Transcript Geology and Nonrenewable Minerals

Geology and Nonrenewable
Minerals
Chapter 12
Section 12-1
What are the earth’s major
geological processes and
hazards?
The earth is a dynamic planet
• Geology is the science devoted to the study
of dynamic processes occurring on the
earth’s surface and in its interior.
• Three major concentric zones.
– The core is the earth’s innermost zone—extremely
hot, with a solid inner part encircled by a liquid core
of molten or semisolid material.
– Surrounding the core is a thick zone called the
mantle—solid rock, but under its rigid outermost
part is the asthenosphere, a zone of hot, partly
melted rock that flows.
The earth is a dynamic planet
– The outermost and thinnest zone of the earth is
the crust.
• Continental crust, which underlies the continents.
• Oceanic crust, which underlies the ocean basins and
makes up 71% of the earth’s crust.
– The combination of the crust and the rigid
outermost part of the mantle (above the
asthenosphere) is called the lithosphere.
Major features of the earth’s
crust and upper mantle
Volcanoes
Abyssal hills
Oceanic
crust
(lithosphere)
Abyssal Oceanic
floor
ridge
Abyssal
floor Trench
Folded
mountain
belt
Craton
Abyssal
plain
Continental
shelf
Continental
slope
Continental
rise
Fig. 12-2, p. 277
The earth beneath your feet is
moving
• Convection cells or currents move large
volumes of rock and heat in loops within
the mantle like gigantic conveyer belts.
• Flows of energy and heated material in
these convection cells caused the
lithosphere to break up into a dozen or so
huge rigid plates, called tectonic plates.
• Continents have split apart and joined as
tectonic plates drifted atop the earth’s
asthenosphere.
The earth beneath your feet is
moving
• The forces produced at these plate boundaries
can cause earthquakes, erupting volcanoes
and mountains to form.
• Oceanic plates move apart from one another
allowing magma, to flow up between them.
• Much of the geologic activity at earth’s surface
takes place at the boundaries between tectonic
plates as they move in the resulting cracks.
– Oceanic ridges may have peaks higher and
canyons deeper than those found on the earth’s
continents.
The earth beneath your feet is
moving
– When two oceanic plates collide, a trench ordinarily
forms at the boundary between the two plates.
– When an oceanic plate collides with a continental
plate, the continental plate usually rides up over the
denser oceanic plate and pushes it down into the
mantle in a process called subduction.
– The area where this collision and subduction takes
place is called a subduction zone.
– Tectonic plates can also slide and grind past one
another along a fracture (fault) in the lithosphere—a
type of boundary called a transform fault.
The earth’s crust is made up of
a mosaic of huge rigid plates
Spreading
center
Subduction
zone
Oceanic
crust
Ocean
trench
Oceanic
crust
Continental
crust
Continental
crust
Cold dense
Material cools
material falls
as it reaches
back through
the outer
mantle
mantle
Mantle
convection
cell
Two plates move
towards each other.
One is subducted back
into the mantle on a
falling convection
current.
Hot
material
rising
through
the
mantle
Mantle
Hot outer
core
Inner
core
Fig. 12-3, p. 277
The earth’s major tectonic
plates
EURASIAN PLATE
NORTH
AMERICAN
PLATE
JUAN DE
FUCA PLATE
PACIFIC
PLATE
ANATOLIAN
PLATE
CARIBBEAN
PLATE
AFRICAN
PLATE
COCOS
PLATE
NAZCA
PLATE
SCOTIA
PLATE
Divergent plate
boundaries
CHINA
SUBPLATE
PHILIPPINE
PLATE
ARABIAN
PLATE INDIA
PACIFIC
PLATE
PLATE
SOUTH
AMERICAN
PLATE
AUSTRALIAN
PLATE
ANTARCTIC
PLATE
Convergent plate
boundaries
Transform faults
Fig. 12-4, p. 278
The San Andreas Fault
Volcanoes release molten rock
from the earth’s interior
• An active volcano occurs where magma reaches
the earth’s surface through a central vent or a long
crack, called a fissure.
