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Study Guide: Topic 1A & 1B – Sustaining a Planet

Study Guide: Topic 1A & 1B – Sustaining a Planet

📖 Key Terms & Concepts

Topic 1A – Introduction to Sustaining a Planet

  • Land Surface Degradation – damage to Earth’s surface (urbanization, deforestation, soil erosion, habitat loss).

  • Resource Depletion – overuse of energy, water, materials, extraction of non-renewable resources.

  • Population Growth – especially in developing countries; links to resource strain.

  • Water Cycle Issues – droughts, floods, over-use, river/aquifer pollution, ocean pollution.

  • Atmospheric & Global Change – air pollution, ozone, smog, global warming, abrupt climate change, sea level rise, hurricanes.

  • Ecosystems – biodiversity loss, food production impacts (fertilizers, pesticides).

  • Dead Zone (Gulf of Mexico) – low oxygen zone caused by nutrient runoff (fertilizers) → algal blooms → kills marine life.

  • Carbon Dioxide Trend – rapid increase (from ~280 ppm pre-industrial → 428 ppm in 2025). Caused by fossil fuels/deforestation → leads to warming, extreme weather, sea level rise.

  • Tipping Points – thresholds beyond which change becomes irreversible.

  • Sustainable Development – meeting present needs without compromising future generations.

Topic 1B – Sustainability & My Generation

  • Sustainability (Brundtland Commission, 1987) – “Meeting the needs of the present without compromising the ability of future generations to meet their own needs.”

  • Sustainability Science – interdisciplinary study of interactions between nature and society.

  • Generational Differences

    • 1960s–70s (Boomers/Gen X): causes included civil rights, women’s rights, ending Vietnam War, space exploration. Heroes: MLK, JFK, RFK, Gloria Steinem, Neil Armstrong.

    • 2000–2025 (Gen Z): climate change, racial justice, gender equality, sustainability. Heroes less centralized, activism often digital (“clicktivism”).

  • Generation Q (Friedman/Ross) – critiques of passive activism (likes, reposts) vs. real action. Need to “get off the couch.”

  • Power of One vs. Power of Many – individual leadership vs. collective action in driving change.

📌 Main Study Questions

From Topic 1A

  1. List pressing problems for Earth in each category:

    • Land Surface Degradation

    • Resource Depletion

    • Population & Social Systems

    • Water Cycle

    • Atmospheric & Global Change

    • Ecosystems

  2. Define and explain the Gulf of Mexico dead zone.

  3. Describe the trend in atmospheric CO₂ over time. What causes it? What are its consequences?

  4. How can we test whether hurricanes will be more intense in a warmer world?

  5. How does mosquito infection with West Nile Virus change with temperature?

From Topic 1B

  1. Define sustainability and sustainability science.

  2. Who are some heroes of today’s generation?

  3. What are the key causes advocated for by today’s generation?

  4. Why are there differences in heroes and causes between generations? How does this connect to sustainability?

🧪 UGS303 – Topic 2: The Scientific Method Study Guide

📖 Key Terms & Concepts

The Scientific Method

  • Observation – factual description of something seen/measured (e.g., “The globe has warmed”).

  • Inference – logical interpretation/explanation of observations (e.g., “The globe will continue to warm”).

  • Hypothesis – tentative explanation that can be tested (educated guess).

  • Theory – well-supported, broad explanation for phenomena (e.g., Theory of Evolution).

  • Law – statement of consistent relationship under specific conditions (e.g., Laws of Thermodynamics).

  • Peer Review – process where other scientists evaluate and critique work before publication, ensuring checks, balances, and integrity.

Science vs. Non-Science vs. Nonsense

  • Science – tentative, testable, falsifiable, peer-reviewed, documented, widely disseminated.

  • Non-Science – does not use the scientific method (e.g., religion, philosophy, art). Can be meaningful but not testable in the same way.

  • Nonsense – claims with no logical/scientific basis (e.g., astrology).

⚡ Voodoo Science (Robert Park, 2000)

Forms of non-science that pretend to be science:

  1. Pathological Science

    • Scientists fool themselves by believing results they want to see.

    • Example: Cold Fusion (unrepeatable experimental results reported prematurely).

  2. Pseudoscience

    • Claims not based on scientific method, but practitioners believe them to be science.

    • Examples: Hologram bracelets, NASA moon landing hoax theories.

  3. Junk Science

    • Claims with little supporting evidence, crafted to mislead the public, lawmakers, or judges.

    • Example: Vitamin O health claims, misleading corporate research (like Coca-Cola funding studies to minimize sugar’s role in obesity).

🧭 Case Studies from Class

  • Cold Fusion → Pathological Science (results not replicable).

  • Hologram Bracelets → Pseudoscience (celebrity belief vs placebo-controlled study = no effect).

  • NASA Moon Hoax → Pseudoscience (misinterpreting evidence, ignoring peer review).

  • Vitamin O → Junk Science (misleading product marketed with false “oxygen boost” claims).

