1. tectonic hazards definitions

define plate boundaries

where tectonic plates meet, resulting in constructive (divergent), destructive (convergent), and conservative (transform) types.

define mantle plume

a column of exceptionally hot rock and magma that rises from deep within the Earth's mantle

define convection currents

the slow, circular movements of magma within the Earth's mantle, driven by heat from the core, that cause the tectonic plates to move

define seismic waves

shock waves generated by sudden energy releases, typically from earthquakes, that travel through the Earth's layers and along its surface

define continental crust 

the thick, less dense, and older part of the Earth's crust that forms the continents, primarily composed of granite (30- 50 km) 

define subduction

the geological process where one tectonic plate is forced to sink beneath another, typically an oceanic plate descending under a less dense continental plate, at a convergent plate boundary

define intra-plate

describes tectonic activity, such as earthquakes and volcanoes, that occurs in the middle of a tectonic plate, away from the plate boundaries

define lithosphere

the Earth's rigid, brittle outer layer, comprising the entire crust and the uppermost part of the mantle

define slab pull

The force contributing to the movement of tectonic plates. Slab Pull is due to the weight of the plate.

define ridge-push

a geological force where gravity causes the high-elevation lithosphere at a mid-ocean ridge to slide downslope, pushing the older tectonic plate away

define oceanic crust

Crust, usually thinner than continental crust, that forms the sea floor. It is on average 7km thick

define palaeomagnetism

the study of Earth's ancient magnetic field, recorded in the magnetic minerals of rocks as they form

define asthenosphere

The upper mantle layer of the Earth. It is semi-molten and approximately 2000km wide

define sea floor spreading

the process by which new oceanic crust forms at mid-ocean ridges and moves laterally away from the ridge as tectonic plates diverge

define hypocentre

the point within the earth where an earthquake originates.

define epicentre

The point on the surface, directly above the earthquake's origin

define the benioff zone

an inclined zone in which many deep earthquakes occur, situated beneath a destructive plate boundary where oceanic crust is being subducted

define water displacement

the phenomenon where water is moved from its original position due to an external force, often related to seismic events like underwater earthquakes.

define pyroclastic flows

fast-moving currents of hot gas and volcanic matter that flow down the sides of a volcano during an explosive eruption.

define Jökulhlaups​

a type of glacial outburst flood that occurs when a glacier dam bursts, releasing water and debris rapidly downstream.

define liquefaction

the process by which saturated soil substantially loses strength and stiffness in response to an applied stress, often during seismic shaking.

define acid lava

a type of lava that is high in silica, resulting in a thicker, more viscous consistency than basaltic lava, often associated with explosive volcanic eruptions.

define basic lava

a type of lava that is low in silica, resulting in a thinner, less viscous consistency than acid lava, typically producing non-explosive volcanic eruptions.

define lahar

a destructive volcanic mudflow composed of volcanic ash, debris, and water, often occurring after heavy rainfall or during volcanic eruptions.

define tephra

a collective term for volcanic materials ejected during an eruption, including ash, lapilli, and volcanic bombs.

define primary waves

is the fastest type of seismic wave that is generated by an earthquake and travels through the Earth as a longitudinal, or compressional, wave.

define secondary waves

a type of seismic body wave that is generated during an earthquake and travels through the Earth

define tsunami

a series of powerful, long-wavelength ocean waves caused by a large-scale and sudden displacement of a significant volume of water

define epicentre

the point on the Earth's surface directly above the focus (or hypocenter), which is the underground point where an earthquake originates. It is often the location where the earthquake's effects are felt most strongly.

define hydro-meterorological

hazards caused by atmospheric (meterological) and hydrological (water-related) processes

define multiple hazard zone

A region that is vulnerable to more than one type of natural hazard, often because different tectonic, hydro-meteorological, and climatic processes overlap.

define rapid onset hazard

A hazard that happens suddenly with little or no warning. e.g earthquakes

define slow onset hazard

A hazard that develops gradually over time, giving longer warning.

define inequality

Differences in wealth, education, housing, access to services, and political power that make some people more vulnerable to hazards than others.

define corruption (of governance)

When officials use their power dishonestly for personal gain, leading to poor building standards, misused aid, unsafe infrastructure, and weakened disaster response.

define governance

The way a country or community is organised, managed, and led, including how decisions are made, how resources are used, and how institutions function.

Good governance means effective planning, strong laws, good communication, and fair distribution of resources, which reduces hazard risk.

define mecalli (scale)

A scale that measures the intensity of an earthquake based on observed effects on people, buildings, and the environment.

define moment magnitude

A scale that measures the total energy released by an earthquake.

define hazard profiles (with examples of characteristics)

A diagram or chart that shows the characteristics of a hazard, including:

Magnitude

Frequency

Duration

Speed of onset

Spatial extent

Economic and social impacts

(Helps compare hazards.)

define mitigation (in context)

Strategies and actions aimed at reducing the severity of a hazard or its impact.

Can be structural (e.g., earthquake-resistant buildings) or non-structural (e.g., education, planning, early warning systems).

define mega-disaster

A hazard event that causes extreme damage and affects multiple countries or regions, overwhelming national response systems.(e.g haiti 2010)

define socio-economic (in context)

Factors relating to people’s wealth, education, occupation, and social conditions that affect how vulnerable they are to hazards.

define spatial predictability

The extent to which the location of a hazard can be anticipated.

define dynamic pressures

Underlying factors that increase vulnerability to hazards by weakening people’s ability to respond.

define resilience

The ability of a community, system, or society to cope with, recover from, and adapt to hazards.