Transcript Understanding Our Environment

Principles of
Environmental Science
Inquiry and Applications
Third Edition
Cunningham • Cunningham
Chapter 11
Lecture Outlines*
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Environmental Geology and Earth Resources
Chapter 11
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Outline:
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Tectonic Processes
Minerals and Rocks
Economic Geology and Mineralogy
 Strategic Resources
Environmental Effects of Resource Extraction
 Mining
- Restoration
Conserving Geologic Resources
Geologic Hazards
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A DYNAMIC PLANET
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A Layered Sphere
 Core - Interior composed of dense,
intensely hot metal. Generates magnetic
field enveloping the earth.
 Mantle - Hot, pliable layer surrounding the
core. Less dense than core.
 Crust - Cool, lightweight, brittle outermost
layer. Floats on top of mantle.
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A Layered Sphere
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Tectonic Processes
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Tectonic Processes
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Upper layer of mantle contains convection
currents that break overlaying crust into a
mosaic of tectonic plates.
 Slide slowly across earth’s surface.
- Ocean basins form where continents
crack and pull apart.
- Magma forced up through cracks in
oceanic crust form mid-oceanic ridges.
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Tectonic Processes
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Tectonic Processes Cont’d
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Earthquakes are caused by grinding and
jerking as plates slide past each other.
 Mountain ranges pushed up at the margins
of colliding plates.
- When an oceanic plate collides with a
continental landmass, the continental
plate will ride up over the seafloor and
the oceanic plate will subduct down into
the mantle.
 Deep ocean trenches mark
subduction zones.
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Pangea
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Geologists suggest that several times in
earth’s history most, or all, of the continents
gathered to form a single super-continent,
Pangea, surrounded by a single global
ocean.
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MINERALS AND ROCKS
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A mineral is a naturally occurring, inorganic,
solid element or compound with a definite
chemical composition and regular internal
crystal structure.
A rock is a solid, cohesive, aggregate of one
or more minerals.
 Each rock has a characteristic mixture of
minerals, grain sizes, and ways in which
the grains are held together.
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Rock Types
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Rock Cycle - Cycle of creation, destruction,
and metamorphosis.
 Three major rock classifications:
- Igneous
- Sedimentary
- Metamorphic
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Igneous Rocks
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Most common type of rock in earth’s crust.
 Solidified from magma extruded onto the
surface from volcanic vents.
- Quick cooling of magma produces finegrained rocks.
 Basalt
- Slow cooling of magma produces
coarse-grained rocks.
 Granite
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GRANITE
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Sedimentary Rock
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Deposited materials that remain in place long
enough, or are covered with enough material
for compaction, may again become rock.
 Formed from crystals that precipitate out
of, or grow from, a solution.
- Shale
- Sandstone
- Tuff
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Metamorphic Rock
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Pre-existing rocks modified by heat,
pressure, and chemical agents.
 Chemical reactions can alter both the
composition and structure of rocks as they
are metamorphosed.
- Marble (from limestone)
- Quartzite (from sandstone)
- Slate (from mudstone and shale)
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Weathering
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Mechanical - Physical breakup of rocks into
smaller particles without a change in
chemical composition.
Chemical - Selective removal or alteration of
specific components that leads to weakening
and disintegration of rock.
 Oxidation
Sedimentation - Deposition of loosened
material.
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ECONOMIC GEOLOGY AND MINERALOGY
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Metals
 Metals consumed in greatest quantity by
world industry (metric tons annually):
- Iron
(740 million)
- Aluminum
(40 million)
- Manganese
(22.4 million)
- Copper and Chromium (8 million ea)
- Nickel
(0.7 million)
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Non-Metal Mineral Resources
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Sand and Gravel
 Brick and concrete construction, paving,
sandblasting and glass production.
Limestone
 Concrete and building stone
Evaporites
 Gypsum and Potash
Sulfur
 Sulfuric Acid
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Strategic Metals and Minerals
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Durable, highly valuable, and easily portable,
gemstones and precious metals have been a
way to store and transport wealth.
 These valuable materials have bankrolled
despots, criminal gangs, and terrorism in
many countries.
 Much of the illegal trade ends up in the
$100 billion per year global jewelry trade,
two-thirds of which sells in the U.S.
