CASE STUDY / Pollution in Mexico City - TheMisterParsons · CASE STUDY / Pollution in Mexico City ... • We destroy resources through pollution of air, water, and ... Central Asia

CASE STUDY / Pollution in Mexico Cityhigh as 5,545 meters (16,900 feet). This giant bowl is open onlyto the north. Prevailing winds from the north enter the basinand back polluted air against the surrounding mountains. Mostof the emissions come from burning fuels in 8 million motorvehicles and 50,000 factories. These emissions are trapped closeto the ground in a stationary cloud, especially in the winter,when the climate is cool and dry and winds are calm. Becausethe city is at a high altitude, the level of available oxygen is low.Thus fossil fuels burn less completely than at lower altitudes,and burning them produces more carbon monoxide and ozone.

Air pollution is not Mexico City’s only environmental prob-lem. Inadequately treated sewage flows into nearby rivers, andone-fourth of the city’s homes are not even connected to thesewer system. Solid waste is deposited at large municipaldumps, where 17,000 people known as pepenadores, or garbagepickers, survive by going through rubbish and, in many cases,actually live at the dump. Dust from fecal matter in unseweredareas increases skin and eye infections. ■

Eight-year-old Carlos and nine-year-old Maria, residents ofMexico City, did not go to school today. Many of their class-mates also did not attend. And many of their teachers failed toreport for work. These people did not leave their homesbecause they feared that breathing outside air in Mexico Citywould be too dangerous.

For much of the year, a stationary cloud hangs over MexicoCity, producing a gray-brown fog that irritates the eyes and burnsthe throat. Residents report frequent conjunctivitis and other eyedisorders, skin rashes, bronchitis, other respiratory diseases, andincreased susceptibility to heart attacks. The air is consideredsafe to breathe for only 31 days a year. The health benefits of out-door sports such as soccer and running are outweighed by thehealth risks of breathing the air. Pregnant women are cautionedthat living in Mexico City increases risk to fetal health.

This severe air pollution partly results from Mexico City’ssite: It rests in a basin some 2,250 meters (about 7,400 feet)above sea level, surrounded by a semicircle of volcanic peaks as

Plants and animals live in harmony with their environment,but people often do not. Geographers study the troubled rela-tionship between human actions and the physical environmentin which we live.

From the perspective of human geographers, Earth offers alarge menu of resources available for people to use. A resourceis a substance in the environment that is useful to people, iseconomically and technologically feasible to access, and issocially acceptable to use. Resources include food, water, soil,plants, animals, and minerals. A natural resource has littlevalue in and of itself. Its value derives from its usefulness tohumans, especially in production. Enterprises extract thoseresources for which humans are willing to pay a sufficientlyhigh price to justify the investment. As the supply of a resourcedwindles, consumers may be willing to pay higher prices, thusencouraging continued exploitation and further depletion ofreserves rather than conservation for future generations.

The problem is that most resources are limited, and Earthhas a tremendous number of consumers. Geographers observetwo major misuses of resources:

• We deplete scarce resources, especially petroleum, naturalgas, and coal, for energy production.

• We destroy resources through pollution of air, water, andsoil.

These two misuses are the basic themes of this chapter.As with other topics, geographers look first at where

resources are distributed across space. Both supply and demandof resources show pronounced local diversity. Some regions arewell endowed with minerals, water, and other resources,whereas other regions have limited supplies. The reason whyproblems arise from this uneven distribution is that resourcesare often located in places different from their users. Differences

in demand may arise from the uneven distribution of peopleacross Earth or from variations in development.

Nowhere is the globalization trend more pronounced thanin the study of resources. The global economy depends on theavailability of natural resources to produce the goods and serv-ices that people demand. Global uniformity in cultural prefer-ences means that people in different places value similarnatural resources, although not everyone has the same accessto them. In a global environment, all places are connected, sothe misuse of a resource in one place affects the well-being ofpeople everywhere.

To study resource problems, we also depend on our under-standing of local scale. As geographers, we understand that ourenergy problems derive from depletion of resources in particu-lar regions and from differences in how consumers useresources in different places. We see that the pollution problemcomes from the concentration of substances that harm thephysical environment in particular regions.

KEY ISSUE 1

Why Are ResourcesBeing Depleted?

■ Energy Resources■ Mineral Resources

Two kinds of natural resources are especially valuable tohumans—minerals and energy resources. We depend onabundant, low-cost energy and minerals to run our industries,

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transport ourselves, and keep our homes comfortable. Butwe are depleting the global supply of some resources. MDCswant to preserve current standards of living, and LDCs arestruggling to attain a better standard. All this demandstremendous resources; so as we deplete our current sources,we must develop alternative ones. ■

Energy ResourcesHistorically, people relied primarily on power supplied by them-selves or by animals, known as animate power. Energy fromflowing water and burning biomass fuel supplemented animatepower. Biomass fuel, such as wood, plant material, and animalwaste, is burned directly or converted to charcoal, alcohol, ormethane gas. Biomass remains the most important source of fuelin some LDCs, but during the Industrial Revolution MDCs con-verted to inanimate power, generated from machines.

