Key Definitions Flashcards
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 approx 2000km wide
Ash
Fine particles and dust ejected during an eruption, which can remain airbourne 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 of as the primary driving force
Convection currents
The circulation of magma within the mantle. Magma is heated by radioactive processes in the core and cools at the surface, so circulates between the 2 places
Deggs 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 earthquakes 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 and prediction, mitigation, preparedness
Hot spot
Volcanoes found away from the plate boundary, due to magma plume closer to the surface
Jokulhlaup
A sudden glacial flood caused by a glacier on top of or near a volcano due to the heat from the eruption
Lahar
A flow of mud and debris
Lithosphere
The upper crust of the Earth (avg 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 earthquakes 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
Parks 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 earthquakes 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 the continental plate as it is more dense
Tsunami
Initial vertical water displacement creates waves, with large destructive power
Volcanic Explosivity Index (VEI)
A measure of the magnitude of a volcanos eruptions
Volcanic island arc
A series of volcanos that are formed consecutively, as a tectonic plate moves across a magma plume