• Many volcanoes form along the boundaries of the
earth’s tectonic plates when one plate slides under
or moves away from another plate.
• Magma that reaches earth’s surface is called lava.
• Volcanic activity can release large chunks of lava
rock, glowing hot ash, liquid lava, and gases into
the environment.
Internal pressure in a volcano can cause
lava, ash, and gases to be ejected
Extinct volcanoes
Eruption cloud
Ash flow
Ash
Acid rain
Lava flow
Mud flow
Landslide
Central
vent
Magma
conduit
Magma
reservoir
Fig. 12-6b, p. 279
Earthquakes are geological
rock-and-roll events
• Forces inside the earth’s mantle and near
its surface push, deform, and stress rocks.
• The stress can cause the rocks to suddenly
shift or break and produce a transform fault,
or fracture in the earth’s crust.
• 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,
causing an earthquake.
An earthquake has certain
major features and effects
Liquefaction of recent
sediments causes
buildings to sink
Landslides
may occur on
hilly ground
Two adjoining plates
move laterally along
the fault line
Earth movements
cause flooding in
low-lying areas
Shock
waves
Epicenter
Focus
Fig. 12-7, p. 280
Earthquakes are geological
rock-and-roll events
• The severity of an earthquake is measured
by the magnitude of its seismic waves.
• The magnitude is a measure of shaking
caused by the earthquake, as indicated by
the size of the seismic waves when they
reach a seismograph.
• Scientists use the Richter scale, on which
each unit has amplitude 10 times greater
than the next smaller unit.
Earthquakes are geological
rock-and-roll events
– 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).
– Great (over 8.0).
Earthquakes are geological
rock-and-roll events
• The largest recorded earthquake occurred
in Chile on May 22, 1960 and measured 9.5
on the Richter scale.
• The primary effects of earthquakes include
shaking and sometimes a permanent
vertical or horizontal displacement of the
ground. These effects may have serious
consequences for people and for buildings,
bridges, freeway overpasses, dams, and
pipelines.
Earthquakes are geological
rock-and-roll events
• One way to reduce the loss of life and
property damage is to examine historical
records and make geologic measurements
to locate active fault zones.
– Map high-risk areas and establish building codes
that regulate the placement and design of buildings
in such areas.
– People evaluate the risk and factor it into their
decisions about where to live.
– Engineers know how to make buildings and
structures more earthquake resistant.
Earthquakes on the ocean floor can
cause huge waves called tsunamis
• A tsunami is a series of large waves generated
when part of the ocean floor suddenly rises or
drops.
• Most large tsunamis are caused when certain
types of faults in the ocean floor move up or
down as a result of a large underwater
earthquake, a landslide caused by such an
earthquake, or in some cases by a volcanic
eruption.
• Tsunamis are often called tidal waves, although
they have nothing to do with tides.
How a tsunami forms
Earthquake in seafloor
swiftly pushes water
upwards, and starts a
series of waves.
Waves move rapidly
in deep ocean
reaching speeds of
up to 890 kilometers
per hour.
As the waves near land
they slow to about 45
kilometers per hour but are
squeezed upwards and
increased in height.
Waves head
inland causing
damage in their
path.
Undersea thrust fault
Upward wave
Bangladesh
India
Myanmar
Thailand
Sri Lanka
Earthquake
Malaysia
Sumatra
Indonesia
December 26, 2004, tsunami
Fig. 12-8, p. 281
Earthquakes on the ocean floor can
cause huge waves called tsunamis
• They can travel far 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, it slows down,
its wave crests squeeze closer together, and
their heights grow rapidly.
• Hits a coast as a series of towering walls of
water that can level buildings.
