Tectonic processes and hazards — WJEC A-Level Geography Revision

    The study of the Earth's structure, tectonic processes within the asthenosphere and lithosphere, and the resulting hazards (volcanic and seismic). It cover

    Topic Synopsis

    The study of the Earth's structure, tectonic processes within the asthenosphere and lithosphere, and the resulting hazards (volcanic and seismic). It covers the global distribution of these hazards, their physical characteristics, impacts on people and the environment, and the management strategies used to mitigate risk and vulnerability.

    Key Concepts & Core Principles

    Exam Tips & Revision Strategies

    Common Misconceptions & Mistakes to Avoid

    Examiner Marking Points

    Tectonic processes and hazards

    WJEC
    A-Level

    The study of the Earth's structure, tectonic processes within the asthenosphere and lithosphere, and the resulting hazards (volcanic and seismic). It covers the global distribution of these hazards, their physical characteristics, impacts on people and the environment, and the management strategies used to mitigate risk and vulnerability.

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    Objectives
    5
    Exam Tips
    5
    Pitfalls
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    Key Terms
    12
    Mark Points

    Topic Overview

    Tectonic processes and hazards explores the dynamic nature of Earth's lithosphere, focusing on plate tectonic theory, the distribution of earthquakes and volcanic eruptions, and the resulting hazards. You will study the internal structure of the Earth, convection currents in the mantle, and the mechanisms driving plate movement, including slab pull and ridge push. The topic examines the three types of plate boundaries—divergent, convergent, and conservative—and the specific hazards associated with each, such as shield volcanoes at constructive margins and composite volcanoes at destructive margins. Understanding these processes is crucial for predicting hazard events and mitigating their impacts on human populations.

    This topic is central to physical geography because it explains the fundamental forces shaping our planet, from mountain building to ocean trench formation. It also links to human geography through the study of hazard risk, vulnerability, and resilience. For example, you will analyse why some communities suffer greater losses than others during earthquakes, considering factors like population density, building standards, and preparedness. The topic also covers tsunami generation, secondary hazards like landslides and liquefaction, and the role of monitoring and prediction in reducing risk. Mastery of this content is essential for understanding global patterns of natural disasters and their socioeconomic consequences.

    In the WJEC A-Level specification, this topic is assessed through both short-answer questions and extended essays. You will need to apply knowledge to case studies, such as the 2015 Nepal earthquake or the 2010 Eyjafjallajökull eruption, evaluating management strategies and the effectiveness of international aid. The topic also requires critical thinking about the relationship between hazard magnitude and frequency, and the concept of disaster risk reduction (DRR). By the end, you should be able to explain why some hazards become disasters while others do not, using models like the hazard management cycle and the Park model.

    Key Concepts

    Core ideas you must understand for this topic

    • →Plate tectonic theory: The Earth's lithosphere is divided into plates that move due to convection currents in the asthenosphere, slab pull at subduction zones, and ridge push at mid-ocean ridges.
    • →Types of plate boundaries: Constructive (divergent) boundaries create new crust via volcanic activity; destructive (convergent) boundaries involve subduction and generate powerful earthquakes and explosive volcanoes; conservative (transform) boundaries cause earthquakes as plates slide past each other.
    • →Primary and secondary hazards: Primary hazards include ground shaking, lava flows, and ash fall; secondary hazards include tsunamis, landslides, liquefaction, and fires. Understanding the distinction is key to risk assessment.
    • →Hazard risk and vulnerability: Risk = hazard × vulnerability / capacity to cope. Factors affecting vulnerability include population density, building quality, education, and access to resources. The disaster risk equation is central to evaluating management strategies.
    • →The hazard management cycle: A model showing four stages—mitigation, preparedness, response, and recovery—used to reduce the impacts of tectonic hazards. It emphasises that management is a continuous process.

    What You Need to Demonstrate

    Key skills and knowledge for this topic

    • Understanding of Earth's internal structure (core, mantle, crust).
    • Mechanisms of plate movement (convection currents, ridge push, slab pull).
    • Processes at plate boundaries (diverging, converging, conservative) and hot spots.
    • Global distribution of tectonic hazards.
    • Hazard profile characteristics (magnitude, predictability, frequency, duration, speed of onset, areal extent).
    • Volcanic types (shield, composite, cinder) and eruption styles (explosive, effusive).
    • Volcanic hazards (pyroclastic flows, lava flows, ash falls, lahars, jökulhlaups, landslides, toxic gases).
    • Earthquake characteristics (P and S waves, focus, depth, epicentre).

