WHAT IS AN EARTHQUAKE AND HOW IT HAPPENS?

EARTHQUAKES:

Our earth composed of three major portions... crust,core,mantle.

Inside the earth crust,there are some blocks of crusts which moves suddenly causing a fix portion of earth to shake, this shaking of earth is called earthquake. The causes of earthquakes are the geological underlying processes. these processes includes volcanism,plate tectonics,intra plate activities.    

CAUSES OF EARTHQUAKE:

 PLATE TECTONICS:

 The earth's outer layer is broken into pieces of about 100km thickness. these pieces are named as plates. these plates move towards or away from each other. there sudden collision cause the earthquake.mostly at the boundaries of crusts, the one plate is forced under the other due to difference in crust's density. This subduction of one of the plate causes the earthquake. thus mostly earthquakes occurs at the boundaries.

VOLCANISM:

Magma or molten material present inside the earth,when squeezes through the rock's fractures it causes the earthquake.sometimes this molten material collects in high level reservoir and when it moves around it causes burst of continuous vibration, called VOLCANIC TREMOR.

INTRA PLATE:

Sometimes due to thrust faulting in rocks being squeezed or compressed,earthquakes occur..these earthquakes do not occur on the boundary. When the plates moves they take the squeezed rocks away from the boundary. these earthquakes are very rare but dangerous.