Earthquakes on the ocean floor can
cause huge waves called tsunamis
• Tsunamis can be detected through a network of
ocean buoys or pressure recorders located on the
ocean floor to provide some degree of early
warning sent through emergency warning centers.
– Between 1900 and 2010, tsunamis killed an estimated
280,000 people along the Pacific Ocean.
– The largest loss of life (279,900) occurred in December
2004 when a great underwater earthquake in the Indian
Ocean with a magnitude of 9.15 caused a tsunami that
generated waves as high as a five-story building.
Banda Aceh before and after
the tsunami of December 2004
Section 12-2
How are the earth’s rocks
recycled?
There are three major types of
rocks
• A mineral is an element or inorganic compound
that occurs naturally in the earth’s crust as a
solid with a regular internal crystalline structure.
• A few minerals consist of a single element such
as gold, silver, and diamond (carbon).
• Most of the more than 2,000 identified minerals
occur as inorganic compounds formed by
various combinations of elements, such as salt
(sodium chloride or NaCl) and quartzite (silicon
dioxide or SiO2).
There are three major types of
rocks
• Rock is a solid combination of one or more
minerals found in the earth’s crust.
– Some kinds of rock, such as limestone and
quartzite, contain only one mineral while most
consist of two or more minerals, such as
granite—a mixture of mica, feldspar, and
quartz crystals.
– Three broad classes:
• Sedimentary rock (e.g. sandstone, limestone).
• Igneous rock (e.g. granite).
• Metamorphic rock (e.g. slate, marble).
Simplified rock cycle
Erosion
Transportation
Weathering
Deposition
Igneous
rock
Granite,
pumice,
basalt
Sedimentary
rock Sandstone,
limestone
Heat, pressure
Cooling
Heat, pressure,
stress
Magma
(molten rock)
Melting
Metamorphic
rock Slate,
marble, gneiss,
quartzite
Fig. 12-10, p. 283
Earth’s rocks are recycled very
slowly
• The rock cycle is the interaction of
physical and/or chemical processes that
change rock from one form to another.
• It takes millions of years for this cycle to
happen.
Section 12-3
WHAT ARE MINERAL
RESOURCES AND WHAT ARE
THE ENVIRONMENTAL
EFFECTS OF USING THEM?
We use a variety of nonrenewable
mineral resources
• A mineral resource is a concentration of
naturally occurring material from the earth’s
crust that can be extracted and processed into
useful products and raw materials at an
affordable cost.
– Found and extracted more than 100 minerals from the
earth’s crust.
– Examples are fossil fuels (such as coal), metallic
minerals (such as aluminum and gold), and
nonmetallic minerals (such as sand and limestone).
– Minerals are classified as nonrenewable resources.
We use a variety of nonrenewable
mineral resources
• An ore is rock that contains a large enough
concentration of a particular mineral—often
a metal—to make it profitable for mining
and processing.
– High-grade ore contains a large concentration
of the desired mineral.
– Low-grade ore has a smaller concentration.
– Aluminum (Al) is used for packaging and
beverage cans and as a structural material in
motor vehicles, aircraft, and buildings.
We use a variety of nonrenewable
mineral resources
– Steel, an essential material used in buildings
and motor vehicles, is a mixture (alloy) of iron
(Fe) and other elements that are added to give
it certain properties.
– Copper (Cu), a good conductor of electricity, is
used for electrical and communications wiring.
– Gold (Au) is used in electrical equipment, tooth
fillings, jewelry, coins, and some medical
implants.
Some environmental impacts of
mineral use
• Metals can be used to produce many products.
• Life cycle of a metal—mining, processing, and
using it—takes enormous amounts of energy and
water and can disturb the land, erode soil, produce
solid waste, and pollute the air, water, and soil.
• The more accessible and higher-grade ores are
usually exploited first.
• As they are depleted, mining lower-grade ores
takes more money, energy, water, and other
materials, and increases land disruption, mining
waste, and pollution.
