Key terms- topic 1 Flashcards
Accretion Wedge
The accumulation of material at the point of subduction.
Asthenosphere
The upper mantle layer of the Earth. It is semi-molten and approximately 2000km wide.
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 subducting plate, most affected by pressure and friction, where most destructive margin earthquakes originate.
Volcanic Explosivity Index (VEI)
A measure of the magnitude of a volcano’s eruptions.
Viscosity
An internal property of a fluid that offers resistance to flow ie low viscosity= runny
Subduction
Oceanic plate is forced below continental plate, due to the oceanic plate being more dense than the continental plate.
Seismic waves
The energy released during an earthquake, in the form of Primary, Secondary, Love and Rayleigh Wave
Secondary waves
An earthquake wave causing vertical displacement within the body of rock.
Richter scale
A logarithmic measure of earthquake’s intensity.
Rayleigh waves
A surface earthquake wave causing both horizontal and vertical displacement
Pyroclastic flows
A mixture of gases and rock fragments, at high temperatures travelling at rapid
speeds.
Primary waves
An earthquake wave causing compressions within the body of rock
Parks model
A model describing the decline and recovery of a country over time, following a natural disaster.
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
Oceanic crust
Crust, usually thinner than continental crust, that forms the sea floor. It is on average 7km thick.
Moment magnitude scale
A measure of an earthquake’s energy released, considered the most accurate measure.
Mid oceanic ridge
Parting oceanic plates at a constructive plate boundary creates a ridge, with new land at the base of the oceanic valley.
Love waves
A surface earthquake wave with horizontal displacement.
Lithosphere
The upper crust of the Earth (average thickness = 100km)
Lahars
- A flow of mud and debris
Jokulhaup
A sudden glacial flood caused by a glacier on top of or near a volcano melting due to the heat from the eruption.
Hot spot
Volcanoes found away from the plate boundary, due to a magma plume closer to the surface.
Hazard Mitigation Cycle
- The sequence of governance of a natural hazard: monitoring & prediction, mitigation, preparedness.
Focus
The place in the crust where the pressure/seismic energy is released
Epicentre
– The point on the surface, directly above the earthquake’s origin.
Deggs model
This model shows that a hazard becomes a disaster if it affects a vulnerable population.
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.
Continental crust
Crust that forms the continents of the lithosphere, on average 35km thick.
Aseismic Buildings
Buildings designed to withstand or minimise destruction during an earthquake.
Subduction
Oceanic plate is forced below continental plate, due to the oceanic plate being more dense than the continental plate.
Crustal fracturing
Occurs when the earths crust causes rock to break and fracture under stress caused by seismic stresses
Liquefaction
Groundwater loose soil and sediments are shaken during earthquake so that the ground loses cohesion and acts as a fluid
Mantle plume
Hotter areas of the mantle that move upwards underneath the crust and push it up. This causes weak spots in the crust called hotspots.
Sea floor spreading
The movement of the oceanic crust away from the a constructive plate boundary, as recorded by the magnetic stripes in the basaltic rock
Slab pull
At a subduction zone the descending part of the oceanic plate pulls the rest of the plate with it
Shield volcano
shield volcano is a type of volcano usually composed almost entirely of fluid lava flows. It is named for its low profile, resembling a warrior’s shield lying on the ground
Strato volcano
A volcano built up of alternate layers of lava and ash.
Hazard
Is any agent that can cause harm or damage to humans, property, or the environment
Disaster
Is a sudden, calamitous event that seriously disrupts the functioning of a community or society and causes human, material, and economic or environmental losses that exceed the community’s or society’s ability to cope using its own resources.
The pressure and release model
Is a model that helps understand risk in terms of vulnerability analysis in specific hazard situations. PAR is a tool that shows how disasters occur when natural hazards affect vulnerable people
Speed of onset
How slowly or rapidly the tectonic hazard develops
Spacial predictability
How likely scientists are to estimate where a tectonic event will strike
Mitigation
Reducing vulnerability
Adaption
Actions taken to adjust to living with tectonic hazards
Modify the event
Change the tectonic process/ hazard
Modify the vulnerability
Plan strategies to make the area/ population more resilient
Modify the loss
Accept/ share losses of the hazard
Divergent boundary
Involves two plates moving away from each other
Conservative boundary
The tectonic plates slide past each other
Convergent (destructive) boundary
Where two plates meet, the oceanic crust sinks or subducts, bellow the less dense and lighter continental crust
Convergent (collision) boundary
Where two oceanic plates converge the denser crust subducts the other= a trench
Intraplate earthquake
Earthquakes that occur away from the plate boundaries and closer to the middle of the tectonic plate
Transform fault
Large scale break in the crust