Energy Supply and DemandAround one-half of the world’s energy is consumed in MDCsand one-half in LDCs. MDCs contain only around one-third ofthe population of LDCs, so per capita consumption of energyis thus around three times higher in MDCs than in LDCs(Figure 14-1). North Americans are the heaviest per capitaconsumers of energy. North America uses one-fourth of theworld’s energy but contains only one-twentieth of the world’speople.

Three of Earth’s substances provide five-sixths of the world’senergy (Figure 14-2):

• Coal. Supplanted wood as the leading energy source inNorth America and Europe in the late 1800s.

• Petroleum. First pumped in 1859, but not an importantresource until the diffusion of motor vehicles in the twentiethcentury.

• Natural Gas. Originally burned off as a waste product ofoil drilling, but now used to heat homes.

In MDCs other energy comes primarily from nuclear andhydroelectric power. Burning wood and hydroelectric powerprovide much of the remaining energy in LDCs.

Energy is used in three principal places in the United States:

1. Businesses. The main energy resource is coal, followedby natural gas and oil. Some businesses directly burn coalin their own furnaces. Others rely on electricity, mostlygenerated at coal-burning power plants.

2. Homes. Energy is used primarily for the heating of livingspace and water. Natural gas is the most common source,followed by petroleum (heating oil and kerosene).

3. Transportation. Almost all transportation systems oper-ate on petroleum products, including cars, trucks, buses,airplanes, and most railroads. Only subways, streetcars,and some trains run on coal-generated electricity.

Petroleum, natural gas, and coal are known as fossil fuels. Afossil fuel is the residue of plants and animals that were buriedmillions of years ago. As sediment accumulated over these

remains, intense pressure and chemical reactions slowly con-verted them into the fossil fuels we use today. When we burnthese substances, we are releasing energy originally stored inplants and animals millions of years ago.

Two characteristics of fossil fuels cause great concern for thefuture:

• The Supply of Fossil Fuels Is Finite. Once the presentsupply of fossil fuels is consumed, it is gone, and we mustlook to other resources for our energy. (Technically, fossilfuels are continually being formed, but the process takesmillions of years, so humans must regard the current sup-ply as essentially finite.)

• Fossil Fuels Are Distributed Unevenly Around theGlobe. Some regions enjoy a generous supply of fossilfuels, whereas others have little, and fossil fuels are notconsumed in the same regions where they are produced.

Finiteness of Fossil FuelsEarth’s resources are divided between those that are renewableand those that are not:

• Renewable energy has an essentially unlimited supply andis not depleted when used by people. Examples includehydroelectric, geothermal, fusion, wind, and solar energy.

• Nonrenewable energy forms so slowly that for practical pur-poses it cannot be renewed. The fossil fuels are examples.

As nonrenewable energy sources, the three main fossil fuels,once burned, are used up for all time. The world faces anenergy problem in part because we are rapidly depleting theremaining supply of the three fossil fuels, especially petroleum.

Because of dwindling supplies of fossil fuels, most of thebuildings in which we live, work, and study will have to beheated another way. Cars, trucks, and buses will have to oper-ate on some other energy source. The many plastic objects thatwe use (because they are made from petroleum) must be madewith other materials. We can use other resources for heat, fuel,and manufacturing, but they are likely to be more expensiveand less convenient to use than fossil fuels. And convertingfrom fossil fuels will likely disrupt our daily lives and cause ushardship.

PROVEN RESERVES. How much of the fossil-fuel supplyremains? Despite the critical importance of this question forthe future, no one can answer it precisely. Because petroleum,natural gas, and coal are deposited beneath Earth’s surface,considerable technology and skill are required to locate thesesubstances and estimate their volume. The amount of energyremaining in deposits that have been discovered is called aproven reserve. Proven reserves can be measured withreasonable accuracy—about 1.3 trillion barrels of petroleum,about 175 trillion cubic meters of natural gas, and about1 quadrillion metric tons of coal.

To determine when remaining reserves of an energy sourcewill be depleted, we must know the rate at which the resourceis being consumed. At the current world petroleum consump-tion rate of about 31 billion barrels a year, Earth’s proven petro-leum reserves of 1.3 trillion barrels will last 43 years. Similarly,

Chapter 14: Resource Issues 441

442 The Cultural Landscape

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been exploited. Newly discovered reserves are generallysmaller and more remote, such as beneath the seafloor,where extraction is costly. Exploration costs have increasedbecause methods are more elaborate and the probability offinding new reserves is less. But as energy prices climb,exploration costs may be justified.

