Download Chapter 14 Geology and Mining 2016

MILLER/SPOOLMAN
LIVING IN THE ENVIRONMENT
17TH
Chapter 14
Geology and Nonrenewable
Mineral Resources
Core Case Study: The Real Cost of Gold
• Gold producers
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China
South Africa
Australia
United States
Canada
• Cyanide heap leaching
• Extremely toxic to birds and mammals
• Spills contaminate drinking water and kill birds and fish
Gold Mine with Cyanide Leach Piles and
Ponds in South Dakota, U.S.
Fig. 14-1, p. 346
Mountaintop Removal
• Video: Plundering Appalachia
About 20% of the coal used for
electricity is mined in central
Appalachia, equating to 8% of
our electricity. Roughly 45% of
central Appalachian coal is from
strip mining, and almost 100%
of that is mountaintop removal.
Therefore, mountaintop removal
coal provides roughly only 3%
of our country's electricity.
At your table, in 5 minutes or less …
Major Features of the Earth’s Crust and
Upper Mantle
Fig. 14-2, p. 348
The Earth’s Crust Is Made Up of a Mosaic of Huge
Rigid Plates: Tectonic Plates
Fig. 14-3, p. 348
The Earth Beneath Your Feet Is
Moving (2)
• Three types of boundaries between plates
• Divergent boundaries
• Magma
• Oceanic ridge
• Convergent boundaries
• Subduction zone
• Trench
• Transform boundaries: San Andreas fault
Arabian
Plate
Caribbean
Plate
Scotia
Plate
Philippine
Plate
Divergent Boundaries
• A divergent boundary occurs when two tectonic
plates move away from each other. Along these
boundaries, lava spews from long fissures and
geysers spurt superheated water. Frequent
earthquakes strike along the rift. Beneath the rift,
magma—molten rock—rises from the mantle. It
oozes up into the gap and hardens into solid rock,
forming new crust on the torn edges of the plates.
Magma from the mantle solidifies into basalt, a dark,
dense rock that underlies the ocean floor. Thus at
divergent boundaries, oceanic crust, made of basalt,
is created.
Convergent Boundaries
• When two plates come together, it is known as a convergent
boundary. The impact of the two colliding plates buckles the
edge of one or both plates up into a rugged mountain range,
and sometimes bends the other down into a deep seafloor
trench. A chain of volcanoes often forms parallel to the
boundary, to the mountain range, and to the trench. Powerful
earthquakes shake a wide area on both sides of the boundary.
• If one of the colliding plates is topped with oceanic crust, it is
forced down into the mantle where it begins to melt. Magma
rises into and through the other plate, solidifying into new
crust. Magma formed from melting plates solidifies into
granite, a light colored, low-density rock that makes up the
continents. Thus at convergent boundaries, continental crust,
made of granite, is created, and oceanic crust is destroyed.
Transform Boundaries
• Two plates sliding past each other forms a transform
plate boundary. Natural or human-made structures
that cross a transform boundary are offset—split
into pieces and carried in opposite directions. Rocks
that line the boundary are pulverized as the plates
grind along, creating a linear fault valley or undersea
canyon. As the plates alternately jam and jump
against each other, earthquakes rattle through a
wide boundary zone. In contrast to convergent and
divergent boundaries, no magma is formed. Thus,
crust is cracked and broken at transform margins,
but is not created or destroyed.
Volcanic arcs and oceanic trenches partly encircling the Pacific Basin form the
so-called Ring of Fire, a zone of frequent earthquakes and volcanic eruptions.
The trenches are shown in blue-green. (Challenger Deep ~ 36,000 ft. deep)
Volcanoes Release Molten Rock from
the Earth’s Interior
• Volcano
• Fissure
• Magma
• Lava
• 1991: Eruption of Mount Pinatubo
• Little-known
• Dormant for 600 years!
• Benefits of volcanic activity
• Mountain, lakes
• Weathering of lava contributes to
fertile soil.
