Causes and Effects of Earthquakes

Earthquake refers to the sudden violent movement of the earth’s crust. It creates seismic waves. It often causes great destruction. Its causes and effects are mentioned below.

Causes of Earthquakes

The important causes of the earthquake are:

Natural Causes of Earthquake:

1. Tectonic Movement: This particularly happens when the continental plate collides against the oceanic plate. The oceanic plate is overridden by the continental plate. By a process called subduction jerky movements are caused along the inclined surface. Tectonic earthquakes have occurred in Assam in 1950.
2. Volcanic Activity: Earthquakes may also be caused by the movement of lava beneath the surface of the earth during volcanic activity. The earthquakes due to Krakatoa volcanic eruption in 1883 is a good example of volcanic eruption.
3. Dislocation of the Earth’s crust: Earthquakes may be caused by the dislocation of the crust beneath the surface of the Earth.
4. Adjustment in inner Rock Beds: Earthquakes are also caused where is an adjustment between Sima [i.e., beneath the ocean is formed by Silica and Magnesium = Si + ma = Sima] and Sial (i.e., Continent is formed by Silica and Aluminium = Si + al = Sial) in the interior of the Earth’s Crust. This Earthquake may be called as a Plutonic Earthquake.
5. Pressure of gases in the interior: The expansion and contraction of gases in the interior of the Earth sometimes cause a sudden shake on the Earth’s surface.
6. Other Causes:
   1. Landslides and avalanches,
   2. Denudation of the Landmasses and depositions of materials,
   3. Faulting and folding in the rock beds are responsible for causing minor earthquakes.

Man-made Earthquakes:

1. The impounding of large quantities of water behind dams disturbs the crustal balance. This causes earthquakes such as the Koyna earthquake in Maharashtra.
2. The shock waves through rocks set up by the underground testing of Atom bombs or Hydrogen bombs may be severe to cause earthquake.

Effects of Earthquake

Destructive Effects:

1. Earthquake causes dismantling of buildings, bridge and other structures at or near epicenter. Many men and animals are killed or buried under collapsed houses.
2. Rails are folded, underground wires broken. Fire breaks out inevitably in large towns.
3. Earthquakes originate sea waves called Tsunamis.
4. Earthquakes result in the formation of cracks and fissures on the ground formation.
5. The earthquakes cause landslides and disturb the isostatic equilibrium.
6. Landslide due to earthquake may block valleys to form lakes.

Constructive Effects:

1. Sometimes the earthquakes cause formation of hot springs which are very useful to people.
2. The earthquakes sometimes cause submergence in coastal land, and result in formation of inlets, bays and gulfs which help to develop of fishing and shipping etc.
3. Sometimes, the earthquakes cause emergence of costs and bring fertile shore out of water to give chance to develop crop production.

Earthquake Belts:

1. The Circum-Pacific Mountain belt: About 70% of all earthquakes happen here. These cover islands areas of Japan, Philippines and Indonesia shaped like an arc. This belt is also known as the Pacific Ring of Fire.
2. The Mid-World Mountain Belt: About 20%, of all earthquakes occur in this belt covering parts of Europe and Asia.
3. Other Belts: Remaining 10% are scattered in 0-700 km range over ocean floor, rift valleys and other areas.