ENV330

G. Tyler Miller, Scott E. Spoolman

Living in the Environment

20th Edition

· Chapter Introduction

· Core Case Study The Real Cost of Gold

· 14.1 Geology and Mineral Resources

· 14.1a The Earth Is a Dynamic Planet

· 14.1b Minerals and Rocks

· 14.1c The Rock Cycle

· 14.1d Nonrenewable Mineral Resources

· 14.2 Supplies of Nonrenewable Mineral Resources

· 14.2a Nonrenewable Mineral Resources Can Be Economically Depleted

· 14.2b Market Prices and Supplies of Mineral Resources

· 14.2c Mining Lower-Grade Ores

· 14.2d Minerals from the Oceans

· 14.3 Environmental Effects of Using Nonrenewable Mineral Resources

· 14.3a Harmful Environmental Effects of Extracting Minerals

· 14.3b Environmental Effects of Removing Metals from Ores

· 14.4 Using Mineral Resources More Sustainably

· 14.4a Finding Substitutes for Scarce Mineral Resources

· 14.4b Using Mineral Resources More Sustainably

· 14.5 Geological Hazards

· 14.5a The Earth Beneath Your Feet Is Moving

· 14.5b Volcanic Eruptions

· 14.5c Earthquakes and Tsunamis

· Tying It All Together The Real Cost of Gold and Sustainability

· Chapter Review

· Critical Thinking

· Doing Environmental Science

· Data Analysis

14.2a

Nonrenewable Mineral Resources Can Be Economically Depleted

Most published estimates of the supply of a given nonrenewable mineral resource refer to its reserves: identified deposits from which we can extract the mineral profitably at current prices. Reserves can be expanded when we find new, profitable deposits or when higher prices or improved mining technologies make it profitable to extract deposits that previously were too expensive to remove.

The future supply of any nonrenewable mineral resource depends on the actual or potential supply of the mineral and the rate at which it is used. Society has never completely run out of a nonrenewable mineral resource. However, a mineral becomes economically depleted when it costs more than it is worth to find, extract, transport, and process the remaining deposits. At that point, there are five choices: recycle or reuse existing supplies, waste less, use less, find a substitute, or do without.

Depletion time is the time it takes to use up a certain proportion—usually 80%—of the reserves of a mineral at a given rate of use. When experts disagree about depletion times, it is often because they are using different assumptions about supplies and rates of use (Figure 14.4).

Figure 14.4

Natural capital depletion: Each of these depletion curves for a mineral resource is based on a different set of assumptions. Dashed vertical lines represent the times at which 80% depletion occurs.

A graph with three curves indicating the depletion of mineral resources. The graph is plotted with time on X-axis and the production on Y-axis. Curve A indicates a great increase in production within a very short time period and then falls drastically to zero level within a short time period. The supporting text associated with the curve reads “Mine, use, throw away; no new discoveries; rising prices”. About 80 percent of depletion of the mineral resources is indicated at a time just after the production begins to fall and is labeled “Depletion time A”. Curve B depicts a gradual increase in production with time and similarly the decrease in production is observed gradually with time. The supporting text associated with the curve reads “Recycle, increase reserves by improved mining technology, higher prices and new discoveries”. About 80 percent depletion of the resources is indicated at a time when the production drops to nearly half compared to the peak production and is labeled “Depletion time B”. Curve C depicts a very slow increase in production with time and the drop in production is also very slow. The supporting text associated with the curve reads “Recycle, reuse, reduce consumption; increase reserves by improved mining technology, higher prices and new discoveries”. About 80 percent depletion of resources is indicated at a time when the production drops to about 75 percent compared to the peak and is labeled “Depletion time C”.

The shortest depletion-time estimate assumes no recycling or reuse and no increase in the reserve (curve A, Figure 14.4). A longer depletion-time estimate assumes that recycling will stretch the existing reserve and that better mining technology, higher prices, or new discoveries will increase the reserve (curve B). The longest depletion-time estimate (curve C) makes the same assumptions as those for curve B and assumes that people will reuse and reduce consumption to expand the reserve further. Finding a substitute for a resource leads to a new set of depletion curves for the new mineral.

The earth’s crust contains abundant deposits of nonrenewable mineral resources such as iron and aluminum. However, concentrated deposits of important mineral resources such as manganese, chromium, cobalt, platinum, and rare earth elements (see the Case Study that follows) are relatively scarce. In addition, deposits of many mineral resources are not distributed evenly among countries. Five nations—the United States, Canada, Russia, South Africa, and Australia—supply most of the nonrenewable mineral resources that modern societies use.

Since 1900, and especially since 1950, there has been a sharp rise in the total and per capita use of mineral resources in the United States. According to the USGS, each American directly and indirectly uses an average of 18.4 metric tons (20.3 tons) of mineral resources per year.

The United States has economically depleted some of its once-rich deposits of metals such as lead, aluminum, and iron. In 2018, the United States imported all of its supplies of 21 key nonrenewable mineral resources and for 32 other minerals and relied on imports for more than half of its supplies. Most of these mineral imports come from reliable and politically stable countries. However, there are serious concerns about access to adequate supplies of four strategic metal resources—manganese, cobalt, chromium, and platinum—that are essential for the country’s economic and military strength. The United States has little or no reserves of these metals. China is a major global supplier of crucial minerals such as arsenic to make semiconductors, tungsten found in heating elements and light bulbs, and cadmium used in rechargeable batteries.