Each metal resource that we
use has a life cycle
Surface
mining
Metal ore
Separation
of ore from
gangue
Smelting
Melting
metal
Conversion
to product
Discarding
of product
Recycling
Stepped Art
Fig. 12-11, p. 285
There are several ways to
remove mineral deposits
• Shallow mineral deposits are removed by
surface mining by:
– Removing vegetation.
– Removing the overburden or soil and rock
overlying a useful mineral deposit.
– Placing waste material set aside in piles,
called spoils.
• Open-pit mining.
There are several ways to
remove mineral deposits
• Strip mining is useful and economical for
extracting mineral deposits that lie in large
horizontal beds close to the earth’s
surface.
– Area strip mining is used where the terrain is
fairly flat; a gigantic earthmover strips away
the overburden, and a power shovel removes
the mineral deposit.
– Contour strip mining is used mostly to mine
coal on hilly or mountainous terrain.
There are several ways to
remove mineral deposits
• Mountaintop removal uses explosives,
large power shovels, and huge machines
called draglines to remove the top of a
mountain and expose seams of coal.
• Subsurface mining removes minerals from
underground through tunnels and shafts.
Harmful effects of extraction, processing, and use
of nonrenewable mineral or energy resources
Types of mining
Open pit, strip, contour strip, and mountaintop removable
Undisturbed land
Overburden
Pit
Bench
Spoil banks
Fig. 12-15, p. 287
Mining has harmful
environmental effects
• Scarring and disruption of the land
surface.
– Mountaintop removal destroys forests, buries
mountain streams, and increases flood
hazards. Wastewater and toxic sludge,
produced when the coal is processed, are
often stored behind dams in these valleys,
which can overflow or collapse and release
toxic substances such as arsenic and
mercury.
Mining has harmful
environmental effects
– In the United States, more than 500
mountaintops have been removed to extract
coal and the resulting spoils have buried more
than 1,100 kilometers (700 miles) of stream.
– Surface mining in tropical forests and other
tropical areas destroys or degrades vital
biodiversity when forests are cleared and
rivers are polluted with mining wastes.
– Produces toxic waste material such as lead
dust, which can cause lead poisoning and
irreversible brain damage in children.
Mining has harmful
environmental effects
• Subsurface mining disturbs less land than
surface mining disturbs, and it usually
produces less waste material.
– Creates hazards such as cave-ins, explosions,
and fires.
– Miners often get diseases such as black lung,
caused by prolonged inhalation of coal dust in
subsurface mines.
– Causes subsidence—the collapse of land
above some underground mines.
Mining has harmful
environmental effects
• Mining operations produce large amounts of solid
waste and cause major water and air pollution.
– Acid mine drainage occurs when rainwater that seeps
through a mine or a spoils pile carries sulfuric acid to
nearby streams and groundwater.
– Mining has polluted about 40% of western watersheds
in the United States, and it accounts for 50% of all the
country’s emissions of toxic chemicals into the
atmosphere.
– Much of this degradation comes from leaking storage
ponds built to hold a toxic sludge that is produced from
the mining and processing of metal ores.
Removing metals from ores has
harmful environmental effects
• Ore mining typically has two components:
– Ore mineral, containing the desired metal.
– Waste material.
• Removing the waste material from ores produces
waste piles called tailings.
• Heating ores to release metals is called smelting.
– Without effective pollution control equipment, smelters
emit enormous quantities of air pollutants, including
sulfur dioxide and suspended particles.
• Chemicals can be used to remove metals from
their ores.
Section 12-4
HOW LONG WILL SUPPLIES
OF NONRENEWABLE
MINERAL RESOURCES LAST?
Mineral resources are
distributed unevenly
• The earth’s crust contains fairly abundant
deposits of iron and aluminum.
• Manganese, chromium, cobalt, and
platinum are relatively scarce.
• The earth’s geologic processes have not
distributed deposits of nonrenewable
mineral resources evenly among
countries.
