Tsunami
Kartavya Desk Staff
Syllabus: Geography
Source: NDTV
Context: An 8.8 magnitude earthquake struck Russia’s Kamchatka Peninsula triggering a tsunami that impacted Russia, Japan, and issued warnings as far as Hawaii and New Zealand.
About Tsunami:
• What is a Tsunami? A tsunami is a series of high-energy sea waves caused by sudden large-scale disturbances like earthquakes or volcanic eruptions. These waves travel rapidly across oceans and cause major destruction upon landfall.
• A tsunami is a series of high-energy sea waves caused by sudden large-scale disturbances like earthquakes or volcanic eruptions. These waves travel rapidly across oceans and cause major destruction upon landfall.
• Tsunami Formation: Seafloor Disturbance: A sudden undersea earthquake, volcanic eruption, or landslide shifts the ocean floor abruptly. This vertical displacement of the seabed pushes up or pulls down large volumes of seawater. It creates a disturbance that initiates tsunami waves spreading outward from the epicentre. Wave Generation: The displaced water forms a series of long-wavelength waves that move outward in all directions. In deep ocean, these waves travel extremely fast—up to 800–900 km/h—like a jet plane. Despite high speed, the wave height in deep water is low (30–50 cm), making it barely noticeable. Drawback Effect: As the tsunami approaches land, the trough may arrive before the crest, pulling water away from shore. This causes the sea to appear to recede dramatically, exposing seabed and marine life abnormally. Many people misinterpret this as low tide, unaware it precedes a devastating incoming wave Wave Amplification: In shallower waters, the tsunami slows down due to friction with the seabed. As the trailing water masses catch up, energy is compressed and wave height rapidly increases. This vertical surge can grow from 1 meter to over 10 meters within minutes, intensifying its force. Coastal Impact: The towering wave crashes onto the coast with immense speed and pressure. It inundates up to several kilometres inland, sweeping away people, buildings, trees, and vehicles. Subsequent retreating waves drag debris and survivors back into the sea, worsening destruction.
• Seafloor Disturbance: A sudden undersea earthquake, volcanic eruption, or landslide shifts the ocean floor abruptly. This vertical displacement of the seabed pushes up or pulls down large volumes of seawater. It creates a disturbance that initiates tsunami waves spreading outward from the epicentre.
• A sudden undersea earthquake, volcanic eruption, or landslide shifts the ocean floor abruptly.
• This vertical displacement of the seabed pushes up or pulls down large volumes of seawater.
• It creates a disturbance that initiates tsunami waves spreading outward from the epicentre.
• Wave Generation: The displaced water forms a series of long-wavelength waves that move outward in all directions. In deep ocean, these waves travel extremely fast—up to 800–900 km/h—like a jet plane. Despite high speed, the wave height in deep water is low (30–50 cm), making it barely noticeable.
• The displaced water forms a series of long-wavelength waves that move outward in all directions.
• In deep ocean, these waves travel extremely fast—up to 800–900 km/h—like a jet plane.
• Despite high speed, the wave height in deep water is low (30–50 cm), making it barely noticeable.
• Drawback Effect: As the tsunami approaches land, the trough may arrive before the crest, pulling water away from shore. This causes the sea to appear to recede dramatically, exposing seabed and marine life abnormally. Many people misinterpret this as low tide, unaware it precedes a devastating incoming wave
• As the tsunami approaches land, the trough may arrive before the crest, pulling water away from shore.
• This causes the sea to appear to recede dramatically, exposing seabed and marine life abnormally.
• Many people misinterpret this as low tide, unaware it precedes a devastating incoming wave
• Wave Amplification: In shallower waters, the tsunami slows down due to friction with the seabed. As the trailing water masses catch up, energy is compressed and wave height rapidly increases. This vertical surge can grow from 1 meter to over 10 meters within minutes, intensifying its force.
• In shallower waters, the tsunami slows down due to friction with the seabed.
• As the trailing water masses catch up, energy is compressed and wave height rapidly increases.
• This vertical surge can grow from 1 meter to over 10 meters within minutes, intensifying its force.
• Coastal Impact: The towering wave crashes onto the coast with immense speed and pressure. It inundates up to several kilometres inland, sweeping away people, buildings, trees, and vehicles. Subsequent retreating waves drag debris and survivors back into the sea, worsening destruction.
• The towering wave crashes onto the coast with immense speed and pressure.
• It inundates up to several kilometres inland, sweeping away people, buildings, trees, and vehicles.
• Subsequent retreating waves drag debris and survivors back into the sea, worsening destruction.
Characters of Tsunami:
• Long Wavelength: Tsunamis have extremely long wavelengths—up to 200 km between successive wave crests.
• High Energy and Speed (Not Height in Deep Water): In the open ocean, tsunami waves travel at jet-like speeds (up to 800–900 km/h) but appear only ~30–50 cm high.
• Multiple Waves Over Hours: Tsunamis are not a single wave but a series of waves, often arriving over several hours. The first wave is rarely the largest and later waves can be more destructive.
• Often Invisible at Sea, Deadly at Shore: In deep waters, ships barely notice a tsunami due to its low amplitude and wide spacing.
Implications of Tsunamis:
• Loss of Lives and Health Hazards: Tsunamis often lead to large-scale fatalities and injuries. For example, the 2004 Indian Ocean tsunami left thousands of dead, with many victims showing signs of drowning and blunt force trauma.
• Infrastructure Damage: Critical infrastructure such as ports, coastal homes, bridges, and even nuclear power plants can be destroyed or rendered inoperable, severely affecting the regional economy.
• Environmental Loss: Tsunamis devastate ecosystems by inundating croplands with saltwater, destroying coastal habitats, and spreading marine and human debris across vast areas of land and ocean.
• Disruption of Services: Basic services such as electricity, clean water supply, road and rail transport, and communication networks often collapse after a tsunami, delaying rescue and rehabilitation.
• Secondary Hazards: Tsunamis triggered by earthquakes can also lead to fires, chemical leaks from damaged facilities, and coastal or underwater landslides, compounding the overall destruction.
Tsunami Early Warning Systems
India’s System:
• Seismic Monitoring: 24/7 seismic stations detect global quakes within 10 minutes, filtering tsunamigenic ones.
• DART Buoys (BPRs): Bottom Pressure Recorders detect sea pressure changes from deep-sea waves in real time.
• Tide Gauges: Installed along coasts, they verify tsunami waves’ actual height and arrival at land.
• Alert Dissemination: INCOIS sends alerts to NDMA, media, and public via SMS, sirens, satellite, and radio.
Global Systems:
• IOC-UNESCO Coordination: Regional warning centres (e.g., PTWC, JMA) coordinate tsunami alerts globally.
• Global Seismic Networks: Real-time quake data from thousands of stations help assess tsunami risk.
• DART and Tide Gauges: Confirm tsunami formation and arrival, supporting accurate regional alerts.
• Satellite and Radar: Radar altimetry and coastal radar detect sea-level anomalies and wave patterns.
Conclusion:
Tsunamis are rare but deadly, demanding constant global vigilance and rapid response systems. India’s robust early warning system and international coordination remain critical to minimizing future risks.