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Causes of Earthquakes, Different Types and Effects

Grade 4
Aug 3, 2023


The crust of the Earth comprises large slabs of rock known as plates. The abrupt movement of these plates causes changes on the Earth’s surface.

We are aware that the Earth’s surface is constantly changing. The majority of changes occur slowly over long periods of time. Some changes, however, can occur very quickly. For example, during the 1989 World Series, a sudden shift in the Earth’s crust changed the Earth’s surface in just 15 seconds. The crust is the Earth’s topmost layer. What causes the crust to move or shift? The answer can be found in the way the Earth’s crust is constructed.

Structure of Earth

Fig. no.1: Structure of Earth

Earth’s Moving Crust

The Earth is divided into layers. The crust is the most delicate layer. It is made up of massive rock slabs known as plates. The map shows how the plates fit together like puzzle pieces. The plates are constantly shifting.

Tectonic plates

Fig. no.2: Tectonic plates


Where the plates collide, there are breaks or cracks in the Earth’s crust. These cracks are known as faults. In some places, the Earth’s plates slowly slide past each other along a fault. Plates push together or move under or over each other in some places. In other places, the plates separate. Earthquakes can occur when plates move. Earthquakes are movements in the Earth’s crust caused by a sudden shift in the Earth’s plates. When plates shift, changes other than earthquakes occur. Mountains and volcanoes emerge as plates shift.


The unexpected shaking of the ground that happens when masses of rock change their position below the Earth’s surface is known as an earthquake. The shifting masses send out shock waves that may be powerful enough to change the Earth’s surface, pushing up cliffs and making big cracks in the ground.


Fig. no.3: Earthquake

Where do Earthquakes Occur? 

Earthquakes do not occur everywhere on the planet. The majority of earthquakes occur near the edges of Earth’s plates, as indicated by the red dots on the map above. Some of Earth’s plates collide in an area around the Pacific Ocean. The majority of earthquakes occur here (around the Pacific Ocean).

Tectonic plates

Fig. no.4: Tectonic plates


Causes of Earthquake

The majority of earthquakes occur where the Earth’s plates collide. The plates are constantly shifting. They can move slowly at times, only a few centimeters per year. Creep is the slow movement along faults. Large earthquakes are uncommon in areas where faults are creeping.

At times, however, the movement is abrupt. The energy released by the sudden movement of plates causes the crust to shake. It has the potential to cause a large earthquake.

What Causes Faults?

The Earth’s surface is constantly moving due to forces within the planet. These forces cause plates on the Earth’s surface to move. The rocks near the plate edges are stressed as a result of this movement. The rocks bend, compress, or stretch to relieve stress. The rocks will break if the force is strong enough. An earthquake is caused by the vibrations caused by rock breaking.

Types of Faults

There are three types of faults.

Types of faults

Fig. no. 5: Types of faults

Normal Fault:

The plates pull apart in a normal fault. Rocks above the fault surface sink. This is how the Sierra Nevada mountains were formed.

Normal fault

Fig. no.6: Normal fault

Reverse Fault

Compression forces squeeze rock, resulting in reverse faults. When a rock breaks due to opposing forces, the rock above a reverse fault surface is forced up and over the rock below the fault surface. The plates push together in a reverse fault.

Reverse fault

Fig. no. 7: Reverse fault

Strike-slip Fault

Rocks slide past each other in opposite directions on a strike-slip fault. The San Andreas Fault is one such example. The San Andreas Fault is the boundary between two plates moving sideways past each other on Earth.

The San Andreas Fault

Fig. no.8: The San Andreas Fault

Strike-slip fault

Fig. no.9: Strike-slip fault

Earthquake’s Vibrations

The ground may vibrate or shake during an earthquake. It may appear to roll. The ground will occasionally split open.

An earthquake’s vibrations are strongest where the earthquake begins—below ground.

Vibrations travel in all directions through the Earth’s crust.

Have you ever dropped a pebble into the water? Did you notice how the water ripples moved? An earthquake’s vibrations move in a similar manner.

The vibrations weaken as they travel away from the epicenters of the earthquake. Despite this, the vibrations could be felt for hundreds of kilometers.

Earthquake vibrations

Fig. no.10: Earthquake vibrations

Richter Scale

Charles Richter developed a scale to compare the energy released by earthquakes in 1935. The Richter scale assigns a value of 1 to 10 to earthquakes. Earthquakes with magnitudes less than 2.5 are rarely felt. Earthquakes with magnitudes greater than 8.0 cause widespread devastation.

Richter scale

Fig. no.11: Richter scale


A seismograph is a device that detects and records earthquakes. It is also referred to as a seismometer. It captures the movement of the ground during a quake.

Fig. no. 12: Seismograph

Earthquakes Have the Following Effects on the Earth’s Geography:

Ground Tremors

  • Earthquakes frequently cause ground shaking.
  • Buildings and roads can be destroyed as a result of ground shaking, and in some cases, people have died horribly after being discovered under a building.

Rupture of the Ground

  • When earthquakes occur, the ground begins to swell.
  • The ground will begin to rupture as earthquakes move along a fault, breaking the Earth’s surface into small pieces and causing ruptures in it.
  • The pipelines in the city will be completely destroyed, as will the wires in the ground.
  • In some countries, underground tunnels exist; these tunnels will be destroyed beyond all expectations. Underground tunnels are very expensive to rebuild, so this is a huge loss.

Land Sliding

  • Ground shaking and ground rupture both cause landslides.
  • Landslides form when the tectonic plates beneath the Earth graze against each other, causing the unstable slopes to shake continuously.
  • Landslides can easily destroy city buildings, roads, and railroad lines, as well as hilltop homes, causing them to tumble down from the hills.


  • The most devastating effect of earthquakes is a tsunami.
  • Tsunamis, also known as tidal waves, are a type of water wave that occurs when the sea bed or sea floor moves vertically upwards during an earthquake.
  • Tsunamis have the power to destroy a city in minutes. Tsunamis pose a serious threat to many parts of the world.

Methods to reduce earthquake impacts

If you’re inside,

  • Stay there. Outside, there could be falling debris.
  • Hide behind an internal door frame, a sturdy table, a bench, or a bed.
  • Avoid windows, mirrors, chimneys, overhead fixtures, and tall furniture.
  • Get under a desk near a pillar or internal wall in high-rise buildings, and avoid elevators.
  • Do not rush for doors in congested areas. Keep away from roof and wall fittings.
  • Before leaving, listen to the radio for any warnings.

When you’re outside,

  • Keep a safe distance from buildings, walls, power lines, and trees.
  • Take shelter from falling debris beneath strong archways or doorways.
  • Do not stand under awnings or parapets/walls as they may collapse.
  • If you are in a vehicle, pull over to the side of the road until the shaking stops.


  • The unexpected shaking of the ground that happens when masses of rock change position below the Earth’s surface is known as an earthquake.
  • A fault is a sharp break in the rocks of the crust.
  • The majority of earthquakes occur near the edges of the Earth’s plates
  • Faults are of three types – Normal fault, reverse fault, and strike-slip fault.
  • An earthquake’s vibrations are strongest where the earthquake begins—below ground.
  • The forces within the planet cause plates on the Earth’s surface to move.
  • A seismograph is a device that detects and records earthquakes.
  • Charles Richter developed a scale to compare the energy released by earthquakes in 1935.
  • Earthquakes affect the Earth’s geography.
  • Though earthquakes are unpredictable, taking some precautions will help to decrease the damage caused by earthquakes and protect people in advance.


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