Lithium (Li), the world’s lightest metal, is a vital component of lithium-ion batteries, which are used in cell phones, iPads, laptop computers, electric cars, and a growing number of other products. The problem is that some countries, including the United States, do not have large supplies of lithium. Bolivia has about 50% of these reserves, whereas the United States holds only about 3%.

Japan, China, South Korea, and the United Arab Emirates have been buying up access to global lithium reserves to ensure their ability to sell lithium and lithium-ion batteries to the rest of the world. Within a few decades, the United States may be heavily dependent on expensive imports of lithium and lithium-ion batteries. A company is building a plant in California that is designed to extract lithium from brine waste produced by geothermal power plants. If it is successful, this process could lessen some U.S. dependence on imported lithium.

The demand for cobalt, which is widely used in lithium-ion electric-car batteries, magnets, and smartphones has been rising sharply. According to the Bank of America, electric vehicles will account for 34% of all global vehicle sales by 2030, which is expected to triple the global demand for cobalt. In 2019, the three largest producers of cobalt, in order, were the Democratic Republic of Congo (by far the largest producer), Russia, and Cuba. Because China is the world’s largest producer of electric cars and lithium ion batteries, it is buying up access to much of the world’s current and future cobalt production from the Democratic Republic of Congo.

Case Study

The Importance of Rare Earth Metals

Some mineral resources are familiar, such as gold, copper, aluminum, sand, and gravel. Less well known are the rare earth metals and oxides, which are crucial to many technologies that support modern lifestyles and economies.

The 17 rare earth metals, also known as rare earths, include scandium, yttrium, and 15 lanthanide chemical elements, including lanthanum. Because of their superior magnetic strength and other unique properties, these elements and their compounds are important for a number of widely used technologies.

Rare earths are used to make liquid crystal display (LCD) flat screens for computers and television sets, energy-efficient light-emitting diode (LED) light bulbs, solar cells, fiber-optic cables, smart phones, and digital cameras. Rare earths are also part of batteries and motors for electric and hybrid-electric cars (Figure 14.5), catalytic converters in car exhaust systems, jet engines, and the powerful magnets in wind turbine generators. Rare earths also go into missile guidance systems, smart bombs, aircraft electronics, and satellites.

Figure 14.5

Manufacturers of all-electric and hybrid-electric cars and other products use a variety of rare earth metals.

An illustration depicting various metals used in the manufacture of electric and hybrid electric cars and other products. An image of car depicting the internal parts of the car has three call outs. A call out pointing to the motor region (represented as a two interconnected drums near the front wheel region) reads, “Electric motors and generator: Dysprosium, Neodymium, Praseodymium, and Terbium.” A call out pointing to the battery (represented as a long yellow rectangle laid flat near the back wheel region) reads, “Battery” Lanthanum, Cerium.” A call out pointing the catalytic converter (represented as small blue rectangle laid flat near the back wheel region) reads, “Catalytic converter: Cerium, Lanthanum”. An image of the windmill (represented as a long pole with three huge blades attached at the tip) reads, “Neodymium.” An image of the camera (represented as a small rectangle with multiple sections and a projection in the front) reads, “Praseodymium.” An image of the monitor (represented as a black rectangle with bright white black center mounted on a small stand) reads, “Europium, Yttrium.”

Without affordable supplies of these metals, industrialized nations could not develop the current versions of cleaner energy technology and other high-tech products that will be major sources of economic growth during this century. Many nations also need these metals to maintain their military strength.

Most rare earth elements are not actually rare, but they are hard to find in concentrations high enough to extract and process at an affordable price. China has the largest share (37%) of the world’s known rare-earth reserves. In 2018, it accounted for 96% of the global mining output of rare-earth metals and in 2019 China gained control of the remaining 4% rare-earth production by acquiring the Molycorp rare-earth mine in Mountain Pass, California. This gives China control over the global price of its rare earth metal exports. China also dominates research and development of rare earth metals. The United States and Japan are heavily dependent on rare earths and their oxides. However, the United States produces no rare earths and has only 1.2% of the global rare-earth reserves. Japan has no rare-earth reserves.

One way to increase supplies of rare earths is to extract and recycle them from the massive amounts of electronic wastes that are being produced. It can also be extracted from large piles of phosphogypsum, a waste product of fertilizer manufacturing. So far, however, less than 1% of rare earth metals are recovered and recycled. Another approach is to find substitutes for rare earth metals. In 2016, Honda produced a hybrid electric car engine with magnets that do not need heavy rare-earth metals and that are 10% cheaper and 8% lighter. 14.2bMarket Prices and Supplies of Mineral Resources

Geological processes determine the quantity and location of a mineral resource in the earth’s crust, but economics determines what part of the known supply is extracted and used. According to standard economic theory, in a competitive market system when a resource becomes scarce, its price rises. Higher prices can encourage exploration for new deposits, stimulate development of better mining technology, and make it profitable to mine lower-grade ores. Higher prices can also promote resource conservation and a search for substitutes.