📝 Main Study Questions

1. Observations vs. Inferences

  • Observation = direct evidence (measured facts).

  • Inference = interpretation or prediction based on observation.

2. Steps of Research → Publication

  • Observation → Hypothesis → Experiment/Testing → Analysis → Peer Review → Publication → Criticism/Replication → Possible revision or replacement.

  • Process is tortuous because: peer review is strict, replication is required, errors are common, and science is self-correcting.

3. Voodoo Science Types & Motivations

  • Pathological Science – scientists fool themselves (motivation: confirmation bias, prestige).

  • Pseudoscience – belief-based, not evidence-based (motivation: sincere belief, misunderstanding of science).

  • Junk Science – deliberately misleading (motivation: money, politics, public manipulation).

🌎 Why This Matters

  • Environmental problems are complex → require sound science to solve.

  • Misapplication (Voodoo Science) leads to misinformation, poor policy, and wasted resources.

  • Peer review, replication, and skepticism protect integrity.

📘 Study Guide – Topic 3: Tragedy of the Commons

🔑 Key Terms & Concepts

  • Tragedy of the Commons: When individuals act in self-interest and overuse shared resources, leading to depletion and collapse of the system.

  • Carrying Capacity: The maximum population size that an environment can sustain indefinitely without depleting resources.

  • Moai: Large stone statues carved by the Rapa Nui people of Easter Island, some weighing up to 82 tons.

  • Deforestation: Loss of trees that reduces resources, causes soil erosion, and accelerates collapse.

  • Commons: Resources shared by many (land, water, atmosphere, fisheries, forests).

🏝 Easter Island Case Study

Early Settlement & Growth (ca. 500 CE)

  • Polynesians arrived, blown off course.

  • Rich resources: fertile soil, palm trees, seabirds, fish, sweet potatoes.

  • Society developed → large population growth.

Cultural Development

  • Moai statues built between 1000–1600 CE.

  • Over 200 completed statues along the coast, plus 700 more unfinished in quarries.

  • Required ropes, logs, canoes, and complex organization.

Observations by Europeans

  • 1722 – Jacob Roggeveen (Dutch explorer)

    • Found only a few hundred hungry, poorly clothed islanders.

    • Island barren, trees gone.

    • Amazed by giant Moai, but puzzled how such a weak society built them.

  • 1774 – Captain James Cook

    • Found population under 200.

    • Canoes poorly made and leaky (no large trees left for good ones).

    • Most Moai had been toppled and destroyed.

Collapse (ca. 1600–1700s)

  • Deforestation → no trees for canoes, rope, fire, or shelter.

  • Soil erosion & food shortages.

  • Conflict → statue toppling.

  • Population collapse before Europeans arrived.

  • Last Palm Tree: Symbol of ecological collapse — without trees, escape was impossible.

🔬 How History Was Reconstructed

  1. Lake sediment cores → pollen evidence of deforestation.

  2. Midden records → trash heaps showed diet changes (less fish, more rats).

  3. Oral traditions & European records → collapse stories.

  4. DNA studies → traced Polynesian ancestry.

🌍 Modern Examples of the Tragedy of the Commons

  • Ogallala Aquifer (U.S.) → over-pumping groundwater.

  • Overfishing → global fisheries depletion.

  • Climate change → burning fossil fuels as a global commons problem.

  • Deforestation (Amazon, Indonesia).

  • Air pollution (smog, CO₂ buildup).

  • Traffic congestion (shared road space).

🌏 Easter Island vs. Earth Island

  • Similarities:

    • Both are isolated systems with finite resources.

    • Overexploitation → collapse risk.

    • Easter Island serves as a warning for Earth.

  • Differences:

    • Earth has trade, technology, renewable energy, and communication.

    • Easter Island was small enough that limits were seen immediately; Earth is bigger but still finite.

📋 Review Questions (Practice)

  1. Define carrying capacity and explain with the sheep meadow example.

  2. What problem did Jacob Roggeveen see when he visited Easter Island in 1722?

  3. What did Captain James Cook report about Easter Island in 1774?

  4. List three methods used to reconstruct Easter Island’s history.

  5. Summarize Easter Island’s 1500-year history of settlement, growth, and collapse.

  6. How big is Easter Island (compared to a U.S. city)?

  7. What was the significance of the last palm tree?

  8. Give at least three modern examples of the tragedy of the commons.

  9. Compare and contrast the analogy of Easter Island = Earth Island.

Study Guide: Topic 3 – Tragedy of the Commons

🔑 Key Terms

  • Carrying Capacity: The maximum population size of a species that an environment can support indefinitely without degrading the environment.

  • Tragedy of the Commons: A situation where shared resources are overused and depleted because individuals act in their own short-term interest instead of long-term collective benefit.

  • Moai: The large stone statues built by the Rapa Nui people on Easter Island.

  • Deforestation: The removal of trees that prevents regrowth of forests and leads to soil erosion, loss of biodiversity, and collapse of ecosystems.

