Chapter 14: Geology and Earth Resources Study Notes

Chapter 14: Geology and Earth Resources

Learning Goals

  • Summarize the processes that shape the Earth

  • Describe several earth resources of economic value

  • Outline the environmental effects of resource extraction.

  • Identify several geological hazards and explain how they occur.

  • Create a conceptual map that explains how a mineral or rock resource forms, how it is used and mined, and how its extraction impacts the environment and communities.

Geology

  • Definition: The study of the Earth, its materials, structure, processes, and history.

  • Importance in Environmental Science:

    • Understanding natural hazards

    • Understanding natural resources

    • Understanding human interactions with the Earth

  • Key Components:

    • Soil: Formed from weathered rock

    • Minerals, metals, and rocks: Used in various applications such as phones, cars, and buildings

    • Energy resources: Include fossil fuels

Earth’s Interior: A Layered Geoid

  • Core:

    • Interior composed of dense, intensely hot metal, mostly iron.

  • Mantle:

    • Hot, semi-solid layer surrounding the core; less dense than the core.

  • Crust:

    • Cool, lightweight, brittle outermost layer that floats on top of the mantle.

Elemental Composition of Earth

  • 90% of Earth is comprised of 4 main elements:

    • Iron (Fe) – 35%

    • Oxygen (O) – 30%

    • Silicon (Si) – 15%

    • Magnesium (Mg) – 10%

A Layered Earth

  • Crust Composition:

    • Silicon (Si), Oxygen (O), Iron (Fe), Magnesium (Mg)

  • Mantle Composition:

    • Iron (Fe), Magnesium (Mg), Silicon (Si), Oxygen (O)

  • Core Composition:

    • Iron (Fe), Nickel (Ni)

Elemental Abundances in Continental Crust

  • Oxygen (O): 46.6%

  • Silicon (Si): 27.7%

  • Aluminum (Al): 8.1%

  • Iron (Fe): 5.0%

  • Calcium (Ca): 3.6%

  • Magnesium (Mg): 2.1%

  • Potassium (K): 2.8%

  • Sodium (Na): 2.6%

  • Notable Uses of Elements:

    • Quartz: Glass

    • Gypsum: Plaster

    • Granite: Buildings

    • Calcite: Lime

Rocks and Minerals

  • Definition of a Mineral:

    • Naturally occurring solid crystalline material formed by geologic processes with a definable chemical composition.

Breaking Down the Definition

  1. Naturally Occurring: True minerals grow in nature; synthetic minerals are those created in labs.

  2. Formed by Geologic Processes: Most minerals grow from the solidification of molten rock or direct precipitation from water solutions.

  3. Solid: Minerals are in solid state.

  4. Crystalline Material: Atoms are arranged in orderly patterns known as crystal structures.

  5. Definable Chemical Composition: Specific chemical formula dictates the structure and properties. Examples:

    • Quartz (SiO4)

    • Halite (NaCl)

    • Exception: Diamond (C)

  6. Inorganic: Generally, minerals do not contain organic substances. Some organisms produce biogenic minerals.

Rock Types

  • Definition of Rock: Solid, cohesive aggregate of one or more minerals.

    • Characteristics: Mixture of minerals, varying grain sizes, and arrangement of grains.

  • Rock Cycle: Cycle of creation, destruction, and metamorphosis.

  • Three Major Rock Classifications: Igneous, Metamorphic, Sedimentary.

Igneous Rocks

  • Most common type of rock in Earth’s crust, formed from solidified magma.

  • Quick Cooling:

    • Produces aphanitic rocks (e.g., basalt).

  • Slow Cooling:

    • Results in phaneritic rocks (e.g., granite).

Metamorphic Rock

  • Rocks modified by heat, pressure, and chemical agents.

  • Examples:

    • Marble (from limestone)

    • Quartzite (from sandstone)

    • Slate (from mudstone and shale).

Sedimentary Rock

  • Formed from accumulating sediments.

    • Processes involved: Closure of sediment layers, compaction, and cementation leads to lithification.

Types of Sedimentary Rock

  • Clastic: Fragments of pre-existing rocks cemented together.

  • Chemical: Precipitation from solutions, commonly seawater (think minerals).

  • Organic: Consist of carbon-rich materials from remains of living organisms.

Weathering and Sedimentation

  • Mechanical Weathering: Physical breakdown of rocks without changing their chemical composition.

  • Chemical Weathering: Selective removal/alteration that weakens and disintegrates rock.

  • Sedimentation: Deposition of particles transported by wind, water, ice, and gravity to settle in new locations.

Economic Geology

  • Branch of geology focusing on minerals and rocks utilized to meet human needs.

  • Economic minerals are those that can be extracted profitably.

  • Implication: The economic mineral deposits of a country are its natural wealth essential for development and prosperity.

Economic Mineralogy/Geology

  • Two main types of ore deposits:

    • Metallic: Contains metals like gold, iron, and copper.

