Natural Hazards: Definitions Flashcards
Mantle
Semi-molten part of the Earth’s structure below the crust. convection currents occur within it.
Natural Hazard
A natural event which threatens people or has the potential to
Convection Currents
Heat driven currents in the mantle caused by the heat of the core. They then move the plates on top.
Magnitude
The size of an event. How it is measured varies depending on the hazard.
Frequency
How often a hazard occurs (e.g every 100 years)
Hazard Risk
Probability or chance that a hazard will take place in a particular location.
Focus
Point within the Earth where energy is released during an earthquake due to a sudden slip.
Epicentre
Point on the surface directly above the focus where the potential for damage from an earthquake is greatest.
Seismometer
A machine used to measure the shaking of the ground caused by an earthquake.
Constructive boundary
where two plates move apart creating mid-ocean ridges and non-explosive volcanoes.
Destructive boundary
Where two plates meet, normally the oceanic plate is subducted below the continental. creates trenches, volcanoes and large earthquakes.
conservative boundaries
two plates slide past each other. no volcanoes but does have the potential to cause large earthquakes.
Coriolis effect
the effect that the earth’s rotation has on tropical storms causing them to spin and move away from the equator.
Global atmospheric circulation
the way in which air/wind moves around the world. this is given by a combination of pressure and temperature gradients along which the air flows.
High pressure
Caused when air is descending towards the surface of the earth. creates stable and dry conditions normally.
