QUE : What causes tsunamis? Discuss at least four factors that lead to tsunami generation. Also explain the effects of tsunamis in coastal areas.

  Tsunami means an earthquake on the seabed and the huge waves generated by it. The huge waves that rush onto the shore due to the energy generated by the earthquake on the ocean floor are known as ‘tsunami’.

•  An earthquake on the oceanic crust is theoretically called a seaquake. The water movement on the sea surface due to gravity and wind is known as tidal waves. These waves are huge in size compared to tidal waves. Tsunamis are not only caused by earthquakes, they can also be caused by volcanic eruptions, undersea landslides, meteorites, hurricanes, tornadoes, and cyclones. Since they frequently occur in the Sea of ​​Japan, which is part of the North Pacific Ocean, the Japanese word ‘tsunami’ (su = harbor, nami = waves; waves in the harbor) is used for them.
  
• Tsunami is a huge wave that is generated on the sea surface due to an earthquake that occurs at a depth under the seabed or due to any other reason resulting in ocean churning. It does not have any special effect in deep ocean water, but as it moves upwards and forwards, it disturbs the upper water surface, causing terrible devastation when it reaches the coast.
  
•  Factors behind tsunami generation:
  

1. Earthquake: When an earthquake occurs in the ocean, a large part of the seabed is lifted or moved down, which suddenly releases a large volume of water, which is responsible for generating tsunami waves. In the case of an earthquake with a magnitude of more than 6.5 on the Richter scale, occurring at a depth of 70 km below the earth’s surface, which causes parallel movement of the seabed, the possibility of a tsunami is higher.

2. Volcanic eruption: When a volcano erupts in the ocean, the lava that comes out of it moves the surrounding water to a large extent, which can turn into a huge wave and take the form of a tsunami.

3. Erosion tsunami: Erosion of the seabed over a large area is responsible for the movement of water. Which can be a factor for tsunamis.

4. External collision: Although not recorded in recent history, if an external celestial body such as a meteorite falls on the ocean, it can cause a tsunami.

a. Landslide: Landslides on the ocean coast and even deep underground can disrupt the water flow and cause tsunamis.

• Effects of tsunamis:
  

•  Fatalities – A large number of human deaths can be recorded due to tsunamis.
•  Flooding – Large waves that come at high speed cause flooding in coastal areas.
•  Diseases – Waterborne diseases such as malaria can increase.
•  Damage to critical infrastructure – Many buildings are damaged due to the force and weight of the waves. They collapse.
•  Fire – Power supply and gas pipelines can be damaged and fire incidents can occur.
•  Environmental impacts – Trees are uprooted. Habitats of animals and birds are destroyed.
•  Waste problem arises due to unlimited solid waste generation.
• Drinking water sources are polluted.
•  Radiation problem can arise due to damage to nuclear plants on the coast.

                                      In India, the damage caused by tsunamis can be reduced with the help of capacity building, education, training, research and development and other efforts of the National Disaster Management Authority at the coastal locations with the help of local and state levels.