TECTONICS hazards definitions Flashcards
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 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(reduce severity), 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 (around 100km)
Love waves
A surface earth wave with horizontal displacement
Rayleigh waves
A surface earthquake causing horizontal and vertical displacement
Convection currents
The circulation of magma within the mantle (asthenosphere). Magma is heated by radioactive processes in the core and cools at the surface, and so circulates between the two places.
Asthenosphere
The upper mantle layer of the earth. It is semi molten and aprox 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, aprox 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 o the plates but now slab pull is thought of as the primary driving force
Mid- Ocean ridge
Parting oceanic plates at a constructive plate boundary creates a ridge, with new land at the base of the oceanic valley.
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 aprox 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 county over time, following a natural disaster.
Primary waves
An earthquake wave causing compressions within the body of rocks
Secondary waves
An earthquake wave causing vertical displacement within the body of rocks
Richter scale
A logarithmic measure of earthquakes intensity
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 to 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 more dense than the continental plate
Tsunami
Initial vertical water displacement (often from a submarine earthquake) creates waves, with large destructive power.
Volcanic explosivity Index (VEI)
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.
Benioff zone
A region of the subduction plate, most affected by pressure and friction, where most destructive margin earthquakes originate.
Pyroclastic flow
A mixture of gases and rock fragments, at high temperatures travelling at rapid speeds.
