Tsunami – UPSC Geography Notes

Table of Contents

The term “Tsunami” originates from the Japanese words “tsu” and “nami,” where “TSU” refers to port and “NAMI” signifies wave. Together, they convey the concept of ‘harbour waves.’ Tsunamis are massive waves caused by sudden shifts in the ocean’s surface, triggered by seismic activity like earthquakes, underwater landslides, coastal collapses, intense volcanic eruptions, or even meteorite impacts. Notably, the most significant recorded tsunami hit Lituya Bay, Alaska, USA, on 9th July 1958.

Tsunamis represent a crucial subject within the context of the UPSC Civil Services Exam. This set of UPSC Geography notes delves into aspects such as the origins, impacts, and mechanisms of tsunamis. Understanding the concept of tsunamis holds significance for both the preliminary and mains stages of the general studies paper. Testbook meticulously crafts top-notch study materials, considering all vital elements, to aid UPSC aspirants in their preparation.

What is a Tsunami?

Tsunamis are characterized by extremely long wavelengths of water
They are typically caused by sudden ocean displacement due to seismic events like earthquakes or volcanic eruptions
Also known as seismic sea waves, they rank among the most potent and destructive natural forces
Upon hitting coastlines, they can result in perilous coastal flooding and long-lasting, powerful currents
While most tsunamis stem from significant earthquakes, not all earthquakes lead to the formation of tsunamis.

Characteristics of Tsunami

Tsunamis, though infrequent, can vary greatly in size and impact.
In deep water, tsunamis have long wavelengths, but these shorten and increase in height as they approach shallow water.
Offshore, tsunamis typically have small wave heights, generally less than 3 meters.
They propagate in all directions from their source and can cover the entire ocean.
Tsunamis consist of a series of waves with varying periods.
These waves result from tremors, not the earthquakes themselves.
Tsunamis do not follow a specific season and can behave unpredictably in terms of location and intensity.
Their impact can differ significantly from one coastline to another.
The magnitude and location of the originating tremor determine the potential impact of a tsunami.
Tsunami speed is higher in shallow water, leading to more significant effects near coastal regions than in deep ocean areas.

Types of Tsunami

Local Tsunamis: Occur within 100 kilometers of the triggering event (e.g., an earthquake), leaving minimal time for escape.
Regional Tsunamis: Impact areas within 100 to 1,000 kilometers, providing a relatively short window for preparation compared to local tsunamis.
Distant Tsunamis: Affect regions over 1,000 kilometers away, allowing more time for safe evacuation due to the extended travel time of the waves.

Amidst the ebb and flow of these waves, tsunamis can cause casualties, injuries, and damage to structures and infrastructure.

While major earthquakes are the leading cause of tsunamis, it’s important to note that not all earthquakes result in these destructive waves.

Causes of Tsunami

What causes Tsunamis to form?

Tsunamis are exclusively triggered by vertical seafloor movements. The primary cause of most Tsunamis is seismic activity, particularly earthquakes. Additionally, Tsunamis can also be generated by volcanic eruptions, underwater explosions, landslides, and meteorite impacts.

Earthquake: Tsunamis are often a result of earthquakes, particularly those occurring along subduction boundaries of plates near ocean trenches. The magnitude of the resulting tsunami correlates with the size of the earthquake.
Underwater explosion: Notably, the US’s nuclear testing in the 1940s and 1950s in the Marshall Islands generated a tsunami.
Volcanic eruption: Volcanoes situated along coastal waters can trigger various events leading to tsunamis.
Landslides: Earthquakes and volcanic eruptions can induce landslides, which, when entering oceans, bays, or lakes, have the potential to generate tsunamis.
Meteorite Impacts: While historical instances of meteorite-induced tsunamis are scarce, evidence suggests that a meteorite impact roughly 5 million years ago resulted in a tsunami, leaving deposits along the Gulf Coast of Mexico and the United States.
Human-Induced Factors: Nuclear explosions, a significant anthropogenic factor, can be a major contributor to the occurrence of tsunamis. Notably, the nuclear testing conducted by the US in the 1940s and 1950s in the Marshall Islands generated a tsunami.

Formation of Tsunami

Undersea Earthquakes

While tsunamis can be triggered by various phenomena such as landslides, volcanic eruptions, and the impact of substantial meteorites hitting water, the most devastating tsunamis are primarily caused by colossal undersea earthquakes.

