Transcript Tectonic Plates

Geology and
Nonrenewable Minerals
Chapter 15
The Earth Is a Dynamic Planet
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What is geology?
Three major concentric zones of the earth
 Core: solid inner part surrounded by a liquid core
 Mantle: mostly solid rock
 Including the asthenosphere: hot,partly melted rock
that flows and can be deformed like plastic
 Crust
 Continental crust
 Oceanic crust: 71% of crust
Major Features of the Earth’s Crust
and Upper Mantle
The Earth beneath your feet is
moving…….
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Convection cells, or currents : move large volumes of
rock and heat in loops within the mantle like gigantic
conveyer belts
Tectonic Plates: dozen or so huge rigid plates move
extremely slowly atop the denser mantle on hot, soft
rock in the underlying asthenosphere
Lithosphere: continental and oceanic crust and the
rigid, outermost part of the mantle
Earth’s Major Geological Processes
and Hazards
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Gigantic plates in the earth’s crust move very slowly
atop the planet’s mantle, and wind and water move
the matter from place to place across the earth’s
surface.
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Natural geological hazards such as earthquakes,
tsunamis, volcanoes, and landslides can cause
considerable damage.
The Earth’s Crust Is Made Up of a Mosaic
of Huge Rigid Plates: Tectonic Plates
The Earth’s Major Tectonic Plates
EURASIAN PLATE
JUAN DE
FUCA PLATE
NORTH
AMERICAN
PLATE
CARIBBEAN
PLATE
ANATOLIAN
PLATE
CHINA
SUBPLATE
AFRICAN
PLATE
PACIFIC
PLATE
COCOS
PLATE
NAZCA
PLATE
Divergent plate boundaries
PACIFIC
PLATE
SOUTH
AMERICAN
PLATE
SOMALIAN
SUBPLATE
SCOTIA
PLATE
PHILIPPINE
PLATE
ARABIAN
PLATE INDIA
PLATE
AUSTRALIAN
PLATE
ANTARCTIC PLATE
Convergent plate
boundaries
Transform faults
Fig. 14-4, p. 347
The Earth beneath your feet is
moving ….
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Three types of boundaries between plates
 Divergent plates –plates move apart
 Magma – flows up through the resulting cracks
 Oceanic ridge – some of which have higher peaks and deeper canyons than
earth’s continents
 Convergent plates – oceanic plate collides with a continental plate,
 Subduction: the latter rides up over the denser oceanic plate and pushes it
down into the mantle
 Subduction zone: area where collision and subduction takes place
 Trench : forms at the boundary between the 2 converging plates
 Transform fault e.g. San Andreas fault: where plates slide and grind past
one another along a fracture. Most located on the ocean floor
The San Andreas Fault as It Crosses Part
of the Carrizo Plain in California, U.S.
Watch!
Volcanoes Release Molten Rock
from the Earth’s Interior
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Volcano: magma reaches the earth’s surface through a..
 Fissure: central vent or a long crack
 Magma
 Lava: magma that reaches the earth’s surface. Debris ranging from large
chunks of larva rock to glowing hot ash, liquid lava and gases such as
water vapor, carbon dioxide and sulfur dioxide . Much of the world’s
volcanic activity is concentrated along the boundaries of the earth’s
tectonic plates
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1980: Eruption of Mount St. Helens
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1991: Eruption of Mount Pinatubo: cooled the earth’ average temperature for
15 months
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Benefits of volcanic activity: highly fertile soil, creates outstanding landforms
(Crater Lake in Oregon)
Creation of a Volcano
Earthquakes Are Geological
Rock-and-Roll Events
Watch
Earthquake
Seismic waves
Focus
Epicenter
Magnitude
Amplitude
Richter scale
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
Foreshocks and aftershocks
Primary effects of earthquakes: shaking, permanent
vertical or horizontal displacement of the ground
Major Features and Effects of an
Earthquake
Areas of Greatest Earthquake
Risk in the United States
Areas of Greatest Earthquake
Risk in the World
Earthquakes on the Ocean Floor
Can Cause Huge Waves Called
Tsunamis
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Tsunami, tidal wave : generated when part of the ocean floor
suddenly rises or drops. Usually occurs offshore in subduction
zones.
Detection of tsunamis: by ocean buoys, pressure recorders on
the ocean floor which measures changes in water pressure as
the waves pass over it; data relayed via satellites tsunami
warning systems
December 2004: Indian Ocean tsunami
 Magnitude of 9.15
 Role of coral reefs and mangrove forests in reducing death
toll
 Japan Tsunami 2011
Formation of a Tsunami and Map of
Affected Area of Dec 2004 Tsunami
Shore near Banda Aceh,Gleebruk
in Indonesia before and after
tsunami
Before :June 23, 2004
After: December 28, 2004
Gravity and Earthquakes Can
Cause Landslides
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Mass wasting: detached or loose rock, soil and mud
to slide down steep slopes near the shores of oceans
or lakes
 Slow movement
 Fast movement
 Rockslides
 Avalanches
 Mudslides : 1970 – Peru, buried the town of Yungay
and killed 17,000 people
Effect of human activities on such geological events:
 forest clearing, road building , crop growing, building
houses
Earth’s Rocks are Recycled……..
