What are Earthquakes?

Outline

• Definition of earthquakes

• Formation of earthquakes:

Definition of earthquakes

Earthquakes are the rumblings, shaking or rolling of the earth's surface. It is usually what happens when two blocks of the earth suddenly slip past one another, or break apart from each other as a result of tension caused by prolonged energy build up. 

Earthquakes come in many forms. It can be felt as a shock under your feet, or may be very powerful and destructive enough to flatten an entire city. They can happen anywhere, land or sea.

Formation of earthquakes

Earth’s makeup:

• In this diagram, you will notice that the inner and outer core of the earth (middle part) are liquid in nature, containing iron and nickel of extreme temperatures (5,500°C). 

• The Mantle is semi-molten rock, also called magma. The outer is the crust, which is the hard part of the earth that forms the surface. This outer crust includes the land on which we live, the oceans and ocean deeps and anything within 40km (approx) down the earth's surface.

• Earthquakes are developed in the outer crust of the earth.

Steps of formation

• 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.

• 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’.

• 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.

• 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.