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Essay on Earthquake for class 8th Students

Essay on Earthquake

Essay on Earthquake 400 word

What is an Earthquake?

An earthquake takes place when two blocks of the earth suddenly slip past one another the surface where they slip is called a fault place the location we below the Earth's surface 

Where the earthquake starts?

Where the earthquake starts is called the hypocenter and the location directly above it on the surface of the earth is called the epicentre sometimes an earthquake has four shocks these are smaller earthquakes that happen in the same place before a large earthquake takes place the largest main earthquake is called the mainshock. 

Main shocks are always followed by aftershocks that occur in the same place and can continue for weeks months and even years 

What causes earthquakes and where do they happen?

The earth has four major layers the inner core outer core-mantle and crusts the crust and the top of the mantle make up a thin skin on the surface of our planet but this skin is not all in one piece it is made up of many pieces covering the surface of the earth 

these pieces are called tectonic plates and the edges of the plates are called the plate boundaries these pieces keep moving around slowly sliding past one another and bumping into each other these plate boundaries are made up of many faults and most earthquakes around the world occur on these faults 

Why does the earth shake?

when there is an earthquake while the edges of the Falls are stuck together and the rest of the block is moving the energy that would normally cause the blocks to slide past one another is being accumulated 

When the force of the moving blocks finally overcomes the friction of the jagged edges of the fault it breaks free and all that store of energy is released the seismic waves shake the earth as they move through it and when the waves reach the Earth's surface 

They shake the ground and anything on it like houses and us the energy radiates outward from the faults in all directions in the form of seismic waves like ripples in a pond 

How are earthquakes recorded?

Earthquakes are recorded by instruments called seismic rocks the recording they make is called a seismograph 

The seismograph has a base that sets formally on the ground and a heavyweight that hangs free when an earthquake causes the ground to shake the base of the seismogram shakes too but the hanging weight does not instead

The spring that is hanging absorbs all the movement the difference in position between the shape and part of the seismograph and this part is recorded.

Essay on Earthquake 500 word

An unexpected movement of the Earth's surface is called an earthquake. When two parts of the Earth's surface suddenly move relative to each other along a fault line, due to tectonic forces, an earthquake occurs. A huge amount of energy is released in the form of tremors and vibrations, these earthquakes are called "tectonic earthquakes".

The point of origin of an earthquake is called the "focus," while the point directly above it, on the surface of the earth, is called the "epicentre." Due to the strong vibrations around the point of origin, the degree of destruction is greater around the epicentre. The branch of knowledge that deals with the study of earthquakes are called seismology and the experts who study seismic waves are called seismologists.

There are three types of seismic waves which propagate in all directions from the focus. These are the P. S and L waves. The compression waves are the first to reach the seismic recording station because they move 1.7 times faster than the shear waves and are therefore called " P '' waves. (primary), while shear waves are called " S '' waves (secondary).

The primary waves vibrate the rock particles forward and backwards in the direction of the waves. In contrast, secondary waves cause the particles to oscillate at right angles to the direction of the waves. When P and S reach the surface of the earth, 

They are converted into long waves in "L" which move along the surface, vibrating horizontally at right angles to the direction of the waves called "love waves" or Rayleigh waves as they also move like Waves. The most violent shocks and the resulting destruction are caused by L waves.

While S waves cannot pass through liquids, P waves can pass through any medium. This helped seismologists learn more about the interiors of the earth.

The instrument used to detect and record seismic waves is called a seismograph. The recorded material appears like a graph and is called a seismogram.

Depending on the depth of their homes, earthquakes are classified into three types. They are:

a) Deep hearth earthquakes that occur at depths greater than 300 km, the reasons for which have not yet been identified.

(b) Intermediate focus earthquakes with depths of focus varying between 55 and 300 km.

(c) Low concentration earthquakes with depths less than 55 Kms.
The area on the earth's surface increases with increasing depth of focus, while intensity increases with decreasing depth of focus.

To measure the magnitude of earthquakes, a Richter scale is used. The point scale is arranged so that each of the scale units is equivalent to 30 times the energy released by the previous unit. While a magnitude of 2 is rarely felt, a magnitude of 7 indicates the lower limit of an earthquake which has a devastating effect on a large area.

Essay on Earthquake 600 words

So what is an Earthquake?

