accident; but studies have shown that lighter, more agile vehicles, with better
turning capacity and more effective braking, are actually safer than heavier SUVs.
At home and in the workplace, wearing a sweater and lowering the thermostat in winter
and using less air-conditioning in summer might reduce the comfort margin but can save
considerable energy. Many other social solutions, however, are cost-free in terms of
inconvenience. When practiced by everyone, simply turning off the lights, the television set,
and other appliances when you leave a room will conserve large amounts of energy.
Chapter 5: Geologic Resources: 5-10 Energy for the st Century
Book Title: Earth
Printed By: Kevin Murray ([email protected])
© 2015, 2011 Cengage Learning, Cengage Learning
5-10 Energy for the st Century
The United States consumes roughly percent of the world’s oil yet owns only percent of
the known conventional oil reserves. In 2011, fossil fuels supplied percent of all energy
used in the United States; oil alone accounted for percent, natural gas for percent,
and coal for percent (Figure 5.26). Thus, oil is our major source of energy. In addition,
oil is the only portable energy resource currently in popular use, and thus is the main
energy resource for transportation in the United States. At current rates of consumption
and production, many estimates indicate that we have up to years of domestic coal
reserves, and at least several decades of natural gas reserves, although the increased
9/3/2014 MindTap - Cengage Learning
http://ng.cengage.com/static/nb/ui/index.html?nbId=49852&nbNodeId=9252906#!&parentId=9252912 46/55
production of shale gas from hydraulic fracturing is extending that supply. Oil, however,
may be another story.
Figure 5.26
In the year 2011, fossil fuels supplied percent of all energy used in the United
States; oil alone accounted for percent, natural gas for percent, and coal for
percent.
Energy Information Administration/Annual Energy Review 2012
http://www.eia.gov/totalenergy/data/annual/perspectives.cfm
In 1956, M. King Hubbert, a geologist, was working at the Shell research lab in Houston,
Texas. Hubbert compared U.S. domestic oil reserves with current and predicted rates of oil
consumption. He then forecast that U.S. oil production would peak in the early 1970s and
would thereafter decline continuously. He predicted that Americans would have to make up
an ever-increasing difference between domestic oil supply and consumption by relying on
larger and larger imports, or they would have to turn to other energy resources. Other
experts and economists ridiculed his prediction, but in 1970 the U.S. domestic oil production
reached its maximum. It declined steadily until 2005, when nonconventional sources of oil,
deepwater discoveries, and the addition of domestically produced biofuels (along with
greater conservation) helped to reverse the downward trend (Figure 5.27). Since 2010, the
United States imports less petroleum than it produces domestically.
Figure 5.27
U.S. oil imports, production, and consumption since 1949. Until very recently, U.S.
reliance on oil imports had been rising, as predicted by M. K. Hubbert. However,
that trend is now heading downward, while U.S. domestic production of petroleum
is increasing. In 2010, the United States produced more than it imported for the first
time since 1997. These trend reversals are due to new U.S. production from
9/3/2014 MindTap - Cengage Learning
http://ng.cengage.com/static/nb/ui/index.html?nbId=49852&nbNodeId=9252906#!&parentId=9252912 47/55
unconventional reservoirs, particularly through hydraulic fracturing.
Energy Information Administration/Annual Energy Review 2012 © Cengage Learning 2015
In 2008, oil prices rose to nearly $ a barrel, a price that many hoped would spur
producers to respond to demand by increasing production. However, some large oil
producers—such as Mexico, Russia, and Saudi Arabia—actually cut back their oil
production, citing cost and expense. At the same time, oil production by OPEC
(Organization of the Petroleum Exporting Countries) was lower than projected because of
turmoil in Iran and Iraq, further contributing to the increase in oil prices. The global
economic downturn in late 2008 and 2009 caused both the demand and the global price to
decrease to about $ per barrel. That decrease was short-lived, however, and by early 2011
world oil prices had climbed back to over $ per barrel, due largely to increased demand
from rapidly industrializing countries such as China and India. Because oil remains the
biggest single source of U.S. energy and the country continues to import nearly half its
supply, it is a virtual certainty that the U.S. energy future will continue to be intimately
linked with the global one.
So what will happen when global oil production drops below demand? First of all,
petroleum will not just “run out” one day, with all the wells suddenly going dry. The world
will run out of “cheap oil” before it runs out of oil. As supply dwindles and demand
increases, the price of fuel will rise and production of petroleum from unconventional oil
sources, including the direct drilling of shale source rocks and the development of oil shales
and tar sands, will likely increase. The production of biofuels also is likely to increase. Some
economists and geologists have suggested that the fluctuations in gasoline prices seen in
recent years are the first wave of disruptions resulting from declining global oil reserves
and that much greater disturbances are imminent.
