Earth's Physical Systems
MYP Unit Framework
Key Concept: SYSTEMS Related Concepts: Patterns, Processes, Interaction Global Context: Globalization and Sustainability (How do Earth's physical systems shape human settlement and how can we live sustainably with them?) Statement of Inquiry: Earth's physical systems — tectonic, atmospheric, hydrological — shape human settlement and require sustainable management.
Inquiry Questions
| Type | Question |
|---|---|
| Factual | What are the layers of the Earth? What causes earthquakes and volcanic eruptions? |
| Conceptual | How do Earth's physical systems interact with each other? How do natural hazards affect human communities? |
| Debatable | Should people continue to live in areas prone to natural disasters? Is it possible to predict (and therefore prepare for) all natural hazards? |
ATL Skills
- Thinking: Understand systems thinking; analyse cause-and-effect relationships in Earth's physical processes
- Research: Interpret maps, diagrams, and data related to Earth's systems
- Communication: Present findings using diagrams, maps, and written explanations
- Social: Collaborate on case study investigations of natural hazards
- Self-Management: Organise research and meet project deadlines
1. The Structure of the Earth
Layers of the Earth
- Crust: The thin outer layer (5-70 km thick). Continental crust (thicker, less dense) and oceanic crust (thinner, more dense).
- Mantle: 2,900 km thick. Mostly solid rock that flows very slowly (convection currents).
- Outer Core: Liquid iron and nickel. Creates Earth's magnetic field.
- Inner Core: Solid iron and nickel. Extremely hot (approx. 5,500 degrees Celsius).
The Lithosphere
The lithosphere is the rigid outer layer of Earth — the crust and upper mantle. It is broken into tectonic plates that move slowly over the asthenosphere (the semi-fluid layer below).
2. Plate Tectonics
What Is Plate Tectonics?
The theory that Earth's lithosphere is divided into plates that move relative to each other, driven by convection currents in the mantle.
Types of Plate Boundaries
Divergent Boundaries: Plates move apart. Magma rises to create new crust. Example: Mid-Atlantic Ridge (Iceland).
Convergent Boundaries: Plates collide. Three types:
- Oceanic-Continental: Oceanic plate subducts (sinks under) continental plate — creates mountains and volcanoes (Andes)
- Oceanic-Oceanic: One oceanic plate subducts under another — creates island arcs (Japan)
- Continental-Continental: Both plates buckle and thicken — creates mountain ranges (Himalayas — India colliding with Eurasia)
Transform Boundaries: Plates slide past each other horizontally. Example: San Andreas Fault (California). Causes earthquakes.
Evidence for Plate Tectonics
- Continental fit (Pangaea — Alfred Wegener's theory)
- Fossil distribution across continents
- Matching rock formations on different continents
- Seafloor spreading (magnetic striping)
- Earthquake and volcano distribution along plate boundaries
3. Earthquakes and Volcanoes
Earthquakes
Causes: Sudden release of energy when rocks break along a fault line. The energy travels as seismic waves.
Key Terms:
- Focus: The point underground where the earthquake starts
- Epicentre: The point on the surface directly above the focus
- Magnitude: The energy released (measured on the Richter or Moment Magnitude Scale)
- Intensity: The effects of the earthquake (Mercalli Scale)
Seismic Waves:
- P-Waves (Primary): Fastest; travel through solids and liquids
- S-Waves (Secondary): Slower; travel only through solids
- Surface Waves: Slowest; cause the most damage
Volcanoes
Formation: Magma from the mantle rises through cracks in the crust. When it reaches the surface, it is called lava.
Types of Volcanoes:
- Shield Volcanoes: Gentle slopes, non-explosive (Hawaii)
- Composite Volcanoes: Steep slopes, explosive (Mount Fuji, Mount Vesuvius)
- Cinder Cone: Small, steep, built from ejected material
Volcanic Hazards: Lava flows, ash falls, pyroclastic flows, volcanic gases, lahars (mudflows)
Living with Natural Hazards
Why do people live near volcanoes and fault lines?