• Enhanced Recovery from Already Discovered Fields.When it was first exploited, petroleum “gushed” from wellsdrilled into rock layers saturated with it. Coal was quarried inopen pits. But now extraction is harder. Sometimes pumpingis not sufficient to remove petroleum, so water or carbondioxide may be forced into wells to push out the remainingresource. The problem of removing the last reserves from aproven field is comparable to wringing out a soaked towel. Itis easy to quickly remove the main volume of water, but thelast few percent require more time and patience and specialtechnology.

• Unconventional Sources. They are called unconven-tional because methods currently used to extract resourceswon’t work. Also we do not currently have economicallyfeasible, environmentally sound technology with which toextract them. Examples include oil shale, which is a “rockthat burns,” and oil sands, which are saturated with a thickpetroleum.

Abundant oil sands are found in Alberta, Canada, aswell as in Venezuela and Russia. Oil shale is found in Utah,Wyoming, and Colorado in the United States. NativeAmericans used the tar to caulk canoes in the eighteenthcentury. The oil shale must be extracted through mining,which can be environmentally damaging, and current tech-nology makes processing expensive. As with exploration,though, as energy prices rise, unconventional sourcesbecome economically feasible. Even then the adverse envi-ronmental impacts of using these sources may be high.

at current rates of use, the world’s proven reserves of naturalgas will last for about 49 years. For coal, the immediate futureis less grim. At current consumption, proven coal reserveswould last 131 years. One-half of U.S. electricity currentlycomes from power plants that burn coal.

POTENTIAL RESERVES. Some deposits in the worldhave not yet been discovered. The energy in deposits that areundiscovered but thought to exist is a potential reserve. Whena potential reserve is actually discovered, it is reclassified as aproven reserve (Figure 14-3). Potential reserves can beconverted to proven reserves in several ways:• Undiscovered Fields. The largest, most accessible

deposits of petroleum, natural gas, and coal have already

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FIGURE 14-1 Per capita energy consumption. MDCs consume on average fivetimes more energy per capita than do LDCs.


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FIGURE 14-2 U.S. energy consumption. U.S. energy consumption increased rapidly during the 1960s, butsince the early 1970s it has increased at a much slower rate. The amount of energy derived from petroleumand natural gas increased rapidly in the 1960s, when use of coal stagnated.

Uneven Distribution of Fossil FuelsGeographers observe two important inequalities in the globaldistribution of fossil fuels: Some regions have abundantreserves, whereas others have little; the heaviest consumers offossil fuel are in different regions than most of the reserves.Given the centrality of fossil fuels in contemporary economyand culture, unequal possession and consumption of fossilfuels have been major sources of global instability.

LOCATION OF RESERVES. Why do some regions haveabundant reserves of one or more fossil fuels, but other regionshave little? This partly reflects how fossil fuels form.

Coal forms in tropical locations, in lush, swampy areas richin plants. Thanks to the slow movement of Earth’s drifting con-tinents, the tropical swamps of 250 million years ago have relo-cated to the midlatitudes. As a result, today’s main reserves ofcoal are in midlatitude countries rather than in the tropics.China is responsible for extracting 39 percent of the world’scoal, and the United States 16 percent (Figure 14-4). Threecountries—the United States, Russia, and China—have nearlytwo-thirds of the world’s proven coal reserves, and five othercountries combined have most of the remainder (Figure 14-5).

Similarly, sources of petroleum and natural gas formed mil-lions of years ago from sediment deposited on the seafloor.Some oil and natural gas reserves still lie beneath such seas asthe Persian Gulf and the North Sea, but other reserves arelocated beneath land that had been under water millions ofyears ago. Southwest Asia produces 40 percent of the world’spetroleum, Central Asia 15 percent, Russia 11 percent, and theUnited States 10 percent (Figure 14-6). Russia and the UnitedStates each account for 18 percent of current natural gas pro-duction (Figure 14-7).

Russia possesses more than one-fourth of the world’s natu-ral gas reserves. Southwest Asia and Central Asia togetherhave more than one-half. Two regions—Southwest Asia andCentral Asia—together account for nearly two-thirds of theworld’s proven petroleum reserves. Canada is now thought tohave 13 percent of world petroleum reserves, second behind

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FIGURE 14-3 Outlook for world petroleum production. As production ofproven reserves declines, new sources of petroleum will be developed. Theseinclude removal of more petroleum from existing fields, discovery of new fields,and exploitation of nonconventional sources. Source: World Energy Outlook 2004.


Saudi Arabia. Despite challenges in extracting the petroleum,extensive deposits of oil in Alberta oil sands have been reclas-sified from potential to proven reserves in recent years becauseof rapidly escalating petroleum prices.

Taken as a group, MDCs have historically possessed a dispro-portionately high percentage of the world’s proven fossil-fuelreserves. Europe’s nineteenth-century industrial developmentdepended on its abundant coalfields, and extensive coal and

petroleum supplies helped the United States to become the lead-ing industrial power of the twentieth century. But this dominanceis ending in the twenty-first century. Many of Europe’s coal mineshave closed because either the coal was exhausted or the remain-ing supply was too expensive to extract, and the region’s petro-leum and natural gas (in the North Sea) account for only smallpercentages of worldwide reserves. Japan has never had signifi-cant fossil-fuel reserves. The United States still has extensive coal

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FIGURE 14-4 Coal production. China is the largest producer. To facilitate comparison, Figures 14-5 and14-6 use the same scale as this map.