People will not be able to afford as much fuel as they would like, so social and technical
conservation strategies—previously rejected—will be implemented. As a result, demand will
decrease. But if this decrease is not sufficient, petroleum prices will continue to rise. Many
economists predict that the price increase could be dramatic. This is an example of an
economic threshold effect. As long as potential supply is greater than demand, the price of
oil reflects mainly the cost of drilling, shipping, and refining. But the moment we cross the
threshold where demand is greater than supply, then an auction occurs where the rich can
outbid the poor.
9/3/2014 MindTap - Cengage Learning
http://ng.cengage.com/static/nb/ui/index.html?nbId=49852&nbNodeId=9252906#!&parentId=9252912 48/55
Is it possible to alter global energy production from a fossil fuel economy to an economy of
renewable energy resources? In 2001, the UN’s Intergovernmental Panel on Climate
Change (IPCC) concluded that significant reduction of fossil fuel use is possible with
renewable “technologies that exist in operation or pilot-plant stage today . . . without any
drastic technological breakthroughs.” In other words, they suggested that if we
vigorously develop all the renewable energy resources listed in Section 5-7, the global
economic system could absorb a drastic decline in petroleum production without massive
disruptions. A year later, prominent energy experts published a rebuttal in Science,
proposing the exact opposite conclusion. Using almost the same phrases, with the simple
addition of the word not, they argued that “energy resources that can produce to
percent of present world power consumption without fossil fuels and greenhouse emissions
do not exist operationally or as pilot plants.” Their basic counterargument is that global
energy consumption is huge and renewable sources have low power densities. Thus, we do
not have the available land, nor could we quickly build, the required infrastructure to
replace fossil fuels. Most recently, in 2011, the IPCC again argued that close to percent of
world energy supplies could be met by the continued growth of renewable energy, provided
they are backed by policies that enable their development. This debate continues, as does
continued development and research into renewable resources.
When experts disagree, it is difficult for laypersons to evaluate the merits of the
contradictory arguments. But whoever is right, it is clear that if global energy demand
significantly exceeds supply, the world will fall into unprecedented economic chaos.
Commerce will slip into unimaginable depression. Food supplies will diminish, and food
distribution will become expensive. Poor people, who are already on the edge of
malnourishment, will starve. We can only hope that human ingenuity will combine with
economic and political commitment to develop alternative energy resources before these
catastrophes become reality.
Chapter 5: Geologic Resources Chapter Review
Book Title: Earth
Printed By: Kevin Murray ([email protected])
© 2015, 2011 Cengage Learning, Cengage Learning
Chapter Review
Key Terms
banded iron formations (Iron-rich sedimentary rocks composed of alternating iron-
rich and silica-rich layers; source of most of the world’s supply of iron.)
bauxite (A gray, yellow, or reddish-brown rock, composed of a mixture of aluminum
oxides and hydroxides, that formed as a residual deposit; the principle source of
aluminum.)
biomineralize (The process by which living organisms produce minerals.)
bitumen (A thick, sticky, oil-like substance that permeates tar sands and can be
converted to crude oil.)
9/3/2014 MindTap - Cengage Learning
http://ng.cengage.com/static/nb/ui/index.html?nbId=49852&nbNodeId=9252906#!&parentId=9252912 49/55
black smokers (A jet of black water spouting from a fracture or vent in the seafloor,
commonly near a mid-oceanic ridge. The black color is caused by precipitation of fine-
grained metal sulfide minerals as the hydrothermal solutions cool on contact with
seawater.)
capacity factor (A measure of the actual to total potential output of an energy
source over a period of time)
coal bed methane (Methane that is chemically bonded to coal. The methane can be
recovered by removing the groundwater from a coal bed, which decreases the
pressure and allows the methane to separate from the coal as a gas.)
conventional petroleum reservoir (A porous, permeable sedimentary rock that is
saturated with trapped oil.)
crystal settling (A process in which the crystals that solidify first from a cooling
magma settle to the bottom of the magma chamber because the minerals are more
dense than magma; the ultimate result is a layered body of igneous rock, each layer
containing different minerals.)
disseminated ore deposit (A large, low-grade hydrothermal deposit in which metal-
bearing minerals are widely scattered throughout a rock body; not as concentrated as
a hydrothermal vein.)