🏝 Easter Island Case Study

  1. Carrying Capacity (Q1)

    • Easter Island exceeded its carrying capacity by overusing limited resources (especially trees).

  2. Jacob Roggeveen’s Observation (Q2)

    • When Roggeveen visited in 1722, he questioned how the Moai statues were built and moved since there were no large trees left for tools, transport, or rafts.

  3. Captain James Cook’s Visit (Q3)

    • In 1774, Cook saw many Moai statues toppled over, reflecting social collapse and conflict.

  4. How History Was Reconstructed (Q4)

    • Archaeological evidence: Excavations of tools, statues, and settlements.

    • Palynology (pollen studies): Showed widespread deforestation.

    • Oral traditions & European records: Gave cultural and historical context.

  5. 1500-Year Timeline of Easter Island (Q5)

    • Settlement around 500 CE.

    • Flourishing society built Moai between 1000–1600 CE.

    • Overuse of resources → deforestation → soil erosion → food shortages.

    • Conflict and statue-toppling by 1700s.

    • Population collapse before European arrival.

  6. Size of Easter Island (Q6)

    • 66 square miles → about the size of Washington, D.C. or comparable to Austin, Texas city limits.

  7. Last Palm Tree (Q7)

    • Symbolized total ecological collapse; once the last tree was cut, the islanders lost canoes, shelter, and food sources.

🌍 Modern Connections

  1. Modern Examples of Tragedy of the Commons (Q8)

    • Overfishing of oceans.

    • Climate change (fossil fuel overuse).

    • Air pollution.

    • Deforestation in the Amazon.

    • Traffic congestion.

  2. Easter Island = Earth Island (Q9)

    • On target: Both are isolated systems with limited resources; overexploitation leads to collapse.

    • Not fully accurate: Earth has global trade, technology, and renewable resource potential that Easter Island lacked.

📘 Study Guide – Topic 4: Drivers of Sustainability

🔑 Key Terms & People

  • Drivers of Consumption: Population growth, affluence (wealth), technology, culture, and policy all shape resource use.

  • Rachel Carson (1907–1964)

    • Marine biologist & author of Silent Spring (1962).

    • Raised awareness about pesticides (DDT) and their ecological harm.

    • Sparked the modern environmental movement.

  • Barry Commoner (1917–2012)

    • Biologist and activist.

    • Advocated that technology drives environmental impacts.

    • Famous for the "Four Laws of Ecology" (everything is connected).

  • Paul Ehrlich (1932– )

    • Biologist, author of The Population Bomb (1968).

    • Warned that overpopulation would cause famine and collapse.

    • Advocated population control.

  • Thomas Malthus (1766–1834)

    • Economist/demographer.

    • Malthusian argument: Population grows exponentially while food supply grows linearly → inevitable shortages, famine, and population checks.

  • I=PAT Equation

    • I = Environmental Impact

    • P = Population

    • A = Affluence (consumption per person)

    • T = Technology (impact per unit of consumption)

    • Framework for analyzing human pressures on the environment.

📊 Main Points & Trends

1. Principal Drivers of Consumption

  • Population: More people → more demand.

  • Affluence: Higher wealth → higher per-person consumption.

  • Technology: Can either increase (e.g., fossil fuels) or reduce impact (e.g., renewables, efficiency).

  • Culture & Values: Consumerism vs. sustainability.

2. U.S. Energy Consumption Trends

  • Consumption: Rose sharply in 20th century, leveling off in recent decades.

  • Production: U.S. now produces much more due to shale oil/gas.

  • Imports: Declining since 2005 (more domestic energy).

  • Exports: Increasing — U.S. is a net exporter of oil and natural gas.

3. Population Growth

  • Current growth rate ~0.9% globally (slowing).

  • Fastest growth: Sub-Saharan Africa, South Asia.

  • Some regions (Europe, Japan) are shrinking.

4. Affluence Growth

  • Global affluence (GDP per capita) rising ~2–3% annually.

  • Fastest growth: China, India, emerging economies.

5. Does Consumption Scale with Affluence?

  • Yes → wealthier nations consume more energy, goods, and services.

  • But → efficiency gains can reduce per-unit consumption.

6. Resource Use per Dollar of Economic Product

  • Trend: Declining resource use per dollar GDP (efficiency gains, dematerialization).

  • However: Total consumption still rising because population + affluence growth outweigh efficiency.

7. Global Energy Consumption

  • Overall → rising steadily.

  • Fossil fuels (oil, coal, natural gas) dominate, though renewables are growing.

  • CO₂ emissions strongly correlated with this trend.

🚗 Example: Applying IPAT to Gasoline Use

  • P (Population): More people → more drivers.

  • A (Affluence): Wealthier people → more cars, larger cars, more driving.

  • T (Technology):

    • Negative: Inefficient engines, reliance on fossil fuels → high impact.