Mt. Pinatubo (USGS.gov)
• The second-largest volcanic eruption of this century, and by far the largest
eruption to affect a densely populated area, occurred at Mount Pinatubo
in the Philippines on June 15, 1991. The eruption produced high-speed
avalanches of hot ash and gas, giant mudflows, and a cloud of volcanic ash
hundreds of miles across. The impacts of the eruption continue to this
day.
• Following Mount Pinatubo's cataclysmic June 15, 1991, eruption,
thousands of roofs collapsed under the weight of ash made wet by heavy
rains (see example in photo above). Ash deposits from the eruption have
also been remobilized by monsoon and typhoon rains to form giant
mudflows of volcanic materials (lahars), which have caused more
destruction than the eruption itself.
Creation of a Volcano
Fig. 14-6, p. 351
Earthquakes Are Geological Rock-and-Roll
Events (1)
• Earthquake
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Seismic waves
Focus
Epicenter
Magnitude
Amplitude
Earthquakes Are Geological Rock-and-Roll
Events (2)
• Richter scale
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Insignificant: <4.0
Minor: 4.0–4.9
Damaging: 5.0–5.9
Destructive: 6.0–6.9
Major: 7.0–7.9
Great: >8.0
• Largest recorded earthquake: 9.5 in Chile in 1960
Major Features and Effects of an
Earthquake
Figure 14.7: An earthquake (left), one of nature’s most powerful events, has certain major features and
effects. In 2010, a major 7.0 earthquake in Haiti (right) killed at least 72,000 people and devastated this
already very poor country.
Fig. 14-7, p. 351
Earthquake Risk in the United States
Figure 16, Supplement 8
World Earthquake Risk
Figure 17, Supplement 8
Earthquakes on the Ocean Floor Can Cause
Huge Waves Called Tsunamis
• Tsunami, tidal wave
• Travels several hundred miles per hour
• Detection of tsunamis
• Buoys in open ocean
• December 2004: Indian Ocean tsunami
• Magnitude 9.15 and 31-meter waves at shore
• Role of coral reefs and mangrove forests in reducing
death toll
2004 Indian Ocean
Earthquake and Tsunami
• Tsunami Animation
14-2 How Are the Earth’s Rocks Recycled?
• Concept 14-2 The three major types of rocks found
in the earth’s crust—sedimentary, igneous, and
metamorphic—are recycled very slowly by the
process of erosion, melting, and metamorphism.
There Are Three Major Types of Rocks (2)
1. Sedimentary
• Sediments from eroded rocks or
plant/animal remains
• Transported by water, wind, gravity
• Deposited in layers and compacted
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Sandstone
Shale
Dolomite
Limestone
Lignite
Bituminous coal
There Are Three Major Types of Rocks (3)
2. Igneous
• Forms below or at earth’s surface from magma
• Granite
• Lava rocks
3. Metamorphic
• Preexisting rock subjected to high pressures, high temperatures,
and/or chemically active fluids
• Anthracite
• Slate
• Marble
Geology of GSMNP
14-3 What Are Mineral Resources, and
What Are their Environmental Effects?
• Concept 14-3 We can make some minerals in the
earth’s crust into useful products, but extracting and
using these resources can disturb the land, erode
soils, produce large amounts of solid waste, and
pollute the air, water, and soil.
The Life Cycle of a Metal Resource
Fig. 14-11, p. 355
Extracting, Processing, Using Nonrenewable
Mineral and Energy Resources
Fig. 14-12, p. 356
There Are Several Ways to Remove
Mineral Deposits (1)
• Surface mining
• Shallow deposits removed
• Overburden removed first
• Tailings: waste material
• Subsurface mining
• Deep deposits removed
Tailings and Overburden
• Tailings are the materials left over after the process
of separating the valuable fraction from the
uneconomic fraction of an ore. Tailings are distinct
from overburden, which is the waste rock or other
material that overlies an ore or mineral body and is
displaced during mining without being processed.
The amount of tailings can be large, ranging from
90–98% for some copper ores to 20–50% of the
other (less valuable) minerals.
