Subject: GS 1
Syllabus: Important Geophysical phenomena such as earthquakes, tsunamis, Volcanic activity, cyclones, etc., geographical features and their location, changes in critical geographical features (including water-bodies and ice-caps) and in flora and fauna and the effects of such changes.
Questions
- What is a tsunami? Explain briefly the factors behind it and discuss the impacts on areas where it makes landfall. (150 Words, 10 Marks)
- What is an earthquake swarm? Give a few examples of areas where an earthquake swarm has impacted recently, also discuss its impacts. (250 Words, 15 Marks)
Model Structure
1. What is a tsunami? Explain briefly the factors behind it and discuss the impacts on areas where it makes landfall. (150 Words, 10 Marks)
Model Structure
Introduction
Tsunamis are giant waves of high wavelength mainly caused by undersea earthquakes and volcanic eruptions. They cannot be observed by the naked eye or heard because of their long wavelength and low amplitude.
Main Body
- These waves include a quick and huge displacement of ocean water, which is seen later as a fast-moving train of water with huge potential for destruction.
- Factors driving the Tsunami:
- Submarine earthquakes: This results in vertical movement of the water column due to sudden motion of blocks or big rocks on the seabed.
- Submarine volcanism disturbs normal movement of water, and the eruption is so sudden and huge that it forms tsunami waves
- Oceanic landslides result in the falling of rocks and turbidity currents, resulting in the displacement of seawater and ultimately in tsunami waves.
- A minor cause is meteorites and asteroids, which, in the case of falling into the ocean water, can result in a similar displacement of water and formation of a tsunami.
- Owing to the gigantic nature and less developed methods of mitigation, damages by tsunamis are huge in the form of:
- There have been many physiographic changes in areas where tsunamis have struck in the past. There are many islands where beaches are split into two due to a rise in water level in coastal areas. Indira Point in the Andaman Islands was washed out in a 2004 tsunami, which reduced the coastline.
- Loss of life and property in low-lying, coastal and island areas because tsunamis are dangerous, but the backwash or seiches are even stronger. Property worth millions is damaged, and it takes a long time to return to normal.
- Inundation of coastal and low-lying areas can result in increased salinity of soil and a decrease in soil fertility and agricultural productivity.
- Marine life is also affected as fish shoals and coral habitat gets damaged.
- Secondary Hazards: Tsunamis may trigger secondary hazards like fires, contamination of water sources, and infrastructure failures, exacerbating the overall impact on affected areas.
- There is a shift in Earth’s magnetic poles due to the release of enormous energy, which has tilted the Earth slightly. This can impact the Earth in the case of solar storms.
Conclusion
- Tsunami is one of the few natural disasters that is hard to predict in advance. The focus of mitigation and adaptation strategies must be to make coastal communities and the ecosystem resilient to such disasters.
2. What is an earthquake swarm? Give a few examples of areas where an earthquake swarm has impacted recently, also discuss its impacts. (250 Words, 15 Marks)
Model Structure
Introduction
- An Earthquake swarm is a sequence of seismic events consisting of many small earthquakes and with a short time span but lacking any main shock.
- Though they are short-lived, at times they can go on for days, weeks, or even months. They occur at active plate boundaries, in volcanic environments and hydrothermal vents.
Main Body
- Earthquake swarms have occurred all over the globe, with few notable examples like-
- Germany - Bohemia region lies between the Czechia and Germany border, where earthquake swarms occurred and were first studied in the 19th century.
- Philippines - lying near the Pacific ring of fire, an earthquake swarm occurred here for four months in 2017, in the province of Batangas.
- India - In Dahanu area of Maharashtra, an earthquake swarm has been occurring since 2018 where 10-20 quakes are felt daily.
- France - In Alpes-de-Haute province, the Ubaye Valley experiences earthquake swarms.
- El Salvador - This country experienced a series of approximately 500 earthquake swarms within 2 days in 2017.
- It is clear that earthquake swarms are spread across the globe and though they are very mild, but their longevity makes a case to understand their impacts like-
- Earthquake swarms can also occur due to self-inflicted stress fields without any external pore pressure, which means that they are also possible in aseismic areas. Dhanau swarm of Maharashtra is an example.
- Because earthquake swarms last for a long time, there is stress redistribution, which can influence future earthquake swarms and their intensity.
- There is no fixed damage potential as some cause considerable damage but others are relatively harmless.
- Earthquake swarms have the potential to trigger the collapse of structures due to aftershocks, which are similar to normal earthquakes. Dhanau swarm has caused damage to structures in the past.
- Low-intensity swarms can be a result of anthropogenic activities like the construction of dams and reservoirs.
Conclusion
- Swarms, just like earthquakes, pose a threat to infrastructure and life. Even though this threat is very less frequent, there is a need to mitigate the risks by repairing and reinforcing building foundations, adhering to seismic building standards and following disaster risk reduction frameworks.
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