According to some economists, this price effect may no longer apply completely in most more-developed countries. Governments in such countries often use subsidies, tax breaks, and import tariffs to control the supply, demand, and prices of key mineral resources. In the United States, for instance, mining companies get various types of government subsidies, including depletion allowances—which allow the companies to deduct the costs of developing and extracting mineral resources from their taxable incomes. These allowances amount to 5–22% of their gross income gained from selling the mineral resources.

Another potential ocean source of some minerals is hydrothermal ore deposits that form when superheated, mineral-rich water shoots out of vents in volcanic regions of the ocean floor. As the hot water meets cold seawater, black particles of various metal sulfides precipitate out and accumulate as chimney-like structures, called black smokers, near the hot water vents ( Figure 14.6 ). These deposits are especially rich in minerals such as copper, lead, zinc, silver, gold, and some of the rare earth metals. Exotic communities of marine life—including giant clams, six-foot tubeworms, and eyeless shrimp—live in the dark depths around black smokers. Companies from Australia, the United States, and China have been exploring the possibility of mining black smokers in several areas.

Figure 14.6

Natural capital: Hydrothermal deposits, or black smokers, are rich in various minerals.

Because of the rapidly rising prices of many of these metals, interest in deep-sea mining is growing. According to some analysts, seafloor mining is less environmentally harmful than mining on land. Other scientists, however, are concerned sediment stirred up by such mining could harm or kill organisms that feed by filtering seawater. Supporters of seafloor mining say that the number of potential mining sites, and thus the overall environmental impact, will be small.

Every metal product has a life cycle that includes mining the mineral, processing it, manufacturing the product, and disposal or recycling of the product (Figure 14.7). This process makes use of large amounts of energy and water, and produces pollution and waste at every step of the life cycle.

Figure 14.7

Each metal product that we use has a life cycle.

Left: kaband/ Shutterstock.com. Second to left: Andrey N Bannov/ Shutterstock.com. Center left: Vladimir Melnik/ Shutterstock.com. Center: mares/ Shutterstock.com. Center right: Zhu Difeng/ Shutterstock.com. Second to right: Michael Shake/ Shutterstock.com. Right: Pakhnyushchy/ Shutterstock.com.

Several mining techniques are used to remove mineral deposits. Shallow mineral deposits are removed by  surface mining , in which vegetation, soil, and rock overlying a mineral deposit are cleared away. This waste material is called  overburden  and is usually deposited in piles called  spoils  (Figure 14.8). Surface mining is used to extract about 90% of the nonfuel mineral resources and 60% of the coal used in the United States.

Figure 14.8

Natural capital degradation: This spoils pile in Zielitz, Germany, is made up of waste material from the mining of potassium salts used to make fertilizers.

LianeM/ Shutterstock.com

Different types of surface mining can be used, depending on two factors: the resource being sought and the local topography. In  open-pit mining , machines are used to dig large pits and remove metal ores containing copper, gold (Core Case Study), or other metals, or sand, gravel, or stone. The open-pit copper mine shown in the opening photo for this chapter is almost 5 kilometers (3 miles) wide and 1,200 meters (4,000 feet) deep, and is getting deeper.

9 Million

Number of people who could sit in Bingham Copper Mine (see chapter-opening photo) if it were a stadium

Strip mining involves extracting mineral deposits that lie in large horizontal beds close to the earth’s surface. In  area strip mining , used on flat terrain, a gigantic earthmover strips away the overburden, and a power shovel—which can be as tall as a 20-story building—removes a mineral resource such as gold (Figure 14.9). The resulting trench is filled with overburden, and a new cut is made parallel to the previous one. This process is repeated over the entire site.

Figure 14.9

Natural capital degradation: Area strip-mining for gold in Yukon Territory, Canada.

Paul Nicklen/National Geographic Image Collection

Contour strip mining  (Figure 14.10) is used mostly to mine coal and various mineral resources on hilly or mountainous terrain. Huge power shovels and bulldozers cut a series of terraces into the side of a hill. Then, earthmovers remove the overburden, an excavator or power shovel extracts the coal, and the overburden from each new terrace is dumped onto the one below. Unless the land is restored, this leaves a series of spoils banks and a highly erodible hill of soil and rock called a highwall.

Figure 14.10

Natural capital degradation: Contour strip mining is used in hilly or mountainous terrain.

Another surface mining method is  mountaintop removal , in which explosives are used to remove the top of a mountain to expose seams of coal that are then extracted (Figure 14.11). After a mountaintop is blown apart, enormous machines plow waste rock and dirt into valleys below the mountaintops. This destroys forests, buries mountain streams, and increases the risk of flooding. Wastewater and toxic sludge, produced when the coal is processed, are often stored behind dams in these valleys. Some dams have overflowed or collapsed and released toxic substances such as arsenic and mercury.

Figure 14.11

Natural capital degradation: Mountaintop removal coal mining near Whitesville, West Virginia.

Jim West/Age Fotostock

In the United States, more than 500 mountaintops in West Virginia and other Appalachian states have been removed to extract coal (Figure 14.11). According to the U.S. Environmental Protection Agency (EPA), the resulting spoils have buried more than 1,100 kilometers (700 miles) of streams.

The U.S. Surface Control and Reclamation Act of 1997 requires mining companies to restore mines abandoned before 1977 and companies are required to restore active mines and mines abandoned after 1977. However, the program is greatly underfunded and many mines have not been reclaimed.