    • Positive: Electric vehicles, hybrids, fuel-efficient engines → reduce impact.

  • Impact: Gasoline use leads to air pollution, CO₂ emissions, oil extraction impacts.

📋 Review Questions (Practice)

  1. What are the main drivers of consumption?

  2. Describe U.S. trends in energy consumption, production, imports, and exports.

  3. Who was Rachel Carson and why is she important?

  4. What did Barry Commoner argue about ecology and technology?

  5. What was Paul Ehrlich’s warning in The Population Bomb?

  6. What is the Malthusian argument about population and food supply?

  7. Write out the I=PAT equation and explain each variable.

  8. Where is global population growing fastest?

  9. Where is affluence growing fastest?

  10. Does consumption increase as affluence increases?

  11. What are the trends in resource use per unit of GDP?

  12. What are the overall trends in global energy consumption?

  13. Use the IPAT framework to explain the environmental impact of gasoline cars.

📖 Key Terms & Definitions

  1. IPAT Equation

    • Formula: Impact = Population × Affluence × Technology

    • A framework to estimate the environmental impact of human activity.

  2. Population

    • The total number of people; growth rates directly increase environmental pressures (resource use, waste, energy demand).

  3. Affluence

    • Measured often as GDP per capita; higher affluence usually means higher consumption and energy use per person.

  4. Technology

    • Refers to the efficiency of resource use and production methods. Can reduce or increase environmental impact (e.g., fuel efficiency vs. rebound effect).

  5. Rebound Effect

    • When improvements in efficiency lead to increased usage, offsetting the environmental benefits (e.g., fuel-efficient cars encourage more driving).

  6. Malthusian Argument

    • Thomas Malthus’ idea that population grows geometrically while food supply grows arithmetically, leading to scarcity.

  7. Rachel Carson

    • Author of Silent Spring (1962), highlighting the dangers of pesticides and environmental contamination.

  8. Barry Commoner

    • Environmentalist who warned that technological advances, while beneficial, also pose existential risks (1966, Science and Survival).

  9. Paul Ehrlich

    • Author of The Population Bomb (1968), predicted mass starvation due to unchecked population growth.

  10. Affluence vs. Consumption

  • Examines whether increased wealth (GDP per capita) always leads to higher consumption, especially energy.

📌 Main Points of the Study (Slides Summary)

  • Consumption, Energy, and Natural Resources

    • Human consumption trends drive environmental impact.

    • Key drivers: Population, Affluence, Technology (IPAT).

  • Population Growth

    • Global population ~8.1 billion (2025).

    • Growth continues at 1–2% annually.

  • Affluence Growth

    • World GDP increasing by 3–5% annually.

    • Largest gains occurring in highly populated regions.

  • Technology Trends

    • Resource efficiency improving (~1–2% per year).

    • Example: Fuel efficiency of cars more than doubled in 50 years.

    • But rebound effect complicates the benefits.

  • Historical Perspectives

    • Rachel Carson, Barry Commoner, and Paul Ehrlich each highlighted dangers of unchecked growth and technological risks.

    • Malthusian concerns about population growth still influence discussions.

  • Net Effect of IPAT

    • Population (+1–2%) + Affluence (+3–5%) > Efficiency gains (–1–2%).

    • Overall, environmental impact continues to rise despite efficiency improvements.

Terms and Definitions

  1. Igneous Rock
    Rock formed from the cooling and solidification of molten magma or lava.

  2. Sedimentary Rock
    Rock formed by the accumulation and compression of sediment, such as sand, minerals, and organic material.

  3. Metamorphic Rock
    Rock formed when existing rock is subjected to heat and pressure, causing physical and chemical changes without melting.

  4. Plate Tectonics
    The scientific theory explaining the movement of Earth's lithospheric plates and how this movement causes geological phenomena.

  5. Lithosphere
    The rigid outer layer of Earth, comprising the crust and upper mantle.

  6. Asthenosphere
    The semi-fluid layer beneath the lithosphere, which allows tectonic plates to move.

  7. Pangea
    A supercontinent that existed during the late Paleozoic and early Mesozoic eras, consisting of most of Earth's landmasses joined together.

  8. Convergent Boundary
    A plate boundary where two plates move toward each other, often causing subduction or mountain formation.

  9. Divergent Boundary
    A plate boundary where two plates move away from each other, typically causing seafloor spreading.

  10. Transform Boundary
    A plate boundary where two plates slide horizontally past one another.

  11. Subduction Zone
    An area where one tectonic plate moves under another and sinks into the mantle, often associated with volcanic activity.

  12. Rock Cycle
    The process through which rocks change from one type to another over geologic time through melting, cooling, erosion, and pressure.

  13. Carbon Reservoir
    Natural storage places for carbon, such as the atmosphere, oceans, biosphere, sediments, and Earth's interior.

Main Points

  1. Three Major Types of Rocks and Formation

    • Igneous: formed from cooled magma or lava.