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FIGURE 14-5 Petroleum production. Saudi Arabia and Russia are the largest producers.


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FIGURE 14-7 Fossil-fuel proven reserves. The largest proven reserves of coalare in the United States, Russia, and China; petroleum in Saudi Arabia, Canada,and Iran; and natural gas Russia, Iran, and Qatar.

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FIGURE 14-6 Natural gas production. The United States and Russia are the largest producers.

reserves, but its petroleum and natural gas reserves are beingdepleted rapidly. It currently produces 18 percent of the world’snatural gas but possesses only 4 percent of proven reserves, and itproduces 10 percent of the world’s petroleum but possesses only 2percent of reserves.

CONSUMPTION OF FOSSIL FUELS. Because MDCsconsume more energy than they produce, they must importfossil fuels, especially petroleum, from LDCs. The UnitedStates and Europe import more than half their petroleum, andJapan more than 90 percent.


Because of more rapid economic development in LDCs,the MDCs face greater competition in obtaining the world’sremaining supplies of fossil fuels. During the first decade ofthe twenty-first century, fossil-fuel consumption in LDCssurpassed that of MDCs for the first time (Figure 14-8).The gap in consumption between LDCs and MDCs isexpected to widen considerably in the years ahead. Con-sumption of fossil fuels has been increasing at around 3 per-cent per year in LDCs, compared to 1 percent per year inMDCs. China consumes 16 percent of the world’s energy,currently second to the United States at 21 percent. China isforecast to take over the top ranking from the United Statesaround 2015.

Control of World PetroleumThe sharpest conflicts over energy will be centered on theworld’s limited proven reserves of petroleum. The MDCs importmost of their petroleum from Southwest and Central Asia,where most of the world’s proven reserves are concentrated.Both U.S. and European transnational companies originallyexploited Asian petroleum fields and sold the petroleum at alow price to consumers in MDCs.

The United States produced more petroleum than it con-sumed during the first half of the twentieth century. But begin-ning in the 1950s the handful of large transnational companiesthen in control of international petroleum distribution deter-mined that extracting domestic petroleum was more expensivethan importing it from Southwest and Central Asia. U.S. petro-leum imports increased from 14 percent of total consumptionin 1954 to 58 percent in 2009. European countries and Japan

have always depended on foreign petroleum because of limiteddomestic supplies. China changed from a net exporter to animporter of petroleum during the 1990s.

OPEC. At first, Western companies set oil prices and paidAsian governments only a small percentage of their oil profits.But government policies changed in the petroleum-producingcountries, especially during the 1970s. Foreign-owned petro-leum fields were either nationalized or more tightly controlled,and prices were set by governments rather than by petroleumcompanies. Several LDCs possessing substantial petroleumreserves created the Organization of Petroleum ExportingCountries (OPEC) in 1960. Arab OPEC members in SouthwestAsia and North Africa are Algeria, Iraq, Kuwait, Libya, Qatar,Saudi Arabia, and United Arab Emirates. OPEC countrieselsewhere in the world include Angola, Ecuador, Iran, Nigeria,and Venezuela.

OPEC’s Arab members were angry at North American andEuropean countries for supporting Israel during that nation’s1973 war with the Arab states of Egypt, Jordan, and Syria. Soduring the winter of 1973–74, they flexed their new economicmuscle with a boycott—Arab OPEC states refused to sell petro-leum to the nations that had supported Israel. Soon gasolinesupplies dwindled in MDCs (Figure 14-9). Each U.S. gasolinestation received a small ration of fuel, which ran out early inthe day. Gasoline was sold by license plate number (cars withlicenses ending in an odd number could buy only on odd-num-bered days). Long lines formed, and some motorists waited allnight for fuel. European countries took more drastic action—the Netherlands, for example, banned all but emergency motorvehicle travel on Sundays.

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FIGURE 14-9 Gas lines, 1973. The Organization of Petroleum ExportingCountries refused to sell petroleum to North American and European countriesfor a few months during the winter of 1973–74 to protest Western countries’support for Israel in the October 1973 war. Motorists in the United States, suchas these in Los Angeles, waited in long lines to purchase gas. Note that the carsare in line to enter the Shell station in the background. The Exxon station in theforeground is closed because it already ran out of its day’s allotment of fuel. Backin 1973, Americans regarded Exxon’s posted price of 74¢ for a gallon of regulargas to be outrageously high.


also dampened demand for petroleum in most MDCs during thelate twentieth century (Figure 14-11). The average vehicledriven in the United States, for example, got 14 miles per gallonin 1975, compared to 22 miles per gallon in 2000. However, withpetroleum prices remaining low into the twenty-first century,consumption increased. Americans bought more gas-guzzlingtrucks and sport-utility vehicles and drove longer distances.Thus, once again, petroleum imports increased to record levels.