Deep deposits of minerals are removed by  subsurface mining , in which underground mineral resources are removed through tunnels and shafts (Figure 14.12). This method is used to remove metal ores and coal that are too deep to be extracted by surface mining. Miners dig a deep, vertical shaft and blast open subsurface tunnels and chambers to reach the deposit. Then they use machinery to remove the resource and transport it to the surface.

Figure 14.12

Subsurface mining of coal.

Subsurface mining disturbs less than one-tenth as much land as surface mining, and usually produces less waste material. However, the environmental damage is significant and can lead to other hazards such as cave-ins, explosions, and fires for miners. Miners often get lung diseases caused by prolonged inhalation of mineral or coal dust in subsurface mines. Another problem is subsidence—the collapse of land above some underground mines. It can damage houses, crack sewer lines, break natural gas mains, and disrupt groundwater systems. Subsurface mining also requires large amounts of water and energy to process and transport the mined material.

Collectively, surface and subsurface mining operations produce three-fourths of all U.S. solid waste and cause major water and air pollution. For example, acid mine drainage occurs when rainwater seeps through an underground mine or a spoils pile from a surface mine. Such water can contain sulfuric acid , produced when aerobic bacteria act on minerals in the spoils. This toxic runoff can pollute nearby streams and groundwater—one of the problems often associated with gold mining (Core Case Study).

According to the EPA, mining has polluted mountain streams in 40% of the western watersheds in the United States. It also accounts for half of all the country’s emissions of toxic chemicals into the atmosphere. In fact, the mining industry produces more of such toxic emissions than any other U.S. industry.

Mining can be even more harmful to the environment in countries where environmental regulations are lacking or not reliably enforced. In China, for instance, the mining and processing of rare earth metals and oxides has stripped land of its vegetation and topsoil. It also has polluted the air, acidified streams, and left toxic and radioactive waste piles.

14.3bEnvironmental Effects of Removing Metals from Ores

Ore extracted by mining typically has two components: the ore mineral that contains the desired metal and waste material. Removing the waste material from ores produces  tailings —rock wastes that are left in piles or put into ponds where they settle out. Particles of toxic metals in tailings piles can be blown by the wind, washed out by rain, or leak from holding ponds, which can contaminate surface water and groundwater.

After the waste material is removed, heat or chemical solvents are used to extract the metals from mineral ores. Heating ores to release metals is called  smelting  ( Figure 14.7 ). Without effective pollution control equipment, a smelter emits large quantities of air pollutants. These pollutants include sulfur dioxide and suspended toxic particles that damage vegetation and acidify soils in the surrounding area. Smelters also cause water pollution and produce liquid and solid hazardous wastes that require safe disposal. A 2012 study found that lead smelting is the world’s second most toxic industry after the recycling of lead-acid batteries.

Using chemicals to extract metals from their ores can also create pollution and health problems, as we saw in the case of using cyanide to remove gold ( Core Case Study ). Millions of poverty-stricken miners in less-developed countries have gone into tropical forests in search of gold. They have cleared trees to get access to gold, and such illegal deforestation has increased rapidly, especially parts of the Amazon Basin and in Africa ( Figure 14.13 ). In these small-scale and illegal gold mines, miners use toxic mercury to separate gold from its ore. They heat the mixture of gold and mercury to vaporize the mercury and leave the gold, causing dangerous air and water pollution. They leave behind land stripped of vegetation and topsoil loaded with toxic mercury. Many of the miners and villagers living near the mines eventually inhale toxic mercury vapor, drink mercury-laden water, or eat fish contaminated with mercury.

Figure 14.13

Illegal gold mining on the banks of the Pra River in Ghana, Africa.

Randy Olson/National Geographic Image Collection

14.4aFinding Substitutes for Scarce Mineral Resources

Some analysts believe that even if supplies of key minerals become too expensive or too scarce due to unsustainable use, human ingenuity will find substitutes. They point to the current materials revolution in which silicon and other materials are replacing some metals for common uses. They also point out the possibilities of finding substitutes for scarce minerals through nanotechnology (Science Focus 14.1), and other emerging technologies (see Case Study that follows).

Science Focus 14.1

The Nanotechnology Revolution

Nanotechnology  uses science and engineering to manipulate and create materials out of atoms and molecules at the ultra-small scale of less than 100 nanometers. The diameter of the period at the end of this sentence is about a half million nanometers.

Currently, nanomaterials are used in more than 1,300 consumer products and the number is growing. Such products include certain batteries, stain-resistant and wrinkle-free clothes, self-cleaning glass surfaces, self-cleaning sinks and toilets, sunscreens, waterproof coatings for cell phones, some cosmetics, some foods, and food containers that release nanosilver ions to kill bacteria, molds, and fungi.

Nanotechnologists envision innovations such as a supercomputer smaller than a grain of rice, thin and flexible solar cell films that could be attached to or painted onto almost any surface, and materials that would make our bones and tendons super strong. Some nanomolecules could be designed to seek out and kill cancer cells or to eliminate the need for allergy shots. Scientists are working on a wearable graphene patch that would help diabetics manage their blood glucose levels without the use of needles. It would measure blood sugar levels in sweat and maintain acceptable levels by delivering a dose of a diabetes drug through the skin without the use of needles. Nanotechnology allows us to make materials from the bottom up, using atoms of abundant elements (primarily hydrogen, oxygen, nitrogen, carbon, silicon, and aluminum) as substitutes for scarcer elements, such as copper, cobalt, and tin.