These calamitous tsunami waves stem from the vertical displacement of the entire water column, which occurs due to sudden, abrupt movements of fault blocks on the seafloor.

It is essential to highlight that a tsunami is typically not caused by horizontal displacement of the sea floor.

Furthermore, not all undersea earthquakes result in the formation of tsunamis, as this outcome hinges upon the specific nature and extent of the displacement of the seawater columns.

Landslides

Natural calamities such as rock falls, landslides, and icefalls have the potential to displace seawater, consequently generating tsunami waves. These waves swiftly propagate from their source, causing widespread destruction along nearby coastlines as their energy dissipates.

Volcanic Eruptions

The occurrence of a robust underwater volcanic eruption leads to the sudden displacement of a considerable volume of seawater, ultimately culminating in the creation of tsunami waves.

Meteorites and Asteroids

If meteorites and asteroids plunge into the water, the possibility of a tsunami arising cannot be discounted. Although such an occurrence is extremely uncommon, researchers emphasize the destructive capability of a tsunami resulting from a near-Earth asteroid impact.

Propagation of the Tsunami

Tsunamis travel as a sequence of extremely long waves in all directions from their point of origin on the ocean’s surface.
In deep water, tsunamis are not visible or audible due to their long wavelengths and low amplitude.
Passengers on boats typically cannot feel or see the tsunami waves passing swiftly beneath them.
As tsunamis move from deep water to shallower regions, they undergo two transformations: a significant decrease in speed followed by a substantial increase in height.

Effects of Tsunami

The impact of a tsunami on a coastline can vary from minor to immensely devastating, determined by factors like its distance from the source, magnitude, and coastal bathymetry.
The primary effect of a tsunami arises from the destructive power of the massive waves it produces.
Secondary effects include the projection of debris as dangerous projectiles and the subsequent loss of crops and water, potentially leading to famine and disease.

How Often Does Tsunami Occur?

The Pacific Ocean experiences an average of one tsunami every 15 years.
- A notable example within India itself is the tsunami that occurred on December 26th, 2004, along the Indian Coast, resulting in significant loss of life and property.
- Tsunamis should not be conflated with large wind-generated waves. Unlike wind-generated waves, which last for mere seconds, tsunamis persist for minutes to hours. Tsunamis can lead to catastrophic consequences, whereas wind-generated waves do not pose such a threat.

Tsunami in the Indian Ocean

Tsunamis are often likened to tidal waves due to their resemblance to rapidly rising tides. However, scientists refrain from using this term as tides are driven by gravitational forces from the sun and moon, whereas tsunamis result from water displacement.
The 2004 tsunami was triggered by a massive earthquake, the third-largest ever recorded on a seismograph, with a magnitude ranging from 9.1 to 9.3 on the Richter scale.
The faulting endured between 8.3 and 10 minutes, making it the longest in history, and spawned numerous aftershocks lasting up to 3 to 4 months.
The seismic event discharged an immense amount of energy, leading to a slight wobble in the Earth’s axis and a shift in its rotation.
The vertical elevation of the seafloor by several meters during the earthquake displaced a vast volume of water, giving rise to the tsunami.
Indonesia, being in close proximity, was the first nation hit by the tsunami and suffered the highest casualties, with approximately 170,000 fatalities.

Tsunami in India

The Indian coastal area has remained largely unaffected by tsunamis for a considerable period. However, seismic activity in the North Bay of Bengal has been accompanied by waves.
The government has identified several tsunami-prone regions along India’s eastern coast, including Puri, Kakinada, Machilipatnam, Nizampatnam-Vetapalem, Chennai, Cuddalore-Pondicherry, Rameshwaram, Thoothukudi, Alappuzha-Chavara, and Kochi.
An earthquake with a magnitude of 7.7 to 8.1 struck the Andaman Islands on June 26, 1941, resulting in significant devastation. Due to the ongoing World War II in Southeast Asia, limited information is available about this event.
The earthquake and ensuing tsunami caused severe destruction in the Andaman and Nicobar Islands, leading to the loss of approximately 8,000 lives in India, Sri Lanka, and potentially in Bangladesh, Myanmar, and Thailand.
In 2004, the tsunami hit the southern coast of the Indian mainland, primarily affecting the states of Andhra Pradesh, Tamil Nadu, and Kerala. Simultaneously, multiple tsunamis coincided with the local high tide in certain areas.
The Andaman and Nicobar Islands were among the most severely impacted due to their close proximity to the epicenter of the earthquake, with Little Andaman and the Nicobar Islands experiencing catastrophic consequences.