    • Sedimentary: formed by compaction and cementation of sediments or chemical precipitation.

    • Metamorphic: formed by alteration of existing rocks under heat and pressure.

  2. Plate Tectonics Function and Earth Phenomena

    • Plates move on the asthenosphere due to convection currents in the mantle.

    • Explains earthquakes, volcanic activity, mountain building, and ocean trench formation.

  3. Importance of Understanding Rocks, Earth Structure, and Plate Tectonics

    • Helps predict natural hazards, locate natural resources, and manage Earth's environment sustainably.

  4. Two Main Ways Sedimentary Rocks Form

    • Clastic: from fragments of other rocks.

    • Chemical/Organic: from precipitation or accumulation of biological material.

  5. Economic Importance of Sedimentary Rocks

    • Source of fossil fuels (coal, oil, natural gas), groundwater reservoirs, and minerals.

  6. Unexplained Phenomena and Scientific Accounting

    • Some phenomena remain initially unexplained (e.g., continental drift).

    • Science uses observation, hypothesis testing, and evidence gathering to explain them.

  7. Pangea and Wegener’s Hypothesis Controversy

    • Pangea was a supercontinent that Wegener proposed existed based on fossil and geological evidence.

    • Controversy arose because Wegener lacked a mechanism for plate movement.

    • Scientific method addresses controversy through further testing and evidence collection.

    • In the 1960s, sea-floor spreading and paleomagnetism confirmed plate tectonics, supporting Wegener’s ideas.

  8. Speed of Lithospheric Plates

    • Plates move typically at rates of a few centimeters per year (about the speed fingernails grow).

  9. Driving Forces of Plate Tectonics

    • Mantle convection, slab pull, and ridge push.

  10. Three Main Types of Plate Boundaries

    • Convergent: plates collide, causing subduction or mountain building.

    • Divergent: plates move apart, creating new crust.

    • Transform: plates slide past each other, causing earthquakes.

  11. Andes Mountains Boundary Type

    • Convergent boundary (oceanic-continental subduction).

    • Evidence: volcanic activity, deep ocean trench adjacent to mountains.

  12. San Andreas Fault Boundary Type

    • Transform boundary.

    • Evidence: lateral motion, frequent earthquakes along the fault line.

  13. Iceland Boundary Type

    • Divergent boundary (mid-Atlantic ridge).

    • Evidence: volcanic activity, rift valleys, and spreading ridges.

  14. Five Carbon Reservoirs and Their Relative Size

    • Atmosphere, oceans, terrestrial biosphere, sediments (including fossil fuels), and Earth's interior.

    • Largest reservoir: sediments and fossil fuels; smallest: atmosphere.

📖 Key Terms & Definitions

  1. Rock Cycle

    • The continuous process by which rocks are formed, broken down, and transformed into other rock types (igneous, sedimentary, metamorphic).

  2. Igneous Rocks

    • Rocks formed from the cooling and solidification of magma or lava.

  3. Sedimentary Rocks

    • Rocks formed by the accumulation and compaction of sediments, or by precipitation of minerals from water. Economically important (fossil fuels, building materials).

  4. Metamorphic Rocks

    • Rocks formed when existing rocks are changed by heat, pressure, or chemically active fluids.

  5. Earth’s Structure (Physical)

    • Lithosphere: Rigid outer shell (crust + upper mantle).

    • Asthenosphere: Weak, ductile layer beneath the lithosphere.

    • Mantle: Solid rock that flows slowly.

    • Core: Outer core (liquid iron/nickel), inner core (solid iron/nickel).

  6. Earth’s Structure (Chemical)

    • Crust: Silicate-rich, lighter rock.

    • Mantle: Silicate rocks with more iron and magnesium.

    • Core: Metallic (mostly iron and nickel).

  7. Alfred Wegener

    • Proposed Continental Drift (1915): Pangea supercontinent broke apart into modern continents.

  8. Pangea

    • Supercontinent that existed ~200 million years ago.

  9. Seafloor Spreading

    • Process where new ocean crust forms at mid-ocean ridges and spreads outward, confirmed in the 1960s.

  10. Plate Tectonics

  • Theory that Earth’s lithosphere is divided into plates that move due to mantle convection and gravity.

  1. Plate Boundaries

  • Divergent (constructive): Plates move apart, form new crust, mild earthquakes/volcanoes (e.g., Mid-Atlantic Ridge, Iceland).

  • Convergent (destructive): Plates collide, one subducts, creates trenches, large earthquakes, volcanoes (e.g., Andes, Marianas Trench).

  • Transform (conservative): Plates slide past each other, earthquakes but no volcanism (e.g., San Andreas Fault).

  1. Reservoirs of Carbon (Gt = gigatons)

  • Rocks (65,000,000 Gt)

  • Oceans (39,000 Gt)

  • Soils (1,580 Gt)

  • Atmosphere (750 Gt)

  • Land plants (610 Gt)

  1. Grand Synthesis

  • Combination of geological evidence (fossils, coastlines, seafloor spreading, earthquakes/volcanoes) into the unified theory of plate tectonics.

