Tectonic Hazards: Key Terms
Tectonic Hazards: Key Terms
Tectonic Hazards: Key Terms
Characteristics of the Earth's structure
Asthenosphere – A partially molten, plastic-like part of the upper mantle that allows tectonic plates to move on top of it.
Continental crust – The thicker (25–100 km), older, and less dense part of the Earth’s crust made mainly of granite.
Convection currents – Circular movements of heated material in the mantle that drive tectonic plate movement.
Core – The central part of the Earth, made up of a solid inner core and a semi-molten outer core, both very hot and made mostly of iron and nickel.
Crust – The Earth's outer layer, made of solid rock. There are two types: oceanic and continental.
Geothermal heat – Heat from within the Earth, mainly caused by radioactive decay, which drives convection currents.
Inner core – The solid centre of the Earth, about 1400 km wide, with temperatures between 5000–6000°C.
Lithosphere – The rigid outer layer of the Earth, made up of the crust and the solid upper part of the mantle.
Lower mantle – The solid part of the mantle beneath the asthenosphere; it is the thickest Earth layer at about 2900 km.
Mantle – The thick layer between the crust and the outer core, mostly semi-molten rock where convection currents occur.
Mantle plume – A column of very hot rock rising through the mantle, sometimes causing volcanoes away from plate boundaries (hotspots).
Oceanic crust – The thinner (5–10 km), denser and younger part of the crust made mostly of basalt; it is constantly being created and destroyed.
Outer core – A liquid metal layer about 2100 km thick beneath the mantle, where temperatures are 4000–6000°C.
Slab pull – A theory that tectonic plates are pulled along as a heavy, subducting oceanic plate sinks into the mantle.
Tectonic plate – Large sections of the Earth's lithosphere that move slowly over the mantle and cause earthquakes and volcanoes.
Processes and Features of Earthquakes & Volcanoes
Ash – Fine volcanic dust, less than 2 mm in size, ejected during eruptions and capable of travelling long distances.
Collision boundary – A type of plate boundary where two continental plates collide, pushing land upwards to form fold mountains.
Composite volcano (Strato-volcano) – A steep-sided volcano with sticky lava and explosive eruptions, usually found at destructive boundaries.
Constructive (divergent) boundary – A plate boundary where tectonic plates move apart, allowing magma to rise and form new crust and volcanoes.
Conservative (transform) boundary – A plate boundary where plates slide past each other, causing earthquakes but no volcanoes.
Destructive (convergent) boundary – A plate boundary where an oceanic plate sinks under a continental plate, causing volcanic eruptions and earthquakes.
Earthquake – A sudden shaking of the ground caused by the release of pressure along faults at plate boundaries.
Epicentre – The point on the Earth’s surface directly above the earthquake’s focus.
Focus – The point underground where an earthquake starts.
Hotspot – A place where magma rises through the mantle at a point away from plate boundaries, forming volcanoes.
Lahar – A dangerous volcanic mudflow formed when volcanic ash mixes with rainwater or melted snow.
Lava – Magma that erupts onto the Earth’s surface through a volcano.
Magnitude – The amount of energy released by an earthquake, measured on the Moment Magnitude Scale.
Mercalli Scale – A scale used to measure the damage caused by an earthquake.
Pyroclastic flow – A fast-moving, hot cloud of gas, ash and volcanic rock that flows down the side of a volcano during an eruption.
Ring of Fire – An area around the edges of the Pacific Ocean where many earthquakes and volcanoes occur.
Seismic waves – The vibrations that travel through the Earth from the earthquake focus, felt as shaking on the surface.
Shield volcano – A volcano with gentle slopes, runny lava, and frequent but mild eruptions, often found at constructive boundaries or hotspots.
Tephra – All material, including ash and rock, that is blasted into the air during a volcanic eruption.
Toxic gases – Harmful gases like carbon dioxide and sulphur dioxide released during a volcanic eruption.
Volcanic Explosivity Index (VEI) – A scale used to measure the strength and explosiveness of a volcanic eruption.
Impacts of Tectonic Hazards
Ash cloud – Fine particles of volcanic rock released into the air during eruptions, which can disrupt flights and affect air quality.
Cholera – A disease spread through contaminated water, often linked to poor sanitation after disasters like earthquakes.
Economic loss – The financial cost of damage caused by a hazard, including repair, loss of income, and business closures.
Fires – Often caused by broken gas pipes after earthquakes, they are a common secondary hazard.
Food insecurity – When access to sufficient food is disrupted, often due to destroyed crops or damaged supply chains.
Homelessness – A primary effect of building collapse during an earthquake or lava flow during an eruption.
Injury and death – Direct effects of falling buildings, ash falls, pyroclastic flows, and tsunamis linked to tectonic events.
Mercalli scale – Measures the intensity of an earthquake by its observed effects on people and buildings, from I to XII.
Moment Magnitude Scale (MMS) – A scale used to measure the amount of energy released by an earthquake, replacing the Richter scale.
Respiratory illness – Health conditions such as asthma, which can worsen due to ash inhalation or poor air quality after eruptions.
Secondary hazard – A hazard that follows a primary event, such as landslides or disease outbreaks after a quake.
Tectonic hazard – A natural hazard caused by movement of the Earth’s crust, including earthquakes and volcanic eruptions.
Managing the Impacts of Tectonic Hazards
Disaster response – The immediate actions taken after a hazard, including rescue, medical aid and provision of shelter.
Early warning system – Technology and communication tools that alert people to an imminent hazard, giving them time to act.
Evacuation – The organised movement of people away from danger zones before or after a tectonic event.
GIS (Geographic Information Systems) – Technology used for hazard mapping and planning by analysing spatial data.
Hazard mapping – Identifying and showing areas at greatest risk from earthquakes or eruptions, used for planning responses.
Long-term response – Actions that happen months or years after an event to rebuild and reduce future risk.
Monitoring – The use of equipment like seismometers, tiltmeters and gas sensors to track tectonic activity.
Park’s hazard response curve – A model showing how quality of life changes over time after a disaster, from disruption to recovery.
Planning – Strategies to reduce the risk of hazards, such as land use zoning and emergency supply stockpiling.
Prediction – Estimating when and where a hazard might occur, especially for volcanic eruptions where warning signs are clearer.
Protection – Measures to keep people and buildings safe, such as strengthening structures or excluding people from dangerous areas.
Seismometer – An instrument that records ground movement, helping scientists monitor earthquakes and volcanic activity.
Earthquake Case Study: Türkiye–Syria
Aftershock – A smaller earthquake that follows the main quake, often causing further damage to already weakened structures.
Arabian Plate – A tectonic plate involved in the Türkiye-Syria earthquake, moving north and causing stress along the fault line.
East Anatolian fault – A transform plate boundary where the 2023 Türkiye-Syria earthquake occurred.
International aid – Emergency help provided by other countries or global organisations after a disaster.
Shelters and camps – Temporary places for displaced people to stay, especially important in Syria where the conflict limited other housing options.
UN appeal – A call for international support launched by the United Nations to help those affected by the Türkiye-Syria earthquake.
World bank funding – Financial support provided for Türkiye's recovery and reconstruction after the earthquake.
Volcanic Eruption Case Study: Cumbre Vieja
Cumbre Vieja – The volcanic ridge on La Palma where the Tajogaite volcano erupted in 2021.
Hot spot – A location in the Earth's crust where magma rises from deep within the mantle, not on a plate boundary.
Lava flow – Molten rock that erupts from a volcano and flows over the surface, destroying buildings and infrastructure.
Magma plume – A rising column of superheated rock in the mantle that creates volcanic activity above it.