List of Tsunami-Prone Areas in India

The government has released a roster of tsunami-prone areas along the coastal belt of India, including:

Orissa: Puri
Andhra Pradesh: Kakinada, Machilipatnam, Nizampatnam-Vetapalem
Tamil Nadu: Chennai, Rameshwaram, Thoothukudi, Cuddalore-Pondicherry
Kerala: Alappuzha-Chavara, Kochi
Andaman & Nicobar Islands

List of Tsunami Affected Areas in India

Bay of Bengal tsunami:
- 1762: Coastal Bangladesh, Myanmar, resulting in the loss of over 200 lives.
- 1868: Port Blair, Andaman Island, with no reported casualties.
- 1881: Nagapattinam, Port Blair, Car Nicobar, with no reported casualties.
Andaman Sea tsunami:
- 1941: Impacting India, Andaman, and Nicobar Islands, as well as Sri Lanka. The Cellular Jail collapsed, and masonry buildings in Port Blair were destroyed.
Gulf of Cambay, Gujarat tsunami:
- 1945: Striking the Gulf of Cambay, Gujarat, and Pakistan, with estimated fatalities ranging from 300 to 4000.
Indian Ocean earthquake and tsunami (2004): Causing more than 200,000 fatalities in various coastal regions of Indonesia, India, Malaysia, Maldives, Sri Lanka, and Thailand.

Damages Caused by Tsunami

Various forms of damage caused by the tsunami are briefly outlined below:

Death Toll

Tsunamis invariably result in the loss of hundreds of thousands of lives.
The Andaman and Nicobar Islands, being closest to the earthquake’s epicenter and the source of the tsunamis, were highly vulnerable.
The coastal regions of Tamil Nadu bore the brunt of the tsunami’s impact on the Indian subcontinent.
Indonesia and Sri Lanka recorded higher death tolls compared to India.

Loss of Property

Tsunami assaults result in the destruction of properties worth millions of rupees, including houses, public buildings, and transportation systems, leading to irreparable damage.
India’s coastal regions, notably in Tamil Nadu, Andhra Pradesh, Pondicherry, and Kerala, suffered losses amounting to billions of rupees, as per initial government estimates.

Physiographical Changes

The tsunami on December 26, 2004, led to increased water levels on various islands, causing some beaches to split. Indira Point, the southernmost tip of the Indian Union, faced significant coastline erosion.

The Earth’s Motion

The massive energy release from the earthquake reportedly caused a slight tilt in the Earth’s axis. Some experts suggest a potential permanent acceleration of the planet’s rotation due to a shift of mass toward its center.

Decline in Soil Fertility and Agricultural Production

Extensive inundation of low-lying coastal areas led to heightened soil salinity, resulting in decreased agricultural productivity and fertility.

Effect on Marine Life

The tsunami severely impacted the marine life in the affected oceanic regions.
The Andaman and Nicobar Islands’ coral reefs were significantly damaged or destroyed, potentially leading to the extinction of certain archipelagic species.
The fishing industry suffered substantial losses, and various large marine mammals faced disruptions in their breeding, feeding, and other activities.

Tsunami Early Warning System

The implementation of a Tsunami early warning system serves to detect and monitor tsunamis beforehand, allowing for the issuance of warnings to prevent the loss of life and damage to property and infrastructure. Given the unpredictable nature of tsunamis, early warning systems represent the most effective means of mitigating their impact.

Numerous regional and global early warning systems are in place worldwide. Following the devastating tsunami in December 2004, India opted to participate in the International Tsunami Warning System.

Indian Tsunami Early Warning System, Hyderabad

INCOIS, Hyderabad, established and operates the Indian Tsunami Early Warning System (ITEWS) in 2007.
The system is a collaborative effort involving various institutions such as the Department of Space (DOS), the Department of Science and Technology (DST), the Council of Scientific and Industrial Research (CSIR), the Survey of India (SOI), and the National Institute of Ocean Technology (NIOT).
ITEWS incorporates a real-time network of seismic stations and tidal gauges, along with a 24X7 operational tsunami warning center, to identify tsunamigenic earthquakes, monitor tsunamis, and issue timely alerts to vulnerable areas.
With the capability to promptly detect significant underwater earthquakes in the Indian Ocean, Indian scientists can provide a tsunami warning within 10-20 minutes.
Emulating the Tsunami Ready initiatives in other coastal towns is essential, enhancing preparedness for cyclones and storm surges.
Effective warning systems can only be successful if communities comprehend official and natural tsunami warning signs and respond promptly and appropriately.