It simply means shaking of the earth? It is caused due to release of energy which generates waves that travel in all directions now the question is why does the earth shake,  a fault is a sharp break in the crustal rocks near a fault tend to move in opposite directions that create friction

But at some point of time, their movements overcome the friction, as a result, they slide past one another this causes the release of energy and the energy waves travel in all directions the point where the energy is released is called the focus of an earthquake

There is also a term given to it called the hypocenter the energy waves travelling in different direction reach the surface the point on the surface nearest to the focus is called epicentre this place is the first one to experience the waves all-natural earthquakes take place in the lithosphere 

The lithosphere refers to the portion of depth up to 200 kilometres from the surface of the earth an instrument called seismograph records the waves reaching the surface the waves look something like this the curve shows three distinct sections each representing different types of wave patterns 

we'll get back to this pattern in a moment earthquake waves are basically of two types body waves and surface waves I need you to understand the term body waves sounds a little larger within the body right 

So the body waves are generated due to the release of energy at the focus that is the epicentre and moves in all direction travelling through the body of the Earth you know it travels internally within the Earth's surface and moves the interior of the earth that's why it is referred to as body waves

Because it is travelling through the body of the earth like a tremor now it is obvious that when these body waves move towards the surface they will come in contact with the surface rocks and like a new set of waves these are called surface waves 

now the velocity of waves changes as they travel through materials with different densities and we know that the materials with higher density reside downwards, therefore, the denser the material the higher is the velocity the direction also changes as they reflect or refract 

when coming across materials with different densities that's why when the Seesmic waves reach towards the surface of Earth they're the materials are of lower density and that slows down the intensity of the waves leaving behind a fault

There are two types of body waves they are called P and S waves so the letter P n S stands for primary and secondary now you can relate when I say primary they are the first one that gets recorded on a seismograph the instrument and then comes the secondary wave you can look at this illustration to understand how this wave looks

The P wave that is the primary or pressure wave is a pulse of energy that travels quickly through the Earth's solid materials as well as liquids it forces the ground to move backwards and forward as it gets compressed and expanded the S wave

That is the secondary or shear wave follows most slowly with a swaying rolling motion that shakes the ground back and forth perpendicular to the direction of the wave if at all the concept of P and S wave isn't clear to you.

Essay on Earthquake 700 words

What could cause an earthquake?

To understand the cause of an earthquake, people must first understand that the earth is made up of four layers: the inner core, the outer core, the mantle and the crust. The coat and the crust are very thin; the mantle is 1,750 miles thick while the crust is only 8 miles thick. 

This thin skin is broken into pieces called tectonic plates, these plates are like puzzle pieces which sometimes slide against each other and stick together. When these parts separate, they create an enormous force which makes the earth tremble and undulate.

How are earthquakes measured? 

There are instruments called seismographs that are used to determine the extent of the earthquake. These instruments are about a ballasted pen and spring and this help when the vibrations of the earthquake appear, they draw lines on paper. 

The way these lines are drawn indicates how small or large an earthquake is; if there is a short wavy line that does not move much, it means a small earthquake and the long wavy line that wiggles a lot means a large earthquake.

What is the Richter scale? 

Richter scale is a device which is used to measure earthquakes, The Richter scale was invented in 1934 by the Californian scientist Charles Richter in order to measure the magnitude of an earthquake and a result is a number from 0 to 10; the higher the number on the scale, the greater the earthquake.

People might not even notice an earthquake unless it measures at least a 3 on the scale. There are different steps on this scale that tell people what to expect: if the scale indicates 4, the earthquake may shake the house and some people may not even notice it. 

If the scale indicates 6, the earthquake could cause cracks in some houses and the items on the shelves could fall and the windows could break. If the scale gives the number 7, it means that old buildings could suffer from cracks and that some streets could also face the same problem. 

If the scale is 8, then people should be aware that many buildings and even bridges could fall and crack and finally, if the scale gives the number 9 or even more, then many losses can occur and many buildings can fall.

What are seismic waves? 

Seismic waves are the shock waves of an earthquake that travel through the ground, these waves are the strongest in the centre of the earthquake, but they travel over a large part of the earth and return to the surface, these waves move quickly 20 times faster than the speed of sound.

What is a fault line? 

Earthquakes form along fault lines, it is a stress area in the earth. Faulty lines, the rocks slide over each other and will eventually cause a crack on the surface of the earth.

What are the shakes and aftershocks? 

In fact, before and after major earthquakes, there are smaller earthquakes, those that occur before are known as tremors and those that occur after are called aftershocks. The main major earthquake is sometimes called the mainshock.

What are the epicentres and centres of earthquakes? 

The epicentre is the point on the earth's surface directly above the fracture of the rocks. The focus of the earthquake is where the rocks actually ruptured, the focus is often miles below the surface of the earth.

What should people do in the event of an earthquake? 

There are some instructions and advice given to people during an earthquake. During an earthquake, people should fall, cover-up and hang on. People should stay indoors until the tremor stops and if they are in bed, they should hang on and stay there protecting their head with a pillow. 

If people are outside, they should find an open area away from buildings, trees, and power lines, and then fall to the ground. If people are in a car, they should also find a safe place and stay in the car until the shaking stops.

Essay on Earthquake 1200 words

What exactly is an Earthquake?

Earthquakes are caused by the release of energy that generates waves which travel in all directions causing the shaking of Earth's surface.

  • what exactly is this energy?
  • what waves? 
  • what's shaking of Earth's surface?