📌 Main Points (Study Guide Style)

  • The Rock Cycle explains how igneous, sedimentary, and metamorphic rocks form and transform into one another.

  • Earth’s Structure can be viewed physically (lithosphere, asthenosphere, mantle, core) or chemically (crust, mantle, core).

  • Unexplained Phenomena (fit of continents, fossil distribution, earthquake/volcano locations, rock ages) led to Wegener’s Continental Drift hypothesis.

  • Plate Tectonics (1960s Revolution): Seafloor spreading + symmetrical rock ages confirmed that plates move.

  • Driving Forces of Plate Tectonics: Mantle convection and gravity (slab pull, ridge push).

  • Plate Boundaries:

    • Divergent → mild earthquakes/volcanoes, new crust (Iceland, Mid-Atlantic Ridge).

    • Convergent → subduction, large earthquakes, volcanism, trenches (Andes, Himalayas).

    • Transform → earthquakes, no volcanism (San Andreas Fault).

  • Case Studies: Andes Mountains (subduction), San Andreas Fault (transform), Iceland (divergent).

  • Reservoirs of Carbon: Rocks hold by far the largest store, followed by oceans; the atmosphere and biosphere hold much less.

  • Sustainability Connection: Understanding rocks, Earth’s structure, and plate tectonics is crucial for resource use, natural hazards, and climate (carbon cycle).

Study Guide – Topic 6: Atmospheric Structure and Composition

Key Terms and Definitions

  1. Atmosphere – A gaseous body bound by gravity to a celestial body; Earth’s outermost layer formed by outgassing of the interior.

  2. Evolution of the Atmosphere – Process by which Earth’s atmosphere changed from mostly CO₂, H₂O, ammonia, and methane to today’s nitrogen–oxygen dominated system with oxygen from photosynthesis.

  3. Troposphere – Lowest layer of atmosphere (up to ~10–15 km); contains ~80% of the mass, 99% of water vapor, and all weather.

  4. Stratosphere – Layer above the troposphere (~15–50 km); contains ozone layer; temperature increases with altitude due to UV absorption.

  5. Mesosphere – Layer from ~50–85 km; temperature decreases with altitude; coldest part of the atmosphere.

  6. Thermosphere – Layer above mesosphere; very high temperatures (600–2000 K) due to solar radiation absorption.

  7. Exosphere – Outermost region of the atmosphere; transitional zone into space where gas molecules may escape Earth’s gravity.

  8. Ozone Layer – Concentration of ozone (O₃) in the stratosphere that absorbs harmful ultraviolet (UV) radiation.

  9. Tropospheric Composition – Primarily nitrogen (N₂) and oxygen (O₂), with trace gases (argon, CO₂, water vapor, methane).

  10. Greenhouse Effect – Natural process where certain gases trap outgoing infrared radiation, keeping Earth’s surface warmer (~+33°C).

  11. Greenhouse Gases (GHGs) – Atmospheric gases that absorb infrared radiation (e.g., CO₂, H₂O, CH₄, N₂O, O₃, CFCs).

  12. Shortwave Radiation – High-energy solar radiation (visible/UV) from the Sun reaching Earth.

  13. Longwave Radiation – Infrared (IR) radiation emitted by Earth’s surface.

  14. Climate Feedbacks – Processes that amplify (positive) or reduce (negative) climate changes.

  15. Positive Feedback – A change that reinforces itself (e.g., ice melt → less reflection → more warming).

  16. Negative Feedback – A change that stabilizes the system (e.g., more vegetation growth removes CO₂).

  17. Energy Budget – Balance between incoming solar radiation and outgoing terrestrial radiation that determines Earth’s climate.

Main Points

  • Atmosphere Basics

    • Thin shell of gases (~100–200 km thick) compared to Earth’s 12,750 km diameter.

    • Essential for life: respiration, climate/weather generation, radiation filtering, space debris protection, water cycle.

  • Atmospheric Evolution

    • Early atmosphere: volcanic gases (CO₂, H₂O, ammonia, methane).

    • Changes:

      • CO₂ decreased → absorbed by oceans and photosynthesis.

      • CH₄ & NH₃ decreased → oxidized to CO₂, H₂O, and N₂.

      • O₂ increased → photosynthesis.

  • Atmospheric Layers

    • Troposphere (~0–15 km): 80% of mass, weather, most water vapor.

    • Stratosphere (~15–50 km): ozone layer, absorbs UV, stabilizing.

    • Mesosphere (~50–85 km): coldest layer.

    • Thermosphere (~85–600 km): hottest due to solar absorption.

    • Exosphere: boundary with space.

  • Atmospheric Composition

    • Dominant gases: N₂ (~78%), O₂ (~21%), Ar (~1%), CO₂ (~0.04%), H₂O (variable).

    • Trace gases critical to energy balance (greenhouse gases).

