Tsunami

Tsunami is also known as “Seismic Sea waves” are serious waves caused due to underwater eruption of volcanoes, earthquakes due to the continuous moving of tectonic plates and other underwater distribution. Tsunamis can Travel 20-30 miles per hour and have waves with heights of 10-100 feet. Tsunami is a Japanese word “tsu” means “Harbour” and “nami” means “Waves”. Tsunami waves are totally different from astronomical tides that arise due to gravitational forces of the moon and sun. a tsunami causes a huge amount of disaster including flooding, disruption of travelling, power cut, water supplies and breakout communication. 

Discussion

Geophysical phenomena Tsunami

Geophysics is associated with the physics of the earth and its environment in space. Internal structure and composition include gravitational and magnetic fields. Dynamics, surface extension, tectonic plates, volcanoes and rock formation are described as geophysical components of Tsunami.  A tsunami can be generated by any of these including earthquakes, landslides, volcanoes and underwater explosions.

Characteristics of Tsunami

Tsunami is a small wave with large heights with long wavelengths often 100km long. They can grow in height when they occur in tidal states and low tide when they occur in inundate coastal areas. When tsunami waves enter shallow water in coastal regions height increases and again slows and amplify when hit the land. The Wavelength of a tsunami is often 10-100 kilometers long. Compared to an earthquake it travels 970 kilometers but a tsunami travels 800 kilometers. The height of these waves is less in deep seas but high in shallow water when it hits the land and can rise up to 100 feet. 

Tsunami waves generally have two parts: crest and trough. Part of the tsunami wave that reaches shore first is trough followed by the crest. Crest hit shore approximately after 5 minutes of through. Unlike astronomic waves, Tsunami waves are a series of waves rather than isolated waves. These waves can stay more than 10-12 minutes. Wavelength is defined as the distance between identical points between two waves normal waves generally have wavelengths of 100 meters but Tsunami waves have wavelengths measuring up to 500 kilometres. Wave velocity in a normal ocean is 90km/hour while the velocity of a Tsunami is 900km/hour hundred times more than normal waves. 

Cause of Tsunami

The Pacific basin has two destructive tsunamis per year, pacific wide tsunamis are rare as they occur once or twice in every 10 years most of the tsunamis are generated due to earthquakes and eruption of volcanoes. This Geophysical phenomenon can also arise due to earthquakes, underwater explosions, volcanic eruptions and other underwater activities. Earthquakes generate Tsunamis by disturbing the seafloor. It can occur on the coastline in the middle of the sea. Tsunami wave size is directly related to the size of earthquakes. Displacement of an earthquake is important for generating Tsunami as only vertical displacement causes tsunami waves. The Pacific Ocean is surrounded by plates thus tsunamis are frequently generated in the Pacific Ocean due to earthquakes. 

Volcanic eruptions occur along coastal zones of Japan and other islands over the world. A large expansion of volcanoes resultes in a pyroclastic flow into the water that generates large waves. Landslides in oceans, rivers and lakes can also generate tsunamis; these landslides generally occur due to earthquakes and volcanoes. A large landslide occurred in Alaska in 1958. Underwater explosions also resulted in generating Tsunami waves. A tsunami is generated when the seafloor deforms or is vertically displaced by overlapping tectonic plates. Tectonic Earthquakes are particular types of an earthquake that are responsible for generating Tsunami waves. 

Tsunami Vulnerability in India

Island of Sri Lanka surrounded by the Indian Ocean, is largely vulnerable to large Tsunamis in 2004 with the 9.2 magnitude Sumatra earthquake. This resulted in killing more than thousands of people. A minute after the earthquake occurred in Andaman and Nicobar Islands it hit the mainland of India, in which Tamil Nadu and Andhra Pradeshwere the two worst-affected states. The total number of deaths in India counted above 18,000 people. This tsunami managed to travel 5,000 km to Africa. The East and west coast of India is highly affected by Tsunami almost every year.

The Indian coastal region in the past few years has not recorded any Tsunami. Due to earthquake activities in 1881 over the North Bay of Bengal, a large Tsunami was reported. During the earthquake of 1819 near Rann of Kutch a movement of water was reported, in 1945 Makran earthquake with 8.1 magnitudes in the Richter scale and height of waves were recorded of 12-15 meters. This tsunami caused a huge deluge and a large loss of properties. Eruption of Krakatoa volcano on 27th August 1883 affected Chennai. East coast of India was affected by an 8.1 magnitude earthquake in Andaman on 26th June 1941. West coast of India was affected on 27th November 1945 due to an earthquake in Baluchistan Pakistan with 8.1 magnitude. 

Conclusion

Tsunami is important to study as it is a natural hazard that can occur at any time in coastal regions and can destroy lives. This causes large damages by washing out entire cities that can take years to rebuild civilization. 80% of Tsunamis occur in the Pacific Ocean as it is surrounded by many tectonic plates. Tsunami waves get bigger when they reach the shore with shallow water.