Question

write the cause of an earthquack

Answer 1

Earthquakes are usually caused when rock underground suddenly breaks along a fault. This sudden release of energy causes the seismic waves that make the ground shake. When two blocks of rock or two plates are rubbing against each other, they stick a little. ... When the rocks break, the earthquake occurs.

there are many reasons for earth quake some of them are:-

1 Volcanic activity

 

Exploding volcanoes release tremendous energy which offsets the Earth’s crust. This is the reason many earthquakes happen in and around volcanic regions. Earthquakes happening due to volcanic eruptions are called volcanic earthquakes.

 

2 Folding and faulting

 

When a fracture occurs in the plane on which the Earth’s crust resides, an earthquake can happen. This type of earthquake is caused either by vertical or horizontal displacements. The movement of rocks along these fractures causes the movement of earth’s crust.

 

3 Plate tectonics

 

The Earth’s surface is comprised of plates. These plates are always moving. When these plates move, their margins become sites of earthquakes. That is why earthquakes are found to be frequent in plate boundaries.
4 Nuclear bombs

 

Human beings test nuclear bombs underground. The explosion releases shock waves. This situation can cause a minor earthquake. The overlying rocks become unstable. They shift their position. It induces a mass chain reaction of shifting rocks.

 

5 Construction activities

 

Blasting of rocks for construction work is common. Rocks are needed for construction. Blasts release energy and render the Earth’s crust unstable. In mountainous regions, rocks that were lying for millions of years could shift. A small shift releases outward energy that renders the whole region unstable. In this event, an earthquake happens.

 

6 Underground mining

 

Deep underground mining creates big gaps beneath the Earth’s surface. This does not do much for the stability of the Earth’s upper layer. Also, mining involves the use of explosives and bombs to blast open rocks. Similar to nuclear bombs, and construction related bombs, explosions for mining release shock waves.

 

7 Dams and reservoirs

 

Water held in dams and reservoirs exerts tremendous pressure on the ground surface. The ground surface spreads this pressure across to sustain itself. This is a natural phenomenon. But over a period of time, water disturbs the equilibrium of the Earth’s surface. The pressure could build up in a way so as to produce mild tremors. Over a period of time, a full-fledged earthquake can happen.

 

8 Landslides

 

Avalanches and landslides disturb the equilibrium of the Earth’s crust. They cause the Earth’s crust to send shock waves as a means to release and distribute energy. Landslides exert tremendous force on the Earth’s crust, which can even cause a full-blown plate movement several kilometers below the Earth’s crust.

 

9 Injecting liquid waste into the ground

In many parts of India, certain industries inject waste into the ground’s surface as a means of disposal. This process causes instability of the Earth’s crust and could lead to earthquakes.

 

10 Creating high rise buildings on inappropriate land


The creation of high rise buildings on land that is not capable of withstanding such pressure can cause Earthquakes.

Answer 2

Causes of Earthquake :
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The uppermost layer of the earth is made up of block of rocks. These blocks float on a layer of semi- liquid rock called Mantle.

Earthquake occurs when the blocks of rocks touch or move against each other in the semi- liquid layer.

This causes a sudden slipping of the position of the earths crust or tectonic plates relative to each other. This movement causes vibrations, Volcanic activity as explosive eruption, caused by gas explosion. Any sudden vibration or movement of a part of the Earth's crust caused by natural or man made forces resulting in the shaking or trembling is called Earthquake..

Following are the main causes of Earthquake :

1. Volcanic Eruption

2. Folding and Falling

3. Plate Tectonics

4. Man- Made explosions.

5. Dislocation of the crust.

Epicentre is the place on the surface of the earth, directly abvove the focus. The intensity of the earthquake is the greatest​ at the epicentre.

Aftershock is a small earthquake that often follows a big one. After the main shock , the rocks have jumped too far and are still unstable . Aftershock are felt as the rocks settle into a more stable position.

Protections against Earthquake :
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we know that some areas in the world are earthquake prone. These are called Seismic Zones. The buildings in these Zones should be designed in such a way that they can sustain the major tremors.

A building should be constructed with the light building material like mud or timber, Roof should be kept light as it will not cause more damage in case a structure falls due to earthquake.

Safety measures during Earthquake :
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♣ leave your home and move to open area.

♣ keep away from high rise buildings.

♣ Hide yourself under a table.

♣ Shut off kitchen Gas.

♣ If you are in a car, slow down and drive to a place away from buildings.

♣ Help others according to their needs.

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