Tectonics key words

Accretion Wedge

The accumulation of material at the point of subduction.

Aseismic Buildings

Buildings designed to withstand or minimise destruction during an earthquake.

Asthenosphere

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

ash

fine particles and dust ejected during an eruption, which can remain airborne as clouds or accumulate on the ground.

continental crust

crust that forms the continents of the lithosphere on average 35km thick.

continental drift

the movement of tectonic plates, due to varying weights of crust. it was originally thought that convection currents caused the movement of the plates, but now slab pull is thought as the primary driving force.

convection currents

the circulation ofmagma within the mantle (asthenosphere), magma is heated by radioactive processes in the core and cools at the surface, and so circulates between the 2 places.

degg’s model

This model shows that a hazard becomes a disaster if it affects a vulnerable population.

epicentre

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

focus

The place in the crust where the pressure/seismic energy is released.

hazard mitigation cycle

The sequence of governance of a natural hazard: monitoring & prediction, mitigation, preparedness.

hot spot

Volcanoes found away from the plate boundary, due to a magma plume closer to the surface.

jokulhaup

A sudden glacial flood caused by a glacier on top of or near a volcano melting due to the heat from the eruption.

lahar

a flow of mud and debris

lithosphere

The upper crust of the Earth (average thickness = 100km).

love waves

A surface earthquake wave with horizontal displacement.

mid-ocean ridge

Parting oceanic plates at a constructive plate boundary creates a ridge, with new land at the base of the oceanic valley.

moment magnitude scale

A measure of an earthquake's energy released, considered the most accurate measure.

oceanic crust

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

paleomagnetism

The alternating polarisation of new land created. As magma cools, the magnetic elements within will align with the Earth’s magnetic field, which can alternate over thousands of years.

park’s model

A model describing the decline and recovery of a country over time, following a natural disaster.

partial melting

Elements within the lithosphere have different melting points, and so rock is partially melted, partially solid.

primary waves

An earthquake wave causing compressions within the body of rock.

Pyroclastic Flow

A mixture of gases and rock fragments, at high temperatures travelling at rapid speeds.

richter scale

A logarithmic measure of earthquake’s intensity.

secondary waves

An earthquake wave causing vertical displacement within the body of rock.

seismic waves

The energy released during an earthquake, in the form of Primary, Secondary, Love and Rayleigh Waves.

slab pull

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

subduction

Oceanic plate is forced below continental plate, due to the oceanic plate being more dense than the continental plate.

tsunami

- Initial vertical water displacement (often from a submarine earthquake) creates waves, with large destructive power.

volcanic explosivitiy index

A measure of the magnitude of a volcano’s eruptions.

volcanic island arc

A series of volcanoes (often in the shape of an arc) that are formed consecutively, as a tectonic plate moves across a magma plume.

Wadati-Benioff Zone

A region of the subducting plate, most affected by pressure and friction, where most destructive margin earthquakes originate.