EARTHQUAKES - LDCs VS MDCs
(My Multimedia 'Presentation')
ABOUT EARTHQUAKES
WHAT IS AN EARTHQUAKE? An earthquake is a type of natural disaster which occurs when two tectonic plates beneath the Earth's surface jolt against each other. The surfaces which meet as they jolt are called 'faults', the location below the surface where the earthquake starts is called the 'focus', and the location above the surface and directly above the focus is called the 'epicentre'.
The energy that would be used to move the plate along is stored up as it gets stuck, finally being released when the stuck part of the plate manages to get back out of its position. The energy then radiates outwards in the form of 'seismic waves', which cause the ground to shake (as well as anything on it!).
THE THREE TYPES OF TECTONIC PLATE MOVEMENT
There are three types of tectonic plate movement. They are:
DESTRUCTIVE PLATE MARGIN
PLATES INVOLVED: OCEANIC & CONTINENTAL
A destructive plate margin occurs when a continental plate tries to move past the oceanic 'plate' - in which the oceanic crust is then forced underneath the continental plate. Having one plate forced beneath the other causes a large build up of friction at the focus, which causes the oceanic crust to begin to melt, which in turn may trigger an earthquake.
CONSTRUCTIVE PLATE MARGIN
PLATES INVOLVED: ANY TWO CONTINENTAL
A constructive plate margin occurs when two plates move apart in opposite directions. In this case, an earthquake is caused by the motion of the Earth's crust forcibly pulling apart. In some places, this divide in the crust is even visible - for example, the Mid-Atlantic Ridge.
CONSERVATIVE PLATE MARGIN
PLATES INVOLVED: ANY TWO CONTINENTAL
A conservative plate margin occurs when two adjacent plates slide past each other in either opposite directions, or in the same direction but at different speeds. It is easy for the plates to get stuck in movement in this way, as the edges of the plates are rough and therefore difficult to slide past smoothly. Energy builds up as the plates are trapped against one another, until it is all released after they manage to free themselves and jolt past each other.