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Strategic Metals and Minerals
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ENVIRONMENTAL EFFECTS OF
RESOURCE EXTRACTION
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Mining
 Placer Mining - Hydraulically washing out
metals deposited in streambed gravel.
- Destroys streambeds and fills water with
suspended solids.
 Strip-Mining or Open-Pit Mining
- Large scars on land surface.
- Tailings
 Toxic runoff
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Mining
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Underground Mining
 Very Dangerous
- Gas
- Inhaling Particulate Matter
- Tunnel Collapse
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Restoration
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Surface Mining Control and Reclamation Act
(1977) requires better restoration of stripmined lands, especially if land classed as
prime farmland.
 Difficult and expensive.
- Often more than $10,000.00 per hectare.
 50% of U.S. coal is strip-mined.
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Processing
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Metals are extracted from ores by heating or
treatment with chemical solvents.
 Smelting - Roasting ore to release metals.
- Major source of air pollution.
 Heap-Leach Extraction - Crushed ore piled
in large heaps and sprayed with a dilute
alkaline cyanide solution which percolates
through the pile to dissolve the gold.
- Effluent left behind in ponds.
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CONSERVING GEOLOGIC RESOURCES
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Recycling
 Aluminum must be extracted from bauxite
by electrolysis.
- Recycling waste aluminum consumes
one-twentieth the energy of extraction
from raw ore.
 Nearly two-thirds of all aluminum
beverage cans in U.S. are recycled.
 Other metals commonly recycled:
- Platinum, gold, copper, lead, iron, steel.
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Substituting New Materials For Old
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Reduce metal consumption by using new
materials or new technologies.
 Plastic pipes in place of metal pipes.
 Fiber-optics in place of metal wires.
 Metal alloys in place of traditional steel.
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GEOLOGIC HAZARDS
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Earthquakes - Sudden movements of the
earth’s crust that occur along faults where
one rock mass slides past another.
 Gradual movement - creep.
- When friction prevents creep, stress
builds up until eventually released with a
sudden jerk.
 Frequently occur along subduction
zones.
 Tsunami - Seismic sea swells.
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Country where
Deaths
deaths occurred Confirmed Estimated1
Injured
Missing
Displace
130,736
167,736
—
35,322
35,322
21,411
India
12,405
18,045
—
5,640
647,599
Thailand
5,395
8,212
8,457
2,817
7,000
Somalia
78
289
—
—
5,000
Myanmar (Burma)
61
400-600
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200
3,200
Maldives
82
108
—
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15,000+
Malaysia
68– 69
75
299
6
—
Tanzania
10
13
—
—
—
Seychelles
3
3
57
—
200
Bangladesh
2
2
—
—
—
South Africa
2
2
—
—
—
Yemen
2
2
—
—
—
Kenya
1
1
2
—
—
Madagascar
—
—
—
—
1,000+
Indonesia
Sri Lanka
2
4
3
37,063
500,000+
516,150
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Volcanoes
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Volcanoes and undersea magma vents are
the sources of most of the earth’s crust.
 Many of world’s fertile soils are weathered
volcanic material.
- Human / Environmental Dangers
 Volcanic Ash
 Mudslides
 Sulfur Emissions
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Volcanic ash from Pinatubo Volcano in the Philippines partly buries
this village. The great 1991 eruption of Pinatubo was the second
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largest in the world during the 20th Century.
Floods
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Excess water that overflows stream banks
and covers adjacent land.
 Biggest economic loss is usually
contamination, not direct property losses.
- Carpet, furniture, drywall, etc.
 Many human activities increase both
severity and frequency of floods.
- Soil compaction
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Floods Cont’d
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Floodplains often help mitigate flooding.
 Usually flat, fertile, and easily farmed.
- Flood control structures have separated
floodplains from rivers.
Flood Control
 Governmental air of flooding victims seems
to have encouraged building on
floodplains.
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Erosion
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Landslides
 A general term for rapid down-slope
movement of soil or rock.
- Many human activities such as forest
clearing and building homes on steep,
unstable slopes increase both frequency
and damage done by landslides.
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Erosion Cont’d
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Barrier Islands
 Stand between mainland and open sea.
 Contain many of world’s sandy beaches.
- Many people place a high value on the
view and beach access, and thus these
are highly prized areas to build
structures.
 Assume modern technology will
provide protection.
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