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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
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Earth’s crust
• Composed of minerals and rocks
Three broad classes of rocks, based on formation
Sedimentary
Igneous
Sandstone
Granite
Shale
Lava rock
Dolomite
Metamorphic
Slate
Anthracite
Lignite
Slate
Bituminous coal
Marble
The Earth’s Rocks Are Recycled
Very Slowly
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Rock cycle: the
interaction of
physical and
chemical
processes that
change rocks
from one type to
another. Slowest
of the earth’s
cyclic processes
Some Parts of the Earth’s Surface
Build Up and Some Wear Down
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Internal geologic processes
 Generated by heat from the earth’s interior ,generally
build up the earth’s surface in the form of continental
and oceanic crust including mountains and volcanoes
External geologic processes
 Weathering : driven directly or indirectly by energy
from the sun(mostly in the form of flowing water and
wind)
 Physical, Chemical, and Biological : soil
 Erosion
 Wind
 Flowing water
 Human activities
 Glaciers
Weathering: Biological, Chemical,
and Physical Processes
What Are Mineral Resources, and
what are their environmental
effects?
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Some naturally occurring materials in the earth’s crust can
be extracted and made into useful products in processes
that provide economic benefits and jobs.
100 minerals: naturally occurring material
fossil fuels(coal);
 metallic(aluminum, iron, copper);
 non-metallic(sand, gravel,limestone)
Ore: large concentration of a particular mineral, often a metal
 High-grade ore – large amount of desired non-renewable resource
 Low-grade ore – small amount of the resource
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Mineral Use Has Advantages and
Disadvantages
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Mine and convert minerals into useful products
Disadvantages: enormous amounts of energy, disturbs land,
erode soil, produce solid waste, air and water pollution
Life cycle of a metal resource
Extracting, Processing, Using
Nonrenewable Mineral and Energy
Resources
There Are Several Ways to Remove
Mineral Deposits
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Surface mining : shallow deposits removed
 mechanized equipment strips away overburden(soil
and rock overlay), discarded as waste called
 Used to extract 90% of the nonfuel mineral and
rock resources and 6-% of the coal
Type of surface mining used depends on
Resource
Local topography
Subsurface mining
 Deep deposits removed
 Used to extract coal and metal ores
Types of Surface Mining
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Open Pit Mining : machines dig hole and remove ore
Strip Mining : earth movers strip overburden and power
shovels remove deposit
Contour Mining : mine coal on hilly terrain. Wall of dirt
left in front of a highly erodible bank of soil and rock called
highwall
Mountain Top Removal : Appalachian Mountains ,
draglines, explosives remove top of mountain to
expose seams
Open-Pit Mine in Western Australia
Undisturbed land
Overburden
Pit
Contour Strip Mining
in hilly areas
Bench
Spoil banks
Fig. 14-17, p. 357
Mountaintop Coal Mining in West
Virginia, U.S.
Mining has harmful effects…….
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Scarring and disruption
of the land surface
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E.g., spoils banks
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Loss of rivers and
streams – 1900 km
have been buried
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Subsidence :collapse
of land
Mining Has Harmful Environmental
Effects
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Major pollution of water and air:
toxin-laced mining waste deposited
in areas other than mining site .
Acid Mine Drainage
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Effect on aquatic life :ph
change,40% of all US watersheds
contaminated
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Large amounts of solid waste
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3/4th of all US solid waste
mining gold
Illegal Gold Mine
Removing Metals from Ores Has
Harmful Environmental Effects
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Ore extracted by mining
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Ore mineral : desired metal
Gangue : waste material. Removing the gangue from the ores
produces tailings, Particles of toxic metals blown by the wind
or leached by rainfall can contaminate surface water and
groundwater.
Smelting: heating ores to release metals.
Without proper equipment, releases sulfur dioxide and
suspended particles, damage vegetation and acidify soils
Water pollution: highly toxic cyanide salts to extract gold
from it’s ore. Leave behind cyanide laden water
Summitville Gold Mining, Co
Summitville Gold Mining Site in Colorado,
U.S.
Ecological Restoration of a Mining
Site in New Jersey, U.S.
How Long Will Supplies of
Nonrenewable Mineral Resources
Last?
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All nonrenewable mineral resources exist in finite
amounts, and as we get closer to depleting any mineral
resource, the environmental impacts of extracting it
generally become more harmful.
Relatively abundant deposits of iron and aluminum
(bauxite)
Scarce : manganese,chromium,cobalt,platinum
An increase in the price of a scarce mineral resource can
lead to increased supplies and more efficient use of the
mineral, but there are limits to this effect.
