What is a Tsunami?

Tsunamis are giant tidal waves that begin from the depth of oceans and violently land on seashores. Underwater earthquakes and volcanic eruptions are the primary causes of tsunamis. Initially, these tidal waves are small where the sea is deep; they can grow up to a hundred feet after reaching shallow waters. 

The largest tsunami ever recorded hit Lituya Bay, Alaska, on July 9, 1958. The massive wave was 1,700 feet tall, and it destroyed everything in a 5-square mile radius. However, the average tsunami wave height is only 3 metres (10 feet). 

Types of Tsunami

Meteotsunamis

A meteotsunami is a large sea wave that reaches a height of 2 metres (about 6 feet). They are milder than seismic tsunamis and are caused by abrupt changes in air pressure, such as those caused by squalls or storm fronts moving through. The difference in pressure causes a collapse in the ocean or lake’s surface, which pushes outward in all directions.

Extraterrestrial tsunamis

Tsunami waves aren’t really restricted to the surface of the earth. A 2016 study of the Martian landscape, which used pictures and infrared images to explore the arid planet’s northern plains, discovered evidence of two different tsunami episodes that occurred many years ago. Comet or asteroid strikes are hypothesised to have triggered these phenomena.

What causes a Tsunami?

Now that you know what a tsunami is, it is important to understand what causes it too. Drastic submarine activities such as earthquakes, underwater volcanic eruptions, underwater landslides, glacier calvings, and nuclear tests are the prime causes of a tsunami. However, meteorite fall has also caused tsunamis. Earthquakes and volcanic eruptions are the most frequent causes of tsunamis. 

Tsunamis are as fast as a jet plane in deep waters, but they slow down upon reaching shores. It is nearly impossible to track a tsunami on time. A satellite must be passing over the mega wave to detect it, which is the rarest of the rare occurrence. 

Characteristics/features of a Tsunami:

• Tsunami is one of the earth’s most infrequent hazards that can be massively destructive at times. 
• In deep water, tsunami’s wavelengths can often go up to a hundred kilometres long, but when a tsunami enters shallow water, its wavelength decreases; however, the period remains unchanged, leading to an increase in height. 

Tsunamis have very little amplitude offshore. It mainly ranges from a few centimetres to more than 30 metres in height. 

• From the point of origin, it radiates in all different directions and covers the whole ocean. 

Tsunamis usually have a series of waves that come with periods ranging from minutes and hours. 

• The depth of the water decides the speed of the waves in the ocean. The speed is generally high in shallow water when compared with deep water. 

Warning and prediction of Tsunamis

There is no accurate detection system to identify the occurrence of a tsunami within time, even if the system has the data on the magnitude and location of an underwater earthquake. Tsunami Warning Systems play a key role in evacuating populations within time. 

Tsunami Warning Systems have two major components 

• A sensor network that observes seismic alerts to predict an upcoming tsunami wave 
• A communication system to relay the warning to the authorities and people 

Tsunami Warning Systems have two types

International: Such systems cover a vast area across international borders and seas. 

• Pacific Tsunami Warning Centre (PTWC) covers the Pacific Ocean.
• The National Tsunami Warning Centre (NTWC) covers North America and the Gulf of Mexico. 
• Integrated Plate Boundary Observatory Chile (IPOC) covers nearly a 600-km seismic area. 
• Tsunami Early Warning and Mitigation System in the North-Eastern Atlantic, the Mediterranean, and Connected Seas (ICG/NEAMTWS) is a joint warning system established with the help of UNESCO. 

Regional – Local warning systems also detect a shorter range of seismic activities. The regional warning systems can relay information in a maximum of 15 minutes. 

Natural warning signs of a tsunami 

• Alarming shaking of the ground
• Receding water from the coast, resulting in ocean floors and reef exposure – it is called a “drawback.”
• A thunder sound, coming from the ocean like a jet plane

 Prevention measures for tsunami waves:

• One of the natural measures which could be adopted for mitigating the impact of a tsunami is using shoreline tree cover.
• Tree plantation is a cost-effective, lasting means of tsunami mitigation compared with artificial barriers.
• Some locations in the Indian Ocean where the tsunami struck in 2004 remained almost intact because the existing coconut palms and mangroves trees absorbed the tsunami’s energy.

Mitigation measures for tsunami waves 

• Constructing, marking, and publicising evacuation routes 
• Construction of evacuation structures
• Public warning
• Educating people on the risks of a tsunami and safety tips
• Issuing of design and construction guidelines to prevent or minimise tsunami damage
• A disaster management plan for tsunami aftermath
• According to tsunami prevention guidelines, reinforcement of existing buildings, houses, and warehouses
• Practising tsunami emergency drills such as moving to higher ground

Conclusion

Tsunamis are a natural disaster capable of destroying thousands of trees, homes, buildings, and lives. The characteristics of tsunami waves have paved the way for modern tsunami warning systems. These systems allow the authorities and people to follow mitigation measures for tsunami waves within a safe time frame. 

We cannot control natural phenomena like earthquakes and volcanic eruptions, but we can bolster our preparedness whenever an imminent tsunami hits our seashores. The best advice for an upcoming tsunami is to seek higher ground or tsunami shelters.