Chapter 14: Geology and Nonrenewable Mineral Resources

14.1 What Are the Earth’s Major Geological Processes and Hazards?

The Earth Is a Dynamic Planet

• Geology: Dynamic processes taking place on the earth’s surface and in the earth’s interior
• Three major concentric zones of the earth
  • Core: Earth’s innermost zone (solid inner part, surrounded by a liquid core of molten rock)
  • Mantle: Thick, solid rock zone surrounding the core
  • Asthenosphere: Hot partly melted rock that flows and can be deformed like soft plastic
  • Crust: Outermost & thinnest zone. (continental crust & oceanic crust – 71%)
  • Lithosphere: The outermost part of the mantle and continental crust oceanic crust.

Tectonic Plates Types of Boundaries

• Divergent boundaries: When ocean plates move apart allowing molten material to flow up through the cracks creating oceanic ridges.
• Convergent boundaries: ocean plates collide with continental plates
  • Subduction Zone: the continental plate rides up over the cooler, denser, oceanic plate and pushes it down into the mantle
• Transform boundaries: continental or ocean plates slide past one another

Some parts of the Earth’s Surface Build Up and Some Wear Down

• Internal geologic processes: Generally build up the earth’s surface
• External geologic processes: Directly or indirectly driven by energy from the sun, wind, flowing water, and glaciers which all contribute to erosion and are influenced by gravity.
• Weathering: Physical, chemical, and biological
• Erosion: Wind, flowing water, human activities, glaciers

Volcanoes Release Molten Rock from the Earth’s Interior

• Volcano
  • Magma
  • Lava
• 1991- Eruption of Mount Pinatubo

Earthquakes Geological Rock-and-Roll Events

• Earthquake
  • Focus: A place where an earthquake begins below the earth’s surface.
  • Epicenter: Found directly above the focus on the earth’s surface.
  • Magnitude: A measure of ground motion indicated by the size of the seismic waves. Used to measure the severity of an earthquake.
  • Richter Scale: Used to measure earthquake intensity. Each unit has an amplitude 10 times greater than the next smaller unit.
  • Aftershocks/Foreshocks: Tremors after or before an earthquake

Tsunamis

• Tsunami: Series of large waves generated when part of the ocean floor suddenly rises or drops.
• December 2004- Indian Ocean tsunami
  • Magnitude 9.15 and 31-meter waves at the shore
  • Role of coral reefs and mangrove forests in reducing the death toll

14.2 How Are the Earth’s Rocks Recycled?

There Are Three Major Types of Rocks

• Minerals: Element or inorganic compound in earth’s crust. Usually a crystalline solid. Regular and repeating arrangement of atoms
• Rock: Combination of one or more minerals
  • Sedimentary: Made of sediments- dead plant and animal remains and existing rocks that are eroded and weathered into tiny particles.
  • Igneous: Forms below the earth’s surface when magma wells up from the earth’s upper mantle or deep crust and then cools and hardens.
  • Metamorphic: Forms when preexisting rock is subjected to high temperatures, high pressures, chemically active fluids, or a combination of these, which
• Deposits of nonrenewable mineral resources in the earth’s crust vary in their abundance and distribution. For example, iron and aluminum are fairly abundant whereas manganese, chromium, cobalt, and platinum are fairly scarce.
• A very slow chemical cycle recycles three types of rock found in the earth’s crust. The earth’s crust contains igneous, sedimentary, and metamorphic rocks that are recycled by the rock cycle.
  • Igneous rock is formed below or on the earth’s surface when molten rock wells up and hardens. They form the bulk of the earth’s crust.
  • Sedimentary rock is formed from small, eroded pieces of rock that are carried to downhill sites. Layers accumulate over time and an increase of weight and pressure plus dissolved minerals bind the sediment particles together to form sedimentary rock.
  • Metamorphic rock is produced from preexisting rock that is subjected to high temperatures, high pressures, chemically active fluids, or some combination of these.

