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Transcript
Geology and Nonrenewable
Minerals
Chapter 12
Three big ideas
• Dynamic forces move matter, recycle the earth’s rocks,
form deposits of mineral resources, and cause volcanic
eruptions, earthquakes, and tsunamis.
• Mineral availability depends on quantity in the earth’s
crust, rate of use, mining technology, market prices,
and the harmful environmental effects of
removing/using it.
• We can use mineral resources more sustainably by
trying to… find substitutes for scarce resources,
reducing waste, and reusing and recycling
nonrenewable minerals.
Section 12-1
What are the earth’s major
geological processes and
hazards?
The earth is a dynamic planet
• Geology is the science of earth’s surface
and in its interior (non-living).
• Three major concentric zones.
1. The core is the earth’s innermost zone—
extremely hot.
2. Surrounding the core is a thick zone called the
mantle—solid rock… but part is the
asthenosphere, a zone of hot, partly melted rock
that flows.
The earth is a dynamic planet
3. 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.
The earth’s crust is made up of
a mosaic of huge rigid plates
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…
this powers continental drift
• Plates can move/respond differently
Major features of the earth’s
crust and upper mantle
The earth’s major tectonic
plates
The San Andreas Fault
Internal pressure in a volcano can cause
lava, ash, and gases to be ejected
An earthquake has certain
major features and effects
What is the
Richter scale?
Earthquakes are geological
rock-and-roll events
– Insignificant (< 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.
Google Earth…
Why?
http://www.neptunuslex.com/
How a tsunami forms
What is a
tidal
wave?
Banda Aceh before and after
the tsunami of December 2004
Earthquakes & Tsunami impacts
• What can be done to minimize impacts of
these geologic events?
• Are they random?
Section 12-2
How are the earth’s rocks
recycled?
Minerals, rocks & “dirt”
• 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.
• Some are of a single element such as…?
• Most of the more than 2,000 identified minerals
occur as inorganic compounds formed by
various combinations of elements, such as…?
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 contain only one mineral
(examples? )
– Most consist of two or more minerals, such as
?
– Three broad classes:
• Sedimentary rock (e.g. sandstone, limestone).
• Igneous rock (e.g. granite).
• Metamorphic rock (e.g. slate, marble).
Simplified rock cycle
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.
– Found and extracted more than 100 minerals from
the earth’s crust.
– Examples are fossil fuels (such as ?), metallic
minerals (such as ?), and nonmetallic minerals (such
as ?).
– Minerals are classified as nonrenewable resources.
Why?
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.
We use a variety of nonrenewable
mineral resources
– What are some examples?
Each metal resource that we
use has a life cycle
Harmful effects of extraction, processing, and use
of nonrenewable mineral or energy resources
Types of mining
Open pit, strip, contour strip, and mountaintop removable
Mining has harmful
environmental effects
• What are the negative/harmful effects?
Video clip…
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 (chatt).
• 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
• What is abundant?
• What is NOT abundant?
Mineral resources are
distributed unevenly
• Five nations—the United States, Canada,
Russia, South Africa, and Australia—
supply most of the nonrenewable minerals
• Concern over 4 strategic metal resources
1. Manganese
2. Cobalt
3. Chromium
4. Platinum
— these are essential for the country’s economy
and military strength… little in U.S.
Supplies of nonrenewable mineral
resources can be economically depleted
• The future supply of nonrenewable
minerals depends on two factors:
1. The actual or potential supply of the mineral.
2. 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
• What are the economic issues related to mining?
Can we get more of our
minerals from the oceans?
• Issues involved with this approach?
Section 12-5
HOW CAN WE USE MINERAL
RESOURCES MORE
SUSTAINABLY?
We can use nonrenewable mineral
resources more sustainably
Three big ideas
• Dynamic forces move matter, recycle the earth’s rocks,
form deposits of mineral resources, and cause volcanic
eruptions, earthquakes, and tsunamis.
• Mineral availability depends on quantity in the earth’s
crust, rate of use, mining technology, market prices,
and the harmful environmental effects of
removing/using it.
• We can use mineral resources more sustainably by
trying to… find substitutes for scarce resources,
reducing waste, and reusing and recycling
nonrenewable minerals.
The End
Material beyond this point is supplemental!
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.
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.
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.
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 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.
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 & Tsunami impacts 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.
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.
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.
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.
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.
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.
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.
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.