    Marking Points

    Key points examiners look for in your answers

    • Understanding of Earth's internal structure (core, mantle, crust).
    • Mechanisms of plate movement (convection currents, ridge push, slab pull).
    • Processes at plate boundaries (diverging, converging, conservative) and hot spots.
    • Global distribution of tectonic hazards.
    • Hazard profile characteristics (magnitude, predictability, frequency, duration, speed of onset, areal extent).
    • Volcanic types (shield, composite, cinder) and eruption styles (explosive, effusive).
    • Volcanic hazards (pyroclastic flows, lava flows, ash falls, lahars, jökulhlaups, landslides, toxic gases).
    • Earthquake characteristics (P and S waves, focus, depth, epicentre).
    • Earthquake hazards (ground shaking, liquefaction, landslides, tsunami).
    • Impacts of tectonic hazards (environmental, demographic, economic, social) at local, regional, and global scales.
    • Human factors affecting risk/vulnerability (economic, social, political, geographical).
    • Management strategies (monitoring, prediction, warning, mitigation, hazard management cycle).

    Examiner Tips

    Expert advice for maximising your marks

    • 💡Ensure case studies are contemporary (within the last two decades).
    • 💡Use specific examples in contrasting contexts to demonstrate varied risk and impact.
    • 💡Explicitly link management strategies to the hazard management cycle.
    • 💡Apply specialised concepts like inequality, resilience, and risk to your analysis.
    • 💡Use the hazard profile characteristics to evaluate why some events have greater impacts than others.
    • 💡Use specific case study details to support your answers. For example, when discussing tsunami impacts, reference the 2004 Indian Ocean tsunami and mention the lack of warning systems in the Indian Ocean at the time. This shows depth of knowledge.
    • 💡Always define key terms like 'hazard', 'risk', and 'vulnerability' in your answers. Examiners look for precise use of geographical terminology. For instance, distinguish between a natural hazard (a potential threat) and a natural disaster (when it causes significant harm).
    • 💡For 20-mark essays, structure your answer using a clear framework: introduce the concept, explain with theory, illustrate with case studies, evaluate management strategies, and conclude with a balanced judgement. Use phrases like 'on one hand... on the other hand' to show evaluation.

    Common Mistakes

    Pitfalls to avoid in your exam answers

    • Confusing primary and secondary hazards.
    • Failing to use contrasting contexts when discussing impacts or management.
    • Generalising impacts without considering the specific hazard profile.
    • Neglecting the role of human factors in turning a hazard into a disaster.
    • Confusing the Mercalli, Richter, and Volcanic Explosivity Index scales.
    • Misconception: Earthquakes are caused by plates 'colliding' head-on. Correction: Most earthquakes occur at conservative or destructive boundaries where plates slide past or one subducts beneath the other, not by direct collision. The focus is on stress release along faults.
    • Misconception: Volcanic eruptions are always destructive and unpredictable. Correction: Many eruptions are effusive (e.g., Hawaiian shield volcanoes) and can be predicted using monitoring techniques like gas emissions and ground deformation. Some volcanoes even have tourism benefits.
    • Misconception: The magnitude of a hazard determines the scale of disaster. Correction: Disaster severity depends on vulnerability and exposure. A moderate earthquake in a densely populated, poorly prepared area can cause more devastation than a larger one in a remote region.

    Frequently Asked Questions

    Common questions students ask about this topic

    Before You Start

    Prior knowledge that will help with this topic

    • •Understanding of the Earth's structure (crust, mantle, core) and the rock cycle, as tectonic processes involve the creation and destruction of lithosphere.
    • •Basic knowledge of global distribution of earthquakes and volcanoes from GCSE Geography, including the 'Ring of Fire' and mid-Atlantic ridge.
    • •Familiarity with the concept of risk and hazard management, as this topic builds on ideas of vulnerability and resilience introduced at GCSE.

    Likely Command Words

    How questions on this topic are typically asked

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    Explain
    Discuss
    To what extent

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