There Are Several Ways to Remove
Mineral Deposits (2)
• Type of surface mining used depends on
• Resource
• Local topography
• Types of surface mining
• Open-pit mining
• Strip mining
• Contour strip mining
• Mountaintop removal
Natural Capital Degradation: Open-Pit Mine in
Arizona
Fig. 14-13, p. 357
Area Strip Mining in Wyoming
Fig. 14-14, p. 357
Natural Capital Degradation: Contour Strip
Mining
Fig. 14-15, p. 358
Mining Has Harmful Environmental Effects
(1)
• Scarring and disruption of the land surface
• E.g., spoils banks
• Mountain top removal for coal
• Loss of rivers and streams
• Air pollution
• Groundwater disruption
• Biodiversity decreased
Mining Has Harmful Environmental Effects
(2)
• Subsurface mining
• Subsidence
• Acid mine drainage
• Major pollution of water and air
• Effect on aquatic life
• Large amounts of solid waste
Mountaintop Coal Mining in West Virginia
Fig. 14-17, p. 359
Ecological Restoration of a Mining Site in
Ohio—Hybrid American Chestnuts
Removing Metals from Ores Has Harmful
Environmental Effects (1)
• Ore extracted by mining
• Ore mineral
• Gangue = waste material
• Smelting using heat or chemicals
• Air pollution
• Water pollution
Smelting
• Metal processing plants and smelters are facilities that extract
various metals from ore to create more refined metal products.
Metals include copper, nickel, lead, zinc, silver, cobalt, gold,
cadmium, etc. Smelting specifically involves heating the ore with a
reducing agent such as coke, charcoal or other purifying agents.
Primary smelting processes mine ore and concentrates, whereas
secondary smelting processes recover scrap.
• Extractive metallurgical and smelting processes can be highly
polluting activities. Some facilities that carry out metal and
smelting processes are known to emit high quantities of air
pollutants such as hydrogen fluoride, sulfur dioxide, oxides of
nitrogen, offensive and noxious smoke fumes, vapors, gases, and
other toxins. A variety of heavy metals: lead, arsenic, chromium,
cadmium, nickel, copper, and zinc are also released by the
facilities.
Removing Metals from Ores Has Harmful
Environmental Effects (2)
• Liquid and solid hazardous wastes produced
• Use of cyanide salt of extract gold from its ore
• Summitville gold mine: Colorado, U.S.
Depletion Curves for a Nonrenewable Resource
Fig. 14-19, p. 361
Market Prices Affect Supplies of
Nonrenewable Minerals
• Subsidies and tax breaks to mining companies keep
mineral prices artificially low
• Does this promote economic growth and national
security?
• Scarce investment capital hinders the development
of new supplies of mineral resources
Case Study: The U.S. General Mining
Law of 1872
• Encouraged mineral exploration and mining of hardrock minerals on U.S. public lands
• Developed to encourage settling the West (1800s)
• Until 1995, land could be bought for 1872 prices
• Companies must now pay for clean-up
Colorado Gold Mine Must Be Cleaned up by the
EPA
Fig. 14-20, p. 363
Is Mining Lower-Grade Ores the Answer?
• Factors that limit the mining of lower-grade ores
• Increased cost of mining and processing larger
volumes of ore
• Availability of freshwater
• Environmental impact
• Improve mining technology
• Use microorganisms, in situ
• Slow process
• What about genetic engineering of the microbes?
14-5 How Can We Use Mineral Resources
More Sustainability?
• Concept 14-5 We can try to find substitutes for
scarce resources, reduce resource waste, and recycle
and reuse minerals.
We Can Recycle and Reuse
Valuable Metals
• Recycling
• Lower environmental impact than mining and
processing metals from ores
• Reuse
Aluminum Cans Ready for Recycling
Fig. 14-22, p. 366
We Can Use Mineral Resources More
Sustainability
• How can we decrease our use and waste of mineral
resources?
• Pollution and waste prevention programs
Solutions: Sustainable Use of Nonrenewable
Minerals
Fig. 14-23, p. 366