Nanotechnology has many potential environmental benefits. Designing and building products on the molecular level would greatly reduce the need to mine many materials. It would also require less matter and energy. Nanofilters might someday be used to desalinate and purify seawater at an affordable cost, thereby helping to increase drinking water supplies. GREEN CAREER: Environmental nanotechnology

What is the catch? The main problem is serious concerns about the possible harmful health effects of nanotechnology. Because of their tiny size, nanoparticles are potentially more toxic to humans and other animals than many conventional materials.

Laboratory studies involving mice and other test animals reveal that nanoparticles can be inhaled deeply into the lungs and absorbed into the bloodstream. Nanoparticles can also penetrate cell membranes, including those in the brain, and move across the placenta from a mother to her fetus.

A panel of experts from the U.S. National Academy of Sciences has said that the U.S. government is not doing enough to evaluate the potential health and environmental risks of using nanomaterials. For example, the U.S. Food and Drug Administration does not maintain a list of the food products and cosmetics that contain nanomaterials. By contrast, the European Union takes a precautionary approach to the use of nanomaterials, requiring manufacturers to demonstrate the safety of their products before they can enter the marketplace. Many analysts call for greatly increased research on the potential harmful health effects of nanoparticles and for labeling all products that contain nanoparticles.

Critical Thinking

1. Do you think the potential benefits of nanotechnology products outweigh their potentially harmful effects? Explain.

Case Study

Graphene and Phosphorene: New Revolutionary Materials

Graphene is made from graphite—a form of carbon that occurs as a mineral in some rocks. Ultrathin graphene consists of a single layer of carbon atoms packed into a two-dimensional hexagonal lattice (somewhat like chicken wire) that can be applied as a transparent film to surfaces (Figure 14.14).

Figure 14.14

Graphene, which consists of a single layer of carbon atoms linked together in a hexagonal lattice, is a revolutionary new material.

Vincenzo Lombardo/Photographer’s Choice/Getty Images

Graphene is one of the world’s thinnest and strongest materials and is light, flexible, and stretchable. A single layer of graphene is 150,000 times thinner than a human hair and 100 times stronger than structural steel. A sheet of this amazing material stretched over a coffee mug could support the weight of a car. It is also a better conductor of electricity than copper and conducts heat better than any known material.

The use of graphene could revolutionize the electric car industry by leading to the production of batteries that can be recharged 10 times faster and hold 10 times more power than current car batteries. Graphene composites can also be used to make stronger and lighter plastics, lightweight aircraft and motor vehicles, flexible computer tablets, and TV screens as thin as a magazine. It might also be used to make flexible, more efficient, less costly solar cells that can be attached to almost anything. In addition, engineers hope to make advances in desalination by using graphene to make the membrane used in reverse osmosis (see Figure 13.17, left).

Researchers are looking into possible harmful effects of graphene production and use. A study led by Sharon Walker at the University of California–Riverside found graphene oxide in lakes and drinking water storage tanks. This could increase the chances that animals and humans could ingest the chemical, which was found in some early studies to be toxic to mice and human lung cells.

Graphene is made from very high purity and expensive graphite. According to the USGS, China controls about two-thirds of the world’s high-purity graphite production. The United States mines very little natural graphite and imports most of its graphite from Mexico and China, which could restrict U.S. product exports as the use of graphene grows.

Geologists are looking for deposits of graphite in the United States. However, a team of Rice University chemists, led by James M. Tour, found ways to make large sheets of high-quality graphene from inexpensive materials found in garbage and from dog feces. If such a process becomes economically feasible, this could reduce concern over supplies of graphite, along with any harmful environmental effects of the mining and processing of graphite.

In 2014, a team of researchers at Purdue University was able to isolate a single layer of black phosphorus atoms—a new material known as phosphorene. As a semiconductor, it is more efficient than silicon transistors that are used as chips in computers and other electronic devices. Replacing them with phosphorene transistors could make almost any electronic device run much faster while using less power. This could revolutionize computer technology. However, phosphorene must be sealed in a protective coating because it breaks down when exposed to air.

For example, fiber-optic glass cables that transmit pulses of light are replacing copper and aluminum wires in telephone cables, and nanowires may eventually replace fiber-optic glass cables. High-strength plastics and materials, strengthened by lightweight carbon, hemp, and glass fibers, are beginning to transform the automobile and aerospace industries. These new materials do not need painting (which reduces pollution and costs) and can be molded into any shape. Use of such materials in manufacturing motor vehicles and airplanes could greatly increase vehicle fuel efficiency by reducing vehicle weights.

Learning from Nature

Without using toxic chemicals, spiders rapidly build their webs by producing threads of silk strong enough to capture insects flying at high speeds. Learning how spiders do this could revolutionize the production of high-strength fibers with a very low environmental impact.

We can also find substitutes for rare earths. For example, electric car battery makers are beginning to switch from making nickel-metal-hydride batteries, which require the rare earth metal lanthanum, to manufacturing lighter-weight lithium-ion batteries, which researchers are trying to improve (Individuals Matter 14.1).

