Good Shepherd Geography-Yr3/4 EARTHQUAKES

How do earthquakes form?

Let us imagine what goes on in the outer crust with the help of this diagram.

Earthquakes develop in the crust of the earth. The crust involves the earth’s surface, submarine levels, down to the ocean floors. The inner part of the earth contains massive energy. Some of this energy escapes through cracks and other volcanic activity, but the bulk of it is stored within the earth’s inner part, contained in the crust.

The earth’s outer crust is held in place like a completed jigsaw puzzle, with rough edges and lines. The energy stored here causes the pieces to slide, glide, knock and move around each piece. These pieces best describe what we call ‘Tectonic plates’ (See illustration below)

After a period of time, the built up energy and movement causes huge tension in the plates, and there is massive pressure on the fault lines. This intense pressure resulting from energy build up causes the fault lines give way, and plates move over, against or apart from each other.

It is important to note that there is usually a very thick natural cover (earth and vegetation) which makes fault lines obscure.

There is an earthquake at this point. In the form of seismic waves (like water ripples) the escaping energy radiates outward from the fault in all directions. The seismic waves shake the earth as they move through it. When the waves reach the earth’s surface, they shake the ground and anything on it, tearing down houses and structures.

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