7th Grade Unit 3, Module 1 - Distribution of Earth’s Resources, Notes

Natural Resources: Core Concepts

• Definition: A natural resource is any item or form of energy that originates in Earth’s systems and is utilized by living organisms to meet biological or societal needs.
  • Includes tangible matter (air, soil, timber, minerals) and energy sources (sunlight, fossil fuels, flowing water).
  • All scales of life— from microbes to whales— depend on these resources.
• Major Spheres that Supply Resources
  • Lithosphere (land) – soils, rocks, ores, fossil fuels.
  • Hydrosphere (oceans, rivers, groundwater) – water for drinking, irrigation, power generation; seafood; transportation routes.
  • Atmosphere (air) – oxygen for respiration, nitrogen for plant growth, wind for energy.
  • Biosphere (living things) – timber, fibers, crops, ecosystem services such as pollination and carbon storage.
• Ethical & Practical Significance
  • Availability determines quality of life, economic development, and ecological health.
  • Management choices today impact future generations because many resources regenerate slowly.

Energy Resources & Human Dependence

• Every-day Energy Uses: lighting, heating/cooling, transportation, manufacturing, communication, and food production.
• Primary Categories
  • Solar – sunlight converted directly (photovoltaics) or indirectly (photosynthesis, wind).
  • Fossil Fuels – coal, oil (petroleum), natural gas; concentrated chemical energy formed over millions of years.
  • Hydrologic – flowing water (hydroelectric), tides.
  • Other – geothermal, biomass, nuclear (not covered deeply in transcript but relevant).
• Electricity Pathways
  • Example: rooftop solar panels require silicon sourced from sand; coal/gas-fired power plants burn fossil fuels to spin turbines.
• Key Insight: Understanding origin, availability, and environmental cost of each energy source guides responsible consumption and policy.

Land Resources & Their Uses

• Living Space: All organisms—including humans— require territory for homes, ecosystems, and infrastructure.
• U.S. Land-Use Snapshot
  • $\approx20\%$ of land → crops.
  • $\approx25\%$ → grazing livestock.
  • Urban areas occupy only a small fraction yet have high per-capita resource demand.
• Forests
  • Provide timber (furniture, paper, cardboard).
  • Historical change: eastern U.S. forests heavily logged by $1920$; regrown stands are shorter, less complex.
• Mineral Ores
  • Definition: economically viable mineral deposits.
  • Average per-person annual use: $22{,}000\ \text{kg}$ (≈ $24$ U.S. tons).
  • Examples: copper (wiring & plumbing), quartz (glass & ceramics).

Air & Water Resources

• Air
  • Oxygen extraction by lungs powers cellular respiration.
  • Quality directly influences public health; most organisms survive only minutes without it.
• Water
  • Composes majority of blood; regulates temperature; medium for biochemical reactions.
  • Daily human uses: drinking, cooking, cleaning, agriculture (irrigation), industry, power generation, recreation.
  • Ecological uses: habitat, nutrient transport.
• Critical Perspective: Unlike some conveniences (e.g., plastic), loss of clean air or water is immediately life-threatening.

Renewable vs. Nonrenewable Resources

• Renewable Resources
  • Replenished on human time scales (< decades).
  • Examples: water (via water cycle), air, sunlight, living biomass, soils (if managed sustainably), wind.
  • Caveat: rate of use must not exceed rate of natural replacement (e.g., deforestation faster than regrowth leads to shortage).
• Nonrenewable Resources
  • Form extremely slowly (thousands–millions of years) or under rare geologic conditions.
  • Include fossil fuels, most minerals, metal ores.
  • Once depleted, effectively unavailable for many future human generations.

Distribution of Mineral Resources

• Hydrothermal Deposits & Plate Tectonics
  • Metallic minerals (copper, gold, silver, lead, iron, zinc) often form where tectonic plates converge, diverge, or have past igneous intrusions.
  • Hot, mineral-rich fluids circulate, cool, and crystallize = hydrothermal deposits.
  • Subduction zones and ocean-floor hydrothermal vents create chimney-like structures rich in metal sulfides.
• Evaporative (Cool-Solution) Deposits
  • Minerals like halite (rock salt) crystallize when water bodies evaporate, leaving behind dissolved solids.
• Uneven Global Distribution
  • Geoscience processes are localized ⇒ mineral availability is patchy.
  • Example: Cyprus copper mines once part of oceanic crust uplifted onto land.
• Conservation Imperative
  • Minerals are largely nonrenewable; prudent use ensures availability for future innovation.

Soil Formation & Distribution

• Definition: Loose, weathered material supporting plant growth; foundation for terrestrial ecosystems and agriculture.
• Five Formation Factors
  1. Parent Material – original rock/sediment; influences texture & chemistry.
  2. Climate – temperature & precipitation control weathering rate and nutrient leaching.
  3. Topography – slope affects erosion vs. deposition; flat areas accumulate thicker soils.
  4. Living Organisms – roots, microorganisms, burrowing fauna enhance breakdown, add organic matter, create porosity.
  5. Time – mature profiles develop distinct layers (horizons); takes $80\text{–}400\ \text{yr}$ to form $1\ \text{cm}$ of topsoil under typical conditions.
• Richest Soils: Moderate climates, gentle slopes, long formation with minimal erosion (e.g., U.S. Midwest mollisols).