As in the 1970s, Americans were unprepared for the shockof steep oil price rises in the twenty-first century when sup-plies were disrupted in the wake of terrorist attacks and sev-eral wars in the Middle East. Gas prices hit historic highs bothin real terms and adjusted for inflation. Yet global demandcontinues to increase, especially demand from LDCs, led byChina. Inadequate refinery capacity makes it difficult toexpand supply.

The world will not literally “run out” of petroleum duringthe twenty-first century. However, at some point extracting theremaining petroleum reserves will prove so expensive andenvironmentally damaging that use of alternative energysources will accelerate, and dependency on petroleum willdiminish. The issues for the world are whether dwindlingpetroleum reserves are handled wisely and other energysources are substituted peacefully. Given the massive growth inpetroleum consumption expected in LDCs such as China andIndia, the United States and other MDCs may have little influ-ence over when prices rise and supplies decline.

Mineral ResourcesEarth has 92 natural elements, but about 99 percent of thecrust is composed of 8 elements—oxygen, silicon, aluminum,iron, calcium, sodium, potassium, and magnesium. Oxygenalone accounts for nearly one-half of the crust and silicon morethan one-fourth (Figure 14-12). The 8 most common elementscombine with rare ones to form approximately 3,000 differentminerals, all with their own properties of hardness, color, anddensity, as well as spatial distribution. Each mineral is poten-tially a resource, if people find a use for it.

Minerals are either metallic or nonmetallic. In weight, morethan 90 percent of the minerals that humans use are nonmetal-lic, but metallic minerals are especially important for economicactivities and so carry relatively high value. Because a mineralis valued primarily for its mechanical or chemical properties,the definition of which minerals constitute resources evolves astechnology and economies change. When a new technologicalprocess or product is invented, demand can suddenly increasefor a mineral that had little use in the past.

Mineral deposits are not uniformly distributed around theworld. Most of the world’s supply of particular minerals isfound in a handful of countries (Figure 14-13). Countries suchas Australia and China rank among leading producers of sev-eral minerals, whereas other countries have abundant suppliesof only one mineral. Further, the leading producers at this timeare not always the countries with the most extensive reserves,an indication that the relative fortunes of states may change inthe future.

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FIGURE 14-10 U.S. gasoline prices. The average price paid for a gallon ofregular increased in the United States from around 25¢ in 1950 to around $3.25in 2008. When adjusted for inflation, the price has been around $1.50 (in 2000dollars) for most of the half-century, with the exception of the early 1980s andbeginning in 2004.

OPEC lifted the boycott in 1974 but raised petroleumprices from $3 per barrel to more than $35 by 1981. Prices atU.S. gas pumps soared from an average of 39 cents in 1973 to$1.38 in 1981. The rapid escalation in petroleum prices duringthe 1970s caused severe economic problems in MDCs. Pro-duction of steel, motor vehicles, and other energy-dependentindustries plummeted in the United States in the wake of the1973–74 boycott and has never regained preboycott levels(recall Figure 11-24, which shows declining steel productionin MDCs since the 1970s). Manufacturers were forced out ofbusiness by soaring energy costs, and the survivors wereforced to restructure their operations to regain internationalcompetitiveness.

The LDCs were hurt even more. They depended on low-costpetroleum imports to spur economic development. Becausemany fertilizers are derived from petroleum, their fertilizercosts shot up. North American and European states cushionedthemselves by creating a profitable return path for money thatwas going to OPEC: They encouraged OPEC countries toinvest in American and European real estate, banks, and othersafe and profitable investments. Comparable investmentopportunities were limited in LDCs.

CHANGING SUPPLY AND DEMAND. The price ofpetroleum plummeted during the 1980s and settled during the1990s at the lowest level in modern history, adjusting forinflation (Figure 14-10). The United States and other majorconsuming nations entered the twenty-first century optimisticthat oil prices would remain low for some time.

The United States reduced its dependency on imported oil inthe immediate wake of the 1970s shocks, and the share ofimports from OPEC countries declined from two-thirds duringthe 1970s to one-third during the 1980s. Conservation measures


NonmetallicMineralsBuilding stones, including largestones, coarse gravel, and fine sand,account for 90 percent of non-metallic mineral extraction. Theseminerals are fashioned into struc-tures, roads, monuments, tools,and many other objects of dailyuse. The rocks and earthen materi-als used for building purposes areso common that differences in dis-tribution are of little consequence,at least at the international scale.

Nonmetallic minerals are alsoused for fertilizer. All crops musthave at least some quantity ofthese minerals and obtain some ofwhat they need from the soil.Because soils are often deficient inthese minerals, farmers add them.Important nonmetallic mineralsources of fertilizers includephosphorus, potassium, calcium,and sulfur (Figure 14-14). Allfour are abundant elements innature with wide distributions.However, mining is highly clus-tered where the minerals are mosteasily and cheaply extracted.

