Detailed Notes - Tectonics - Edexcel Geography A-level

Page 1

  • Title: PMT Resources - Edexcel Geography A-level

    • Links to detailed notes available at PMT Education.

Page 2: The Global Distribution of Hazards

  • Definition of Hazard

    • A hazard is a potential threat to human life and property.

  • Types of Natural Hazards

    • Hydro-meteorological: Caused by climatic processes.

    • Geophysical: Caused by land processes, occur near plate boundaries.

  • Geophysical Hazards

    • Caused by the movement of tectonic plates (different speeds/directions can cause collisions, earthquakes, and volcanic activity).

    • Intraplate Earthquakes: Occur away from plate boundaries, possibly due to pre-existing weaknesses in the crust.

    • Volcanic Hotspots: Area of high temperature due to upwelling molten material (e.g., Hawaii hotspot).

  • Location of Powerful Earthquakes

    • Most powerful earthquakes occur at convergent or conservative boundaries.

  • Fracture Zones

    • Oceanic Fracture Zone (OFZ): Activity through oceans and mid-ocean ridges.

    • Continental Fracture Zone (CFZ): Activity along mountain ranges from Spain through the Alps to the Himalayas.

Page 3: Tectonics Trends since 1960

  • Trends Observed

    • Total recorded hazards have increased.

    • Fatalities decreased overall yet spikes during mega disasters.

    • Increasing number of people affected due to population growth.

    • Economic costs rising due to higher development and infrastructure costs.

  • Challenges in Reporting Disaster Impacts

    • Direct versus indirect death reporting challenges.

    • Location difficulties (rural vs urban data collection).

    • Varied data collection methods by organizations.

    • Risk of biased death counts by governments (e.g., 2004 Indian Ocean tsunami).

Page 4: Tectonic Theory - Earth's Structure

  • Sections of the Earth

    • Crust: Thinnest layer, lightest; oceanic (7km) vs. continental crust (up to 70km).

    • Mantle: Semi-molten silicate rocks, convection currents contributing to tectonic movement (depth: 700km-2890km).

    • Outer Core: Dense, semi-molten rocks (depth: 2890km-5150km).

    • Inner Core: Solid due to pressure, high temperatures from primordial and radiogenic heat.

Page 5: Different Plate Boundaries

  • Types of Plate Boundaries

    • Plates move towards (destructive), away (constructive), or parallel (conservative) to each other.

    • Landforms and Processes: Vary between different boundaries.

Page 6: Destructive Plate Boundaries

  • Continental and Oceanic

    • Oceanic plate subducts under continental, creating ocean trench; magma forms composite volcanoes.

  • Oceanic and Oceanic

    • Heavier plate subducts, creates ocean trench and underwater volcanoes forming island arcs.

  • Continental and Continental

    • Collision creates fold mountains due to pressure build-up, little subduction occurs.

Page 7: Constructive Plate Boundaries

  • Oceanic and Oceanic

    • Magma rises to form new land, smaller volcanos known as sea floor spreading.

  • Evidence for Plate Movement

    • Paleomagnetism: Study of rock magnetic fields showing alternating magnetic polarity in ocean floors as evidence of spreading.

  • Continental to Continental

    • Rift valleys form, volcanoes may arise, possibly filling with water later creating separations.

Page 8: Conservative Plate Boundaries

  • Characteristics

    • Parallel plates moving in different directions; pressure builds with no landform creation.

  • Plate Composition

    • Oceanic: Basalt, low density.

    • Continental: Granite, thick, higher density affecting subduction.

  • Mechanisms for Plate Movement

    • Mantle Convection: Thermal energy from decay causes mantle movement pushing plates.

    • Slab Pull: Describes how dense plates sink causing further pull.

Page 9: Earthquakes

  • Movement Characteristics

    • Plates become stuck due to friction, pressure builds until release leads to earthquakes.

  • Focus and Epicenter

    • Focus: underground origin of the quake; Epicenter: point above ground.

  • Types of Seismic Waves

    • Primary Waves: Compressional waves through solids.

    • Secondary Waves: Travel through solid rocks at right angles.

    • Love Waves: Rolling surface movements.

    • Rayleigh Waves: Cause vertical displacement.

Page 10: Earthquake Effects

  • Aftershocks: Results of differing seismic wave speeds, with intensity decreasing from epicenter.