Fossil Fuels: Formation & Regional Concentrations

• General Process
  1. Accumulation of organic matter (plants or plankton).
  2. Rapid burial by sediments (anoxic conditions reduce decay).
  3. Heat & pressure convert matter over millions of years.
• Coal
  • Originates in prehistoric swamps; plant remains → peat → lignite → bituminous → anthracite with increasing pressure & temperature.
  • Regions once swampy (eastern U.S., China’s Shanxi) host major coal seams.
• Oil & Natural Gas
  • Derived mainly from marine plankton; form first oil, then (if hotter/deeper) natural gas.
  • Accumulate in geologic traps where impermeable rock seals hydrocarbons; tectonic plate motions later position these deposits under land or sea.
• Uneven Availability
  • World’s largest oil fields: Middle East, Russia, North America— all ancient ocean basins with proper traps.
  • Natural gas often co-located with oil; coal independent.
• Time Constraint: Geological formation times far exceed human lifespans ⇒ effectively finite for current civilization.

Groundwater: Storage, Movement, & Distribution

• Subsurface Freshwater (~$\frac13$ of global freshwater) resides in pores and fractures of soil, sediment, rock.
• Porosity (Storage Capacity)
  • Ratio of void volume to total volume; high in well-sorted or coarse sediments.
• Permeability (Flow Capacity)
  • Connectivity of pores; essential for water extraction.
  • Even porous rock is unusable if pores aren’t interconnected.
• Aquifers
  • Permeable bodies storing “significant” water; tapped by wells.
  • Best aquifers: thick sedimentary basins in tectonic valleys.
• Geologic & Hydrologic Controls
  • Mountain ranges direct precipitation patterns; infiltration recharges aquifers.
  • Impermeable basement rock (e.g., granite) halts downward percolation → perched water tables.

Human Impacts on Resource Availability

Mining & Mineral Depletion

• Extraction Methods: open-pit, underground, placer, solution mining.
• Environmental Effects
  • Habitat fragmentation, landscape alteration, acid mine drainage, heavy-metal pollution.
  • Regulation & reclamation reduce but do not eliminate impacts.
• Economic Trend
  • Rising demand (population + industrialization) → intensified exploration.
  • Technological advances locate low-grade ores, delaying depletion but raising energy cost and ecological footprint.

Fossil Fuel Extraction & Consumption

• Coal: surface or underground mining; abundant (projected >275 years of reserves).
• Oil & Gas: drilling, hydraulic fracturing; reliant on impermeable traps.
• Risks: spills, methane leakage, CO$_2$ emissions, habitat loss.
• Supply/Demand Equation$\text{Remaining\,Supply} = \text{Known\,Reserves} - \text{Cumulative\,Use}$
  • If (\text{Use\,rate} > \text{Discovery\,rate}), supply declines.

Groundwater Overdraft

• Over-Extraction (withdrawal > recharge) lowers water table, dries wells, and induces land subsidence.
• Salt-Water Intrusion in coastal aquifers contaminates freshwater.
• Societal Fallout: abandonment of farms/towns, increased pumping costs, food insecurity.

Conservation & Sustainable Management

• Key Principles
  • Match consumption rates to natural renewal where possible.
  • Substitute renewables for nonrenewables when feasible (e.g., solar for coal electricity).
  • Recycle minerals (aluminum, copper) to extend reserves.
  • Enforce pollution controls to preserve water & air quality.
• Interdisciplinary Relevance
  • Economics: supply-and-demand, externalities.
  • Ethics: intergenerational equity— today’s use affects tomorrow’s options.
  • Engineering: innovations in efficiency and extraction technologies reshape resource timelines.

Key Vocabulary & Concepts (Quick Reference)

• Resource – naturally occurring material/energy used by life.
• Ore – mineral deposit large enough for profit.
• Hydrothermal – relating to hot, mineral-laden water.
• Parent Material – original rock/sediment from which soil forms.
• Porosity/Permeability – storage capacity vs. flow capacity of subsurface media.
• Aquifer – permeable rock/sediment body that stores/releases groundwater.
• Geologic Trap – impermeable layer sealing hydrocarbons.
• Renewable vs. Nonrenewable – time scale of natural replacement relative to human use.
• Groundwater Overdraft – extraction faster than recharge.
• Deplete – to exhaust supply.

Numerical & Statistical Highlights

• Average mineral use per person per year: $22{,}000\ \text{kg}$.
• U.S. coal consumption per person: $3.8\ \text{tons}$ annually (≈ three pickup trucks).
• Soil formation rate: $80\text{–}400\ \text{yr}\,\Rightarrow\,1\ \text{cm}$ topsoil.
• Coal reserve longevity estimate: >275 years (at current usage rates).
• Groundwater comprises $\approx\frac13$ of global freshwater.

Concept Connections & Exam Tips

• Plate Tectonics explains distribution of minerals and fossil fuels— know examples.
• Water & Rock Cycles jointly control groundwater; be ready to trace movement paths.
• Renewability is rate-dependent; illustrate with forest harvest vs. regrowth time.
• Resource Interdependence: Energy required to mine minerals; minerals required to build energy infrastructure— a feedback loop.
• Human Impact Scenarios: Be prepared to evaluate consequences of a new mine, a large aquifer withdrawal, or switching from coal to solar.