Earth is not just one piece it is made up of jigsaw puzzles of around 19 to 20 pieces, which are called as tectonic plates these plates are placed on a hot partially molten layer of Earth's mantle this is the reason why these pieces are continuously moving, these plates move around one to ten centimetre each year but don't worry all these movements can be felt by us 

Sometimes these movements are extremely strong and can be felt like a lot of vibrations under your feet or it can also destroy an entire city that's called an earthquake 

The earthquakes occur in the lithosphere region of the earth an earthquake generates underneath the earth and this releases the energy across the point at which the earthquake occurs under the earth is called hypocenter in the exact place above it and the surface of the earth is called the epicentre 

The most horrifying earthquake recorded till date was of magnitude nine points five out of ten this happened in Valdivia in southern Chile in 1960 another one that happened in Japan into hookah region was of the magnitude of 9.0 which happened on March 11th 2011 this earthquake caused massive and enormous damage and destruction and took nearly sixteen thousand people's life with him 

Geologists use a device that can sense the waves created by the movement of the tectonic plates these waves are known as seismic waves and the device is called as a seismograph, the earthquake events are scaled according to the magnitude of the shock and are known as Richter scale this magnitude relates to the energy released during the earthquake magnitude is expressed in absolute numbers zero to ten,

Where zero is lowest where people feel nothing and ten being the highest that can create severe destruction and loss of life over a large in order to know more about earthquake let's jump to the simulator, 

The inner core of the earth and then we have an outer core, mantle and crust the inner core as the name suggests is the innermost layer or the central layer of earth it is like a solid spherical ball in nature with a radius of twelve hundred and fifty kilometres the temperature of Earth's core ranges between 4,500 to 5,500 degrees Celsius facing pressure of 300 to 360 Giga Pascal's.

Next is outer core it is of about 2200 kilometre thickness and has a temperature similar to the inner core that is off 4500 to 5,500 degrees Celsius then we have the mantle layer which is the semi-solid state of about 2900 kilometre thickness this layer makes around 84 per cent of Earth's total volume 

And the last layer is the crust which is like an apple skin when compared to other layers runs from 0 to 70 kilometres in thickness which is specifically 8 kilometres under C to 32 kilometres under continents and this is only 1% of the Earth's total mass 

EarthQuake magnitude on the Richter scale

If the intensity is between zero to 2 it can be barely sensed when the intensity is more than 2 and less than 4 we can feel minor vibrations and sense it a little, from 4 to 4.9 it is considered as small or a light earthquake range from 5 to 5.9 are considered moderate earthquakes and from the range, 6 to 6 point 9 are considered as strong earthquakes,

In some time we will see how much damage these magnitudes can do and anything above 7 is considered as major earthquakes which can destroy cities and continents these readings are recorded on a seismograph 

Now let's set the four to 4.9 magnitude to see how this earthquake happens, the earthquake starts from a point called a hypocenter inside the earth during an earthquake two types of waves are formed one is called body waves and the other is called as surface waves 

What are called body waves?

Body waves are the waves that move through the interior of the earth and through the body of the earth and hence the name when these body waves move these waves come across the surface rocks and generate the surface waves 

Detail about these body waves and surface waves 

From the point that is the hypocenter waves are released these waves are called primary waves or P waves now what are these p waves, p waves are seismic waves that shake the ground back and forth in the same direction and the opposite direction as the direction of the wave is moving which is similar to the movement of these sound waves this is how a p wave looks like 

These P waves are the first to be recorded on a seismograph now after a fraction of second when these P waves hit the rocks closer to the surface gives rise to the new set of waves the S waves or called as secondary waves

These ways are towards the earth crust and these are tremors and vibrations that we feel S waves are the wave motion in a solid medium weather medium moves perpendicular to the direction of the wave after the p waves these S waves are recorded on a seismograph 

Now these S waves hit the surface and start the earthquake the point at which the earthquake originates on the surface is called an epicentre after the P and S waves come to the surface waves which are the most destructive waves as they cause the movement or the displacement of the rocks which leads to falling of structures and causing harm to life

The thing to notice is that the higher the magnitude the close of the hypocenter is to the epicentre when we move to six to six point nine magnitude the damage is enormous buildings are gonna broken roads are cracked and small houses are collapsed earthquakes can really be an extremely damaging natural calamity 

If this is the case when the magnitude is limited to seven imagine how nine and nine-point five might even look since these are quite commonly occurring magnitudes, it is extremely difficult to predict an earthquake based on a seismograph which is also known as seismometer but even our smartphones can now detect these seismic waves and scientists can use this data to predict earthquake and one people 

NASA can use this information in the quakes and software which can use this data to generate more efficient information, recent studies showed that before an earthquake nearby regions record very high concentrations of radioactive pair radon and thoron this happens because right before the earthquake these gases are released on the surface from small cracks and if we can detect these gases we can predict a quake at least seven days in advance.

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