Advance Warning about Tsunamis

Providing advance notice of impending tsunamis is the most effective strategy to protect vulnerable communities.
Studying the speed, wavelength, and depth of the sea aids in predicting the onset of tsunamis.
Tsunamis often travel slowly from their origin to the coastline and experience reduced wavelength and speed in shallow seas.
Upon reaching the coastal regions, their energy amplifies, leading to devastating waves.
Timely warnings issued hours in advance can prevent significant loss of lives and property damage.

Tsunami Mitigation Strategies

Tsunamis rank among the rarest natural calamities on Earth. Although infrequent, major tsunamis can result in severe repercussions for life and property.

Here are several precautionary measures that can be adopted to mitigate the impact of tsunamis:

Hazard Assessments: Conducting comprehensive hazard assessments can aid in comprehending how tsunamis of varying magnitudes and origins might impact coastal communities. This information helps create tsunami danger zone maps, enabling focused preparedness and response efforts.
Public Awareness: Educating the public through awareness campaigns and regular advisories on tsunamis and safety measures can significantly enhance preparedness.
Use of Technology: Implementing advanced technology, such as tsunami prediction and warning systems, along with the development of mobile applications for early alerts, can enhance community preparedness.
Protection of Coastal Ecosystem: Safeguarding coastal ecosystems like mangroves and coral reefs can serve as natural barriers, reducing the risks associated with tsunamis.
Evacuation Routes: Familiarizing communities with well-designed evacuation routes is crucial, as awareness of these routes can save lives during emergency situations.
Proper Building Codes: Adhering to meticulous planning and stringent building codes in coastal areas is vital for minimizing the potential harm to both individuals and infrastructure caused by tsunamis.

Tsunami: Key Facts

Meaning of Tsunami: Translates to ‘Harbour waves’
Types:
- Local Tsunami
- Regional Tsunami
- Distant Tsunami
Speed: Ranges from 20-30 miles per hour
Height: Varies between 10-100 feet
Occurrence: Relatively infrequent
Causes: Stem from vertical seafloor movement due to earthquakes, volcanic eruptions, etc.
Tsunami-prone areas in India:
- Andaman Islands
- Bay Of Bengal
- Eastern Coast
Major Tsunamis: Notably, the devastating event on December 26th, 2004, severely impacted the Indian Coast, causing significant harm to both lives and property.
Monitoring agency: Indian Tsunami Early Warning System (ITEWS) operates at the Indian National Centre for Ocean Information Services (INCOIS) in Hyderabad.

Why the Problem is Consistent

Tsunamis, being a natural calamity, largely remain beyond human control; however, human activities have contributed significantly to exacerbating their impact.
Violations of the legal regulation that prohibits constructions within 500 meters of the coast are a prime example. In India, despite legal restrictions, various development projects, including residential, commercial, and recreational ventures, continue to disregard these laws. Consequently, the population residing in these regions is highly vulnerable to the dangers posed by tsunamis and other maritime threats.
Extraction of sand and other minerals from coastal areas renders these regions increasingly susceptible to the destructive potential of tsunamis. The presence of sand along the coast serves as a buffer, absorbing energy from the waves and mitigating their impact on the coastal areas. Consequently, it is crucial to address unregulated construction and mining activities in ecologically sensitive coastal zones.

Conclusion

Over 700 million individuals reside in low-lying coastal areas and Small Island Developing States worldwide, making them highly susceptible to the perils of tsunamis and other catastrophic sea-level disasters.
Addressing these natural calamities requires a comprehensive approach. While progress has been made in this regard, further measures are imperative to ensure the protection of a larger population from potential harm and property damage.
Mitigating future tsunami risks entails establishing resilient infrastructure, implementing early warning systems, and enhancing public awareness.

FAQs for Tsunami

Q: What is the mechanism of a tsunami as per the UPSC syllabus?

