U.S. Raw Nonfuel Mineral Materials Put into Use Annually, 1900–2006

1900

Million metric tons

3600

3200

2800

2400

2000

1600

1200

800

400

0

1910

Year

1920 1930 1940 1950 1960 1970 1980 1990 2000 2006

Recessions

World War

Oil crisis

Great Depression

Primary metals

Recycled metals

Industrial minerals

Construction materials

World War

Courtesy of USGS Mineral Resources Program, 2008.

12

Mineral and

Soil Resources

Interpreting Data

Explain the differences in use of various mineral

categories—why do you suppose usage has

increased so much more in some groups than

in others?

COPPER BASIN, TENNESSEE

T

he United States—like countries worldwide—

is growing increasingly more dependent on

nonfuel mineral resources (see graph), but this

dependence can trigger high environmental costs.

Copper Basin, Tennessee, provides an example of

environmental degradation caused by smelting, a

stage of mineral processing that removes impurities

from metals. During the 19th century mining

companies in southeastern Tennessee extracted

copper ore—rock containing copper—from the

ground and dug vast pits to serve as open-air

smelters. They cut down the surrounding trees to

fire the smelters, producing the high temperatures

needed for separating copper from other

substances in the ore. One of these substances,

sulfur, reacted with oxygen in the air to form sulfur

dioxide. The sulfur dioxide entered the atmosphere,

reacted with water vapor there, and became

sulfuric acid that returned to Copper Basin as acid

precipitation.

Ecological ruin took only a few short years (see

larger photograph, taken in 1973). Acid precipitation

killed plants. Without plants to hold the soil in place,

erosion cut gullies in the rolling hills. The forest

animals disappeared along with the plants, their

food and shelter destroyed.

State and federal reclamation efforts were

only marginally successful until the 1970s, when

specialists began using new replanting techniques.

The new plants had a greater survival rate, and as

they became established, their roots held the soil

in place (see inset photo of a reforested section, in

2008). Birds and field mice slowly began to return.

Today, reclamation of Copper Basin continues;

the goal is to have the entire area under plant cover

by the middle of the 21st century. The return of the

original forest ecosystem will take at least a century

or two. Plant scientists and land reclamation

specialists have learned a lot from Copper

Basin, and they will put this knowledge to use in

future reclamation projects around the world.