  • Without Atmosphere

    • Earth’s temperature would be ~ -20 °C (instead of ~15 °C).

  • Greenhouse Effect

    • Sun’s shortwave radiation passes through atmosphere.

    • Earth emits longwave IR radiation, partly trapped by GHGs.

    • Main GHGs: CO₂, H₂O, CH₄, N₂O, O₃, CFCs.

    • To be a greenhouse gas: must (1) absorb IR radiation and (2) have a long atmospheric lifetime.

  • Feedback Mechanisms

    • Positive:

      • Warming → ice melts → more absorption of sunlight → more warming.

      • Warming → permafrost melts → methane release → more warming.

    • Negative:

      • More vegetation growth from CO₂ → more carbon sequestration → cooling.

      • Warming → more cloud formation → reflects sunlight → cooling

opic 6 – Atmospheric Structure and Composition

🔑 Terms & Definitions

  • Atmosphere – Thin layer of gases bound to Earth by gravity, formed by outgassing.

  • Evolution of Atmosphere – Shift from CO₂, H₂O, NH₃, CH₄ → today’s N₂/O₂ atmosphere due to oceans + photosynthesis.

  • Troposphere – 0–15 km; ~80% of mass; 99% of water vapor; all weather occurs.

  • Stratosphere – 15–50 km; contains ozone layer; absorbs UV; temperature rises with altitude.

  • Mesosphere – 50–85 km; decreasing temps; coldest layer.

  • Thermosphere – Above 85 km; temps up to 2000 K due to solar radiation absorption.

  • Exosphere – Outermost layer, transition to space.

  • Ozone Layer – Region in stratosphere that absorbs harmful UV radiation.

  • Tropospheric Composition – Mostly N₂ (78%), O₂ (21%), with Ar, CO₂, H₂O, trace gases.

  • Greenhouse Effect – Process where gases trap outgoing IR radiation, warming Earth by ~33 °C.

  • Greenhouse Gases (GHGs) – CO₂, H₂O, CH₄, N₂O, O₃, CFCs.

  • Shortwave Radiation – Incoming solar radiation (visible/UV).

  • Longwave Radiation – Outgoing Earth radiation (infrared).

  • Energy Budget – Balance between absorbed solar energy and emitted IR radiation.

  • Climate Feedbacks – Processes that amplify (positive) or counteract (negative) climate changes.

  • Positive Feedback – Change reinforces itself (ex: ice melt → more absorption → warming).

  • Negative Feedback – Change stabilizes system (ex: more clouds → reflect sunlight → cooling).

📌 Main Points

  • Importance of Atmosphere: Enables respiration, creates climate/weather, filters radiation, shields from debris, drives water cycle.

  • Thickness: 100–200 km vs. Earth’s 12,750 km diameter (like paper around a baseball).

  • Evolution: Early CO₂- and H₂O-rich atmosphere → CO₂ absorbed by oceans/plants, NH₃ & CH₄ oxidized, O₂ increased via photosynthesis.

  • Layers:

    • Troposphere: weather, water vapor.

    • Stratosphere: ozone, UV absorption, warming with altitude.

    • Mesosphere: coldest.

    • Thermosphere: hottest.

    • Exosphere: transition to space.

  • Without Atmosphere: Earth ~ –20 °C instead of +15 °C.

  • Greenhouse Effect: Sun’s shortwave passes through; Earth emits IR; GHGs absorb/re-emit IR, warming planet.

  • Conditions for GHGs: Must absorb IR & have long lifetime.

  • Feedbacks:

    • Positive: melting ice, permafrost methane release.

    • Negative: more vegetation growth, more cloud cover.

📖 Key Terms & Definitions

  1. Atmospheric Circulation

    • The large-scale movement of air that redistributes heat from the equator to the poles.

  2. Drivers of Atmospheric Circulation

    • Sun’s Radiation: Provides energy and creates temperature differences.

    • Gravity: Holds the atmosphere to Earth, driving pressure gradients.

    • Earth’s Rotation & Orbit: Cause seasonal changes and the Coriolis effect.

  3. Solar Insolation

    • The amount of solar radiation received at a location; varies by latitude, season, and time of day.

  4. Coriolis Effect

    • The apparent deflection of moving air (and water) due to Earth’s rotation. Deflects right in the Northern Hemisphere, left in the Southern Hemisphere.

  5. Pressure Gradient

    • The difference in air pressure across a horizontal distance that drives wind movement.

  6. High-Pressure System

    • Region where air sinks, leading to clear skies and dry conditions.

  7. Low-Pressure System

    • Region where air rises, leading to cloud formation and precipitation.

  8. Principles of Atmospheric Circulation

    • Hot air rises.

    • Wind = air movement due to pressure differences.

    • Winds deflected by Earth’s rotation.

    • Warm air holds more moisture than cold air.

    • Sun’s rays are most direct at low latitudes.

    • Land and water heat differently due to varying heat capacity.