energy resources (Geologic resources—including petroleum, coal, natural gas, and
nuclear fuels—used for heat, light, work, and communication)
fossil fuels (Energy resources including petroleum, coal, and natural gas, which
formed from the partially decayed remains of plants and animals; they are
nonrenewable and unrecyclable.)
fuel cell (An electrochemical energy-conversion device that produces electricity from
an external supply of fuel, such as hydrogen.)
hydraulic fracturing (The process of fracturing an unconventional reservoir—
usually an organic-rich shale—by forcing large volumes of pressurized fluid into it.)
hydrogen economy (An energy economy in which hydrogen is used as a fuel.)
hydrothermal processes (Geologic processes in which hot water or steam dissolves
metals and minerals from rocks or magma; the solutions then seep through cracks
before cooling, to create ore deposits.)
hydrothermal vein deposit (A rich, sheetlike mineral deposit that forms when
economically-valuable minerals precipitate from hot water solutions along a fault or
other fracture.)
kerogen (The waxy, solid organic material in oil shales that yields oil when the shale
9/3/2014 MindTap - Cengage Learning
http://ng.cengage.com/static/nb/ui/index.html?nbId=49852&nbNodeId=9252906#!&parentId=9252912 50/55
is heated; the precursor of liquid petroleum.)
magmatic processes (Geologic processes that form ore deposits as liquid magma
solidifies into igneous rock.)
manganese nodules (A potato-shaped rock found on the ocean floor and rich in
manganese and other metals precipitated from seawater through biomineralization)
mineral reserves (A term to describe the known supply of ore in the ground; can be
used on a local, national, or global scale.)
mineral resources (Economically valuable geological materials including both metal
ore and nonmetallic minerals.)
natural gas (A mixture of naturally occurring light hydrocarbons composed mainly
of methane, , that is used for home heating and cooking and to fuel large electric
generation plants.)
nonmetallic mineral resources (Economically useful rocks or minerals that are not
metals; examples include salt, building stone, sand, and gravel)
nuclear fuels (Radioactive isotopes, such as those of uranium, used to generate
electricity in nuclear reactors.)
oil shale (A kerogen-bearing shale or fine-grained limestone that yields liquid or
gaseous hydrocarbons when heated.)
petroleum (A complex liquid mixture of hydrocarbons, formed from decayed plant
and animal matter, that can be extracted from sedimentary strata and refined to
produce propane, gasoline, and other fuels. Also called crude oil or simply oil.)
petroleum source rock (The shale or other sedimentary rock from which oil or
natural gas originates.)
placer deposit (A surface mineral deposit formed along stream beds, beneath
waterfalls, or on beaches when water currents slow down and deposit high-density
minerals.)
pump jack (The above-ground portion of a reciprocating piston pump on an oil well.)
residual ore deposits (A mineral deposit formed from relatively insoluble ions left in
the soil near Earth’s surface after most of the soluble ions were dissolved and
removed by abundant water.)
scavenging (The process by which hydrothermal fluids sweep through large volumes
of country rock and dissolve low concentrations of metals, concentrating them
elsewhere as an ore deposit.)
secondary and tertiary recovery techniques (Methods of extracting oil or natural
9/3/2014 MindTap - Cengage Learning
http://ng.cengage.com/static/nb/ui/index.html?nbId=49852&nbNodeId=9252906#!&parentId=9252912 51/55
gas by artificially augmenting the reservoir energy or fluid composition, as by
injection of water, pressurized gas, solvents, or other fluids.)
solar cell (A device that produces electricity directly from sunlight; also sometimes
called a photovoltaic (PV) cell.)
submarine hydrothermal ore deposits (Ore deposits that form when hot seawater
dissolves metals from seafloor rocks and then, as it rises through the upper layers of
oceanic crust, cools and precipitates the metals.)
surface mine (A hole excavated into Earth’s surface for the purpose of recovering
mineral or fuel resources.)
tar sands (Sand deposits saturated with heavy oil and an oil-like substance called
bitumen.)
unconventional reservoir (A sedimentary rock that is capable of producing oil with
the application of special techniques, such as hydraulic fracturing.)
underground mine (A mine consisting of subterranean passages that commonly
follow ore veins or coal seams.)
Chapter 5: Geologic Resources Chapter Review
Book Title: Earth
Printed By: Kevin Murray ([email protected])
© 2015, 2011 Cengage Learning, Cengage Learning
Chapter Review
Chapter Review
5-1
Mineral Resources
Useful rocks and minerals are called mineral resources; they include both
nonmetallic mineral resources and metals. All mineral resources are
nonrenewable. Ore is rock sufficiently enriched in one or more minerals to be
mined profitably; geologists usually use the term to refer to metallic mineral
deposits.