Individuals Matter 14.1

Yu-Guo Guo: Designer of Nanotechnology Batteries and National Geographic Explorer

© Jinsong Hu

Yu-Guo Guo is a professor of chemistry and a nanotechnology researcher at the Chinese Academy of Sciences in Beijing. He has invented nanomaterials that can be used to make lithium-ion battery packs smaller, more powerful, and less costly, which makes them more useful for powering electric cars and electric bicycles. This is an important scientific advance, because the battery pack is the most important and expensive part of any electric vehicle.

Guo’s innovative use of nanomaterials has greatly increased the power of lithium-ion batteries by enabling electric current to flow more efficiently through what he calls “3-D conducting nanonetworks.” With this promising technology, lithium-ion battery packs in electric vehicles can be fully charged in a few minutes, as quickly as filling a car with gas. They also have twice the energy storage capacity of today’s batteries, and thus will extend the range of electric vehicles by enabling them to run longer. Guo is also interested in developing nanomaterials for use in solar cells and fuel cells that could be used to generate electricity and to power vehicles.

Despite its potential, resource substitution is not a cure-all. Finding acceptable and affordable substitutes for some resources may not always be possible.

14.4bUsing Mineral Resources More Sustainably

Figure 14.15  lists several ways to use mineral resources more sustainably. One strategy is to focus on recycling and reuse of nonrenewable mineral resources, especially valuable or scarce metals such as gold ( Core Case Study ), iron, copper, aluminum, and platinum. Recycling, an application of the chemical cycling principle of sustainability, has a much lower environmental impact than that of mining and processing metals from ores.

Figure 14.15

Ways to use nonrenewable mineral resources more sustainably.

Critical Thinking:

1. Which two of these solutions do you think are the most important? Why?

For example, recycling aluminum beverage cans and scrap aluminum produces 95% less air pollution and 97% less water pollution, and uses 95% less energy, than mining and processing aluminum ore. We can also extract and recycle valuable gold ( Core Case Study ) from discarded cell phones. Cleaning up and reusing items instead of breaking them down and recycling them has an even lower environmental impact.

Using mineral resources more sustainably is a major challenge in the face of rising demand for many minerals. For example, one way to increase supplies of rare earths is to extract and recycle them from the massive amounts of electronic wastes that are being produced. So far, however, less than 1% of rare earth metals are recovered and recycled.

Another way to use minerals more sustainably is to find substitutes for rare minerals, ideally, substitutes without serious environmental impacts. For example, electric car battery makers are beginning to switch from making nickel-metal-hydride batteries, which require the rare earth metal lanthanum, to manufacturing lighter-weight lithium-ion batteries, which researchers are now trying to improve ( Individuals Matter 14.1 ).

Scientists are also searching for substitutes for rare earth metals that are used to make increasingly important powerful magnets and related devices. In Japan and the United States, researchers are developing a variety of such devices that require no rare earth minerals, are light and compact, and can deliver more power with greater efficiency at a reduced cost.

14.5aThe Earth Beneath Your Feet Is Moving

We tend to think of the earth’s crust as solid and unmoving. However, the flows of energy and heated material within the earth’s convection cells (Figure 14.2) are so powerful that they have caused the lithosphere to break up into seven major rigid plates and many minor plates, all called  tectonic plates , which move extremely slowly atop the asthenosphere (Figure 14.16).

Figure 14.16

The earth’s crust has been fractured into 7 major and many minor tectonic plates. White arrows and the bottom of the figure show where plates are sliding past one another at transform faults, colliding at convergent plate boundaries, or moving away from one another at divergent plate boundaries.

Question:

1. Which plate are you riding on?

Tectonic plates are somewhat like the world’s largest and slowest-moving surfboards on which we ride without noticing their movement. Their typical speed is about the rate at which your fingernails grow. Throughout the earth’s history, landmasses have split apart and joined as tectonic plates shifted around, changing the size, shape, and location of the earth’s continents (Figure 4.B). This slow movement of the continents across the earth’s surface is called  continental drift .

Much of the geological activity at the earth’s surface takes place at the boundaries between tectonic plates as they slide past one-another at a transform fault, move toward one another at a convergent plate boundary, or move away from one another at a divergent plate boundary (Figure 14.16, bottom). The tremendous forces produced at these boundaries can form mountains and deep crevices and cause earthquakes and volcanic eruptions.

The boundary that occurs where two plates move away from each other is called a  divergent plate boundary  (Figure 14.17). At such boundaries, magma flows up where the plates separate, sometimes hardening and forming new crust and sometimes breaking to the surface and causing volcanic eruptions. Earthquakes can also occur because of divergence of plates, and superheated water can erupt as geysers.

Figure 14.17

The North American Plate and the Pacific Plate slide very slowly against each other in opposite directions along the San Andreas fault (see photo), which runs almost the full length of California (see map). It has been the site of many earthquakes of varying magnitudes.

Kevin Schafer/Age Fotostock

Another type of boundary is the  convergent plate boundary  (Figure 14.16), where two tectonic plates are colliding. This super-slow-motion collision causes one or both plate edges to buckle and rise, forming mountain ranges. In most cases, one plate slides beneath the other, melting and making new magma that can rise through cracks and form volcanoes near the boundary. The overriding plate is pushed up and made into mountainous terrain.