  9. Earth’s Tilt (23.5°)

    • The reason for the seasons; affects solar intensity and day length.

  10. Solstices and Equinoxes

  • Winter Solstice (Dec 21): Shortest day in Northern Hemisphere.

  • Summer Solstice (Jun 21): Longest day in Northern Hemisphere.

  • Equinoxes (Mar 21, Sep 21): Equal day and night.

  1. Radiation Balance by Latitude

  • Equator: Radiation surplus (absorbs more than emitted).

  • Poles: Radiation deficit (emit more than absorbed).

  1. Circulation Cells

  • On a non-rotating Earth → 1 cell per hemisphere.

  • On a rotating Earth → 3 cells per hemisphere (Hadley, Ferrel, Polar).

📌 Main Points (Study Guide Style)

  • Atmospheric Circulation is driven by:

    • Solar energy differences (insolation varies by latitude & tilt).

    • Gravity, which creates pressure gradients.

    • Earth’s rotation, causing Coriolis deflection.

    • Earth’s orbit & tilt, causing seasonal changes.

  • Principles of Circulation:

    • Hot air rises, cold air sinks.

    • Pressure gradients move air → winds.

    • Coriolis effect deflects winds.

    • Warm air stores more water vapor.

    • Land vs. ocean heating creates differential circulation.

  • Seasons Explained:

    • Caused by Earth’s tilt (23.5°), not distance from the Sun.

    • Different hemispheres tilt toward/away from the Sun → solstices & equinoxes.

  • Radiation Balance:

    • Equator absorbs more than it radiates → surplus.

    • Poles radiate more than they absorb → deficit.

    • Atmospheric circulation redistributes this imbalance.

  • Wind & Pressure Systems:

    • High pressure → descending, dry, clear weather.

    • Low pressure → rising, wet, stormy weather.

  • Circulation Models:

    • Non-rotating Earth: Simple 1-cell model.

    • Rotating Earth: Complex 3-cell system per hemisphere (Hadley, Ferrel, Polar).

🌍 Study Guide: Atmospheric Circulation & Climate (Topics 7A–7C)

1. Where on Earth would you find the following year-round?

  • Coldest air: Near the poles (Arctic and Antarctic).

  • Rising air with the least moisture: Around 30° N and 30° S latitudes (subtropics). These are dry zones where air descends, leading to deserts.

2. How the tilt of the Earth causes the seasons

  • Earth’s axis is tilted 23.5° relative to its orbital plane.

  • This tilt changes the insolation footprint (how spread out or concentrated the Sun’s rays are).

  • Summer (NH): Northern Hemisphere tilts toward the Sun → more direct sunlight, smaller footprint, longer days → higher temperatures.

  • Winter (NH): Northern Hemisphere tilts away from the Sun → more spread-out rays, larger footprint, shorter days → cooler temperatures.

3. The Coriolis Effect

  • Definition: The apparent deflection of moving air/water due to Earth’s rotation.

    • Deflects right in the Northern Hemisphere.

    • Deflects left in the Southern Hemisphere.

  • Impact on deserts: Creates Hadley Cell circulation. Air rises at the equator (wet tropics), moves poleward, then descends dry at ~30° N/S, forming desert belts (Sahara, Kalahari, Arabian, Australian deserts).

4. Atmospheric circulation & ancient explorers

  • Trade winds (easterlies): Near the equator, winds blow east-to-west; helped ships cross the Atlantic but made return voyages difficult.

  • Westerlies: At mid-latitudes (~30°–60°), winds blow west-to-east; used by explorers for return trips to Europe.

  • Challenges:

    • Crossing calm equatorial regions (doldrums) with little wind.

    • Fighting against prevailing winds on return journeys.

5. Why does hot air rise?

  • Hot air is less dense than cooler air.

  • When heated, air molecules move faster and spread apart, reducing density → the air becomes buoyant and rises.

6. Incoming vs. outgoing radiation by latitude (NH focus)

  • Equator/low latitudes: Receive more incoming solar radiation than they emit → radiation surplus.

  • Poles/high latitudes: Emit more energy than they receive → radiation deficit.

  • Observed temps: Not as extreme as expected because atmospheric circulation (and ocean currents) redistribute heat from low latitudes to high latitudes.

  • Conclusion: Circulation systems balance Earth’s heat budget.

7. Latent heat of evaporation & hurricanes

  • Latent heat: Energy absorbed when water evaporates from the ocean’s surface.

  • In hurricanes, this energy is released when water vapor condenses into clouds and rain.

  • Acts as the fuel source for hurricanes, powering strong winds and heavy rainfall.

8. Hurricanes & 21st-century warming

  • Expected changes with warming:

    • Fewer hurricanes overall (uncertain).

    • Stronger intensity: Warmer oceans provide more energy (higher wind speeds, heavier rainfall).

    • More rainfall: Warmer atmosphere holds more moisture.

    • Storm surge risk increases due to sea-level rise.