• Phosphorus: Essential to plant growth, but easily exhaustedin cultivation. The chief sourceof phosphorus is phosphaterock (apatite), found amongthe marine sediments of oldseabeds. One-fourth of theworld’s supply of phosphaterock is mined in the UnitedStates; another one-third inMorocco and China. Moroccopossesses one-half of the world’sreserves.

• Potassium: Obtained primarily from the evaporation ofsaltwater. Principal sources of potassium include formerSoviet Union countries, Canada, and the United States, aswell as the Dead Sea, shared by Israel and Jordan.

• Calcium: Essential for formation of strong bones andteeth, and especially important for growing corn. High lev-els of calcium are concentrated in subhumid soils such asthe plains and prairies of the western United States andCanada, as well as Russia’s steppes.

• Sulfur: Used to make insecticides and herbicides, as wellas fertilizers. The United States and Canada are responsiblefor one-fourth of the world’s sulfur production, withanother one-fifth coming from China and Russia.

Oxygen46.6%

Silicon27.7%

Aluminum8.1%

Iron 5.0%

Calcium 3.6%

Sodium 2.8%Potassium 2.6%

Magnesium 2.1%Others 1.5%

FIGURE 14-12 Elements in Earth’s crust. Oxygen comprises nearly one-halfof Earth’s crust, silicon more than one-fourth, and six elements nearly all of theremainder.

Domestic69

Other non-OPEC

Canada

Other OPEC

VenezuelaNigeria

Other Persian GulfSaudi Arabia

Other non-OPEC

Mexico

Iraq 2Angola 2Other OPEC

Algeria 3

Nigeria 4

VenezuelaSaudi Arabia

Domestic57 Canada

11Netherlands Antilles

Other Caribbean 2

Russia 4U.K. 2

7

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12

6

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54

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Domestic

OPEC imports

Non-OPEC imports

1973 2009

U.S. petroleum sources(Percentage of barrels a day)

FIGURE 14-11 U.S. petroleum imports. The United States imported 58 percent of its crude oil in 2009, compared toonly 31 percent in 1973. Since the 1980s, domestic production has declined 40 percent, whereas consumption hasincreased 30 percent. The gap has been covered by a 60 percent increase in imports.

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Nitrogen, obtained from the atmosphere, is an even moreimportant fertilizer. Capturing it from the atmosphere utilizes alot of energy, so its supply and demand are more closely associ-ated with issues of energy resources rather than the other fertil-izer elements.

Another group of nonmetallic minerals, gemstones, are val-ued highly for their color and brilliance when cut and polished.Diamonds are especially useful in manufacturing because they

ARCTIC OCEAN

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OCEAN

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DiamondsNitrogen

PhosphorusSulfur

Iron oreChromiumMagnesiumManganeseMolybdium

NickelTinTitaniumTungsten

BauxiteCopperGoldLead

PlatinumSilverZinc

MINERALSNonmetallic Minerals

Nonferrous Metals

Ferrous Metals

DN

PS

FECRMGMNMO

NISNTIW

BCUAUPB

dn

fecr

mgmnmo

bcuaupb

PTAGZN

ps

nisntiw

ptagzn

*XX represents 15% and above xx represents 5-15%

FIGURE 14-13 Production of important minerals. Australia and China are leading producers of several of the most important minerals.

are the strongest and hardest knownmaterial and have the highest thermalconductivity of any material at room tem-perature. Two-thirds of the world’s dia-monds are currently mined in Australia,Botswana, and Russia.

Metallic Minerals:FerrousMetallic minerals have properties that areespecially valuable for fashioning machin-ery, vehicles, and other essential compo-nents of an industrialized society. They areto varying degrees malleable (able to behammered into thin plates) and ductile(able to be drawn into fine wire) and areconductors of heat and electricity. Manymetals are also capable of combining withother metals to form alloys with yet otherdistinctive properties. A mineral bearing ametal such as aluminum or iron is knownas an ore. Nearly all ore contains at leastsome metallic mineral, although the con-

centration is often too low to justify extracting it.Metals are known as ferrous or nonferrous. Ferrous metals

include iron ore and other alloys used in the production of ironand steel. The term “ferrous” refers to the Latin word for iron,and the symbol for iron in the periodic table of elements is Fe.

IRON ORE. By far the world’s most widely used ferrousmetal is iron, which accounts for 5 percent of Earth’s crust by

FIGURE 14-14 Mining. Sulfur is being mined in Kawah Ijen, Indonesia. Miners carry chunks of sulfur byhand out of the bottom of an active volcano.


weight and 95 percent of ferrous metal mineral extraction. It isalso found in the Sun and other stars and is thought to be themain component of Earth’s core.

