Tsunami
A tsunami is a series of large ocean waves caused by sudden, large-scale disturbances of water. The primary triggers include submarine earthquakes, volcanic eruptions, underwater landslides, and meteorite impacts. Of these, undersea earthquakes account for the majority of destructive tsunamis worldwide. When the seafloor suddenly shifts during an earthquake, it displaces the water column above it, initiating waves that radiate outward in all directions at high speeds.
Wave Characteristics and Propagation
Tsunamis differ from typical wind-driven ocean waves in both origin and behavior. In deep ocean water, tsunami waves may have long wavelengths and low amplitudes, traveling at speeds of 500–800 kilometers per hour while remaining relatively inconspicuous to ships. As the waves enter shallow coastal waters, the sea floor friction reduces wave speed while conserving energy, causing the waves to compress and grow substantially in height. Waves that were only a meter high in deep water can reach heights of 10 meters or more when reaching the shore.
Coastal Impacts and Warning Systems
Tsunamis can strike coastlines with little warning, particularly for areas close to the epicenter of an initiating earthquake. The initial wave is often preceded by a dramatic recession of water from the beach, as the trough of the wave train reaches shore first. Multiple waves typically follow the first, with dangerous conditions persisting for hours after the initial impact. Modern tsunami warning systems use networks of seismic stations and ocean buoys to detect disturbances and issue alerts to coastal communities, significantly reducing casualties in regions with established monitoring infrastructure.