    • Non-Metallic: Other minerals such as gypsum, potash, and salt.

  • Ore Definition: A rock containing enough value to justify mining (e.g., CuFeS2, Copper Iron Sulfide).

Table 14.2: Primary Uses of Some Major Metals Consumed in the United States

  • Aluminum: Used in packaging (38%), transportation, electronics.

  • Chromium: Used in high-strength steel alloys.

  • Copper: Key in building construction and electric industries.

  • Iron: Involved in heavy machinery and steel production.

  • Lead: Used in batteries, paints, ammunition.

  • Manganese: Essential for high-strength, heat-resistant steel alloys.

  • Nickel: Important in the chemical industry and steel alloys.

  • Platinum-group metals: Used in medical and electronic applications.

  • Gold: Found in jewelry and as monetary standards.

  • Silver: Utilized in electronics and jewelry.

Economic Geology and Mineralogy: Metallic

  • Metals consumed in greatest quantities annually include:

    • Iron: 740 million metric tons

    • Aluminum: 40 million metric tons

    • Manganese: 22.4 million metric tons

    • Copper and Chromium: 8 million metric tons each

    • Nickel: 0.7 million metric tons.

Non-Metallic Mineral Resources

  • Includes gemstones valued for beauty and color, sand and gravel, used extensively in construction and various industries.

Other Resources

  • Fossil Fuels:

    • Coal, oil, and natural gas come from deposits of living organisms from the Carboniferous period (360-300 million years ago).

    • Coal: Formed from vegetation.

    • Oil and gas: Resulted from buried deposits of plankton and algae.

Environmental Effects of Resource Extraction

  • Definition: Extraction of minerals valuable for industrial processes, manufacturing, and energy production.

  • Types of mining and their environmental impact:

    • Strip Mining: 50% of U.S. coal extracted; involves removing layers of soil to expose ore.

    • Environmental Damage Ranking:

    1. Surface Mining (most damaging)

    2. Mountaintop Removal

    3. Placer Mining

    4. Underground Mining (least damaging).

Mountaintop Removal

  • Involves removing the mountaintop to access coal beds.

  • Advantages: Efficient for coal access; lower extraction costs.

  • Disadvantages: Severe habitat destruction; changes permanent landscape; legal implications under the Clean Water Act.

Clean Water Act of 1972

  • Aim: To protect and improve U.S. water resource quality.

  • Violations include discharge of wastewater into streams without a permit; lawsuits can be filed by environmental groups.

Surface Mining

  • Involves extracting minerals near the Earth's surface.

  • Common Methods: Open-pit mining.

  • Advantages: Less expensive; faster and more efficient.

  • Disadvantages: Causes land degradation, waste pile formation, and creates large holes that can fill with contaminated groundwater.

Surface Mining Control and Reclamation Act of 1977

  • Legislation aimed at regulating surface mining, ensuring restoration of disturbed lands, and addressing environmental impacts.

Placer Mining

  • Involves extracting minerals from riverbeds and beaches using methods like panning and sluicing.

  • Advantages: Low impact if done responsibly; can be conducted on a small scale.

  • Disadvantages: Limited to mineral concentration locations; potential water pollution and habitat destruction if mismanaged.

Underground Mining

  • Extracting minerals through tunnels and shafts.

  • Advantages: Minimizes surface impact; accesses deep deposits.

  • Disadvantages: Dangerous due to cave-ins and gas leaks; expensive and labor-intensive.

Geologic Hazards

  • Definition: Sudden movements of Earth’s crust along faults (earthquakes) can be caused by friction that builds up until sudden release.

  • Epicenter: Point of initial movement in an earthquake.

  • High death tolls often linked to poor construction standards; modern buildings are designed to be earthquake-resistant.

Earthquake Facts

  • Most active seismic regions in the U.S. are the West Coast, particularly California and Alaska.

  • Earthquakes can trigger tsunamis, as seen in Japan’s 2011 earthquake.

Human Induced Earthquakes

  • Fluid Injection (Fracking): Can increase fault line pressure.

  • Reservoir-Induced Seismicity: Caused by filling of reservoirs behind dams which changes fault pressures.

  • Mining and Geothermal Energy Extraction: Resource extraction can destabilize surrounding rock.

Landslides

  • Defined as mass wasting, a movement of geologic materials downslope.

  • Speed varies; can be caused by road construction, forest clearing, and building on slopes.

Summary

  • Earth processes shape landforms, create resources, and drive hazards.

  • Extraction of natural resources like minerals and fossil fuels can harm the environment.

  • Natural hazards such as earthquakes can be intensified by human activities like mining.

Concept Maps

  • Concept maps visually depict ideas and their connections.

  • Useful for organizing thoughts and demonstrating relationships within a topic.

  • Task: Create a concept map showing the formation of a mineral/rock resource, how it is used, mined, and its environmental and community impacts.