Why in news?
An earthquake of magnitude 8.8 struck Russia’s remote Kamchatka Peninsula in July 2025. The undersea quake triggered a tsunami that prompted warnings not only along Russia’s Far East but also in Japan, Hawaii and as far as New Zealand. Fortunately, major settlements were largely spared, but the event renewed focus on tsunami science and preparedness.
What is a tsunami and how does it form?
- Seafloor disturbance: A sudden shift of the ocean floor caused by an earthquake, volcanic eruption or landslide displaces huge volumes of water. In the case of Kamchatka, tectonic plates slipped under the Pacific Ocean.
- Wave generation: The displaced water creates long‑wavelength waves that radiate in all directions. In the deep ocean these waves travel at jet‑plane speeds—up to 800–900 km/h—yet their height is often less than half a metre, so ships barely notice them.
- Drawback effect: As a tsunami nears shore, the trough may arrive first, causing the sea to recede dramatically. Uninformed people may be tempted to walk into the exposed seabed, unaware that a towering wave follows.
- Wave amplification: In shallow water the tsunami slows down and the trailing waves pile up, increasing in height to several metres or more. The water then surges inland, inundating coastal areas and dragging debris back to the sea as it retreats.
Impacts of tsunamis
- Human toll: Tsunamis can cause thousands of deaths and injuries. The 2004 Indian Ocean tsunami, for example, devastated coastlines from Indonesia to India and Africa.
- Infrastructure damage: Ports, houses, bridges and power plants can be destroyed by the force of the waves, leading to long‑term economic disruption.
- Environmental harm: Saltwater inundation ruins croplands and contaminates freshwater sources. Coastal ecosystems are torn apart, and debris can travel great distances.
- Secondary hazards: Fires, chemical leaks and underwater landslides may follow the initial wave, compounding the disaster.
Early warning systems
Timely warnings can save lives. India’s tsunami early warning centre monitors seismic activity and sea‑level changes around the clock.
- Seismic monitoring: A network of sensors detects earthquakes and quickly determines whether they could generate tsunamis.
- DART buoys and tide gauges: Bottom Pressure Recorders (DART) and coastal tide gauges measure minute changes in sea level to confirm whether a tsunami has formed.
- Alert dissemination: The Indian National Centre for Ocean Information Services (INCOIS) uses satellite, SMS, sirens and media to warn authorities and the public.
- Global cooperation: Under the coordination of UNESCO’s Intergovernmental Oceanographic Commission, regional centres share data to improve accuracy of warnings.
While tsunamis cannot be prevented, understanding their physics and maintaining robust warning systems can minimise the loss of life.