Transcript Geology and Nonrenewable Minerals

Geology and
Nonrenewable Minerals
AP Environmental Science
14-1. What Are The Earth’s Major Geological
Processes and Hazards?
• Gigantic plates in the Earth’s crust move very
slowly atop the planet’s mantle, and wind and
water move matter from place to place across
the Earth’s surface.
• Natural geological hazards such as earthquakes,
tsunamis, volcanoes, and landslides can cause
considerable damage.
Earth: The Dynamic Planet
• Earth is divided into three main “zones”:
– Crust: Hard, cracked outer shell
(Crust + Solid Mantle = Lithosphere)
– Mantle: Softer rock, liquid to hard
(Softer layer of mantle = Asthenosphere)
– Core
• Inner: Hottest & under greatest pressure - solid
• Outer: Extremely hot, but liquid
Natural Processes Shape Earth
• Internal Processes
– Usually “build up” the
Earth’s surface
• External Processes
– Usually “wear down” the
Earth’s surface
– Physical weathering:
Wind, rain, freezing, etc.
– Chemical weathering:
Water, acids, gases, etc.
– Biological weathering:
Living things break up
parent material
How We Go Places: Plate Tectonics
• The crust is cracked into large slabs called
tectonic plates and float on magma
• Convection currents move plates around
• Collisions between plates cause EQ!
Earth’s Major Plates
Types of Plate Boundaries
• Where plates meet = plate boundaries
– Convergent
• Plates come together, usually one dives under
another (subduction)
– Divergent
• Plates move apart, magma bubbles up (ridges)
– Transform
• Plates move side to side
Plate Boundaries
Effects of Plate Tectonics
• Volcanoes
– Large hill/mountain formed due to magma
reaching the surface
• Earthquakes
– Sudden release of stored up energy from
plates rubbing together
Earthquake Terms
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Focus: The true location of an EQ
Epicenter: Location of EQ on surface
Richter Scale: Used to quantify EQ’s energy
Amplitude: Size of EQ wave on seismograph
Aftershocks: Smaller
shakings after EQ
• P-Wave: Primary wave
• S-Wave: Secondary wave
Tsunami!
• Series of waves generated by EQ
• No “Day After Tomorrow” surfer waves
• Can cause widespread
devastation
Tsunami Before & After
Banda Aceh Shore, Indonesia
Tsunami of December 28, 2004
Before
After
168,000 people died
14.2 How Are The Earth’s Rocks Recycled?
• The three major types of rocks found in the
Earth’s crust – sedimentary, igneous, and
metamorphic – are recycled very slowly by the
processes of erosion, melting, and
metamorphism.
The Three Types of Rocks
• Sedimentary
– Small particles pressed together
• Igneous
– Rock that forms below surface, wells up and
cools off
• Metamorphic
– Igneous or sedimentary rock is exposed to
heat, pressure, and chemical changes
How Sedimentary Rock is Formed
• Parent is weathered into small pieces
(sediment)
• Sediments are deposited (usually layer
after layer)
• Pressure compacts and cements sediment
into rock
• Erosion can turn rock back into sediment
How Igneous Rock is Formed
• Igneous rock starts as magma
• As it surfaces, it cools and solidifies –
depending on how it happens, different
results:
– Extrusive – cooling above ground, quick, only
small crystals form
– Intrusive – cooling below ground, slow, larger
crystals form
Examples of Igneous Rock
Diorite – intrusive
Obsidian – extrusive
(notice the large crystals/grains)
(notice lack of crystals/grains)
How Metamorphic Rock is Formed
• Hardest to identify
• Igneous and sedimentary rock can be
turned into metamorphic rock through the
use of heat and pressure
• Heat and pressure causes a literal
“metamorphosis” to occur as rocks are
rearranged
Examples of Metamorphic Rock
Gneiss
(“nice”)
Marble
The Rock Cycle
(You need to KNOW this!)
A SLOW series of chemical or
physical processes that can
change one type of rock into
another
14.3 What Are Mineral Resources and What Are The
Environmental Effects of Using Them?