A: The mechanism of a tsunami involves the sudden displacement of a large volume of water, usually triggered by underwater seismic activity, volcanic eruptions, or landslides, leading to the generation of powerful ocean waves.

Q: What is the deep impact of tsunami height on coastal areas as per the UPSC syllabus?

A: The height of a tsunami can have a significant impact on coastal areas, leading to widespread flooding, destruction of infrastructure, loss of life, and long-term environmental consequences, especially in low-lying regions.

Q: How deep can a tsunami be in the ocean as per the UPSC syllabus?

A: A tsunami wave can extend from the ocean surface to the ocean floor, reaching depths of hundreds or even thousands of meters, depending on the magnitude of the triggering event.

Q: How is the geography of a region related to tsunamis as per the UPSC syllabus?

A: The geography of a region, particularly its proximity to tectonic plate boundaries, underwater volcanic activity, and coastal topography, significantly influences the susceptibility of the area to tsunamis.

Q: How does a tsunami occur as per the UPSC syllabus?

A: A tsunami occurs when there is a sudden vertical movement of the ocean floor, displacing a large volume of water and generating powerful waves that propagate across the ocean.

Q: What are the processes involved in the generation of a tsunami as per the UPSC syllabus?

A: Tsunamis are generated by various geological events such as underwater earthquakes, volcanic eruptions, submarine landslides, or meteorite impacts, leading to the rapid displacement of water and the formation of destructive waves.

Q: Why do tsunamis happen as per the UPSC syllabus?

A: Tsunamis occur due to the sudden disturbances in the Earth’s crust, primarily caused by underwater earthquakes, volcanic activity, or landslides, which result in the displacement of large volumes of water and the propagation of devastating waves.

Q: What are the primary causes of tsunamis as per the UPSC syllabus?

A: Tsunamis are primarily caused by seismic activities, including underwater earthquakes, volcanic eruptions, and landslides, which lead to the rapid displacement of water and the subsequent formation of powerful waves.

Q: When do tsunamis typically occur as per the UPSC syllabus?

A: Tsunamis can occur at any time of the year, triggered by sudden geological events such as earthquakes or volcanic eruptions that displace large bodies of water and generate powerful waves with long wavelengths.

Q: Where have tsunamis impacted India in the past as per the UPSC syllabus?

A: India has experienced significant tsunami events, with the most notable recent one being the Indian Ocean tsunami of 2004, which had a devastating impact on the coastal regions of southern India and other countries bordering the Indian Ocean.

Q: Where do tsunamis typically occur as per the UPSC syllabus?

A: Tsunamis primarily occur in regions located near subduction zones, tectonic plate boundaries, and areas with active underwater volcanic activity, where sudden geological disturbances can lead to the displacement of large bodies of water and the generation of powerful waves.

Q: Where can a tsunami be located as per the UPSC syllabus?

A: A tsunami can occur in any ocean or large body of water, especially in regions prone to seismic activity and underwater disturbances, such as subduction zones, volcanic regions, and areas with active fault lines.

Q: Will a tsunami occur again in a specific region as per the UPSC syllabus?

A: While the possibility of a tsunami recurrence cannot be ruled out, it largely depends on the geological activity and potential seismic events in the specific region, as well as the implementation of effective early warning systems and disaster preparedness measures.

Q: What are the key points to remember about tsunamis in the UPSC syllabus?

A: Notes on tsunamis in the UPSC syllabus typically include information about the causes, mechanisms, impacts, and mitigation strategies related to these natural disasters, emphasizing the importance of disaster management and preparedness.

Q: What are the main topics related to tsunamis in the UPSC mains examination?

A: The UPSC mains examination may include questions on the geological processes behind tsunami generation, the environmental impacts, the socio-economic consequences, and the measures for disaster risk reduction and management associated with tsunamis.

Q: What are the primary effects of tsunamis on coastal regions as per the UPSC syllabus?

A: The effects of tsunamis include widespread flooding, destruction of infrastructure, loss of lives, displacement of populations, environmental damage, and long-term socio-economic repercussions, emphasizing the need for effective disaster preparedness and mitigation strategies.

Q: How is the topic of tsunamis relevant for the UPSC examination?

A: The topic of tsunamis is relevant for the UPSC examination as it highlights the importance of understanding natural disasters, their causes, impacts, and management, emphasizing the significance of disaster risk reduction and sustainable development practices.

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