Mineral resources are
distributed unevenly
• Five nations—the United States, Canada,
Russia, South Africa, and Australia—
supply most of the nonrenewable mineral
resources used by modern societies.
• Experts are concerned about four strategic
metal resources—manganese, cobalt,
chromium, and platinum—which are
essential for the country’s economy and
military strength. The United States has
little or no reserves of these metals.
Supplies of nonrenewable mineral
resources can be economically depleted
• The future supply of nonrenewable
minerals depends on two factors:
– The actual or potential supply of the mineral.
– The rate at which we use it.
– Minerals may become economically depleted
when it costs more than it is worth to find,
extract, transport, and process the remaining
deposits. Options when this occurs are:
• Recycle or reuse existing supplies.
• Waste less or use less.
• Find a substitute or do without.
Market prices affect supplies of
nonrenewable minerals
• Geologic processes determine the quantity and
location of a mineral resource.
• Economics determines what part of the known supply
is extracted and used.
• An increase in the price of a scarce mineral resource
can lead to increased supplies and encourage more
efficient use.
• Standard economic theory may not apply because
most well-developed countries often use subsidies,
taxes, regulations, and import tariffs to control the
supply, demand, and price of minerals.
• Most mineral prices are kept artificially low.
Is mining lower-grade ores the
answer?
• Extraction of lower grades of ore is
possible due to new earth-moving
equipment, improved techniques for
removing impurities from ores, and other
technological advances in mineral
extraction and processing.
• Mining low-grade ores is limited by:
– Increased cost of mining and processing
larger volumes of ore.
Is mining lower-grade ores the
answer?
– Increasing shortages of freshwater—which is
needed to mine and process some minerals—
especially in arid and semiarid areas.
– Environmental impacts of the increased land
disruption, waste material, and pollution
produced during mining and processing.
• Can use microorganisms that can break
down rock material and extract minerals in
a process called in-place, or in situ, mining
or biomining.
Can we get more of our
minerals from the oceans?
• Some ocean mineral resources are dissolved
in seawater.
• Low concentrations take more energy and
money than they are worth.
• Hydrothermal ore deposits are rich in
minerals such as copper, lead, zinc, silver,
gold, and some of the rare earth metals.
• Growing interest in deep-sea mining.
• Manganese nodules cover large areas of
ocean floor.
Section 12-5
HOW CAN WE USE MINERAL
RESOURCES MORE
SUSTAINABLY?
We can find substitutes for
some scarce mineral resources
• Human ingenuity will find substitutes.
• Current materials revolution in which
silicon and other new materials,
particularly ceramics and plastics, are
being used as replacements for metals.
• Finding substitutes for scarce minerals
through nanotechnology.
We can recycle and reuse
valuable metals
• A more sustainable way to use nonrenewable
mineral resources (especially valuable or
scarce metals such as gold, copper, and
aluminum) is to recycle or reuse them.
• Recycling has a much lower environmental
impact than mining and processing ores.
• Cleaning up and reusing items instead of
melting and reprocessing them has an even
lower environmental impact.
We can use mineral resources
more sustainably
• Instead of asking how we can increase
supplies of nonrenewable minerals, we
should be asking, how can we decrease
our use and waste of such resources?
• Since 1990, a growing number of
companies have adopted pollution and
waste prevention programs that have led
to cleaner production.
We can use nonrenewable mineral
resources more sustainably
Three big ideas
• Dynamic forces that move matter within the earth and on
its surface recycle the earth’s rocks, form deposits of
mineral resources, and cause volcanic eruptions,
earthquakes, and tsunamis.
• The available supply of a mineral resource depends on
how much of it is in the earth’s crust, how fast we use it,
the mining technology used to obtain it, its market prices,
and the harmful environmental effects of removing and
using it.
• We can use mineral resources more sustainably by
trying to find substitutes for scarce resources, reducing
resource waste, and reusing and recycling
nonrenewable minerals.