This definitions covers Key Terms within Tectonic Hazards for GCSE Geography. Revise Tectonic Hazards in The Challenge of Natural Hazards for GCSE Geography with 14 exam-style questions and 24 flashcards. This topic shows up very often in GCSE exams, so students should be able to explain it clearly, not just recognise the term. It is section 7 of 12 in this topic. Make sure you can use the exact wording confidently, because definition marks are often lost through vague language.
Topic position
Section 7 of 12
Practice
14 questions
Recall
24 flashcards
📖 Key Terms
lithosphere — The rigid outer layer of the Earth, comprising the crust and the uppermost part of the mantle. It is divided into tectonic plates.
tectonic plate — A large, rigid section of the lithosphere that moves slowly across the surface of the Earth, driven by convection currents in the mantle below. There are roughly 12 major plates.
plate margin — The boundary where two tectonic plates meet. There are three types: destructive (converging plates — subduction or collision), constructive (diverging plates — new crust forms), and conservative (plates sliding past each other). Most earthquakes and volcanoes occur at or near plate margins.
subduction — The process by which a denser oceanic plate is forced downward beneath a less dense continental plate at a destructive margin. The subducting plate melts in the mantle, generating magma and volcanic activity above.
seismic wave — A wave of energy released when rock fractures during an earthquake. Seismic waves travel outward from the focus in all directions, shaking the ground as they pass.
focus — The point underground where an earthquake originates and energy is first released. Also called the hypocentre. Shallow-focus earthquakes (less than 70 km deep) cause the most surface damage.
epicentre — The point on the Earth's surface directly above the focus of an earthquake. It usually experiences the most intense shaking and is the reference point for reporting earthquake locations.
Moment Magnitude Scale (Mw) — The current standard scale for measuring earthquake energy. Each whole number increase represents approximately 32 times more energy released. Chile 2010 was 8.8 Mw; Nepal 2015 was 7.8 Mw — meaning Chile released roughly 32 times more energy.
tsunami — A series of ocean waves generated by a sudden large movement of the seafloor, most commonly caused by an underwater earthquake. Waves can travel at 800 km/h across open ocean and rise to devastating heights as they approach shallow coastal water.
liquefaction — The process by which saturated soil behaves like a liquid during intense shaking. Waterlogged ground loses its strength, causing buildings to tilt and sink. Common in coastal areas and river deltas during major earthquakes.
pyroclastic flow — A fast-moving mixture of superheated gas, ash and rock fragments produced by a volcanic eruption. Pyroclastic flows travel at up to 700 km/h and 1,000°C — essentially unsurvivable without advance evacuation.
lahar — A volcanic mudflow created when volcanic material mixes with water. Lahars can travel at 60 km/h and continue occurring for years after an eruption as rainfall remobilises ash deposits.
vulnerability — How susceptible a population is to the effects of a tectonic hazard, determined by poverty, quality of housing and infrastructure, access to healthcare and emergency services, and the effectiveness of government planning and building regulations.
preparedness — Actions taken before a tectonic event to reduce its impact, including earthquake-resistant building design, early warning systems, regular evacuation drills, stockpiling emergency supplies, and land-use planning to keep people away from the highest-risk zones.