Health & Fitness

What causes earthquakes?

Earthquake and its impact

I know all of you have experienced an intensive or mild affliction of the earthquake at least once in your life. Our elders tell us about past incidences that how a sudden intensive earthquake hit the surface of the earth and how much devastation they experienced as the result. Not only past events but there are also countless examples in which it hits any part of the earth and we get frightened.

Earthquake and its after effects on infrastructure.

Being frightened over it is quite natural because sometimes it costs thousands of lives. A question comes in the mind, what happens inside the earth’s surface that few minutes before it was supporting life smoothly and then suddenly started shaking? Obviously, there is a phenomenon inside the earth that causes a disturbance. In this article, we are going to discuss the reasoning behind the earthquake. Also, we will find out that how much devastation it can cause for humans as well as for other species.

Layers of the earth:

Erath is basically composed of four layers.

  • There is an inner core which is solid in consistency
  • Right after inner core, there is an outer core which is molten.
  • There is a thick and solid mantle which occupies nearly 84% volume of the earth
  • The outer layer of the earth which is visible to us is the crust and is about 5-50 Km in its thickness.
demonstration of various layers of the earth.
Layers of earth

Tectonic plates and fault zone:

Some of the faults are normal however they may cause a disturbance if frictional force is unable to overcome the motion. The following image shows how a fault that is other than a normal fault can displace tectonic plates to cause earthquake.

various types of the faults

Theory of plate tectonics:

The outer layer of the earth’s planet looks like a solid shell known as the lithosphere. According to the theory of plate tectonics, the outer hard shell is broken down into massive rigid sacks. These sacks are known as tectonic plates. It is just like puzzle pieces that are floating on the hot molten mass known as the asthenosphere. The movement is very slow and happens all the time. Most of the time, we do not feel the movement but sometimes the movement becomes violent and it can slide 100 miles away. These plates travel across sic inches per year. Right now our earth is divided into seven large plates, and many other small plates.

North American


North America





The boundary between plates is very violent places. These edges make and break the earth’s crust.

Types of earthquake:

Divergent boundary:

The relative movement of the plates forms three types of boundaries. One is the divergent boundary in which two plates move away from each other. It forms a rift zone between two plates. These two plates are of earth crust which is over the mantle. Now when plates will move away, the volcano unveiled at that part of the earth cools down and it forms another continent over there. There is an addition of a new continent.


The Great Rift valley in Africa is an example of a divergent boundary. If this spread remains continues then the Indian ocean can fluid the valley. As the result, the continent of Africa can be converted into a massive island.

Transform boundary:

The two plates pass in opposite directions. It is called the strike-slip It may be a basic reason for the earthquake to happen. The tectonic plates are displaced from their position and there is no smooth plane where the volcano can cool down to form another continent.


The most important example is the San Andreas Fault in which a portion of Southern California slides 2 inches to Northern California each year.

Convergent boundary:

The two plates collide with one another. This is called a thrust fault. It results in the formation of the mountains. Two plates collide with one another and there are oceans and continents over crust. Now, these continents mess up into huge mountains.


Many hills and mountains have been formed due to convergent boundaries.

Hypocenter and epicenter:

The zone from where the earthquake originates is known as the hypocenter. And the zone where it occurs on the earth’s surface is known as the hypocenter.

Effects of earthquake:

Earthquake hits the earth’s surface and grants various outcomes. These outcomes include damaging the man-made infrastructure, change in geological features, and some of the disturbing impacts on animals and human life. Mostly all of these impacts occur on the surface of the earth but we know that mostly the origin of the earthquake is the bottom of the ocean so the impact may also be observed along the coastline or ocean margin.

Surface impacts:

The earthquake causes the earth’s movement in the vertical or horizontal direction which is also followed by the up and down movement. It can cause some of the geomorphic changes that we observe on the surface of the earth such as changes in the flow of groundwater, land sliding, and mudflow. We may experience a significant amount of damage to the tall buildings, bridges, railways, and other infrastructures.

the after effects and devastation
Impacts of earthquake

The whole damage depends upon the extent of the sliding of the earth’s surface from its original location. It is also associated with distinctive sounds and lights. The sound is very low and is observed like a train passing through the railway track and we observe it while standing near or far. The luminous flash of light that we observe in the sky is due to the electric induction in the air which is associated with the earthquake.

It is not compulsory that the earthquake will occur on the surface of the earth rather rit can also be under the seabed. A tsunami occurs when an earthquake occurs underwater.

Safety precautions during incidence:

It is true that the harm of the intensive earthquake is unavoidable especially when you are residing in a dense place at that time. But there are some safety precautions that can be taken in order to avoid it. You should try to stay away from hanging objects, walls, or windows. But if you are unable to move away from your place then try to cover yourself with the blanket or any large pillow so that even if an object falls on it, you can reduce the damage. It is safest if you are in an open place.

Wrapping up/ Conclusion:

Earthquake occurs due to the intensive displacement of the tectonic plates in the lithospheric region of the earth’s crust. Up to a certain limit, the friction between faults and tectonic resists displacement. But when the force of displacement, overcomes the friction it causes an earthquake. So earthquakes are nothing but shaking, lowering, or a sudden shock of the earth’s surface. It damages the various man-made infrastructures. Most of the time the origin of the earthquake is the bottom of the ocean so we have observed its effects on the edges of the sea and on the coastline. The intensity of destruction depends upon the displacement. The seismic waves formed as the result are spread over the long distance to grant the consequences. The tidal-like movement in the ocean causes tsunami is another effect of the earthquake. Also, a luminous flash of light on the sky may also be observed due to the electric induction in air.

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