• 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.
• Extracting and using mineral resources can
disturb the land, erode soils, produce large
amounts of solid waste, and pollute the air,
water, and soil.
Minerals
• Mineral Resource: Naturally occurring,
inorganic, material from crust
• Ore: Rock that contains a large
concentration of a mineral
– High Grade Ore: Large amount of mineral
– Low Grade Ore: Smaller amount of mineral
Ore Examples
• If you can’t grow it, you have to MINE it!
Element
Ore
Silicon
Quartz
Aluminum
Bauxite
Iron
Magnetite or Hematite
Calcium
Gypsum or Calcite
Sodium
Halite
Magnesium
Magnesite or Dolomite
Potassium
Sylvite
Copper
Chalcopyrite
Tin
Cassiterite
Lead
Galena
Zinc
Sphalerite
Estimating Mineral Resources
• Key terms used by USGS:
– Identified: location, quantity, and quality
known based on direct measurements.
– Undiscovered: potential supplies assumed to
exist.
– Reserves: identified resources that can be
extracted profitably.
Effects of Mineral Use
• No matter the mineral, all steps use large
amounts of energy and creates pollution.
• High grade = less energy needed
• Low grade = more energy needed
Harmful Effects
Extracting Minerals from Deposits
• Surface Mining
– Remove overburden (discarded as spoils) to
get to mineral deposits
• Types
– Open-Pit
– Strip
– Contour Strip
– Mountain-Top Removal
Open Pit Mining
• Machines dig large holes in ground, remove ores
• Toxic water can collect at bottom of pit
Strip Mining
• Similar to open-pit, but only useful when deposits
are horizontal and near surface
Contour Strip Mining
• Used in hilly
or mountain
areas
• Cut terraces
• Remove
overburden
and use to
make new
terrace
Mountain-Top Removal
• Literally remove the top of mountains (!!!)
Mountain-Top Removal Example
Removing Metals from Ores
• Negative consequences:
– Scarring/disruption of land surface
– Large amount of spoils
– Large amounts of solid waste
– Toxic or acidification of water (H2SO4, etc.)
– Gangue (“gang”)
– Air pollution
14.4 How Long Will Supplies of
Nonrenewable Mineral Resources Last?
• 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.
• 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.
Depletion of Resources
• Future supply depends
on two factors:
– Actual supply
– Rate of use
• Depletion time
– Use up 80% of
resource
• After depletion:
– Recycle, waste less, use
less, find a substitute,
do without
Economic Depletion
UNDISCOVERED
RESERVES
(known supplies)
Increasing cost
SUBECONOMIC
ECONOMIC
IDENTIFIED
OTHER RESERVES
(potential supplies)
Increasingly uncertainty
• As known resources
are depleted, it
becomes more
expensive and
difficult to get to
new supplies
• We might still have
resources left, but it
will be TOO COSTLY
to utilize them on a
wide-scale
U.S. General Mining Law of 1872
• To encourage mining of “hard rock” minerals
• How it works:
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File claim that you believe land contains valuable minerals
Promise to spend $500 to improve it
Purchase public land for $2.50 to $5.00 an acre (!!!)
Pay $120 a year for each 20-acre parcel of land
• Law frozen in 1995 – by that time, estimated $285
billion of public land “given away” at 1872 prices
• Since clean up requirements only came in 1992, there
are an estimated 500,000 sites that will cost taxpayers
$32-72 billion to clean up!
Example of 1872 Law “Give Away”
• In 2004, a mining company purchased 155
acres of public land near Crested Butte for
$875
• Land could be worth $155 million
• Each year, companies remove $4 billion
worth of minerals each year and only pay
2.3% of the value in tax (compared to
13.2% for oil or 14% for grazing rights)
14.5 How Can We Use Mineral
Resources More Sustainably?
• We can try to find substitutes for scarce
resources, reduce resource waste, and recycle
and reuse minerals.
Reclamation
• The good news: Mining now requires reclamation
• Reclamation: Returning the land as close as
possible to original state.
Industrial Ecosystems
• Design industrial process to mimic nature