Uneven distribution of minerals
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Most of the nonrenewable mineral resources supplied
by
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Canada
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United States
8% of world population, consume
Germany
75% of the world’s key metals
China increasing consumption
Russia
South Africa: self sufficient in all key minerals, largest
producer of gold, chromium and platinum
Australia
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Four Strategic metal resources….
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Manganese
Cobalt
Chromium
Platinum
US has little or no reserves of these metals which are
essential for the country’s economy and military
strength
May ave to switch to nano materials
The Nanotechnology Revolution
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Nanotechnology, tiny tech : use carbon, oxygen and
silicone atoms to create everything from medicines,solar
cells to automobile bodies
Currently used in more than 400 items : odor eating
socks, wrinkle –free clothes, cosmetics, sun screens
Nanoparticles
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Are they safe?
Investigate potential ecological, economic, health, and
societal risks
Develop guidelines for their use until more is known
about them
Economic Depletion of non
renewable mineral resources
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Future supply depends on
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Actual or potential supply of the mineral
Rate at which it is used
When it becomes economically depleted
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Recycle or reuse existing supplies
Waste less
Use less
Find a substitute
Do without
Depletion Curves for a Nonrenewable
Resource
Depletion time : time it
takes to use up
approximately 80% of the
reserves of a mineral at a
given rate of use
Market Prices Affect Supplies of
Nonrenewable Minerals
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Subsidies and tax breaks to mining companies keep
mineral prices artificially low
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Does this promote economic growth and national
security?
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Scarce investment capital hinders the development of
new supplies of mineral resources
The U.S. General Mining Law of
1872
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Encouraged mineral exploration and mining of hardrock minerals on U.S. public lands
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Developed to encourage settling the West (1800s)
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Until 1995, land could be bought for 1872 prices
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Companies must pay for clean-up now
Is Mining Lower-Grade Ores the
answer?
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Factors limit the mining of lower grade ores
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increased cost of mining
limited availability of fresh water , specially in arid areas
environmental impacts of increased land disruption, waste material
and pollution produced during mining and processing
Use microorganisms that can extract minerals “in-place” or “insitu”mining.
Biomining : genetic engineering techniques used to produce
bacteria that can be used to extract a particular metal without
disturbing the surrounding environment
Extend Supplies by Getting More
Minerals from the Ocean…
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Mineral resources dissolved in the ocean-very low
concentrations, requires more energy and money
than they are worth
Only magnesium, bromine and sodium chloride are
abundant enough to be extracted profitably
Deposits of minerals in sediments along the shallow
continental shelf and near shorelines : sand,
gravel,phosphates,sulfur,tin.copper,iron,tungsten,silver,
titanium,platinum,diamonds
Extend Supplies by Getting More
Minerals from the Ocean
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Hydrothermal ore deposits : sulfides, zinc, silver, copper
precipitate out and build up as mineral deposits
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currently costs too much to extract,
disputes over ownership
Metals from the ocean floor: potato sized manganese
nodules, that cover 25-50% of the Pacific ocean floor
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Effect of mining on aquatic life
Environmental impact : sea bed mining ,less impact than land (??)
How Can We Use Mineral Resources
More Sustainability?
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Find substitutes for some scarce mineral resources
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materials revolution : silicon, ceramics, plastics
houses made of styroform sprayed with ceramic spray called
Grancrete, reduces use of timber
high strength plastics and composite materials strengthened by light
weight carbon and glass fibers are transforming the automobile and
aerospace industries
making plastics requires fossil fuels and oil
Substitution may not always be possible :
platinum, industrial catalyst
chromium : stainless steel
We Can Recycle and Reuse
Valuable Metals
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Recycling
 Lower environmental impact than mining and
processing metals from ores
Reuse : gold, silver, iron, copper, steel, aluminum,
platinum
Recycling aluminum beverage cans and scrap
aluminum produces 95% less air pollution, 97% less
water pollution and uses 95% less energy
There Are Many Ways to Use Mineral
Resources More Sustainability
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How can we decrease our use and waste of mineral
resources?
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Pollution and waste prevention programs
 3M : Pollution Prevention Pays (3P)
 Cleaner production : air pollution 70% lower, saved
$750 million in waste disposal and material costs
Sustainable Use of Nonrenewable
Minerals
Industrial Ecosystems: Copying
Nature
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Mimic nature: recycle and reuse most minerals and
chemicals : waste outputs of one organism becomes the
nutrient inputs of another
Resource exchange webs : wastes of one
manufacturer becomes the raw materials for another
Ecoindustrial parks on brownfields, which are
abandoned industrial sites
Industrial forms of biomimicry
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Benefits : come up with new environmentally beneficial and less
resource-intensive chemicals
Better image among consumers
An Industrial Ecosystem in
Denmark Mimics Natural Food Web