Iron is prized for its many assets: a good conductor of heatand electricity, able to be attracted by a magnet and to be mag-netized, and malleable into useful shapes. Humans began fash-ioning tools and weapons from the silver-gray metal about2000 B.C. The critical importance of iron to the past 4,000 yearsof human history is reflected by the application of the term“Iron Age” to the period. Iron remains an important element inevery modern society, from least to most developed.

Mining of iron ore, from which iron is extracted, is con-centrated in a handful of countries, including two-thirds inChina, Brazil, and Australia. Major importers of iron oreinclude the steel-producing countries of Europe plus Japanand the United States. Because of the high cost of transportinglarge quantities of iron ore, accessibility to market is an espe-cially important determinant in the selection of deposits forexploitation, more so than for other metals used in smalleramounts. Iron deposits of indifferent quality but close to mar-ket are actively mined, whereas large known deposits inremote areas are ignored for now, although they may becomemore important in the future once more accessible depositsare exhausted.

OTHER FERROUS METALS. Several less common ferrousmetals are important for alloying with iron to produce steel:

• Chromium: A principal component of stainless steel,because it helps keep a sharp cutting edge even at high tem-peratures. Chromium is extracted from chromite ore, one-half of which is mined in South Africa.

• Manganese: An especially vital alloying metal for makingsteel because it imparts toughness and carries off undesir-able sulfur and oxygen. Manganese ore is a relatively plen-tiful element in Earth’s crust, so total world supply is not aproblem. Responsible for one-half of world manganeseproduction are Brazil, Gabon, and South Africa.

• Molybdenum: Imparts toughness and resilience tosteel. Unlike the other rare metals discussed here, aleading role in providing this mineral is played by theUnited States, the leading producer, with one-third ofworld production.

• Nickel: Used primarily for stainless steel and high-temperature and electrical alloys. World reserves are around100 years at current rates of use. Russia, Australia, andCanada are responsible for one-half of current production.

• Tin: Valued for its corrosion-resistant properties. Tin is usedfor plating iron and steel and has been used for more than5,000 years as an alloy of copper for making bronze. Chinaextracts two-fifths of the world’s tin, Indonesia one-fourth,and Peru one-sixth. World reserves are estimated at onlyaround 50 years.

• Titanium: A lightweight, high-strength, corrosion-resistantmetal used as an alloy of steel, although its main use is aswhite pigment in paint. Titanium is extracted primarily fromthe mineral ilmenite. Sixty percent of world production isclustered in Australia, South Africa, and Canada.

• Tungsten: Makes very hard alloys with steel and is used tomanufacture tungsten carbide for cutting tools. China isresponsible for 90 percent of world production.

Metallic Minerals: NonferrousNonferrous metals are utilized to make products other than ironand steel. The most abundant nonferrous metal is aluminum.

ALUMINUM (BAUXITE). Rarely used commercially priorto the twentieth century, aluminum is now in greater demandthan any metal except iron. Aluminum has replaced some ironand steel components in motor vehicles and airplanes because itis lighter, stronger, and more resistant to corrosion. Aluminumhas replaced copper wire in high-tension power transmissionlines and is used to make paint, foil, and jewelry.

The most economically feasible way of obtaining aluminumis to extract it from bauxite ore. Australia is responsible formining one-third of the world’s bauxite ore. World reserves ofaluminum are so large—more than 1,000 years at current ratesof use—that it is essentially regarded as inexhaustible at realis-tic projections of future demand.

OTHER NONFERROUS METALS. Other especiallyimportant nonferrous include:

• Copper: Valued for its high ductility, malleability, thermaland electrical conductivity, and resistance to corrosion.Rated third in metal consumption behind iron and alu-minum, copper is used primarily in electronics and con-structing buildings. Chile is responsible for one-third ofworld production.

• Lead: Very corrosion-resistant, dense, ductile, and mal-leable. This blue-gray metal has been used for a variety ofpurposes for several thousand years, first in building mate-rials and pipes, then in ammunition, brass, glass, and crys-tal, and now primarily in motor-vehicle batteries. Australiaand China each supply one-fourth of the world’s lead.

• Magnesium: Relatively light yet strong, so it is used toproduce lightweight, corrosion-resistant alloys, especiallywith aluminum to make beverage cans. China supplies three-fourths of the world’s magnesium.

• Zinc: Used primarily as a coating to protect iron and steelfrom corrosion and as an alloy to make bronze and brass.Again, China is the leading producer, with one-fourth of theworld total. Australia and Peru together supply anotherone-fourth.

World supplies of some nonferrous metals are extremely limited—less than 60 years for copper, 25 years for lead, and 45 yearsfor zinc. Supplies of magnesium are abundant because it can beremoved from seawater brine.

PRECIOUS METALS. Nonferrous metals also includeprecious metals—silver, gold, and the platinum group. Inaddition to jewelry, both silver and gold are used in a variety ofindustrial applications, such as electrical and electronic products,and silver is a component of photographic film, whereas gold isimportant in dentistry. The principal use of the platinum group is


in motor-vehicle catalytic converters to treat exhaust emissions,as well as in fuel cells.