  • Impact Factors: Include local geology, geological location, local education, building durability.

  • Secondary Hazards

    • Soil Liquefaction: Weakens soil structure causing landslides.

    • Landslides: Triggered by earthquake shaking.

    • Tsunamis: Generated when sea floor shifts displacing water.

Page 11: Tsunamis Impact

  • Characteristics

    • Generated typically at convergent margins, common in the Pacific Ring of Fire.

  • Impact Factors

    • Population density, coastal defenses, and warning systems significantly influence outcomes.

  • Volcanic Primary Hazards

    • Lava flows, pyroclastic flows, tephra, ash, volcanic gases (e.g. SO2 & CO).

  • Secondary Hazards

    • Lahars, Jokulhlaup, acid rain caused by volcanic activity.

Page 12: Classification and Theories of Tectonic Events

  • Definition of Disaster: Community disruption exceeding recovery capabilities.

  • Risk Calculation

    • Includes factors like hazard intensity, community vulnerability, and coping capacity.

  • Degg's Model

    • Disaster occurs only if a vulnerable population is exposed to a hazard.

  • Various Classifications

    • People affected, economic costs evaluated differently by organizations.

Page 13: Hazard Evaluation Processes

  • Park Model

    • Graphical representation of recovery stages post-disaster (relief, rehabilitation, reconstruction).

    • Steeper curve indicates higher impact and slower recovery.

  • Pressure and Release Model (PAR)

    • Analyzes root causes of vulnerability (economic, political, social processes).

Page 14: Vulnerability Definitions

  • Types of Vulnerability

    • Physical, economic, social, knowledge, environmental vulnerability.

  • Influence of Infrastructure: Poor infrastructure increases hazard impacts.

  • Common Factors Impacting Vulnerability

    • Weak governance, population density, geography, urbanization levels.

Page 15: Socioeconomic Factors Contributing to Vulnerability

  • Inequalities: Asset, political, social, entitlement inequalities affect resilience.

  • Governance Impact: Basic needs and planning contribute to community resilience against hazards.

Page 16: Tectonic Hazard Profiles

  • Hazard Profile Characteristics

    • Frequency, magnitude, duration, speed of onset, fatalities, economic loss.

    • Useful for resource allocation decisions.

Page 17: Effectiveness of Hazard Models

  • Questions for Evaluation

    • Applicability to hazard types, incorporation of development levels, and forecasting accuracy.

  • Considerations for Climate Change Impact: Models must adapt to cope with changing hazard dynamics.

Page 18: Measuring Tectonic Events

  • Volcanic Explosivity Index (VEI): Measures eruption explosiveness (0-8 scale).

  • Modified Mercalli Scale: Measures earthquake destructiveness based on felt experiences.

  • Moment Magnitude Scale: Measures energy released during an earthquake.

  • Richter Scale: Measures wave amplitude, widely used but can be misleading.

Page 19: Managing Tectonic Hazards

  • Response Strategies:

    • Prevention, preparedness, mitigation, adaptation.

    • Hazard Management Cycle: Phases include preparedness, response, recovery, mitigation.

Page 20: Hazard Management Stages

  • Preparedness: Awareness and training.

  • Response: Immediate action post-event (evacuation, medical help).

  • Recovery: Long-term rebuilding efforts.

  • Mitigation: Methods to lessen future impacts through planning and zoning strategies.

Page 21: Management Approaches

  • Three Approaches

    • Modify the Event: Can’t control hazards but can modify building designs and land use.

    • Modify Vulnerability: Improve monitoring, educate communities.

    • Modify Loss: Implement short and longer-term support systems.

Page 22: Modification Types

  • Modify Event: Building regulations and land zoning strategies.

  • Modify Vulnerability: Community preparedness programs and high-tech monitoring.

  • Modify Loss: Immediate aid and long-term recovery strategies.

Page 23: Development and Governance Impact

  • Investment in Hazard Management: Developing countries may prioritize growth over mitigation, increasing vulnerability.

  • Risk Poverty Nexus: Illustrates how poverty exacerbates disaster impacts.

  • Governance Factors: Political stability and resources directly affect responses and preparedness.

Page 24: Tectonic Mega-Disasters

  • Characteristics of Mega-Disasters

    • Affect large areas/populations, challenge effective management.

  • Examples: 2011 Tohoku earthquake & tsunami, Eyjafjallajökull eruption impacting trade.