1. Environmental Geology
Chapter 16
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.

2. Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
Outline:
Tectonic Processes
Rocks and Minerals
Economic Geology and Mineralogy
Strategic Resources
Environmental Effects of Resource Extraction
Mining
Restoration
Conserving Geologic Resources
Geologic Hazards
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3. Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
A DYNAMIC PLANET
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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5. Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
Tectonic Processes
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
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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Tectonic Processes
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Pangea
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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10. Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
ROCKS AND MINERALS
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
Rock Cycle - Cycle of creation, destruction, and metamorphosis.
Three major rock classifications:
Igneous
Sedimentary
Metamorphic
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Igneous Rocks
Most common type of rock in earth’s crust.
Solidified from magma extruded onto the surface from volcanic vents.
Quick cooling of magma produces fine-grained rocks.
Basalt
Slow cooling of magma produces coarse-grained rocks.
Granite
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Weathering
Mechanical - Physical break-up 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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Sedimentary Rock
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
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)
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.

16. ECONOMIC GEOLOGY AND MINERALOGY
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)
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.

17. Non-Metal Mineral Resources
Sand and Gravel
Brick and concrete construction, paving, sandblasting and glass production.
Limestone
Concrete and building stone
Evaporites
Gypsum and Potash
Sulfur
Sulfuric Acid
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.

18. Strategic Metals and Minerals
Of the 80 industrial metals and minerals, between one-third and one-half are considered strategic resources.
A country uses, but cannot produce.
Considered capable of crippling national economy or military strength if supplies were cut off.
Many less-developed nations depend on steady mineral exports for foreign exchange.
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19. Strategic Metals and Minerals
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.

20. ENVIRONMENTAL EFFECTS OF RESOURCE EXTRACTION
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
Underground Mining
Very dangerous.
Gas
Inhaling Particulate Matter
Tunnel Collapse
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Restoration
Surface Mining Control and Reclamation Act (1977) requires better restoration of strip-mined lands, especially if land classed as prime farmland.
Difficult and expensive.
Minimum reclamation costs about $1,000 / acre while complete restoration may cost $5,000 / acre.
50% of US coal is strip mined.
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Processing
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.
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.

24. CONSERVING GEOLOGIC RESOURCES
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 US are recycled.
Other metals commonly recycled:
Platinum, gold, copper, lead, iron, steel.
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.

25. Substituting New Materials For Old
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
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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Volcanoes
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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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.
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.

29. Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
Summary:
Tectonic Processes
Rocks and Minerals
Economic Geology and Mineralogy
Strategic Resources
Environmental Effects of Resource Extraction
Mining
Restoration
Conserving Geologic Resources
Geologic Hazards
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.

30. Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.