• Gold: Prized since ancient times for its beauty and durability.In addition to jewelry, gold is used in a variety of industrialapplications and in dentistry. One-third of the world’s gold ismined in Australia, South Africa, and the United States.

• Silver: Like gold, also long prized for its beauty and durabil-ity, and used in photographic film as well as other industries.Associated with copper, lead, and zinc deposits, it is oftenmined at great depths. One-half of current production is inPeru, China, Mexico, and Australia.

• Platinum group: Includes six related and especially scarcemetals that commonly occur together in nature—platinum,palladium, rhodium, ruthenium, iridium, and osmium.Platinum has the most highly clustered distribution of themajor precious metals: South Africa is responsible for three-fourths of production.

World supply of most metals is high, including the mostwidely used ferrous metal (iron) and the most widely used non-ferrous metal (aluminum). However, reserves of some metalsare low, posing a challenge to manufacturers to find economi-cally feasible substitutes.

KEY ISSUE 2

Why Are ResourcesBeing Polluted?

■ Air Pollution■ Water Pollution■ Land Pollution

In our consideration of resources, consumption is half ofthe equation—waste disposal is the other half. All of theresources we use are eventually returned to the atmos-phere, bodies of water, or land surface, through burning,rinsing, or discarding. We rely on air, water, and land toremove and disperse our waste. Pollution occurs whenmore waste is added than a resource can accommodate.

In this section, we look at air, water, and land pollution.Each has distinctive features that illustrate the close connec-tion between human activities and environmental quality. ■

Air PollutionAt ground level, Earth’s average atmosphere is made up of about78 percent nitrogen, 21 percent oxygen, and less than 1 percentargon. The remaining 0.04 percent includes several trace gases,some of which are critical. Air pollution is a concentration oftrace substances at a greater level than occurs in average air.

The most common air pollutants are carbon monoxide,sulfur dioxide, nitrogen oxides, hydrocarbons, and solid partic-ulates. Concentrations of these trace gases in the air can damage

property and adversely affect the health of people, other ani-mals, and plants. Three human activities generate most air pol-lution—motor vehicles, industry, and power plants. In all threecases, pollution results from the burning of fossil fuels. Burninggasoline or diesel oil in cars, trucks, buses, and motorcycles pro-duces carbon monoxide, hydrocarbons, nitrogen oxides, andother pollutants. Factories and power plants produce sulfurdioxides and solid particulates, primarily from burning coal.

Global-Scale Air PollutionAir pollution concerns geographers at three scales—global,regional, and local. At the global scale, air pollution may con-tribute to global warming. It also may be damaging the atmos-phere’s ozone layer.

GLOBAL WARMING. Human actions, especially theburning of fossil fuels, may be causing Earth’s temperature to rise.The average temperature of Earth’s surface has increased by 1°Celsius (2° Fahrenheit) during the past century (Figure 14-15).

Earth is warmed by sunlight that passes through the atmos-phere, strikes the surface, and is converted to heat. When theheat tries to pass back through the atmosphere to space, somegets through and some is trapped. This process keeps Earth’stemperatures moderate and allows life to flourish on the planet.A concentration of trace gases in the atmosphere can block ordelay the return of some of the heat leaving the surface headingfor space, thereby raising Earth’s temperatures. When fossilfuels are burned, one of the trace gases, carbon dioxide, is dis-charged into the atmosphere.

Plants and oceans absorb much of the discharges, butincreased fossil-fuel burning during the past 200 years hascaused the level of carbon dioxide in the atmosphere to rise bymore than one-fourth, according to the UN IntergovernmentalPanel on Climate Change. Even if fossil-fuel burning is reducedimmediately, the level will continue to increase because of lin-gering effects of past emissions. Carbon dioxide is also increas-ing in the atmosphere from the burning and rotting of trees cutin the rain forests. Contributing to the warming has been thebuildup of carbon dioxide emissions at an annual rate of morethan 1 percent, although scientists disagree on whether itcaused most or only a small percentage of the warming. Unlesscarbon dioxide emissions are sharply curtailed in the nearfuture, average temperatures at the surface of Earth willincrease by several degrees over the next century.

The anticipated increase in Earth’s temperature, caused bycarbon dioxide trapping some of the radiation emitted by thesurface, is called the greenhouse effect. The term is somewhatmisleading, because a greenhouse does not work in the sameway as do trace gases in the atmosphere. In a real greenhouse,the interior gets very warm when the windows remain closed ona sunny day. The Sun’s light energy passes through the glass intothe greenhouse and is converted to heat, while the heat trappedinside the building is unable to escape out through the glass.Although an imprecise analogy, “greenhouse effect” has been awidely adopted term to evoke the anticipated warming ofEarth’s surface when trace gases block some of the heat trying toescape into space.

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