- Fertile soil (volcanic ash is rich in nutrients)
- Geothermal energy
- Tourism
- Cultural and historical ties
4. The Atmosphere and Climate
Structure of the Atmosphere
- Troposphere (0-12 km): Weather occurs here; temperature decreases with height
- Stratosphere (12-50 km): Ozone layer; temperature increases with height
- Mesosphere (50-80 km): Temperature decreases; meteors burn up here
- Thermosphere (80-700 km): Temperature increases; auroras occur here
Weather and Climate
Weather: Short-term atmospheric conditions (hours to days) Climate: Long-term patterns (30+ years)
Factors Affecting Climate
- Latitude: Temperature decreases toward the poles
- Altitude: Temperature decreases with height
- Distance from the Sea: Coastal areas have milder climates (maritime); inland areas have more extremes (continental)
- Ocean Currents: Warm currents warm coastal areas; cold currents cool them
- Prevailing Winds: Distribute heat and moisture globally
5. The Water Cycle and Hydrology
The Hydrological Cycle
The continuous movement of water between the atmosphere, land, and oceans:
- Evaporation: Water turns to vapour from oceans, lakes, and rivers
- Transpiration: Water vapour from plants
- Condensation: Vapour cools and forms clouds
- Precipitation: Rain, snow, hail, sleet
- Collection: Water returns to oceans, lakes, and rivers
- Infiltration: Water soaks into the ground (groundwater)
Rivers and Drainage Basins
A drainage basin is the area of land drained by a river and its tributaries. The watershed is the boundary between drainage basins.
River Processes:
- Erosion: Wearing away of the river bed and banks
- Transport: Movement of eroded material
- Deposition: Dropping of material when the river loses energy
Flooding
Causes: Heavy or prolonged rainfall, snowmelt, storm surges, deforestation (reduces infiltration), urbanisation (impermeable surfaces increase runoff)
Management:
- Hard Engineering: Dams, levees, channel straightening (effective but expensive and environmentally disruptive)
- Soft Engineering: Flood warnings, land-use planning, wetland restoration (sustainable and cost-effective)
6. Human Interaction with Physical Systems
Climate Change
Human activities (burning fossil fuels, deforestation, agriculture) increase greenhouse gases in the atmosphere, trapping more heat.
Impacts: Rising sea levels, extreme weather events, changing rainfall patterns, biodiversity loss.
Sustainable Management
- Reducing greenhouse gas emissions
- Protecting natural buffers (wetlands, forests, mangroves)
- Building resilience in vulnerable communities
- International cooperation (Paris Agreement, IPCC)
Summative Assessment
Task: Case study report (800-1000 words) on a natural hazard or climate-related issue in a specific location.
Criteria:
- A: Knowing and Understanding — Demonstrate knowledge of Earth's physical systems
- B: Investigating — Research a specific case; use evidence from multiple sources
- C: Communicating — Present findings with maps, diagrams, and structured writing
- D: Thinking Critically — Analyse the causes, impacts, and management of the hazard
Structure: Location and background | Physical processes involved | Impacts on people and environment | Management strategies | Evaluation and recommendations
Formative Assessment
- Diagram: label Earth's layers with properties
- Map activity: plot tectonic plate boundaries and major earthquake/volcano zones
- Case study analysis: impacts of a recent natural disaster
- Weather vs. climate sorting activity
- Water cycle diagram with explanations
- Debate: 'Hard engineering is the best solution for flood management'
Interdisciplinary Connections
- Science: Chemistry of the atmosphere; physics of plate movement (convection); geology
- Mathematics: Interpreting earthquake magnitude scales; calculating flood return periods
- English: Writing about natural disasters — news reports, personal accounts, persuasive pieces about climate action
Service as Action
- Disaster Preparedness: Create an emergency preparedness guide for your school or community for a specific natural hazard.
- Climate Action: Conduct an energy audit of your school. Present recommendations for reducing the school's carbon footprint.
IB Learner Profile
- Inquirers: Ask questions about how Earth's systems work and affect human life
- Knowledgeable: Understand tectonic, atmospheric, and hydrological processes
- Caring: Develop concern for communities affected by natural hazards and climate change
- Principled: Act responsibly toward the environment
Self-Test
- List Earth's four layers and one characteristic of each.
- What is the theory of plate tectonics?
- Describe THREE types of plate boundaries and give an example of each.
- What is the difference between an earthquake's focus and epicentre?
- Name TWO types of seismic waves and describe their properties.
- What are the main hazards associated with volcanoes?
- List the layers of the atmosphere and identify where weather occurs.
- Explain the difference between weather and climate.
- Describe the water cycle using correct terminology.
- What are TWO human activities that contribute to climate change?
This unit aligns with IB MYP Individuals & Societies guide, developed for Year 3 (Class 8) students.