The third major type of boundary is the  transform fault , or  transform plate boundary  (Figure 14.16), where two plates grind along in opposite directions next to each other. The tremendous forces produced at these boundaries can form mountains or deep cracks and cause earthquakes and volcanic eruptions.

14.5bVolcanic Eruptions

A  volcano  is an opening in the earth’s crust through which magma, gases, and ash are ejected explosively or from which lava flows. An active volcano occurs where magma rising in a plume through the lithosphere reaches the earth’s surface through a central vent or a long crack, called a fissure (Figure 14.18). Magma or molten rock that reaches the earth’s surface is called lava.

Figure 14.18

Sometimes, the internal pressure in a volcano is high enough to cause lava, ash, and gases to be ejected into the atmosphere (photo inset) or to flow over land, causing considerable damage.

beboy/ Shutterstock.com

Many volcanoes form along the boundaries of the earth’s tectonic plates when one plate slides under or moves away from another plate (Figure 14.15, bottom). A volcanic eruption releases chunks of lava rock, liquid lava, glowing hot ash, and gases (including water vapor, carbon dioxide, and sulfur dioxide). Eruptions can be explosive and extremely destructive, causing loss of life and obliterating ecosystems and human communities. They can also be slow and much less destructive with lava gurgling up and spreading slowly across the land or sea floor.

While volcanic eruptions can be destructive, they can also form majestic mountain ranges and lakes, and the weathering of lava contributes to fertile soils. Hundreds of volcanoes have erupted on the ocean floor, building cones that have reached the ocean’s surface, eventually to form islands that have become suitable for human settlement, such as the Hawaiian Islands.

We can reduce the loss of human life and some of the property damage caused by volcanic eruptions by using historical records and geological measurements to identify high-risk areas, so that people can avoid living in those areas. Scientists and engineers are also developing monitoring devices that warn us when volcanoes are likely to erupt.

Forces inside the earth’s mantle put tremendous stress on rock within the crust. Such stresses can be great enough to cause sudden breakage and shifting of the rock, producing a fault, or fracture in the earth’s crust (Figure 14.17). When a fault forms, or when there is abrupt movement on an existing fault, energy that has accumulated over time is released in the form of vibrations, called seismic waves, which move in all directions through the surrounding rock—an event called an  earthquake  (Figure 14.19). Most earthquakes occur at the boundaries of tectonic plates (Figures 14.16).

Figure 14.19

An earthquake (left) is one of nature’s most powerful events. The photo shows damage from a 2010 earthquake in Port-au-Prince, Haiti.

AP Images/Jorge Cruz

Seismic waves move upward and outward from the earthquake’s focus like ripples in a pool of water. Scientists measure the severity of an earthquake by the magnitude of its seismic waves. The magnitude is a measure of ground motion (shaking) caused by the earthquake, as indicated by the amplitude, or size of the seismic waves when they reach a recording instrument, called a seismograph.

Scientists use the Richter scale, on which each unit has an amplitude 10 times greater than the next smaller unit. Seismologists, or people who study earthquakes, rate earthquakes as insignificant (less than 4.0 on the Richter scale), minor (4.0–4.9), damaging (5.0–5.9), destructive (6.0–6.9), major (7.0–7.9), and great (over 8.0). The largest recorded earthquake occurred in Chile on May 22, 1960, and measured 9.5 on the Richter scale. Each year, scientists record the magnitudes of more than 1 million earthquakes, most of which are too small to feel.

The primary effects of earthquakes include shaking and sometimes a permanent vertical or horizontal displacement of a part of the crust. These effects can have serious consequences for people and for buildings, bridges, freeway overpasses, dams, and pipelines.

One way to reduce the loss of life and property damage from earthquakes is to examine historical records and make geological measurements to locate active fault zones. We can then map high-risk areas (Figure 14.20) and establish building codes that regulate the placement and design of buildings in such areas. Then people can evaluate the risk and factor it into their decisions about where to live. In addition, engineers know how to make homes, large buildings, bridges, and freeways more earthquake resistant, although this is costly.

Figure 14.20

Comparison of degrees of earthquake risk across the continental United States.

Question:

1. What is the earthquake risk where you live or go to school?

Learning from Nature

Because a spider can squeeze through tight spaces and quickly change directions, German researchers used the spider as a model for a new robot that can probe hazardous disaster sites where people cannot safely go, looking for survivors or sending out data to help deal with the disaster. It could be reproduced inexpensively on a 3D printer to be made available for all sorts of natural and industrial catastrophes.

A  tsunami  is a series of large waves generated when part of the ocean floor suddenly rises or drops (Figure 14.21). Most large tsunamis are caused when certain types of faults in the ocean floor move up or down because of a large underwater earthquake. Other causes are landslides generated by earthquakes and volcanic eruptions.

Figure 14.21

Formation of a tsunami. The map shows the area affected by a large tsunami in December 2004—one of the largest ever recorded.

Left: Science Source. Right: Science Source.

