Transcript ch 15 ppt - Walton High School

Geology and
Nonrenewable Mineral
Resources
Chapter 15
Chapter Overview Questions
• What major geologic processes occur
within the earth and on its surface?
• What are nonrenewable mineral resources
and where are they found?
• What are rocks, and how are they recycled
by the rock cycle?
• How do we find and extract mineral
resources from the earth’s crust, and what
harmful environmental effects result from
removing and using these minerals?
Chapter Overview Questions
(cont’d)
• Will there be enough nonrenewable
mineral resources for future generations?
• Can we find substitutes for scarce
nonrenewable mineral resources?
• How can we shift to more sustainable use
of nonrenewable mineral resources?
Earth’s Structure
• Lithosphere – cool, brittle layer; contains the
crust and uppermost mantle
• Asthenosphere – sits below the lithosphere;
– Weak layer of partial melting
– Is said to be “plastic”; has the ability to flow
• Mantle – beneath asthenosphere
– Comprises 80% of Earth’s volume
– Solid
• Core
– Outer core; liquid
– Inner core; solid
Earth’s Structure
Spreading
center
Collision between
two continents
Subduction
zone
Continental
crust
Oceanic
crust
Ocean
trench
Oceanic
crust
Continental
crust
Material cools Cold dense
as it reaches material falls
the outer back through
mantle
mantle
Hot
Mantle
material
convection
rising
cell
through
the
mantle
Two plates move
towards each other.
One is subducted
back into the mantle
on a falling convection
current.
Mantle
Hot outer
core Inner
core
Fig. 15-3, p. 337
Geologic Processes
• Internal processes
– Convection currents within the asthenosphere
– Mantle plumes where hot mantle rock rises
then spreads out, causing crust to split open
– Hot spots where a hot spot in the mantle
forms volcanoes in the overlying crust
– Plate tectonics, which is movement of crustal
plates due to underlying convection currents
Hawaiian Hotspot
Yellowstone Hotspot
http://volcanoes.usgs.gov/
Plate Boundaries
• Kinds of plate boundaries
– Divergent: plates move away from each other (Mid
Atlantic Ridge)
– Convergent: plates collide with each other
• Subduction Zone occurs when one plate is thrust under the
other plate (Japan Island Arc, Himalayas)
– Oceanic vs. oceanic will form an island arc
– Continental vs. continental will form large mountains
– Continental vs. oceanic will form a mountain range
• Transform: two plates slide past each other (San Adreas
Fault)
Divergent vs. Convergent Boundaries
• Divergent occurs
at upwelling from
asthenosphere
• Convergent occurs
when two plates
collide
Photo of Mid Atlantic Ridge in Iceland
• Is an example of a
divergent plate
boundary
• Other examples
include the Mid
Atlantic Ridge and the
East Pacific Rise
Three examples of subduction zones
• (a): oceanic
vs. continental
plate
• (b): oceanic
vs. oceanic
plate
• (c):
continental vs.
continental
plate
Ocean vs Ocean Boundary
Island Arc
Satellite image of Japan from Google Earth
Ocean-Continent Boundaries
• Magmas produced in mantle wedge above
subducting slab
Ocean vs Continent
c.) Continent vs Continent
Transform Boundary
http://www.berkeley.edu/news/media/releases/2004/01/09_quakes.shtml
Picture of several small faults in road cut outside of Arches
National Park, Utah
Rocks
• Three types of rocks
– Sedimentary – composed of sediments
cemented together
– Igneous – formed from cooled molten rock
– Metamorphic – formed from submitting rocks
to high temperatures, pressures, or both
• Rocks are made of minerals
– Minerals are elements or compounds that
have a definite composition and crystal
structure
Wearing Down and Building Up
the Earth’s Surface
• Weathering
is an
external
process that
wears the
earth’s
surface
down.
Figure 15-6
Rock Cycle
• Any rock type can turn into any other rock
type through the rock cycle
– Rocks change due to chemical or physical
conditions that change over time
– Slowest of earth’s cyclic processes
Rock Cycle
Figure 15-8
MINERALS, ROCKS, AND THE
ROCK CYCLE
• The earth’s crust consists of solid
inorganic elements and compounds
called minerals that can sometimes be
used as resources.
– Mineral resource: is a concentration of
naturally occurring material in or on the
earth’s crust that can be extracted and
processed into useful materials at an
affordable cost.
Economic Geology
• What is an economic geological
resource?
– A mineral that is heavily used in some
human endeavor (e.g., metal ores) and
therefore is an important part of
domestic/international commerce.
• What are some mineral resources that
are economically important?
– metals. examples?
– non-metal resources. examples?
General Classification of
Nonrenewable Mineral Resources
• Examples are
fossil fuels (coal,
oil), metallic
minerals (copper,
iron), and
nonmetallic
minerals (sand,
gravel).
Figure 15-7
General Classification of
Nonrenewable Mineral Resources
• The U.S. Geological Survey classifies
mineral resources into four major categories:
– Identified: known location, quantity, and quality
or existence known based on direct evidence and
measurements.
– Undiscovered: potential supplies that are
assumed to exist.
– Reserves: identified resources that can be
extracted profitably.
– Other: undiscovered or identified resources not
classified as reserves
Pyrite, FeS2
Galena, PbS
Bauxite, Aluminum oxides
Average Concentration of
Valuable Metals in the Crust
Aluminum ~8%
Iron
~5% most Fe and Al is in silicate minerals
and is not used as an ore
Titanium 0.44%
Nickel
75 ppm or 0.0075%
Zinc
70 ppm or 0.0070%
ppm =
Copper 55 ppm 0.0055%
parts per million
Lead
13 ppm or 0.0013%
Silver
0.07 ppm
Gold
0.004 ppm
Mining: Extract Ore from
Ground
Types of Mining:
• Surface Mining: Scoop ore off surface or earth.