14.3 What Are Mineral Resources, and What Are Their Environmental Effects?

We Use a Variety of Nonrenewable Mineral Resources

• Mineral resource: Can be extracted from the earth’s crust and processed into raw materials and products at an affordable cost
  • Metallic minerals: aluminum, gold
  • Nonmetallic minerals: sand, limestone
• Ore: Rock that contains large concentrations of a particular mineral (often metal).
  • High-grade Ore: Contains large amounts of desired nonrenewable resources.
  • Low-grade Ore: Contains a small amount of desired nonrenewable resources.

Important Metals

• Aluminum: Packaging, structural material
• Steel: Alloy of Fe, and other elements such as Mn, Co, Mo, and Cr. Used in all types of products.
• Copper: Electrical and communications
• Platinum: Electronics, catalyst in industry, and in automobile pollution control converters
• Gold: Electrical equipment, jewelry, coins, medical implants, and as a catalyst to speed up certain chemical reactions

Important Nonmetals

• Sand: Primarily SiO2 or silicon dioxide. It is used to make glass, bricks, and concrete.
• Gravel: Used for roadbeds and to make concrete.
• Limestone: Mostly CaCO3 or calcium carbonate. It is crushed to make road rock, concrete, and cement.
• Phosphate salts: Mined and used in inorganic fertilizers and some detergents.
• Reserves: Identified resources from which the mineral can be extracted profitably at current prices

Mining Techniques

• Surface Mining: Used to harvest shallow deposits
• Subsurface Mining: Used to harvest deep deposits
• Open Pit Mining: Machines dig massive holes and remove ores
• Strip Mining: Used for extracting deposits that lie close to the earth’s surface and lie in horizontal beds.
• Area Strip Mining: Used where the terrain is fairly flat
• Contour Strip Mining: Used where the terrain is hilly or mountainous
• Mountaintop Removal: Use of explosives, large power shovels, and huge machines to remove tops of mountains
• Hydraulic Mining: Sing water cannons to wash entire hillsides into collection boxes. (outlawed in the U.S.)
• Overburden: Soil and rock overlying a useful mineral deposit.
• Spoils: Overburden discarded as waste material
• Tailings: The unused materials left on land from dredging ore deposits from streams

Mining Has Harmful Environmental Effects

• Subsurface mining (less common, produces less waste)
  • Subsidence: Collapse of land above mines
  • Acid mine drainage: Rainwater seeps through the mine or spoil pile and carries sulfuric acid (from bacteria acting on iron sulfide)
• Major pollution of water and air
• Effect on aquatic life
• Large amounts of solid waste (3/4 of all U.S. solid waste)

Removing Metals from Ores Has Harmful Environmental Effects

• Ore extracted by mining
  • Ore mineral
  • Gangue = waste material
  • Smelting: Uses heat or chemicals
• Air pollution
  • sulfur dioxide
  • suspended toxic particles
• Water pollution

14.4 How Long Will Supplies of Nonrenewable Mineral Resources Last?

• The future supply of a resource depends on its affordable supply and how rapidly that supply is used. A nonrenewable resource generally becomes economically depleted rather than totally depleted.
• Economics determines what part of a known mineral supply is extracted and used. Higher prices often mean more resources can be used (at a higher extraction cost), but this can be affected by national policies that subsidize exploration or restrict exports/imports.
• New technologies can increase the mining of low-grade ores at affordable prices, but harmful environmental effects can limit this approach.

Supplies of Nonrenewable Mineral Resources Can Be Economically Depleted

• When it becomes economically depleted
  • Recycle or reuse existing supplies
  • Waste less
  • Use less
  • Find a substitute
  • Do without
• Depletion time: time to use a certain portion of reserves

14.5 How Can We Use Mineral Resources More Sustainability?

We Can Find Substitutes for Some Scarce Mineral Resources

• Materials revolution: Ceramics, high-strength plastics
• Nanotechnology
• Substitution is not a cure-all
  • Pt: Industrial catalyst
  • Cr: An essential ingredient of stainless steel

We Can Recycle and Reuse Valuable Metals

• Recycling and Reusing: Lower environmental impact than mining and processing metals from ores

Solutions for 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 mining subsidies Increase subsidies for recycling, reuse, and finding substitutes
• Redesign manufacturing processes to use fewer mineral resources and to produce less pollution and waste (cleaner production)
• Use mineral resource wastes of on manufacturing process as raw materials for other processes
• Slow population growth

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