Tsunamis are often called tidal waves, although they have nothing to do with tides. They can travel across the ocean at the speed of a jet plane. In deep water, the waves are very far apart—sometimes hundreds of kilometers—and their crests are not very high. As a tsunami approaches a coast with its shallower waters, it slows down, its wave crests squeeze closer together, and their heights grow rapidly. It can hit a coast as a series of towering walls of water that can level buildings.

The largest recorded loss of life from a tsunami occurred in December 2004 when a great underwater earthquake in the Indian Ocean with a magnitude of 9.2 caused a tsunami that killed more than 230,000 people and devastated many coastal areas of Indonesia (Figure 14.22 and map in Figure 14.21), Thailand, Sri Lanka, South India, and eastern Africa. It displaced about 1.7 million people (1.3 million of them in India and Indonesia), and destroyed or damaged about 470,000 buildings and houses. There were no recording devices in place to provide an early warning of this tsunami.

Figure 14.22

The Banda Aceh Shore near Gleebruk, Indonesia on June 23, 2004 (left), and on December 28, 2004 (right), after it was struck by a tsunami.

New York Public Library/Science Source

In 2011, a large tsunami caused by a powerful earthquake off the coast of Japan generated 3-story high waves that killed almost 19,000 people, displaced more than 300,000 people, and destroyed or damaged 125,000 buildings. It also heavily damaged three nuclear reactors, which then released dangerous radioactivity into the surrounding environment.

In some areas, scientists have built networks of ocean buoys and pressure recorders on the ocean floor to collect data that can be relayed to tsunami emergency warning centers. However, these networks are far from complete.

· Matt Benoit/ Shutterstock.com

· In this chapter’s Core Case Study, we considered the harmful effects of gold mining as an example of the impacts of our extraction and use of mineral resources. We saw that these effects make gold much more costly, in terms of environmental and human health costs, than is reflected in the price of gold.

· In this chapter, we looked at technological developments that could help us to expand supplies of mineral resources and to use them more sustainably. For example, if we develop it safely, we could use nanotechnology to make new materials that could replace scarce mineral resources and greatly reduce the environmental impacts of mining and processing such resources. For example, we might use graphene to produce more efficient and affordable solar cells to generate electricity—an application of the solar energy principle of sustainability. We can also use mineral resources more sustainably by reusing and recycling them, and by reducing unnecessary resource use and waste—applying the chemical cycling principle of sustainability. In addition, industries can mimic nature by using a diversity of ways to reduce the harmful environmental impacts of mining and processing mineral resources, thus applying the biodiversity principle of sustainability.

Chapter Review

Critical Thinking

1. Do you think that the benefits we get from gold—its uses in jewelry, dentistry, electronics, and other uses—are worth the real cost of gold (Core Case Study)? If so, explain your reasoning. If not, explain your argument for cutting back on or putting a stop to the mining of gold.

2. You are an igneous rock. Describe what you experience as you move through the rock cycle. Repeat this exercise, assuming you are a sedimentary rock and again assuming you are a metamorphic rock.

3. What are three ways in which you benefit from the rock cycle?

4. Suppose your country’s supply of rare earth metals was cut off tomorrow. How would this affect your life? Give at least three examples. How would you adjust to these changes? Explain.

5. Use the second law of thermodynamics (see Chapter 2) to analyze the scientific and economic feasibility of each of the following processes:

1. Extracting certain minerals from seawater

2. Mining increasingly lower-grade deposits of minerals

3. Continuing to mine, use, and recycle minerals at increasing rates.

6. Suppose you were told that mining deep-ocean mineral resources would mean severely degrading ocean bottom habitats and life forms such as giant tubeworms and giant clams (Figure 14.6). Do you think that such information should be used to prevent ocean bottom mining? Explain.

7. List three ways in which a nanotechnology revolution could benefit you and three ways in which it could harm you. Do you think the benefits outweigh the harms? Explain.

8. What are three ways to reduce the harmful environmental impacts of the mining and processing of nonrenewable mineral resources? What are three aspects of your lifestyle that contribute to these harmful impacts?

Chapter Review

Doing Environmental Science

Do research to determine which mineral resources go into the manufacture of each of the following items and how much of each of these resources are required to make each item:

1. a cell phone,

2. a wide-screen TV, and

3. a large pickup truck.

Pick three of the lesser-known mineral materials that you have learned about in this exercise and do more research to find out where in the world most of the reserves for that mineral are located. For each of the three minerals you chose, try to find out what kinds of environmental effects have resulted from the mining of the mineral in at least one of the places where it is mined. You might also find out about steps that have been taken to deal with those effects. Write a report summarizing all of your findings.

Chapter Review

Data Analysis

Rare earth metals are widely used in a variety of important products (see  Case Study  , this chapter). According to the U.S. Geological Survey, China has about 37% of the world’s reserves of rare earth metals. Use this information to answer the following questions.

1. In 2017, China had 44 million metric tons of rare earth metals in its reserves and produced 105,000 metric tons of these metals. At this rate of production, how long will China’s rare earth reserves last?

2. In 2017, the global demand for rare earth metals was about 130,000 metric tons. At this annual rate of use, if China were to produce all of the world’s rare earth metals, how long would their reserves last?

3. The annual global demand for rare earth metals is projected to rise to at least 180,000 metric tons by 2020. At this rate, if China were to produce all of the world’s rare earth metals, how long would its reserves last?