5-2
Ore and Ore Deposits
Four types of geologic processes concentrate elements to form ore.
9/3/2014 MindTap - Cengage Learning
http://ng.cengage.com/static/nb/ui/index.html?nbId=49852&nbNodeId=9252906#!&parentId=9252912 52/55
1. Magmatic processes form ore as magma solidifies.
2. Hydrothermal processes transport and precipitate metals from hot
water.
3. Sedimentary processes form placer deposits, evaporite deposits, and
banded iron formations.
4. Weathering removes easily dissolved elements from rocks and
minerals, leaving behind residual ore deposits such as bauxite.
Figure 5.3
Hot water scavenges metals from crystallizing igneous rock and
the country rock that surrounds it. The hydrothermal water then
deposits metallic minerals in ore-rich veins that fill fractures in
bedrock. It also deposits low-grade disseminated metal ore in
large volumes of rock surrounding the veins.
© Cengage Learning
5-3
Mineral Reserves vs. Mineral Resources
Mineral reserves are the known amount of ore in the ground.
5-4
Mines and Mining
Metal ores and coal are extracted from underground mines and surface
mines.
9/3/2014 MindTap - Cengage Learning
http://ng.cengage.com/static/nb/ui/index.html?nbId=49852&nbNodeId=9252906#!&parentId=9252912 53/55
5-5
Energy Resources: Coal, Petroleum, and Natural Gas
One important energy resource is fossil fuels: coal, oil, and natural gas. Fossil
fuels are nonrenewable and unrecyclable. Plant matter decays to form peat.
Peat converts to coal when it is buried and subjected to elevated temperature
and pressure. Petroleum forms from the remains of organisms that settle to
the ocean floor or lake bed and are incorporated into source rock. The
organic matter converts to liquid oil when it is buried and heated. The
petroleum then migrates to a reservoir, where an oil trap retains it. Natural
gas forms in source rock or in an oil reservoir subjected to high temperature,
and consequently many oil fields contain a mixture of oil with natural gas
floating above the heavier liquid petroleum.
Figure 5.10
The Bingham Canyon, Utah, open-pit copper mine is the largest
human-created excavation on Earth. It is over kilometers in diameter
and kilometer deep.
AGRICULTURAL STABILIZATION AND CONSERVATION SERVICE/USDA
5-6
Unconventional Petroleum and Gas Reservoirs
Secondary and tertiary recovery can extract additional supplies of petroleum
from old wells, tar sands, and oil shale.
9/3/2014 MindTap - Cengage Learning
http://ng.cengage.com/static/nb/ui/index.html?nbId=49852&nbNodeId=9252906#!&parentId=9252912 54/55
5-7
Energy Resources: Nuclear Fuels and Reactors
Nuclear power is expensive, and questions about the safety and disposal of
nuclear wastes have diminished its future in the United States. Nuclear fuels,
like mineral resources, are nonrenewable, although uranium is abundant.
Inexpensive uranium ore will be available for a century or more.
5-8
Energy Resources: Renewable Energy
Solar, wind, geothermal, hydroelectric, and biomass fuels are renewable
sources of energy.
5-9
Conservation as an Alternative Energy Resource
The single quickest and most effective way to decrease energy consumption
and to prolong the availability of fossil fuels is to conserve energy.
5-10
Energy for the 21st Century
Alternative energy resources currently supply a small fraction of our energy
needs but have the potential to provide abundant renewable energy.
Chapter 5: Geologic Resources Review Questions
Book Title: Earth
Printed By: Kevin Murray ([email protected])
© 2015, 2011 Cengage Learning, Cengage Learning
Chapter Review
Review Questions
1. Describe the two major categories of geologic resources.
2. Describe the differences between nonrenewable and renewable resources. List
9/3/2014 MindTap - Cengage Learning
http://ng.cengage.com/static/nb/ui/index.html?nbId=49852&nbNodeId=9252906#!&parentId=9252912 55/55
one example of each.
3. Discuss the formation of hydrothermal ore deposits.
4. Describe the unique advantages of hydrogen fuel.
5. What is ore? What are mineral reserves? Describe three factors that can
change estimates of mineral reserves.
Chapter 5: Geologic Resources Review Questions
Book Title: Earth
Printed By: Kevin Murray ([email protected])
© 2015, 2011 Cengage Learning, Cengage Learning
© 2014 Cengage Learning Inc. All rights reserved. No part of this work may by reproduced or used in any form or by any
means - graphic, electronic, or mechanical, or in any other manner - without the written permission of the copyright holder.