• cheap.
• safe for miners.
• large environmental destruction.
• Underground Mining: Use of shafts to reach deeply buried ores.
• expensive.
• hazardous for miners.
• less environmental damage.
Types of Surface Mining
open pit mining:
• machines dig holes and remove
ores, sand, gravel, and stone
Types of Surface Mining
• Strip-mining: scoop off rock
overburden, and then scoop off
ore material. After mineral is
removed, trench is filled with
overburden and new cut is made
parallel to first one.
• Large land area can be involved,
especially for coal and bauxite.
Types of Surface Mining
• Strip mining
– Often leaves highly
erodible hills of
rubble called spoil
banks, tailings
Canadian Oil Sands — Photo Gallery —
National Geographic Magazine
Figure 15-12
Contour Strip Mining
• Used on hilly or
mountainous
terrain.
• Unless the land is
restored, a wall of
dirt is left in front of
a highly erodible
bank called a
highwall.
Figure 15-13
Types of Surface Mining
• Mountaintop removal:
removes top of a
mountain and
exposes seams of
mineral underneath.
Common in West
Virginia
Mining Impacts
• Metal ores are
smelted or treated
with (potentially
toxic) chemicals to
extract the desired
metal.
Figure 15-15
Environmental Damage
•
•
•
•
•
Scarring and disruption of land surface
Collapse or subsidence of land above underground mines
Wind-or water-caused erosion of toxin-laced mining wastes
Emission of toxic chemicals into atmosphere
Exposure of wildlife to toxic mining wastes stored in holding
ponds and leakage of such waste
• Contamination of nearby streams and groundwater from
sulfuric acid (H2SO4) produced through weathering of iron
sulfide (FeS2, pyrite) in tailings.
4FeS2 + 14H2O = 4Fe(OH)3 + 8H2SO4
• Contamination from heavy metals (cyanide, mercury) from
mining gold.
Acid Mine Drainage
SUPPLIES OF MINERAL
RESOURCES
• The future supply of a resource depends on
its affordable supply and how rapidly that
supply is used.
• A rising price for a scarce mineral resource
can increase supplies and encourage more
efficient use.
SUPPLIES OF MINERAL
RESOURCES
• Depletion curves
for a renewable
resource using
three sets of
assumptions.
– Dashed vertical
lines represent
times when 80%
depletion occurs.
Figure 15-16
SUPPLIES OF MINERAL
RESOURCES
• New technologies can increase the mining of
low-grade ores at affordable prices, but
harmful environmental effects can limit this
approach.
• Most minerals in seawater and on the deep
ocean floor cost too much to extract, and
there are squabbles over who owns them.
Getting More Minerals from the
Ocean
• Hydrothermal
deposits form
when mineral-rich
superheated water
shoots out of vents
in solidified
magma on the
ocean floor.
Figure 15-17
ENVIRONMENTAL EFFECTS OF
USING MINERAL RESOURCES
• The extraction, processing, and use of
mineral resources has a large environmental
impact.
Figure 15-9
USING MINERAL RESOURCES
MORE SUSTAINABLY
• Scientists and engineers are developing
new types of materials as substitutes for
many metals.
• Recycling valuable and scarce metals
saves money and has a lower
environmental impact then mining and
extracting them from their ores.
Natural Capital Degradation
Extracting, Processing, and Using Nonrenewable Mineral and Energy Resources
Steps
Environmental effects
Mining
Disturbed land; mining
accidents; health hazards,
mine waste dumping, oil
spills and blowouts; noise;
ugliness; heat
Exploration,
extraction
Processing
Use
Solid wastes; radioactive
material; air, water, and
soil pollution; noise;
safety and health
hazards; ugliness; heat
Transportation or
transmission to
individual user,
eventual use, and
discarding
Noise; ugliness; thermal
water pollution; pollution
of air, water, and soil;
solid and radioactive
wastes; safety and health
hazards; heat
Transportation,
purification,
manufacturing
Fig. 15-10, p. 344
Solutions
Sustainable Use of Nonrenewable Minerals
• Do not waste mineral resources.
• Recycle and reuse 60–80% of mineral resources.
• Include the harmful environmental costs of
mining and processing minerals in the prices
of items (full-cost pricing).
• Reduce subsidies for mining mineral resources.
• Increase subsidies for recycling, reuse, and
finding less environmentally harmful substitutes.
• Redesign manufacturing processes to use less
mineral resources and to produce less pollution
and waste.
• Have the mineral-based wastes of one
manufacturing process become the raw
materials for other processes.
• Sell services instead of things.
• Slow population growth.
Fig. 15-18, p. 351
Surface Mining Control and
Reclamation Act of 1977
• Regulates existing mines
• Requires mining companies to restore
surface-mined land by grading and
replanting.
– In most cases it’s only partially successful
– Can take several decades
– Some land ends up as permanent desert
Abandoned Mines Reclamation in Montana
Case Study:
The Ecoindustrial Revolution
• Growing signs point to an ecoindustrial
revolution taking place over the next 50
years.
• The goal is to redesign industrial
manufacturing processes to mimic how
nature deals with wastes.
– Industries can interact in complex resource
exchange webs in which wastes from
manufacturer become raw materials for
another.
Sludge
Pharmaceutical plant
Sludge
Greenhouses
Waste
heat
Fish farming
Waste heat
Oil refinery
Surplus
sulfur
Local farmers
Surplus
Electric power
natural gas
plant
Waste
calcium
sulfate
Cement manufacturer
Sulfuric acid
producer
Wallboard factory
Area homes
Fig. 15-19, p. 352